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Bull Trout Population Responses to Reductions in Angler Effort and Retention Limits
Author(s) -
Parker Brian R.,
Schindler David W.,
Wilhelm Frank M.,
Donald David B.
Publication year - 2007
Publication title -
north american journal of fisheries management
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.587
H-Index - 72
eISSN - 1548-8675
pISSN - 0275-5947
DOI - 10.1577/m06-051.1
Subject(s) - trout , fishery , abundance (ecology) , fishing , catch and release , fish measurement , population , catch per unit effort , salmo , biology , geography , ecology , fish <actinopterygii> , demography , recreational fishing , sociology
We compared historical (1977–1980) and recent (1997–2001) abundance, catch‐per‐unit‐effort (CPUE), and growth data to assess whether the implementation of restrictive sportfishing regulatory regimes in the 1990s led to changes in abundance and population structure of bull trout Salvelinus confluentus in two small Rocky Mountain lakes in Alberta, Canada. For remote Harrison Lake, we used changes in gill‐net CPUE to infer a fivefold increase in bull trout abundance after closure of an access road and implementation of catch‐and‐release (CR) regulations. Bull trout growth rates decreased as their abundance increased. All large (fork length > 420 mm), old (age >12) bull trout were eliminated after regulatory changes were imposed. Reductions in prey abundance and size as bull trout abundance increased probably contributed to the demise of the large bull trout. For road‐accessible Osprey Lake, no change in bull trout mark–recapture abundance estimates or growth rates were observed despite implementation of CR regulations and, later, closure of the lake to angling. We speculate that illegal angling and migration of bull trout between Osprey Lake and its tributary streams limited abundance responses at this site. A variety of site‐specific factors, including ease of access, angler noncompliance with regulations, and local metapopulation structure of bull trout, led to variable bull trout population responses to the implementation of restrictive angling regulations. Active advertisement and enforcement of regulations may be required to achieve increased bull trout abundance at small, easily accessible waterbodies.