Florida Chapter, American Fisheries Society 20th Annual Meeting 28-30 March 2000, Brooksville Florida ABSTRACTS

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Can Fishery Managers Detect Fish-Population Responses to a Minimum Length Limit?

Mike S. Allen and William E. Pine III. Department of Fisheries and Aquatic Sciences, The University of Florida, 7922 NW 71 ^st Street, Gainesville, FL 32653. Phone: 352/392-9617 ext. 252. Email: msal@gnv.ifas.ufl.edu,

We used a simulation model to evaluate how population density, population biomass, total catch (fish harvested and released), yield, and proportional stock density (PSD) of largemouth bass Micropterus salmoides would differ in response to a single three-year or five-year length limit evaluation at various recruitment variabilities. Recruitment variation modeled (coefficient of variation, CV= SD/0 * 100% in recruits to age-1) ranged from 20-100%. Minimum length limits modeled were 305, 356, and 457-mm. Simulations revealed that largemouth bass populations would not exhibit detectable differences in any population parameter (all P> 0.1) unless recruitment variability was #40% for a 305-mm and #65% for a 356-mm length limit, respectively. Values of CV in recruits to age-1 for 13 largemouth bass populations averaged 66% (range 11-189). A 457-mm length limit provided detectable differences in total biomass and PSD up to CV in recruits of 100%. Five-year evaluation periods yielded more detectable differences than three-year evaluations. Proportional Stock Density (PSD) was the variable most likely to change in response to the size limit. However, at recruitment variabilities > 90%, detectable differences did not occur unless the size limit was 457-mm. Fishery managers should consider effects of variable recruitment and duration of evaluation period when evaluating the success of a length limit.

STUDENT

Clinal Variation of Vertebral Growth in the Bluntnose Stingray, Dasyatis say: Eastern Gulf of Mexico and Coastal Mid-Atlantic

Kristen Andrews ¹and Jim Gelsleichter, ¹Eckerd College, 4200 54th Ave South, St. Petersburg, FL 33711, Email: andrewke@eckerd.edu, Ph.D.

Age and growth of the bluntnose stingray, Dasyatis say, was estimated using growth increments in the vertebra of 57 individuals. Two populations were sampled for the purposes of the clinal variation study: an Atlantic sample from the Virginia coast of 26 individuals ranging from 204 mm to 525 mm DW and a Gulf of Mexico sample from Tampa Bay of 31 individuals ranging from 150 mm to 602 mm DW. Stingrays were collected only from June to September, thus vertebral growth zones were assumed to be deposited annually. Centra were sectioned longitudinally and annuli were counted multiple times by multiple counters. Index of Average Percent Error was used to calculate precision. Back-calculated size-at-age data were used to estimate von Bertelanffy growth function parameters. These parameters were used to describe clinal variation between the two populations. This research represents a major addition to the meager amount of information on this species.

Automated Monitoring Platforms for Estuaries

Brian Bendis. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 8th Avenue SE, St. Petersburg, FL, 33701. Phone: 727/896-8626 Email: brian.bendis@dep.state.fl.us.

The occurrence, extent and impacts of harmful algal blooms (HABs) are believed to be increasing around the world, including in the Gulf of Mexico. Florida is considered one of the hotspots for HABs. It is critical to understand the environmental conditions that initiate and control blooms in order to adequately predict their occurrences and potentially mitigate their economic and resource impacts. Unfortunately, most of our current efforts for monitoring HABs occur during or after a bloom or fish kill event. Personnel and time resources are often the prohibitive factors in monitoring programs. Furthermore, the dynamic nature of the estuarine and brackish water systems where HABs occur require high resolution sampling, spatially and temporally. These are some of the reasons that the application of continuously recording sensors has become so prominent. Beyond the classic measurements of dissolved oxygen, salinity, and temperature, sensors that measure chlorophyll and nutrients are becoming more common. An autonomous water quality platform with several continuously recording sensors is planned for the St. Johns River. Data from the platform will be linked to intensive sampling data from five other stations. Investigators will examine the data for potential relationships among water quality, HAB biomass, and fish lesions. This pilot project has the potential to become a model for monitoring coastal and estuarine systems around Florida, perhaps the nation.

A Vague Zoogeographic Barrier Along the Northern Gulf of Mexico: Past and Present Evidence

Stephen A. Bortone. The Conservancy of Southwest Florida, 1450 Merrihue Drive, Naples, FL 34102. Phone: 941/403-4302. Email: sbortone@conservancy.org

The distribution of fishes and other aquatic organisms along the nearshore, coastal, and near shelf areas of the Gulf of Mexico display a pattern indicative of the presence of a significant zoogeographic barrier. Many species, for example, have a zoogeographic limit along the northern Gulf of Mexico between Mobile, Alabama and Apalachicola, Florida. Interestingly this zone is quite broad for a zoogeographic limit and does not seem to present any obvious, present day physical limitations to the distribution of many of these species. This is in deference to the intuitive notion that a natural zoogeographic barrier should occur at the Mississippi Delta region where profound and dynamic changes take place in salinity and turbidity. Marine and estuarine organisms that show this northern Gulf distribution anomaly are from a variety of groups including: sparids, stone crabs, seabasses, puffers, and blennies. Examination of geological formations and current geophysical features hint at features that may have been responsible for a historical zoogeographic barrier that is no longer functioning. Subsequently, however, the modern distribution of organisms serves as a reminder of its effectiveness and invite explanation. Combining a knowledge base from Geology and Biology may provide the answer to this perplexing situation. Other features of the distribution of organisms in the northern Gulf indicate strong links to the northern coast of South America.

Cyanobacteria Blooms in Florida’s Surface Drinking Water Supplies

John Burns. St. Johns River Water Manaement District, Palatka, Florida 32178. E-mail: john_burns@district.sjrwmd.state.fl.us.

Cyanobacteria blooms may present significant problems for Florida’s surface drinking water supplies due to the potential for toxin production. Toxins produced by cyanobacteria include hepatotoxic peptides, a cytotoxic alkaloid, neurotoxic alkaloids, saxitoxin derivatives, allergens and lipopolysaccharides. Following a 1999 survey of cyanobacteria blooms in Florida, results suggest that hepatototoxic compounds (i.e., microcystin and cylindrospermopsin) are most prevalent in fresh surface waters. The first North American record of cylindrospermopsin, a hepatotoxic compound associated with Cylindrospermopsis raciborskii, was recorded during this study.

Hepatotoxins (e.g., microcystin, nodularin, cylindrospermopsin) predominately cause liver injury with outbreaks of hepatoenteritis ocurring in human populations following the oral consumption of toxin laden water. Children are particularly at risk to toxins in drinking water since they drink more water per unit body weight than adults. For example, 140 children and 10 adults required medical treatment following a bloom of C. raciborskii in a public water supply in Australia. Recreational exposures to water containing toxic blue-green algae have caused illnesses ranging from acute pneumonia to hepatoenteritis and skin irritations. Recent reports have confirmed the carcinogenic activity of microcystin in liver following repeated intraperitoneal injections to mice. Water safety guidelines for cyanobacterial toxins are under development by the World Health Organization (WHO) and the U.S. Environmental Protection Agency. A provisional guideline for microcystin-LR of 1 ug/L has been approved by the WHO.

There can be no separation of quality and quantity in Florida water supply planning if cyanotoxins persist in the state’s drinking water supplies. Demands on groundwater supplies in Florida are currently exceeding or threatening to exceed sustainable yields, thereby forcing water managers to turn more often to surface drinking water supplies. Existing surface water treatment plants in Florida are currently not required to monitor for algal toxins and many are not adequately equipped to treat surface waters for taste, odor and toxins associated with immense cyanotoxic blooms. Surface water problems, human health risks and potential solutions required to address cyanotoxic blooms will be discussed in regards to water quality and surface water supply planning.

Taxonomy and Ecology of Florida Harmful Blue-green Algae

Andrew D. Chapman. St. Johns River Water Management District, Palatka, Florida 32178. Email: andrew_chapman@district.sjrwmd.state.fl.us.

