STOP BLAMING THEM: Marine mammals are not the culprits behind decreased fish stocks, and culling them would not help the fisheries.
A new study published in PLoS-one clarifies the role of seals, dolphins and whales in the ocean. RIMOUSKI - Large-scale cullings of marine mammals would not benefit the fisheries, according to a new paper supported by the Lenfest Ocean Program and published today in the journal PLoS-One. For years, it has argued that reducing the number of whales, seals or dolphins in the oceans would improve fisheries because they eat fish that are caught for human consumption. The study published today found that even a complete eradication of marine mammal populations in seven different ecosystems of the world would not lead to any significant increase in commercially important fish populations. Countries in favor of resuming commercial whaling have been arguing that this might the solution to increase fisheries catches. At the International Whaling Commission (IWC), this “whales eat fish” debate has been on for a long time, and the vote in favor of resuming commercial whaling is based on the understanding that culling whales would result in increased fisheries catches. Similarly, the potential negative impacts of seals and sea lions on commercially important fish stocks have been of great concern in ecosystems such as Atlantic Canada, Bering sea (USA) or Benguela (South Africa), and large-scale cullings are often seen as the solution. “When we examine the potential competition between marine mammals and fisheries in 7 different ecosystems of the world, our results clearly demonstrate that whales, seals or dolphins are not a threat to fisheries” said Dr. Lyne Morissette, lead author and marine mammal expert at Institut des sciences de la mer de Rimouski. “Even when simulating the complete eradication of marine mammals from these ecosystems, we do not see any clear benefit for fisheries and moreover, this lead to important alterations in the structure of the ecosystems.” The authors constructed ecosystem models, which account for feeding interactions between marine mammals, fish and fisheries, to understand the role that marine mammals play in the ocean. The scientists used global and regional data, validated by experts from the 7 ecosystems they modelled. “Competition within ecosystems is a complex issue and needs to be investigated using the appropriate scientific tools” said Dr. Villy Christensen, an author based at the University of British Columbia. Regrettably, in this “marine mammals vs fisheries” debate, it is difficult to assess whether it is based on any scientific evidence, considering the lack of evidence for existing large-scale competition between whales and fisheries, the well documented fact that the world's oceans increasingly are overexploited, and the unpredictable consequences of culling. “All countries should adopt leadership roles in a common effort to manage our fisheries better,” said Dr. Daniel Pauly, an author from the University of British Columbia. “Over time, we have exploited and depleted the best marine resources, and now we are turning to what is left. The assertion that fish supply is in peril is legitimate, but the problem is resolved with better management, not large-scale cullings.” ### The paper “Marine Mammal Impacts in Exploited Ecosystems: Would Large Scale Culling Benefit Fisheries?” is available online at http://dx.plos.org/10.1371/journal.pone.0043966. Lyne Morissette, Ph.D.Marine mammals & Ecosystem Ecology Institut des sciences de la mer de Rimouski Observatoire Global du Saint-Laurent 310, Allée des Ursulines Rimouski QC G5L 3A1 CANADA [email protected]
