Politics – reduced quotas – and environment – survival rate – have been equally important in rebuilding the Baltic cod stocks, a new report shows.
The eastern Baltic cod stock has increased since 2005 and is now higher than ever during the last decade, according to scientists at the International Council for the Exploration of the Seas (ICES),. In an ongoing study researchers at Stockholm University have analyzed whether this increase is a result of management action or improved environmental conditions.
Model simulations show that neither reproduction alone, nor reduced catches, could explain the increase. Each factor could only explain 25 per cent of the total increase. Synergies between both factors were necessary for the current increase in the Baltic Sea cod stock, exceeding the sums of both factors. Those are the preliminary results from the ongoing analysis by at Stockholm University (Department of Systems Ecology, Baltic Nest Institute at Stockholm Resilience Centre).
“This analysis clearly illustrates the importance of management actions, such as targeting the illegal fisheries, but it also underlines the non-linear dynamics in nature and the challenges involved in ecosystem management”, says Henrik Österblom at Baltic Nest Institute, one of the scientists behind the study.
The results underline the importance of following the scientific advice from ICES for fishing quotas for cod during 2009, he adds.
“We are in a window of opportunity to rebuild the cod stock”, says Olle Hjerne, another researcher at Stockholm University. “High catches will decrease the stock. For example, a similar increase in reproduction and stock size in the early the 1990´s was rapidly nullified by unsustainable catches”.
On the consequences of a change in environmental factors, on the other hand, their colleague Thorsten Blenckner of the Baltic Nest Institute notes that continued climate change would affect cod stocks, as well, adding that “research on cod in other seas has underlined the importance of high stock levels for its capacity to cope with environmental change. Climate change will thus underline the importance of adaptive management”.
The EU Fisheries Ministers will set new cod quotas for the Baltic for 2009 at their Council meeting in Luxembourg October 27-28.