Blue-green algae (cyanoprokaryotes, cyanobacteria) are ubiquitous photosynthetic organisms, common in Florida’s lakes, rivers and estuaries. A number of blue-green algae species can negatively affect water quality and water use. Under certain environmental conditions the unique physiological, morphological and ecological adaptations of these species allow them to form dense surface or subsurface blooms. Unbalanced algal communities, dominated by nuisance blue-green algae, can negatively affect food webs and energy flow in aquatic systems, lead to loss of fisheries habitat and create hypoxic or anoxic conditions upon decomposition. Some nuisance blue-green algae can also produce taste and odor compounds that can lead to off-flavor fish or toxins that are potentially harmful to wildlife, livestock and humans when ingested.

A number of blue-green genera include at least some potentially harmful species. Most common harmful blue-green algae found in Florida are species of Anabaena, Cylindrospermopsis, Microcystis and Planktothrix. Morphological, physiological and ecological traits of the common genera and species of Florida harmful algae and their potential impacts will be presented.

Trophic interactions of large-piscivorous and small-omnivorous fishes in freshwater marshes of the Florida Everglades

John H. Chick*, Pamela Geddes, Joseph H. K. Pechmann, and Joel C. Trexler. Department of Biological Sciences, Florida International University Miami, Florida 33199. Phone: 305/348-6253 Email: chickjh@fiu.edu

Two important features of freshwater marshes in the Everglades have not been thoroughly researched. First, a lack of information about large-piscivorous fishes has led to dichotomous descriptions of their importance, from suggestions that they control population growth of small fishes to suggestions that they are too rare to be ecologically important. Second, Everglades marshes support an unusually large standing stock of periphyton, often manifested in a calcareous floating mat. Interactions between grazers and periphyton are complex because nutrient regeneration by omnivores can stimulates algal growth and physical features of mature periphyton mats can impede grazing. We conducted caging experiments to clarify the role of large-piscivorous and small-omnivorous fishes in the Everglades food web. Closed treatments demonstrated that mosquito fish, the numerically dominant small-omnivorous fish, significantly reduced recruitment of macroinvertebrates, but had no significant net effects on periphyton. We also used open and refuge treatments to examine effects of large-piscivorous fishes, and found significantly greater use of the refuge treatment by small fishes, amphibians, and macroinvertebrates.

Greater abundance of grazers in the refuge treatment significantly reduced new growth of epiphytic algae, but did not affect mature periphyton mats. Our experiments suggest large fishes in the Everglades may be abundant enough to at least influence habitat selection by prey taxa. Additionally, patterns of grazer effects suggest physical features of mature periphyton mats that impede grazing may be critical to food web interactions in this system.

STUDENT

Culture of Neotropical Pacu, Colossama bidden, in Florida and its Potential for Exotic Introduction

Bruce Cooper and Wayne A. Bennett. University of West Florida, Department of Biology,11000 University Parkway, Pensacola, FL 32514-5751. Phone: 850/474-3362.

Red-bellied pacu, Colossoma biddens, is a native characid to freshwater streams in central South America. The fishes' tasty flesh, hardy nature, rapid growth rate, and ability to tolerate poor water quality make it a favorite culture species in many parts of the world. In the U.S., however, the fish is a popular aquarium species but is rarely cultured. Pacu are frequently caught outside of captivity in Florida and there is a certain amount of concern among fisheries scientists that it may establish permanent populations within the state. We found that pacu are capable of tolerating high temperatures of nearly 45°C (among the highest measured for fishes), but could not be acclimated to temperatures below 16.3°C. We combine, low and high temperature tolerance data for pacu acclimated at five temperatures between 16.5 and 39.0°C with surface water temperatures to identify areas within Florida where pacu will reach marketable size within a single season, but will not survive low winter temperatures.

Effects of a major red tide on seagrass and nearshore fishes in Sarasota Bay, Florida: Initial impacts and recovery patterns.

Randy E. Edwards and Richard H. Pierce. Mote Marine Laboratory, 1600 Ken Thompson Pkwy., Sarasota, FL 34236. Phone: 941/388-4441 X319, Fax: 941-388-4312.

A major red tide event occurred in Sarasota Bay, Florida in September 1995. A reconnaissance survey of the of the bay on September 15, 1995, indicated that shallow water fauna had been severely impacted and that grassbed and nearshore fishes were almost totally non-existent along at least 26 km of the western side of the bay. Three study stations (two grass beds and one tidal lagoon) in the impacted area were sampled for three months to determine the impacts and patterns of recovery. Initially, almost all grassbed fishes, with the exception of remarkable abundances of rainwater killifish ( Lucania parva), and almost all epibenthic invertebrates were absent from the grassbed sites, whereas abundances and diversity were less dramatically reduced in the lagoon. Subsequent sampling showed that repopulation occurred almost exclusively through recruitment of postlarvae or early juveniles. Substantial numbers of newly recruited, early-juvenile spotted seatrout ( Cynoscion nebulosus) were collected at the seagrass sites one month after the red tide, indicating that a complete year class failure did not occur. Red drum ( Sciaenops ocellatus) became exceptionally abundant at the lagoon site in late November. Overall, the red tide had initial catastrophic and major lasting effects on the fish populations, but the populations showed considerable resiliency. Considerable numbers of juvenile fishes were recruited to the area soon after the red tide had subsided.

Recovery of jewfish (Epinephelus itajara) populations in the eastern Gulf of Mexico: assessment of population parameters and essential habitat characterization.

Anne-Marie Eklund, Christopher C. Koenig, and Felicia C. Coleman. National Marine Fisheries Service, 75 Virginia Beach Drive, Miami, FL 33149. Phone: 305/361-4271 Email:Anne.Marie.Eklund@noaa.gov

Jewfish, Epinephelus itajara, are large, long-lived groupers that were severely overfished on their spawning aggregations and have, subsequently, been protected from all harvest in U.S. waters since 1990.

The species is now a candidate for the US threatened/endangered species list. To assess the recovery of this species, we have been monitoring the density and fidelity of adult spawning aggregations and the distribution and habitat requirements of juveniles. Our censuses on four aggregation sites continue a spearfishers' log that began in 1982.

The censuses show a precipitous decline in abundance in the 1980's, followed by a gradual increase in abundance through 1999. The size structure of the aggregations suggest, however, that these adult fish are not new recruits to the population. We have tagged over 700 adults on and off aggregation sites and are now beginning to get reports of tagged fish from popular dive spots on artificial and natural reefs 65-89 nautical miles from the aggregation sites where the fish were tagged. In June 1997 we began tagging juveniles and quantifying significant features of their habitat along mangrove shorelines of the Ten Thousand Islands area of southwest Florida. We have processed scales and dorsal fin spines and rays for age determination in juveniles. The age of the juveniles we have tagged range from 2-7 years, with a mean age of 4. We are mid-way through an experiment using both visual tagging methods and acoustic telemetry to compare jewfish abundance and distribution in altered and unaltered habitats of the Ten Thousand Islands.

STUDENT

The effects of prey type on the feeding biomechanics of Archosargus probatocephalus

M. Fougerolle and R. G. Turingan. Florida Institute of Technology, 150 W. University Blvd., Melbourne, FL 32901. E-mail: mfougero@fit.edu .

Species that are ubiquitous within heterogeneous, coastal habitats typically encounter variable prey-resources. The biomechanical basis for the ability of A. probatocephalus to consume both soft and hard prey organisms within its environment was examined in an attempt to understand the mechanisms that underlie the abundance and distribution of this species. Fish from the same location within the Indian River Lagoon were reared under two diets: whole bean clams ( Donax gouldii) [hard prey] and D. gouldii with shells removed (soft prey). At the end of a 70-day rearing period, fish were measured for key biomechanical features of the prey-capture and processing mechanism. Analysis of Covariance revealed that biting muscles and bones of fish fed hard prey were more massive than fish fed soft prey. Total body mass and mechanical advantage of the feeding mechanism did not differ between diet treatments. We hypothesize that the ability of A. probatocephalus to consume different prey organisms is associated with its ability to alter the development of its feeding mechanism. Phenotypic plasticity appears to be one of the mechanisms that underlie a species ability to exploit locally available prey-resource.

