Evaluating ecological drivers of fish cannibalism: impacts of populational and environmental factors

Cannibalistic behavior is common in many fish species, yet the specific ecological factors influencing this behavior remain underexplored. We utilized bottom trawl survey data from 2019 in the southern inshore of Zhejiang Province, China. A proportion of Harpadon nehereus individuals were selected for anatomical measurements and stomach content analysis to confirm cannibalism, and a generalized linear mixed model (GLMM) was applied to investigate the drivers of cannibalism in H. nehereus. Body size, conspecific density, alternative prey density, body condition, season, and temperature were identified as significant factors affecting cannibalistic behavior. The likelihood of cannibalism was highest at higher densities of small H. nehereus, which were defined as having a body size smaller than 38 % of dissected conspecifics. Further GLMM analysis showed that cannibalism rates increase with conspecific density but are mitigated by the presence of alternative prey, such as skinnycheek lanternfish and bridle cardinalfish. This supports the hypothesis that cannibalism is prevalent in conditions of food scarcity. In addition to biological density factors, the quadratic terms of temperature and main prey density are nonlinear to the probability of cannibalism; the influence of temperature on cannibalism exhibits a unimodal relationship with an overall upward trend, peaking during autumn temperatures. Improved body size and condition also have the potential to enhance cannibalistic behavior in H. nehereus. This indicates that cannibalism is driven by a variety of biological and abiotic factors, influenced either indirectly or directly. We used H. nehereus as a case study to provide valuable insights into the possible mechanisms of cannibalism in regulating fish population dynamics.