We surveyed 50 state agencies and Puerto Rico, of which 82% reported the use of abiotic habitat enhancements.  The state agencies which did not report the use of these enhancements included Alabama, Alaska, Hawaii, Louisiana, New Mexico, North Dakota, Rhode Island, South Dakota, and Vermont.  Habitat structures were divided into four main categories: cover, spawning, shoreline stabilization, and substrate structures.  Most structures were included in the cover category (75%), whereas the spawning, substrate, and stabilization categories accounted for only 14, 9, and 2% of the responses, respectively.  The primary agency objectives of habitat enhancements were to attract fish to improve angler catch and harvest, but other objectives included improved recruitment of juvenile fish, creation of adult habitat or sanctuary, and increased fish production via creation of spawning habitat (see Table below).  Cost and availability of materials were the most common factors influencing an agency's choice of enhancement structure.  Thus, it is not surprising that the most commonly used enhancement structure in U.S. lakes was brush piles (used in 88% of the states that conduct abiotic habitat enhancements).
 

 Table 1. Number and percentage of responses corresponding to agency goals.

    Agency biologists reported a wide range of percent lakes that need habitat enhancements (Table 2), but 21% of respondents reported not knowing what percent of lakes/reservoirs need habitat enhancements.  Most respondents (58%) reported that 0-20% of the lakes/reservoirs in their state or region received habitat enhancements.
 

Table 2.  Percentage of lakes/reservoirs that respondents believed need enhancements in their state or region versus the percentage of lakes that actually receive enhancements.

% of Lakes in State/Region	% of Total Responses
	Lakes that Need Enhancements	Lakes that Receive Enhancements
0 - 20	23	58
21 - 40	5	18
41 - 60	8	5
61 - 80	15	10
81 - 100	29	10
Unknown	21	0

       Of the states which conducted habitat enhancements, 60% evaluated the effectiveness of structures to some degree. Most evaluations involved either catch-per-effort (CPE) comparisons, direct observation (e.g., SCUBA surveys) or angler catch rate comparisons.  However, only 40% of all reported structures were evaluated and seldom did these evaluations take into account fish-population responses.  We conclude that efforts to document fish-population responses to habitat enhancements are needed.

For other review studies and summaries of habitat enhancements in lakes and reservoirs, please refer to the following publications.

Brown, A. M.  1986.  Modifying reservoir habitat with artificial structures.  Pages 98-102 in G. E. Hall and M. J. Van Den Avyle, editors.  Reservoir Fisheries Management: Strategies for the 80's.  Southern Division Reservoir Committee, American Fisheries Society,
Bethesda, Maryland.

Kelso, J. R. M., and C. Wooley.  1996.  Introduction to the international workshop on the science and management for habitat conservation and restoration strategies (HabCARES).  Canadian Journal of Fisheries and Aquatic Sciences.  53(Suppl 1):1-2. (Block of papers in this session)

Kimmel, B. L., and A. W. Groeger.  1986.  Limnological and ecological changes associated with reservoir aging.  Pages 103-109 in G. E. Hall and M. J. Van Den Avyle, editors.  Reservoir fisheries management: strategies for the 80's.  Reservoir Committee, Southern Division American Fisheries Society, Bethesda, Maryland.

Summerfelt, R. C.  1993.  Lake and reservoir habitat enhancement.  Pages 231-261 in C. Kohlerand W. A. Hubert, editors.  Inland fisheries management in North America.  American Fisheries Society, Bethesda, Maryland.

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