STUDENT

Summer Flounder Feeding Biomechanics and Its Implications for Fish Population Dynamics

A. W. Francis, Jr. and R. G. Turingan. Department of Biological Sciences, Florida Institute of Technology, 150 West University Blvd., Melbourne, FL 32901. Phone: 321/674-7222. Email: whiteshark@earthlink.net

Juvenile summer flounder, Paralichthys dentatus, were examined for differences in feeding biomechanics between the left (ocular) and right (blind) sides of fish. Seventy-two day post-hatch fish were preserved and measured for standard length, wet weight, developmental stage, head depth, jaw gape, and biomechanical properties of the lower jaw. Biomechanical properties included closing in-lever, opening in-lever, and out-lever arms. Biomechanical advantage of both left and right lower jaws was calculated from lever arms by dividing each in-lever by the out-lever. Morphometrics were log transformed while lever ratios were arcsine-transformed for subsequent hypothesis testing with analysis of covariance (ANCOVA) or analysis of variance (ANOVA). To determine the direction of asymmetry, an index of symmetry (IS) was calculated by dividing measurements on the ocular side by measurements on the blind side of the head. Closing in-lever, opening in-lever, and out-lever arms were significantly different between left and right sides of the head P < 0.01). Closing and opening lever ratios were also found to be different between sides P < 0.01). Closing lever ratios were smaller on the ocular side than on the blind side (IS < 1). Opening lever ratios were also found to be asymmetrical with either the ocular (IS > 1) or blind side (IS < 1) having the larger ratio. Asymmetry in lower jaw mechanical advantage is expected to influence flatfish prey-capture kinematics, a measure of feeding performance. The design of feeding mechanisms is linked to patterns of resource use by performance. Patterns of resource use have implications for fish population and community dynamics.

A Comparative Study of Mercury Concentrations in Tissue of Coastal Gulf of Mexico and Estuarine Red Drum Sciaenops ocellatus) from Tampa Bay, Florida.

Steven Harkey, Florida Marine Research Institute, Fish and Wildlife Conservation Commission, 100 8th Ave SE, St. Petersburg, FL 33701, (727) 896-8626 Ext. 2100. Email: Steven.Harkey@dep.state.fl.us.

High mercury concentrations in recreationally and commercially caught marine fish is a serious health concern in Florida. To limit the public's exposure to high concentrations of mercury in consumed fish, mercury concentrations must be monitored. Total mercury concentrations were analyzed from fillet tissue of 92 red drum taken from estuarine waters of Tampa Bay and tissue of 139 red drum taken from coastal Gulf of Mexico waters just outside of Tampa Bay. Red drum were measured and identified to gender, otoliths were removed for age determination, and a piece of muscle tissue for total mercury concentration analysis was removed. The mean total mercury concentration in estuarine red drum was 0.27 ppm, where as the mean total mercury concentration in coastal red drum was 1.67 ppm. Estuarine red drum, in general, were younger (mean age of 3 years) and smaller (mean total length of 614 mm) than coastal red drum were (mean age of 10 years, mean total length of 920 mm). The smaller (males < 825 mm TL, females < 925mmTL) and younger (males 2-5 years of age, females 2-7 years of age) coastal red drum had higher mercury concentrations (ppm) than did estuarine red drum of similar size and age. Coastal female red drum (2-7 years of age) had a mean mercury concentration of 1.11 ppm, and males (2-5 years of age) had a mean total mercury concentration of 0.77 ppm. Mercury is known to accumulate in fish over time, but this age-related accumulation may be exacerbated by dietary changes as the red drum migrate from estuarine to coastal habitats.

Species Composition of Fishes at Selected Oceanside Beaches in the Florida Keys

Chris Harnden and Derke Snodgrass. Florida Marine Research Institute, Indian River Lab, 1220 Prospect Ave, Suite 285, Melbourne, FL 32901. Phone: 407-984-4828. Email: Harnden_C@dep.state.fl.us.

We analyzed species composition of fishes for 135 samples collected in 21.3-m beach seines from July 1994 to July 1997. Samples were collected at six fixed, oceanside sites in the lower and middle Florida Keys. We collected 46,703 fish representing 125 species and/or species complexes. Many of the taxa collected are economically important in the Florida Keys Albula spp.,Trachinotus falcatus, Haemulon spp., and,Lutjanus spp.). There were no apparent seasonal trends in the overall fish abundance or in the diversity of the assemblages. However, by plotting relative occurrence and by using correspondence analysis seasonal trends were detected in the habitat usage of individual species.

Ichthyological Survey of a Low Salinity Restoration Site in an Urban Creek System

Donald C. Hicks. Pinellas County Department of Environmental Management, Water Resources Management Section, 300 South Garden Avenue, Clearwater, FL 33756. Phone: 727/464-4425. Email: hicks@co.pinellas.fl.us.

A one-hectare low salinity marsh was constructed in a branch of Allen's Creek about 5 kilometers upstream from Old Tampa Bay in Pinellas County, Florida. The fish community was sampled by seine at 4 to 6 week intervals from May 1997 to June 1999. A total of 40,778 fish representing 35 taxa and 18 families were collected during 17 sampling events. Dominant species (abundances >5%) included Poecilia latipinna (34%),Oreochromis aureus (20%),Brevoortia spp. (14%),Anchoa mitchilli (7%),Gambusia holbrooki (6%) andCyprinodon variegatus (5%). Several economically important estuarine species were collected includingMugil cephalus, Leiostomus xanthurus, Elops saurus, Centropomus undecimalis, Megalops atlanticus, Mugil curema, Cynoscion nebulosus,Sciaenops ocellatus and Pogonias cromis. Abundances of selected species will be compared to similar work done in the Tampa Bay area.

Some species were seasonal in occurrence.Cynoscion nebulosus were collected in October and December, while Sciaenops ocellatus were collected in February and March. Rainfall strongly influenced the occurrence of some species. Heavy winter rains caused salinities to fall below 0.5 ppt from December 1997 to April 1998. Centropomus undecimalis were absent from December 1997 through October 1998. Conversely, Micropterus salmoides appeared in collections in April and persisted through November 1998. Further monitoring of the fish community will be conducted as the succession of vegetation warrants.

STUDENT

Size-selective predation by peacock cichlids and trial duration in laboratory prey size selectivity experiments.

Jeffrey E. Hill and Charles E. Cichra, Department of Fisheries and Aquatic Sciences, University of Florida, 7922 NW 71st Street, Gainesville, FL 32653. Phone:352/392-9617.

Prey size selectivity is an important concept in fish feeding ecology and has been studied in various piscivorous species. Trial duration has not been a consistent factor in these studies and could potentially affect experimental outcome. A laboratory experiment was conducted to determine if peacock cichlid Cichla ocellaris is a size-selective piscivore and to examine trial duration as a possible factor influencing prey size selectivity. Eight peacock cichlids were used as predators and blue tilapia Oreochromis aureus were used as prey. Each predator was offered ten individuals each of two size classes of prey, with daily replacement, for a total of five days. Although there was slight individual variation, overall peacock cichlid prey size selectivity was consistent, favoring small prey over large prey, each day of the trial (p < 0.05). Trial duration had no effect, thus a single day gave comparable results to trial durations of two, three, four, or five days (p < 0.05). Therefore, there is no advantage to extending a laboratory prey size selectivity experiment for peacock cichlids beyond a single 24-h period. Published laboratory prey size selectivity studies of piscivorous fish were reviewed to determine trends in length of trial durations used. There was a negative correlation (rs = -0.465) between date of publication and trial duration. Of nineteen studies reviewed, seven trial durations were shorter, two equal in length, and nine longer than the 24-h period recommended by the present study. One study gave no time of trial duration. No direct comparison of trial durations within the reviewed studies was possible.

STUDENT

Growth and Mortality of Two Populations of Ladyfish ( Elops) in east-central Florida

Andrij Zenon Horodysky1 and Richard S. McBride. 1 Eckerd College, 4200 54th Ave S, St. Petersburg, FL 33711-4700. Email: horodyaz@eckerd.edu.

Two forms of ladyfish Elops) exist in the western North Atlantic: a northern (southeastern US) morph featuring a high-count range of 79-87 myomeres/vertebrae and a southern (Caribbean Sea) morph with a low-count range of 73-78 myomeres/vertebrae. It is believed that these are two distinct populations, and meristic differences occur due to latitudinal temperature variation (i.e. Jordan's rule). Geographic plots of each morph show a mixing zone in the Gulf of Mexico and western North Atlantic, but not in the Caribbean Sea. This study examined growth and mortality rates of 509 leptocephalus larvae and 947 sub-adult and adult ladyfish collected in the Indian River Lagoon. Early/mid-metamorphic leptocephali recruited nearly year-round into the Lagoon; high-count larvae were dominant in collections from December through April and low-count larvae from August through October. Summer growth rates of age-0 juveniles were not significantly different between morphs, but low-count fish appeared to have higher overwinter mortality. This is presumably due to late-season recruitment into unfavorable estuarine conditions. Low initial abundance and high mortality of low-count fish lead to a reduced potential for interbreeding despite ecological mixing. This study suggests that Florida's ladyfish fishery is probably composed of two distinct stocks rather than a single unit.

