Evaluating fishing effects on the stability of fish communities using a size-spectrum model

Abstract

Abstract Effects of fishing on the stability of fish populations have been examined in numerous studies; however, species interactions and their changes with life history stages may complicate such effects at the community level, which has not been well understood. We simulated trophic interactions within fish communities using a size-spectrum model and examined the effects of fishing on community stability for a variety of scenarios. We focused on two characteristics of community stability, the level of fluctuations in community status and recovery rates after perturbation, measured by spawning stock biomass (SSB) and two size-based indicators, mean body size (MW) and slope of the size spectrum (Slope). Increasing variability of fishing pressure was found to lead to linear increases in the variation of community status, whereas the impact was limited on integrated indicators such as MW, Slope and total SSB. The interaction of fishing pressure with given levels of recruitment variability amplified the fluctuations in SSB, but reduced those in MW and Slope. For a variety of random perturbations, all scenarios showed similar recovery trajectories, in which MW and Slope showed a steep decrease and slow recovery. Fishing pressure had substantial influences on the recovery of SSB and MW, but less effects on Slope, except for the non-fishing scenarios. The recovery time of SSB was highly variable among species and decreased with the increasing fishing pressure in general. The indirect effect of fishing on stability could be largely attributed to the changes in feeding conditions. Our stability evaluations have several implications for fisheries management, suggesting the potential and challenge for the recovery of depleted fisheries stocks in the absence of environmental changes.