Climate Feedback

PICES conference: disentangling the drivers of change

Olive Heffernan

I’ve been attending the PICES conference on Climate Change Effects on Fish and Fisheries in Sendia, Japan this week in an effort to reconnect with my fisheries research roots. Since leaving research seven years ago, I’ve covered little in the way of fisheries, partly because I’m now focused on climate change, a topic that the fisheries community is only recently turning its attention to. While there’s been a long history within the community of research focused on how the environment influences fish – from the behaviour of individuals all the way up to catch statistics – few studies have looked at attributing observed environmental changes to anthropogenic warming.

And judging from the talks here this week, that’s still largely the case. Many of the talks here this week have reported changes in fisheries that correlate well with temperature changes, but few have factored out other drivers of change and untangled climate variability from human-induced warming.

Some of the experts here say that changes in exploited marine species are so heavily driven by fishing pressure that human-induced warming is likely a secondary – and much smaller – driver of change. Speaking at the opening session on Monday, Rashid Sumaila of the University of British Columbia in Vancouver pointed to the fact that fisheries such as Bluefin tuna in the Atlantic and lingcod in British Columbia are in serious trouble – even without climate change. That’s because more vessels are seeking to exploit an increasingly depleted resource. But, said Sumaila, climate change can affect the productivity and the distribution of fish biomass in the ocean, and over time this will likely impact human welfare through changes in catch, food security and income.

Accoridng to John Pinnegar, head of climate change research at the Centre for Environment, Fisheries and Aquaculture Science in Lowestoft, UK, the relationship between climate change and fisheries is two-way. Climate change can increase the vulnerability of a stock to fishing pressure by reducing its carrying capacity – or population size (by narrowing the habitable area, for example), but equally a heavily exploited population comprised mostly of young fish will be less resiliant to environmental change than one with older animals.

While disentangling the various drivers of changes in fisheries is interesting from an academic perspective, from a managment point of view it might be less important. After all, “We can’t turn the climate around quick enough”, says John Pinnegar, head of climate change research at the Centre for Environment, Fisheries and Aquaculture Science in Lowestoft, UK, “so the only lever we have is to manage fishing pressure”.


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