Interpopulation Variation in Prey Resource Use and Oral Jaw Morphometrics in Largemouth Bass, Micropterus salmoides.

S.H. Huskey. Florida Institute of Technology, Biological Sciences Department,150 West University Boulevard, Melbourne, FL 32901. Phone: 321/674-7222. Email:lmbassphd@aol.com

Food habits, jaw gape, and jaw width, throughout an ontogenetic series of largemouth bass, Micropterus salmoides, were examined to explore interpopulational differences in prey resource use and jaw biomechanical properties. Stomach contents from two endemic populations (Michigan and Florida) of largemouth bass were classified into functional categories (plankton, insect, crustacean, and fish) and compared for volumetric contributions of each prey type. Jaw gape was measured as the greatest dorso-ventral distance between the premaxilla and dentary bones. Jaw width was measured as the greatest interior distance between the dentary bones.

Stage-specific differences in food habits were observed between populations. M. salmoides in Florida (n=265) shifted from feeding on plankton and invertebrates to piscivory before 20mm standard length (SL); shortly thereafter subtropical bass eliminated plankton from their diets. Michigan bass (n=272) did not begin consuming fish until 33mm SL and continued utilizing plankton up to 62mm SL. After the onset of piscivory, Florida bass 75mm to 200mm SL, consumed more crustaceans than fish, whereas Michigan bass maintained piscivorous feeding habits. Also, analyses of covariance revealed statistical differences in jaw gape and jaw width between the two populations. Michigan bass had larger oral jaw openings relative to Florida conspecifics. Future research will determine whether this interpopulation variation in gape has implications for the kinematics of prey capture in M. salmoides.

Intraspecific variations in feeding ecology and jaw biomechanics may underlie the overall distribution and survival of a fish species. This underscores the need to address interpopulation differences when proposing management strategies for species that occur over broad geographic regions.

Movement and Habitat Use of Subadult Gulf Sturgeon

Laura G. Jenkins, US Fish and Wildlife Service, 1612 June Avenue, Panama City, FL 32405,

phone: 850-769-0552 x 231, fax: 850-763-2177, email: laura_jenkins@fws.gov

The Gulf sturgeon Acipenser oxyrinchus desotoi) is a threatened anadromous species restricted to both the marine and riverine systems of the Gulf of Mexico. Much effort has been directed toward its life history studies during freshwater residence, but very little is known about their overwintering habitats. Twenty-one subadult Gulf sturgeon were tagged with ultrasonic transmitters in the Choctawhatchee River and Bay during the fall in 1996 and 1997 before their entry into marine habitat. The movement and habitat use of Gulf sturgeon in the marine environment was determined from November through March, 1996 - 1998. Over 150 sonic contacts were made during the study period. Fish exhibited movement throughout Choctawhatchee Bay, but mostly used shoreline areas. Most of the tagged fish overwintered in the Bay during the study period.

Avoiding Common Mistakes During a Fish Kill Investigation

Ruth Ellen Klinger and Ruth Francis-Floyd, Large Animal Clinical Sciences, College of Veterinary Medicine and Dept. of Fisheries and Aquatic Sciences, University of Florida, 7922 NW 71st St., Gainesville, FL 32653. Phone:352/392-9617. Email: rek@gnv.ifas.ufl.edu and rff@gnv.ifas.ufl.edu.

Fish kill investigations can be difficult, especially when wild populations of animals are involved. Extreme interest by the public or press can confound efforts to collect meaningful data during "high profile" mortality events. To be effective, and get the best possible answers for all interested parties, biologists need to be well-versed in proper sample collection and protocol. This presentation will review procedures that ensure a correct evaluation and include 1) collection of representative species and numbers that are involved in the mortality event, 2) handling protocols in collection and transport to the diagnostic laboratory, and 3) compiling the complete history and documentation of the fish kill site. We will discuss the proper way to collect the best samples for diagnosis of the etiologic agent causing the mortality. We will also discuss what procedures work best for samples that have been held on ice, frozen, or preserved. Contact information will be provided for laboratories in the state that may be available to provide support to biologists investigating fish kills.

STUDENT

The Role of Seasonal Hydrology in the Dynamics of Fish Communities Inhabiting Karstic Wetlands of the Florida Everglades.

Robert M. Kobza* and J. C. Trexler. Florida International University, Dept. of Biological Science, Miami, FL, 33199. (305) 348-1966.

We studied the role of hydrological variation and availability of dry-season refugia in shaping the structure of fish communities in karstic wetlands of the Florida Everglades. The Rocky Glades is a wetland region of the extreme southeastern Everglades that is flooded for less than 6 months in most years. Solution holes serve as refugia for aquatic organisms, especially fishes, during the dry season. Our study addressed the following questions: Do fishes accumulate into predictable assemblages in solution holes during the dry season? Do abiotic characteristics of solution holes such as depth, water quality, or habitat complexity determine the assemblage of fishes that persist there? And, how do biotic interactions, especially predation, influence which species survive the dry season to recolonize the marsh surface when the rainy season arrives? To assess relative abundance of fishes, we sampled 19 solution holes in Everglades National Park weekly, between December and June, 1999, with non-destructive activity traps, coupled with mark-release-recapture techniques. We collected over 2,500 fishes in 17 species during the study period. The abundance of fishes increased early in the dry season, followed by intense mortality in mid-April. Principal components analysis indicated that fish relative abundance changed during the dry season with early colonization by bluefin killifish and sailfin mollies, followed by piscivorous species in mid-March with concomitant decline in small-sized species. Over 50% of the piscivorous fish were introduced species, such as walking catfish and two cichlids. Introduced fishes appeared to tolerate the stressful solution-hole environment in the late dry season better than most native species. Our results suggest that secondary production of fishes in the Rocky Glades is reduced by mortality during the annual dry season because solution hole refugia are limited in number and experience poor water quality.

Early Ontogeny of feeding performance on larval red drum, Sciaenops ocellatus

Justin M. Krebs. Florida Marine Research Institute, 100 Eighth Ave SE, St. Petersburg, FL, 33701, 727/896-8626. Email: justin.krebs@dep.state.fl.us

The relationship between mouth gape and prey consumption in larval red drum, Sciaenops ocellatus, was investigated to test the hypothesis that feeding performance improves through the early life history stages. Gape size and prey consumed were determined for laboratory-reared larval red drum from hatching to metamorphosis to examine stage-specific differences in terms of gape height and width, and number and size of prey consumed. Feeding success, considered one aspect of performance, was measured as the percentage of feeding larvae in each stage and increased from 0.02% at first-feeding (3 days post-hatch [dph]) to 97.4% at metamorphosis (18 dph). Gape height and width increased linearly with fish body length. Prey length consumed also increased from around the time of first-feeding to that of metamorphosis. However, the width of prey consumed did not increase and ranged from only 18.7% to 39.1% of the gape width during the larval period. Moreover, the gape width-SL relationship had a greater slope than prey width-SL, suggesting that gape width did not limit the size of prey consumed by laboratory-reared fish. It is hypothesized that, rather than mouth gape, there exist other developmental aspects of the prey-capture mechanism that may influence feeding performance during the early life history stages of red drum.

The Effects of Harmful Algal Blooms on the Health of Florida’s Fish

Jan H. Landsberg. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 Eighth Avenue SE, St. Petersburg, Florida, 33701-5095. Phone: 727/896-8626. Email: jan.landsberg@dep.state.fl.us.

