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7/14/2009 5:02:30 PM
Creation date
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UCREFRP
UCREFRP Catalog Number
7405
Author
Bain, M. B., ed. 1990.
Title
Workshop Synopsis,
USFW Year
Ecolog
USFW - Doc Type
U.S. Department of the Interior,
Copyright Material
NO
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<br />18 BIOLOGICAL REPORT 90(5) <br /> <br />Centrarchid-Habitat Associations in Ozark Streams <br /> <br />by <br /> <br />Charles F. Rabeni <br /> <br />U.S. Fish and Wi[d[ife Service <br />Missouri Cooperative Fish and Wi[dMfe Research Unit <br />112 Stephens HaU, University of Missouri <br />Co[umbia, Missouri 65211 <br /> <br />Any goal of sportfish management should include <br />satisfactory sustained angling benefits, which can <br />occur only by maintaining satisfactory habitat and <br />balanced fish populations and communities. Ap- <br />propriate habitat is an important prerequisite for <br />balanced fish populations in streams. Yet, not <br />enough is known about habitat requirements of most <br />fish. Unless the stream is highly degraded, it is not <br />possible to take a generalized habitat model devel- <br />oped from the literature and apply it to a particular <br />stream with much hope of identifying ways to in- <br />crease fishing quality. Each stream, or at least each <br />stream type, must be considered individually be- <br />cause fish are often plastic in their behavior and <br />requirements, and a limiting variable in one geo- <br />graphic area may be unimportant in another. <br />Two approaches have been taken by researchers <br />working on species-habitat relations. The first is to <br />determine how individual fish use particular habitat <br />elements and then infer something about the entire <br />population. This is dangerous because there is no <br />known empirical linkage between the two. Drawing <br />ecological meaning from data on habitat use or <br />preference is similar to trying to evaluate mechan- <br />isms from correlations. Habitats of a stream fish are <br />often measured in terms of either absolute or <br />relative use, yet these data reveal nothing about how <br />important a particular habitat variable might be nor <br />how the variables are interrelated. <br />A second approach is to correlate some population <br />characteristics, generally density or biomass, with <br />some habitat feature. While some studies are suc- <br />cessful in relating fish quantity to some habitat quan- <br />tity, their usefulness in a management context is <br />limited. There is generally no consistent relation <br />between fish amounts and habitat amounts. Al- <br />though a biologist can often distinguish a "good" <br />fishing stream from a "bad" one, unless a stream <br />is initially severely degraded there is little evidence <br />that altering a particular habitat variable will cause <br /> <br />a predictable corresponding change in the fish <br />population. We have little understanding of fac- <br />tors affecting carrying capacity of a warm water <br />stream-especially the relation between food and <br />habitat. While Our goal is to quantify critical factors <br />of the stream environment, it does not appear that <br />this goal can be attained in the near future. What <br />we as fishery researchers should do is isolate a <br />subset of environmental variables, pertinent to the <br />particular situation at hand, from a larger set of <br />variables considered generally important to a <br />species-such as those listed in the U.S. Fish and <br />Wildlife Service's Habitat Suitability Index Models. <br />If done carefully, we should be able to pinpoint par- <br />ticularly important habitat variables that influence <br />the success of a population and on which manage- <br />ment efforts can be focused. <br />Habitat conditions can be related to a life stage <br />in one of three ways. Nonuseful habitat conditions <br />are those not required for the population's survival <br />and may have an adverse relation to a population <br />(e.g., extremely high water velocity). Useful habitat <br />conditions provide a necessary element for the <br />population's well-being when other habitats also pro- <br />vide the same elements (e.g., rootwads and log <br />jams). Essential habitats are those required for the <br />population's well-being. <br />We must determine which habitat elements fit into <br />which category to effectively manage a species. Un- <br />fortunately, nonuseful habitats are often impossible <br />to identify because even if an area is unused by fish <br />it may still be important as a food-source area or <br />barrier to predators Of competitors. Useful habitats <br />can be detailed if the species is studied in more than <br />one location. Essential habitat features mayor may <br />not be limiting to a population. <br />Based on the preceding concepts, I evaluated the <br />habitat relations of Ozark stream centrarchids, with <br />emphasis on smallmouth bass (Micropterus dolo- <br />mieui) and lesser emphasis on rock bass (A mbloplites <br /> <br />J <br />
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