“Nets versus Nature: Have we indadvertedly made our fish smaller?”
April 9th 2015. H. Baumann contributed to Avery Point’s Global Cafe Series “The Omnivore at Sea” by talking about the topic of fisheries-induced evolution.
When hearing and talking about sustainable seafood, issues such as overfishing, fishing-related habitat destruction (e.g., trawls tearing through bottom habitat, dynamite fishing) or changes to the architecture of marine ecosystems (‘fishing down the foodweb’) often come to mind. Baumann talked about another potential effect of heavy decade-long commercial fishing, which is less clear but perhaps even more insidious. Nature’s age-old rule of survival in the ocean, i.e., that faster growing fish have better chances of survival, is suddenly reversed when size-selective fishing becomes the dominant agent of mortality. Because in fishing, a faster growing fish will just be susceptible sooner to get caught by the meshes of a fishing trawl. We instinctively know that life on earth has adjusted before to changing selection pressures, and there’s little reason to suspect that this case might be different. Commercial fishing may trigger fisheries-induced evolution, and this may mean smaller, earlier maturing fish and less total biomass for centuries to come. The brief talk will summarize the problem as we know it, explore alternative explanations and look at examples, which show that the issue is also inextricably linked to all the other natural and man-made changes (warming, food web) that affect fish stocks. A cautionary approach that considers evolutionary processes within the framework of sustainable fisheries is surely warranted.