In Florida’ coastal waters, at least 40 species of toxic microalgae, including 11 ichthyotoxic species, cause massive fish kills and animal mortalities, neurotoxic shellfish poisoning, and respiratory irritation in humans. Historically, many fish kills have been associated with low dissolved oxygen, often produced as a consequence of a nontoxic algal bloom. However, it is possible that many kills associated with HABs are caused by small, ephemeral dinoflagellates such as Heterocapsa, Gymnodinium, Gyrodinium, or Pfiesteria-like species that were not, until recently, recognized as being toxic. The presence of fish with lesions has been used as a biomarker of Pfiesteria piscicida presence. There is an ongoing controversy as to the exact role of Pfiesteria piscicida or other Pfiesteria-like species (PLS) in the initiation of fish lesions. P. piscicida is not distributed throughout all areas where characteristic fish lesions are being found, but it is possible that other PLS could be involved. Recently, attention has also been drawn to the fact that HAB toxins and their chronic effects need to be considered as major threats to fish health. Effects may be expressed in terms of susceptibility to disease, abnormal development, and in the induction of tumors. Chronic dietary exposure of fish to biotoxins can exert lethal or sub-lethal effects at all trophic levels, leading to impaired feeding, avoidance behavior, physiological dysfunction, impaired immune function, reduced growth and reproduction, pathological effects, and mortality.

The Development of the Florida Fishes Database

Eric J. Nagid and Theodore S. Hoehn. Florida Fish and Wildlife Conservation Commission, 7922 NW 71st St., Gainesville, FL 32653. Phone: 352/392-9617, Fax: 352/846-1088, email: nagide@gfc.state.fl.us.

A Florida statewide fisheries database is needed due to the state. s vast range of habitat and water resources. Florida Fish and Wildlife Conservation Commission (FWC) electrofishing and blocknet data from regional and field offices have been collected and targeted specifically for all species/community samples. The database will facilitate short and long-term regional and statewide biomass and abundance comparisons. In addition, the database will be converted into a Geographic Information System (GIS) format to examine species distribution, to make predictions of species occurrence in specific drainage basins, and in land acquisition planning and regulatory assessments. Upon project completion, the complete database will be sent to all FWC offices, other affiliated fisheries agencies, and limited portions will be provided to water resource agencies and made available on the Internet.

Fisheries Survey of the St. Sebastian River, Florida: Overview and Preliminary Findings.

Richard Paperno and Russell Brodie. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 1220 Prospect Ave, Suite 285, Melbourne, Florida 32901. Phone: 321/984-4828. Email: paperno_r@epic7.dep.state.fl.us.

In March 1999, a survey to monitor the distribution and abundance of fishes and selected invertebrates of the St. Sebastian River was initiated. The objectives of the program were to 1) provide the Department of Environmental Protection's, St. Sebastian River Buffer Preserve staff with a species inventory, 2) compare the current species inventory with historical records, and 3) characterize the community composition spatially and seasonally within the river. Monthly sampling was conducted following standard procedures of the Florida Marine Research Institute's Fisheries Independent Monitoring program and consisted of eight sets of a 21.3-m center-bag seine supplemented by quarterly sampling with four 183-m haul seines and four 6.1-m otter trawls. A total of 67,894 animals representing 75 taxa were collected from March to the end of December 1999. Bay anchovies Anchoa mitchilli) and Irish pompano (Diapterus auratus) accounted for 83.3% of the total catch. To date, we have been able to document the presence of more than 60%of the fish taxa historically recorded to occur in the river and we believe we have identified eleven species not previously recorded. Documented distributions for several species (~12) within the system are wider than previously thought. Species composition was found to vary within the river in response to changes in salinity and also varied between the two river forks, with the south fork being dominated by more freshwater-tolerant taxa.

STUDENT

Comparison of Trawls versus Trap Nets for Collecting Black Crappie Pomoxis nigromaculatus in Two Florida Lakes

William E. Pine III ¹,Mike S. Allen ¹ and Marty M. Hale,¹Department of Fisheries and Aquatic Sciences, The University of Florida, 7922 NW 71^st Street, Gainesville, FL 32653. Phone:352/392-9617 ext. 252. Email: msal@gnv.ifas.ufl.edu,

Effective fisheries management requires unbiased and precise estimates of population size structure and relative abundance. Here we compared a recreational shrimp Penaeus spp. trawl to trap nets for assessing black crappie Pomoxis nigromaculatus populations. Lakes Griffin and Monroe were sampled with both gears simultaneously during October-December 1997. Coefficients of variation (CV=SD/˙*100) on mean catch-per-effort (CPE) values ranged from 105 to 161 for trap nets and from 62-96 for trawls. Both trawls and trap nets collected fish < 150 mm total length (TL), but trawls sampled significantly more adult fish (> 250 mm TL). Variable catches in trap nets would require more sampling effort (up to four times as much) to obtain precise estimates of mean CPE than trawl sampling. Trawl sampling was preferable to trap nets based on size of fish captured, precision of abundance estimates, cost of the gear, and required sampling effort to estimate mean CPE. However, trawl sampling may be impractical in water bodies with excessive submerged structures, debris, and submersed macrophytes. We are encouraged by the effectiveness of the trawl for assessing black crappie populations in lakes where it is possible to use a bottom-sampling trawl.

STUDENT

Swimming and Feeding of Bahamian Epibathyal Sharks with Comments on Fin Morphology

Eric A. Reyier, Florida Institute of Technology, Dept. of Biological Sciences, 150 West University Blvd., Melbourne, FL 32901, (407) 768-8000

Between March 27 and April 1, 1997, 14 submersible dives were made off Bimini and South Cat Islands, Bahamas, ranging in depth from 1,100 to 2,200 feet, in an attempt to record the swimming and feeding behavior of Odantaspis ferox, at the location of its first W. Atlantic capture. The search area was contained between 25 ° 30.0' and 25 ° 50.0' N. and 79 ° 18.0' and 79 ° 23.0' W. Of over 14 hours of recorded bottom time, seven species of shark were attracted via baited traps and filmed. They included Hexanchus griseus, Hexanchus vitulus, Centrophorus uyato, Squalus cubensis, Carcharhinus signatus, Carcharhinus perezi, and Mustelus canis insularis. Using mounted lasers and other reference objects, it was possible to estimate the size of these animals as well as their swimming speed and turn angles. Unique feeding behaviors are also described. Four of these species differ from the "typical" shark design in that they lack a full fin complement. Results suggest that these species generally conform to the hydrodynamic limitations postulated by previous authors. Through the synthesis of these observations with recent behavioral and paleontological information, conclusions are drawn as to the ecological and evolutionary forces that have defined unique shark fin morphology.

Alligator mortality and algal toxins: a preliminary report.

James Perran Ross, H. Franklin Percival, Allan Woodward, Dwayne Carbonneau, Trenton R. Schoeb, John Burns, Chris Williams and Wayne Carmichael. Central Florida Lakes Wildlife Initiative, Florida Museum of Natural History, University of Florida, Gainesville FL 32611. Phone: 352/846 2566, fax: 352/ 392 9367. Email: prosscsg@flmnh.ufl.edu.

Since 1997, an unusually large number of alligators (Alligator mississippiensis) have died on lake Griffin in central Florida. Alligator mortalities have ranged from 2 - 20 per month and over 180 deaths are recorded to date. This mortality is far above the normal background rate. The mortality involves adult sized alligators that appear to be in good physical condition and die quite abruptly following a short period of locomotory impairment. In approximately the same period, the success of hatching of alligator eggs from Lake Griffin has also been greatly depressed. Veterinary necropsy and a wide variety of tests have failed to indicate any obvious cause of alligator death. However, neurological examination and histology of neural tissue revealed slowed periferal nerve transmission rates, axonal degeneration and brain lesions. Possible causes of such pathology include dietary deficiencies (e.g. Thiamine, Selenium), poisoning by heavy metals and organophosphates and toxins produced by blue green algae. Other contaminants, dietary factors and disease are also under investigation.

We present preliminary results of algal bloom frequency and species composition, algal toxity, levels of some algal toxins in alligator tissues and the observed pathology of the alligators to examine the possibility that the alligator mortality is caused by a blue green algae. Four toxigenic genera of cyanobacteria (blue-green algae) were found to have a common occurrence in Lake Griffin during the sampling period. From composite waterbloom samples or laboratory isolates of cyanobacteria from Lake Griffin two cyanotoxin groups have been identified to date-microcystins and cylindrospermopsin. Analyses for these toxins in alligator tissues or in the food chain to alligators is at this time preliminary-additional work is in progress.

Assessment of fish assemblage recovery at the Mavro Vetranic grounding site in Dry Tortugas National Park, Florida.

