Protection from fishing improves body growth of an exploited species

Abstract

Hunting and fishing are often size-selective, which favours slow body growth. In addition, fast growth rate has been shown to be positively correlated with behavioural traits that increase encounter rates and catchability in passive fishing gears such as baited traps. This harvest-induced selection should be effectively eliminated in no-take marine-protected areas (MPAs) unless strong density dependence results in reduced growth rates. We compared body growth of European lobster ( Homarus gammarus ) between three MPAs and three fished areas. After 14 years of protection from intensive, size-selective lobster fisheries, the densities in MPAs have increased considerably, and we demonstrate that females moult more frequently and grow more during each moult in the MPAs. A similar, but weaker pattern was evident for males. This study suggests that MPAs can shield a wild population from slow-growth selection, which can explain the rapid recovery of size structure following implementation. If slow-growth selection is a widespread phenomenon in fisheries, the effectiveness of MPAs as a management tool can be higher than currently anticipated.

Southern California marine protected areas promote bolder fish populations

“…These results are consistent with other metrics of fish community health inside of MPAs, such as increases in abundance and biomass (Carr et al, 2021;Hamilton et al, 2021). And the increases in bold behavior of fish inside of MPAs should lead to increases in the other metrics of fish community health (Biro and Post, 2008;Sørdalen et al, 2022). As such, FID represents a new and useful tool for evaluating the effectiveness of the MPA network in Southern California.…”

“…It has been shown that fish with traits correlated to increased foraging behavior, such as greater boldness and activity rates, are more likely to be caught by fishermen (Biro and Post, 2008). It has also been observed that populations outside of protected areas begin to evolutionarily self-select traits that lead to slower growth rates, while those inside MPAs exhibit behaviors leading to faster growth (Sørdalen et al, 2022). Larger fish, in turn, lead to more and greater viability of offspring (Qvarnström and Price, 2001;Birkeland and Dayton, 2005;Pew Charitable Trusts, 2016), allowing populations to recover to pre-fishing levels.…”

Genetic rescue from protected areas is modulated by migration, hunting rate, and timing of harvest

“…Most empirical research on how protected areas could mitigate harvest‐induced evolution has focused on marine ecosystems (Hutchings & Fraser, 2008 ; Hutchings & Kuparinen, 2020 ). These studies suggest that marine protected areas can sometimes preserve or restore abundance, age structure and phenotypic trait distribution of exploited fish and invertebrate populations (Gillespie & Vincent, 2019 ; Sørdalen et al, 2020 , 2022 , synthesized by Lester et al, 2009 ; Baskett & Barnett, 2015 ). For instance, Russ et al, 2004 found that a no‐take reserve in the Philippines increased density and harvest of surgeonfish ( Acanthuridae spp) and jacks ( Carangidae spp) in nearby exploited areas.…”