Fishery-independent and fishery-dependent
data: which should be used to manage the resource?
Patrick Harris
South Carolina Department of Natural Resources, P.O. Box 12559,
Charleston, SC 29422. Phone: (843) 762-5000 ext 2082; Fax: (843)
762-5110; email: harrisp@mrd.dnr.state.sc.us
As more pressure is placed on fished populations
around the world, fishery managers are often requested to place
increasingly severe restrictions on the exploitation of a given stock.
In the United States, managers are required by the Magnuson-Stevens
act to base their decisions on the "best available data."
The most commonly available data in the southeastern United States are
landings data from commercial fisheries, with some length-frequency
information available, and sometimes with enough fish sampled to
provide age-length keys. Recreational data are available for some
species. Fishery-independent data, however, is available for many
species from this region. Samples from commercial and recreational
fisheries are often biased due to the selectivity of the commercial or
recreational gear - whether from fishermen desiring to maximize their
harvest in the face of a bag limit, size limits, etc.
Fishery-independent data are usually collected without regard to size
and may be more representative of a population. Various population
parameters were compared between data sources for five species of
reef-associated fish: red porgy, Pagrus pagrus; grey
triggerfish, Balistes capriscus; vermilion snapper, Rhomboplites
aurorubens; white grunt, Haemulon plumieri; and scamp, Mycteroperca
phenax. Our data shows that estimates of yield per recruit, F0.1,
and Fmax can vary tremendously depending on the data source
used, with estimates based solely on fishery-dependent data often
being higher than those derived from fishery-independent data.
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