David A. Rydene. Dynamac Corporation/ Florida Institute of Technology, mailcode DYN-8, Kennedy Space Center, FL 32899. Phone: 407/ 853-5390. Email: daveryde@gate.net

On November 1989 the 475-foot freighter Mavro Vetranic went hard aground on a shallow reef area (water depth 7-10 m) within Dry Tortugas National Park. The impact pulverized the substrate and created a 3465 m2 grounding scar. To assess the extent of post-grounding recovery by the fish community, visual censuses were performed by SCUBA divers using a modified Bohnsack-Bannerot method. Twenty-five censuses were done in the "scar" area and 25 were done in adjacent "control" areas (within 150 m of the "scar" area) during 3 expeditions (August 1993, October 1994, May 1995) to the park. The resulting dataset allowed the generation of relative abundance and relative biomass estimates in concert with species identity information. Abundance/ species and biomass/ species data were analyzed using non-metric multidimensional scaling (NMDS). NMDS plots of abundance/ species data seem to indicate that the abundances of fishes were changing in the general vicinity of the grounding area, but that they were changing in the same manner at both the "scar" and "control" sites. Fish species composition and abundances at these 2 sites were already very similar when censusing began at 45 months post-grounding. However, NMDS plots of biomass/ species data indicate that the fish species biomasses were different in "scar" and "control" areas at 45 and 59 months post-grounding (August 1993, October 1994), but had become quite similar by 66 months post-grounding (May 1995). I propose that the "scar" and "control" areas mutually influenced each other, eventually producing a single hybrid assemblage.

Harmful Microalgae in Florida Marine Waters

Karen A. Steidinger. Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 Eighth Ave. SE, St. Petersburg, FL 33701. Phone: 727/896-8626. Email: karen.steideinger@dep.state.fl.us.

Florida has 8000 miles of coastline, crosses six degrees of latitude and has a high diversity of marine habitat from coral reefs to salt marshes. It also has about 40 toxic or potentially toxic marine microalgae that can cause animal mortality and disease as well as human illness and discomfort. Many of the Florida strains have been shown to be toxic by isolating, culturing, and testing them for specific toxins or toxic effects. Interestingly, although some of the Florida isolates (e.g., those associated with Amnesic Shellfish Poisoning) produce toxins, their harmful effects are not always realized. Florida has four marine microalgal issues, i.e., tropical fish poisoning called ciguatera caused by toxins originating in benthic dinoflagellates, Neurotoxic Shellfish Poisoning and animal mortalities caused by a toxic dinoflagellate known as Gymnodinium breve, animal tumors thought to be caused by benthic dinoflagellates, and fish lesion events thought to be triggered by Pfiesteria or Pfiesteria-like dinoflagellates. It is not surprising that these resource and public health problems are caused by dinoflagellates since >75% of the marine toxic microalgae belong to the Dinophyceae. Florida’s Harmful Algal Bloom Task Force is charged with developing a contingency/response plan for such events. Currently, there is a State Biotoxin Control Plan for G. breve blooms and Neurotoxic Shellfish Posioning. The plan involves monitoring shellfish growing areas and surrounding waters for the causative organism and determining toxin levels in shellfish meats. This information is then used in management of the harvesting areas that pose a risk to human health. Management consists of “closures” during red tide events.

STUDENT

Habitat and Diet Comparison of Largemouth Bass and Shoal Bass in the Upper Chipola River, Florida

A. P Wheeler and M. S. Allen. Department of Fisheries and Aquatic Sciences, The University of Florida, Gainesville, FL 32653-3071. Phone: 352/392-9617. Email: scmods@ufl.edu

The shoal bass Micropterus cataractae is a recently described species endemic to the Apalachicola, Chattahoochee and Flint River drainages of Alabama, Georgia and Florida, but the Florida population occurs primarily in the upper Chipola River. The objectives of this study were to compare diet and habitat associations of largemouth bass M. salmoides and shoal bass in the upper Chipola River. Electrofishing was used to sample fish in the summer (May-August) and fall (September-December) 1999. Chi-square analyses revealed significant differences (P<0.001) between the proportion of adults and age-0 of each species collected from pool, riffle and shoal habitat areas. Largemouth bass were collected in higher proportions in pool and riffle habitats than shoal bass, whereas shoal bass were collected in higher proportion in shoal areas than largemouth bass. These habitat trends were identical for both adult and age-0 fish. Stomach content analysis revealed that crayfish dominated the diets of large >300 mm total length (TL) largemouth bass whereas fish dominate the diets of adult largemouth bass <300 mm TL and all sizes of adult shoal bass. Age-0 diet contents of both species were mainly small fish but also included insects as secondary prey.

A National Overview of Harmful Algal Blooms

Donna Turgeon. National Oceanic and Atmospheric Administration, 8701 Running Fox Ct., Fairfax Station, VA 22039. Phone: 301/713-3034 x 174. (Bio)

Abstract from her National Overview of HABs at 1999 AFS Meeting, National Pfiesteria Strategy and 1993 Article on Contaminants)

An Assessment of Toxigenic Cyanobacteria in Florida’s Surface Water.

Chris Williams, Andrew Chapman, Marek Pawlowicz, Wayne Carmichael, and John Burns. 1St. Johns River Water Management District, Highway 100 West, Palatka, FL. 32178. Phone: 904/312-2342, Fax: 904/329-4329.

Harmful algal blooms (HABs) are defined by their negative impacts on the environment, economy, and human health. In 1998, the Florida Harmful Algal Bloom Task Force was established to determine the extent to which HABs posed a problem for the state of Florida; cyanobacteria (blue-green algae) were identified as a research priority. In June of 1999, the St. Johns River Water Management District initiated a collaborative study to determine the geographical distribution of toxigenic cyanobacteria and cyanotoxins in Florida’s surface waters. A total of 167 water samples were collected throughout the state between June 10 - November 4, 1999. Results showed that Microcystis, Cylindrospermopsis, and Anabaena spp. were the most frequently observed toxigenic cyanobacteria. Species of Planktothrix/Oscillatoria, Coelosphaerium, Lyngbya, and Aphanizomenon also were observed but much less frequently. A total of 88 samples, representing 75 individual water bodies, were reported to contain significant levels of toxigenic cyanobacteria. Thus far, cyanotoxins, specifically microcystins and cylindrospermopsin, have been positively identified in 77 and 34 water bodies throughout the state of Florida, respectively. Mouse bioassays showed that 80% of these samples were lethally toxic to mice. The high prevalence and wide-spread distribution of cyanobacteria and their associated toxins indicate a statewide potential for poisonous HAB events. In addition, the widespread distribution of Cylindrospermopsis raciborskii warrants further attention as its biology and toxic capabilities are relatively unstudied in Florida.

POSTERS

STUDENT

The Life History of the Parasitic Isopod Glossobius hemiramphi (Isopoda: Cymothoidae) and its Relationship to its Host Hemiramphus brasiliensis (Pisces: Hemiramphidae).

Micah Bakenhaster¹, Richard S. McBride, and W. Wayne Price¹. ¹University of Tampa, Department of Biology, 401 W. Kennedy Blvd., Tampa, FL  33606. Phone:  813/253-3333. Email: wprice@alpha.utampa.edu.

This study documents relatively high infestation rates of the isopod Glossobius hemiramphi on Hemiramphus brasiliensis, a valuable baitfish harvested in south Florida.  A sample of 2928 H. brasiliensis collected year-round between Palm Beach and Key West had an average infestation rate of 10.1%. Monthly infestation rates ranged from 4.6- 18.2% and were highest in the summer on small young-of-the-year fish. Prevalences declined with fish size from a high of 38% for fish 11-16 cm to a low of 3.3% for fish 25-29 cm.  No evidence of host stress resulting from parasitism was found when weight-length relationships were compared by ANCOVA between infested and non-infested fish. Isopods occurred in the oral-branchial cavity of the host, primarily as single male-female pairs. G. hemiramphus exhibits apparent protandric hermaphroditism with marked sexual dimorphism. Male isopods (2.8-12.4 mm) were located on the gill arches of the host, while females (12.7-35.6 mm) were attached to the tongue. Embryos present within the brood pouch of female isopods were divided into five ontogenetic stages. The following life cycle is proposed after examination of isopods from 154 parasitized H. brasiliensis:  Brooding females release free-swimming larvae (mancas), which are immediately infective. After attachment to hosts, mancas enter the gill chamber and begin to mature into functional males.  After further maturation, males move into the mouth, where they transform into females.  Sex reversal may be stimulated by the presence of a new male or the absence of a resident female.

