Anthropogenic forcing of fish boldness and its impacts on ecosystem structure

Abstract

Modified fish behaviors in response to anthropogenic stressors, such as chemicals, microplastics, acoustic emissions and fisheries, are a debated driver of change in freshwater ecosystems and oceans. Our ability to judge the severity of observed behavioral responses is hampered by limited knowledge regarding how subtle behavior modifications in prey fish affect ecosystems. Here we show that anthropogenic stressors affecting fish boldness are not expected to cause population collapse, but rather elusive effects on fish length, population biomass, reproduction and ecosystem state shifts. We use a physiologically structured population model (three trophic levels), well fed with empirical data, to simulate how previously suggested alterations of fish boldness traits due to anthropogenic stressors affect ecosystem structure. Our results suggest that these stressors may cause ecosystem structure effects, such as skewed size distributions, reduced fish biomass and reduced reproduction success, by altering the foraging behavior of fish. However, the specific structure effects depend on where the boldness–shyness continuum change occurs and on the species‐specific life stages. The model also highlights somewhat counterintuitive effects leading to possible extinction of predators when the foraging behavior of the prey is hampered. We conclude that anthropogenic forcing of fish behavior may be a hidden mechanism behind ecosystem structure changes in both freshwater and marine ecosystems.

The battle between harvest and natural selection creates small and shy fish

“…This is a justification of further research. Before this research becomes available, our work suggests that recreational angling or other forms of hook and line fishing can counteract the natural selection for large body length and can increase the survival of timid fish that are harder to catch, which potentially can also have ecosystem effects (87,88).…”

Fish microplastic ingestion may induce tipping points of aquatic ecosystems

“…In the model (1), boldness was introduced for consumer individuals and described by a boldness parameter (i.e. τ), ranging from 0 to 1 (Wang et al, 2021), where larger values imply higher boldness and increased boldness leads to increased foraging (Réale et al, 2007). As a trade-off, elevated boldness increased active maintenance costs as…”

“…Therefore, microplastic ingestion can alter energy uptake, impacting ontogenetic development and reproduction at the individual level (Cedervall et al., 2012). If microplastic ingestion happens on system‐wide scales, these changes in life‐history traits may be expected to induce trophic cascading effects on the dynamics of populations and ecosystems (de Roos & Persson, 2002; Wang et al., 2021). This raises an important question how the microplastic effects at the individual level scale up to influence higher organization levels through cascading trophic interactions.…”

Impacts of Oxazepam on Perch (Perca fluviatilis) Behavior: Fish Familiarized to Lake Conditions Do Not Show Predicted Anti-anxiety Response

“…Here, collapsing fish populations, due to additions of synthetic estrogen and their direct effect on fish reproduction, serve as one striking example of how pharmaceuticals can impact aquatic ecosystem . A less direct environmental risk comes from dissolved anxiolytic drugs that reduce anti-predator behaviors and, thus, threaten to increase mortality for prey fish or change ecosystem structure . However, researchers currently struggle to show that non-lethal effects, such as behavioral modifications, from chemical stressors are expressed in natural aquatic ecosystems where drugs are greatly diluted .…”

“…5 A less direct environmental risk comes from dissolved anxiolytic drugs that reduce anti-predator behaviors and, thus, threaten to increase mortality for prey fish 6 or change ecosystem structure. 7 However, researchers currently struggle to show that non-lethal effects, such as behavioral modifications, from chemical stressors are expressed in natural aquatic ecosystems where drugs are greatly diluted. 8 Hence, there is an urgent need to test whether or not the nonlethal effects from pharmaceutical exposure observed in laboratories are present also in complex, natural environments.…”