Abstract
Exploitation can modify the characteristics of fish populations through the selective harvesting of individuals, with this potentially leading to rapid ecological and evolutionary changes. Despite the well-known effects of invasive fishes on aquatic ecosystems generally, the potential effects of their selective removal through angling, a strategy commonly used to manage invasive fish, are poorly understood. The aim of this field-based study was to use the North American pumpkinseed Lepomis gibbosus as the model species to investigate the consequences of selective removal on their population characteristics and juvenile growth rates across 10 populations in artificial lakes in southern France. We found that the maximal individual mass in populations decreased as removal pressure through angling increased, whereas we did not observed any changes in the maximal individual length in populations as removal pressure increased. Total population abundance did not decrease as removal pressure increased; instead, here was a U-shaped relationship between removal pressure and the abundance of medium-bodied individuals. In addition, population biomass had a U-shaped curve response to removal pressure, implying that invasive fish populations can modulate their characteristics to compensate for the negative effects of selective removals. In addition, individual lengths at age 2 and juvenile growth rates decreased as removal pressure through angling increased, suggesting a shift toward an earlier size at maturity and an overall slower growing phenotype. Therefore, these outputs challenge the efficiency of selective management methods, suggesting the use of more proactive strategies to control invasive populations, and the need to investigate the potential ecological and evolutionary repercussions of nonrandom removal.
Highlights
Invasive species are recognized as a major driver of global change that can invoke major ecological, evolutionary, and economic consequences (Pimentel et al 2005)
The level of removal pressure peaked from April to September, overlapping with the spawning period of L. gibbosus when individuals are more vulnerable to removal through angling because of nest guarding behaviors
The impacts of recreational angling on fish populations are usually underappreciated (Arlinghaus et al 2010) and this is true for the cases where angling is used as a removal method to extirpate or regulate invasive fish species
Summary
Invasive species are recognized as a major driver of global change that can invoke major ecological, evolutionary, and economic consequences (Pimentel et al 2005). Where introductions of non-native fish result in invasions, their management is inherently difficult and often limited to removals via targeted captures that are commonly performed through fishing, including angling (Britton et al 2011). While the potential efficiency of methods used to decrease the stock of invasive populations has been reported (Cucherousset et al 2006a; Britton et al 2011), the removal of individuals is often selective (Coltman et al 2003; Wilson et al 2011) and might lead to counterproductive results, including an increased abundance of the targeted invasive species through releases from intraspecific competition or cannibalism (Lewin et al 2006).
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