Intra-cellular and extra-cellular toxins in the red tide organism Gymnodinium breve

P. C. Blum, Henry M. S., Pierce R. H., and J. I. Lyons. Mote Marine Laboratory, 1600 Ken Thompson Parkway, Sarasota, FL 34236. Phone: 941/388-4441 X319, Fax: 941-388-4312. Email: pcblum@mote.org.

The dinoflagellate, Gymnodinium breve (Davis), produces several neurotoxins that cause neurotoxic shellfish poisoning (nsp), massive fish kills and respiratory irritation in marine mammals and humans. The common method for discerning dangerous concentrations of G. breve toxins for public health advisories is enumeration of live cells in the water. In this study, laboratory cultures were used to test a stirred ultra-filtration cell concentrator which separated viable cells containing intra-cell toxins from ambient water containing extra-cell toxins. This method was subsequently applied to water samples collected during natural G. breve blooms along two different areas of the Florida Gulf coast. The results show that extra-cell toxins remain viable outside of the cell as the bloom progresses. This indicates that shellfish contamination, finfish intoxication and mammalian respiratory impacts could result from water masses carrying suspended/dissolved neurotoxins in the absence of viable G. breve cells. Therefore, enumeration of cells may be insufficient and additional toxin quantitation is necessary.

A comparison of faunal communities from seagrass and unvegetated habitats in three Florida estuaries

K.Y. Guindon-Tisdel and J. Wallin, Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 Eighth Avenue SE, St. Petersburg, FL 33701-5095. Phone: 727/896-8626. Email: tisdel_k@dep.state.fl.us

We described and compared the juvenile fish and selected invertebrate communities of seagrass and unvegetated (bare sand or mud) habitats in three estuaries: Tampa Bay (TB), Choctawhatchee Bay (CB), and Indian River Lagoon (IR). Fish were collected monthly in 1996 with 21.3-m seines (3.2-mm stretch mesh) in shallow waters (<1.5-m) stratified by the presence/absence of seagrass Thalassia spp., Halodule spp., Syringodium spp., Ruppia spp., Halophila spp., or Valisneria spp.). Mean relative fish abundance varied significantly between months in TB and CB, but in all three estuaries, mean abundance and numbers of species were always significantly higher in seagrass habitats than in unvegetated habitats. Comparison of Bray-Curtis similarity indices between the two habitats indicated that faunal communities in the seagrass habitats were more similar to each other than to the communities in the unvegetated habitats in each estuary. The discrimination of species between habitat types was principally due to differences in faunal abundance rather than shifts of species composition. Nodal analyses indicated that several small resident species and transient species, which include a few recreationally important species (i.e. Cynoscion nebulosus and Sciaenops ocellatus), exhibited higher constancy and fidelity for seagrass habitats in CB than in IR or TB.

STUDENT

Life history and population dynamics of the Bearded Brotula, Brotula barbata, in the northwestern Gulf of Mexico

Anthony MacWhinnie II, University of West Florida, Department of Biology, 11000 University Parkway, Pensacola, FL 32514-5751. Phone: 850/474-3362.

The Bearded Brotula Brotula barbata) is an unfamiliar species of fish to most consumers yet to commercial fish houses it is one of the most highly prized catches, commanding 6 to 10 times the original purchase price once it reaches market. It is the norm for this fish to be mislabeled in one way or another, either at the market or on the state of Florida commercial trip ticket, or both. No directed study of this fish has been conducted in the Gulf of Mexico. Due to the combination of a lack of accurate catch statistics and no data in the scientific literature there is no accurate data on the health of this fish stock. Likewise, there is no good baseline information on the biology or the population dynamics of the Gulf of Mexico stock ofB. barbata.

The primary thrust of this project will be to determine the growth rate of B. barbata in the Gulf of Mexico. This will be accomplished by aging the fish via collection of scales and their analysis. Also, since very little is known about the Bearded Brotula, baseline information on the feeding habits of this fish will be collected via stomach content analysis. Contents will be identified to the lowest taxonomic level in an effort to detail prey preference and ontogenetic dietary shifts. Ratios of males to females will be determined, as well as the generation of a gonadosomatic index. This index, generated by determining the ratio of the total weight of the fish vs. the weight of the gonad, will clearly show when the Bearded Brotula breeds. I will identify reproductive season, age at reproductive maturity, and possibly fecundity of the Bearded Brotula.

The results of this study will be a useful tool for both fisheries managers and the scientific community as a whole. The new focus, both federally and on the state level, on the relationship between both "Essential Fish Habitat" and the concept of the "Keystone Species" are areas that will be directly addressed with this study. This study will help to determine what role the Bearded Brotula plays in natural environment and what potential role it may play in our future economic environment.

Halfbeak, Hemiramphus spp., fishing and spawning grounds in south Florida

R.S. McBride¹, J. Styer and R Hudson. ¹Florida Fish and Wildlife Conservation Commission, Florida Marine Research Institute, 100 8th Avenue SE, St. Petersburg, FL 33710-5095. Phone: 727/896-8626. Email: rich.mcbride@dep.state.fl.us

We observed changes in the fishing patterns of halfbeak fishers in south Florida and are evaluating how these changes may affect the halfbeak fishery and the target species of that fishery: ballyhoo Hemiramphus brasiliensis) and balao (H. balao). A specific question from managing agencies and the industry itself was how much the fishing grounds and spawning grounds overlapped. Data available prior to the present study pertained mostly to ballyhoo and were not spatially explicit, so new collections were necessary. Using both fishery-dependent and fishery-independent collections, we monitored fishing effort, catch, and halfbeak reproduction from November 1995 to February 1999.

Both species mix above the coral reef tract, but ballyhoo are also distributed widely inshore of the reef tract. The reproductive biology of halfbeaks is similar to other Atheriniformes but is quite different from other coral reef fishes. Females have group-synchronous oocyte development, a common marine fish trait, but batch fecundities are relatively low (500-2000 eggs) and hydrated oocytes are relatively large (about 2.5 mm diameter). At least some females appear capable of spawning daily for several months (March-August), so annual fecundity may be quite high. Neither species is well represented in regional ichthyoplankton surveys, so to determine spawning areas, we mapped the distribution of females whose oocytes were in the final stages of maturation. Our data show that both species spawn throughout the Atlantic Ocean fishing grounds. Florida Bay is also identified as an important spawning area for ballyhoo, but not balao.

Downstream Effects of Altered Freshwater Inflow on Fish, Shrimp and Crabs of the 10,000 Islands Estuary of Southwest Florida

Pat O'Donnell and Todd Hopkins. Rookery Bay National Estuarine Research Reserve, 300 Tower Road, Naples, FL 34113-8059. Phone: 941/ 417-6310 Fax: 941/417-6315. Email: patrick.odonnell@dep.state.fl.us.

Pumpkin Bay, Faka Union Bay and Fakahatchee Bay lie downstream of the Southern Golden Gate Estates, a failed development which built 813 miles of roads and 138 miles of canals during the 1960's to drain the swamps of Collier County in SW Florida. Over-drainage through the Fake Union Canal has resulted in a permanent 8-12 ppt salinity decrease in Faka Union Bay compared to adjacent Pumpkin and Fakahatchee Bays. Canals and roads in the Southern Golden Gate Estates should begin to be removed in 2002, which will result in a more even distribution of water to the three bays. In July 1998, we began a stratified random fisheries independent trawling program to establish current baseline distributions and relative abundances of fish and invertebrates prior to the restoration. Data collection will continue indefinitely during and after the proposed freshwater restoration. All three bays have significantly different daily and annual salinity regimes with the greatest differences occurring during the wet season (August through January). Monthly catches of fish increased in all bays during the wet season with Pumpkin Bay having 2-4 times larger catches (mainly due to Eucinostomus spp.) than the other bays. Pink shrimp (Penaeus spp.) and blue crab (Calinectes sapidus) also peaked during the wet season with Pumpkin Bay's catches again higher than the others.

Elemental signatures of red drum (Sciaenops ocellatus) otoliths from the Gulf of Mexico and western Atlantic

Heather M. Patterson¹, Richard S. McBride, Roy E. Crabtree and Neal Julien, ¹Florida Marine Research Institute, Florida Fish and Wildlife Conservation Commission, 100 Eighth Avenue SE, St. Petersburg, FL 33701-5095. Phone: 727/896-8626. Email: heather.patterson@dep.state.fl.us.

