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Influence of a Minimum‐Length Limit Regulation on Wild Brown Trout: an Example of Recruitment and Growth Overfishing
Author(s) -
SánchezHernández Javier,
Shaw Stephanie L.,
Cobo Fernando,
Allen Mike S.
Publication year - 2016
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 - 10.1080/02755947.2016.1184204
Subject(s) - overfishing , brown trout , fishing , catch and release , fishery , stock (firearms) , biology , recreational fishing , salmo , population , trout , abundance (ecology) , fish stock , ecology , fish <actinopterygii> , geography , demography , archaeology , sociology
Abstract The relative abundance of the largest size‐classes of individuals within a fish population has an important influence on recruitment success. Fishing regulations with a basis in size (e.g., minimum‐length limits) can directly impact the abundance of these larger individuals and thus potentially influence recruitment. We analyzed whether recruitment of exploited native Brown Trout Salmo trutta populations was affected via the extraction of large individuals (>220 mm, i.e., minimum‐length limit). The study was replicated temporally (2007–2009) and spatially across seven recreational fishing sections (four exploited and three catch‐and‐release sections) within the River Tormes located in central Spain. Catch‐and‐release sections were used as reference points to compare with exploited sections. We tested the hypothesis that minimum‐length limit regulations would adversely affect fish recruitment through fishing‐induced mortality of large individuals. Spawning stock (measured as fish >220 mm) and young‐of‐the‐year abundances were estimated using multiple‐pass depletion methods. We modeled the relationship between spawning stock and subsequent recruitment using a nonparametric approach (generalized additive models) to fit the best stock–recruit relationship. Additionally, von Bertalanffy growth and yield‐per‐recruit models were generated to evaluate the potential for growth and recruitment overfishing. The restrictive length limits used to regulate harvest in the study area limited both recruitment and adult abundance. The present study provides evidence that the use of minimum‐length limit regulations in the management of recreational fisheries has the potential to adversely affect the species’ recruitment. Such adverse impacts could be occurring via both recruitment overfishing and growth overfishing, exemplifying that the removal of the larger size‐classes of individuals through recreational fishing could have important consequences for recruitment. Management actions should be directed to protect large individuals (e.g., via harvest slots) rather than promote their removal, thereby reducing the chances of overfishing. Received November 25, 2015; accepted April 18, 2016Published online August 24, 2016