Fishing-induced life-history changes degrades and destabilizes fishery ecosystems

Background/Question/Methods

Fishing is widely known to magnify fluctuations in the abundance of the targeted population which are correlated with shifts of populations towards young, small, and more quickly maturing individuals.  However, the existence and nature of the mechanistic basis for these correlations and their potential ecosystem impacts remain poorly known. Here, we elucidate this basis and associated impacts by showing how empirically parameterized network models of a well-studied fishery ecosystem increase such fluctuations when subjected to the decreased body sizes and advanced maturation characteristic of fishing-induced life-history changes.  Our models are based on those of the seasonal population dynamics of the food web within the Lake Constance fishery ecosystem in central Europe previously published by Boit et al.  Our model development added age structured populations of the two primary comercially fished species, Whitefish and Perch.

Results/Conclusions

Decreased body size of adults decrease their abundance and increase variability of themselves and their ecosystem as previously suggested by closely related food-web models.  Advanced maturation has relatively little effect except to increase variability in juvenile populations and their food resources.  Our work illustrates how different mechanisms underlying life-history changes that may arise as evolutionary responses to intensive, size-selective fishing can rapidly and continuously destabilize and degrade fisheries ecosystems even after fishing has ceased.  These results broadly suggest that life-history changes reduce fishes’ resilience to fishing and fishery ecosystems’ resistance to environmental variations and make catastrophic population collapses more likely. Further exploration of the intensity and generality of these mechanisms may help develop more sustainable fishing strategies.