The red drum (Sciaenops ocellatus) is an important estuarine-dependent species that supports recreational fisheries in the Gulf of Mexico and western Atlantic. In the mid-1980s, concerns about overfishing of red drum resulted in recreational catch limits and a ban on commercial fishing in Florida. Recent studies offshore of Tampa Bay, FL, suggest that at least in that area the species is recovering. However, the exact stock structure of red drum in the entire Gulf of Mexico remains unclear, despite its importance in management practices. Although genetic studies have shown that there are weakly differentiated populations in the Gulf of Mexico and a separate population in the Atlantic, for the purposes of fisheries management a single stock is considered to reside in the Gulf. However, as is the case in any genetic study that is unable to distinguish among sample locations, it is impossible to determine if connectivity is ecologically significant as well because only a small amount of genetic exchange is required to maintain homogeneity between stocks. Otolith chemistry has recently proven to be a useful natural tag for examining the stock structure of fishes because it can reflect the elemental composition of the water in which the fish resides. Juvenile red drum otoliths from Texas, South Carolina, and Georgia and from several sites in Florida, including Tampa Bay, Cedar Key, and Indian River, were analyzed using solution-based ICP-MS. Five elements (Mg, Mn, Zn, Sr, and Ba) were routinely detected above background levels. Discriminant function analysis indicated significant differences in the otolith chemistry of the red drum collected at different sites (Wilk's Lambda = 15.80, P=0.0001). A cross-validation procedure was able to correctly classify otoliths from the Florida sites with an accuracy of up to 95%. Although the origins of the otoliths from the other sites were not so clearly identifiable, this research demonstrates the potential of using otolith chemistry to delineate the stock structure of red drum throughout their range.

Aerial survey of the Northern IRL and Lower Mosquito Lagoon to document the extent of a mortality event of the Horseshoe crab (Limulus polyphemus).

D. M Scheidt and R. H. Lowers. Dynamac/LSSC/KSC, Mail-Code: Dyn-2, Kennedy Space Center, Florida 32899. Phone: 407/476-4105 or 407/853-3281. Email: douglas.scheidt-1@ksc.nasa.gov.

These data describe the results of an aerial survey of the Indian River Lagoon and Mosquito lagoon conducted on 21 July 1999. This survey was brought about after a large mortality event of horseshoe crabs (Limulus polyphemus) was first seen on 9 July 1999 in a mosquito impoundment (T-24 D) on the Kennedy Space Center/Merritt Island National Wildlife Refuge. The survey was conducted using a helicopter flying at an average ground speed of 50 knots at an altitude ranging from 50-100 feet. This method is similar to those used in other helicopter surveys conducted at KSC for birds and manatees. During the survey it was noted if the crabs were on the IRL shoreline or in the impoundment and number. The number of dead horseshoe crabs was enumerated by counting the number of carcasses in a 100-meter section. This value was then used until there was a noticeable increase or decrease in numbers. In the case of large concentrations, an estimate was made for the area and expressed as a total number for that area. At the same time, the large concentrations were marked using an Aviation Grade GPS (Lowrance). Larger concentrations were documented, using a digital still camera or a digital video camera to help quantify numbers. The survey started on the eastern shoreline/dike interface of the IRL at the NASA Causeway and proceeded north to Turnbull creek area. The survey then proceeded to Mosquito lagoon and went down the western shoreline from Haulover canal, south for 4.3 km and then traversed to the eastern shore and proceeded south for 6.1 km. The total survey covered over 69 km of shoreline and documented over 129,177 dead horsehoe crabs. In the Indian River Lagoon portion, 25,427 were observed inside impoundments and 94,255 on the IRL shoreline. In the Mosquito lagoon portion, 104 were observed in the impoundments and 9,391 along the shoreline. At the time of the die off no other organisms were observed to be affected in this event (i. e. fishkill). The cause for this event is unknown at this time. Several possible hypotheses for the event range from: a low D.O event, high sulfide levels in lower water column, bacterial or viral infection or even a natural cyclical event that had not been recognized or documented in the past. The fisheries implications of this die off can be far reaching, since the Horseshoe crab is found in the diet of estuarine fish, sea turtles and is used in the eel fishery and for biomedical research. This event could be an indicator of failing water quality and habitat.

Economic and scientific development of Florida's marine ornamental aquarium species sector.

William Seaman, Department of Fisheries and Aquatic Sciences, and James C. Cato, Department of Food and Resource Economics, University of Florida, Florida Sea Grant, PO Box 110400, Gainesville, Florida 32611-0400. Phone 352/392-5870, fax 352/392-5113. Email: seaman@gnv.ifas.ufl.edu.

The ornamental aquarium species industry of Florida is the largest of any state in America. Most of this trade is derived from a well-developed freshwater organism culture, trade and sales sector. A partnership of Sea Grant and Land Grant university scientists and business and technical interests is working to emulate this success for the marine sector. A major goal is to breed marine species in closed systems in Florida.

Marine ornamental species culture has been a formal priority of the Florida Sea Grant (FSG) long-range plan since 1996. This was based on the advice of a statewide meeting of industry, agency and academic representatives. Key subjects identified for ornamental species include life history (close life cycle, broodstock management, diet, health), economics (feasibility analysis, market), production and conservation of wild species. Earlier FSG involvement in this area was through pilot projects (e.g., live rock ecology). The first large-scale research project was successful in rearing ornamental shrimp species in captivity, with practices adopted by a commercial facility.

Current FSG efforts focus in research, building ties with users, and developing an outreach/extension capability. Research by faculty at four Florida universities addresses (1) diet for larval fishes, (2) nutritional management of fishes, (3) economic structure and competitiveness of the ornamental species industry, and, indirectly (4) culture of sea urchins. An industry advisory committee has been organized, reflecting the breadth of interests that includes producers, culturists, wholesalers and oceanarium operators. FSG program management fosters close communication between research and user interests. The feasibility of establishing an extension agent position to assist industry and guide university research and development is under study.

The Florida Sea Grant theme area for ornamental aquarium species culture and industry development is arguably one of the largest of any of the 29 U.S. Sea Grant programs. FSG facilitated a state academic-industry delegation of 15 to attend the "Marine Ornamentals '99" conference, the first international program of its kind (Kona, Hawaii, November 1999). It will work with these interests to promote the international leadership of Florida in this field, both economically and scientifically. One effort in this direction is to host the second international conference on marine ornamental species culture, collection and conservation (tentatively set for November 2001).

Egress of adult sport fish from an estuarine fish replenishment zone within Merritt Island National Wildlife Refuge, Florida.

Philip W. Stevens and Kenneth J. Sulak. Florida Caribbean Science Center, U.S. Geological Survey, 7920 NW 71 St., Gainesville, FL, 32653. Phone: 352/378-8181. Email: stevens@ufl.edu.

Harmful Microalgae in Florida Marine Waters

A mark-recapture study was conducted within Merritt Island National Wildlife Refuge in the waters surrounding Kennedy Space Center, Florida (where public access has been restricted since 1962) to document egress of adult sport fish from a potential estuarine fish replenishment zone. A total of 3,358 sport fish were tagged within the restricted areas. The species tagged were red drum Sciaenops ocellatus (n = 1,366), spotted seatrout Cynoscion nebulosus (n = 927), black drum Pogonias cromis (n = 760), and common snook Centropomis undecimalis (n = 305). Results showed that adult sport fish moved from the restricted areas within Merritt Island National Wildlife Refuge to surrounding areas open to fishing. The recapture rate based on angler responses outside of the restricted areas were 3.1, 0.7, 2.6, and 16.1 percent for red drum, spotted seatrout, black drum, and common snook, respectively. In general, red drum, spotted seatrout, and black drum were recaptured in waters adjacent to the restricted areas. Common snook, however, migrated from the restricted areas south to inlets. Mark-recaptures for red drum, spotted seatrout, and black drum, together with a previous study that found greater abundance and size of sport fish in the restricted areas than in adjacent areas open to fishing, substantiate the fish replenishment zone function of the restricted areas. The restricted areas within Merritt Island National Wildlife Refuge protect fish populations and subsequently export large adult sport fish to surrounding waters open to fishing.