Saving endangered whales at no cost

The North Atlantic right whale is one of the most critically endangered marine species. Drastic overexploitation has driven this large, slow-swimming baleen whale to virtual extinction in Europe, while a small remnant population of ~350 individuals remains on the US and Canadian east coast. Although this species has been protected for 70 years, recovery has been slight and extinction is still looming because of accidental mortality from shipstrikes and fishing gear (Figure A,B) [ ]. Seventy five percent of appropriately photographed whales show evidence of entanglement, predominantly with lobster fishing gear, and this percentage has increased from 52% in the 980s [2,3]. At the same time, the US lobster fishery is severely overexploited (the inshore fishing mortalities in the two main US regions are 0.69 and 0.84 [4], while 0.2 achieves maximum yield per recruit [5]). We argue here that this endangered whale species can be protected from entanglement mortality, and the fishery can benefit simultaneously, by a large reduction of lobster traps used; a classic win–win situation. Lobster catches have increased substantially over the last 20 years, mostly in the Gulf of Maine, the world’s most important lobster producing area (Figure C) [4,6]. Hence, lobster has become one of the most important fisheries in the US ($367 million in 2004) and Canada (CDN $650 million in 2003). Along with the increase in catch came an expansion of fishing effort, here defined as the total allowed number of lobster traps in the water per day. Traps are tied to the surface via a buoy line, and to other traps via ground lines, all of which can cause whale entanglement [2]. The US has implemented regulations in which fishing activity is modified but not reduced, and whale entanglement is still an increasing problem [7]. We highlight a stark contrast between the American side (state of Maine), and Canadian side (Lobster Fishing Area 34), of the Gulf of Maine (Figure C). These two areas have very similar biological characteristics, and have experienced similar increases in catch, although relative increases have been higher in Canadian waters (Figure C). The Canadian fishery is restricted to a winter fishing season, using only about 2% of the traps that are used on the US side. Considering that Maine has about 30% higher catches than LFA 34, a year-round season, and eight to nine times more traps in the water at any given time, we derive that the number of traps used in Maine is 3 times greater than in LFA 34 to harvest the same catch (Table ). The instantaneous fishing mortality that is optimal to obtain maximum yield per recruit is estimated around 0.2 [5]. The fishing mortality for Canadian lobsters is estimated to be much greater, usually 0.8 or higher [8]. This implies that even the Canadian catch should be reduced by about a factor of four to achieve maximum yield per recruit. Thus, Canadian fishing effort is about four times that required for maximum biological yield, and the fishing effort in the Gulf of Maine may be 50 times above what is required. Consideration of the pattern of whale sightings (Figure D)