As mentioned under 'Current abundance and trends', there has been an apparent but not statistically significant decline in the summer abundance of pilot whales in the northern North Atlantic over the period 1987–2007 (Pike et al. 2013). Given the minimum size of the population, as indicated by the 1989 survey, of over 500,000 animals just for the Icelandic–Faroes area, it seems very unlikely that an annual harvest of around 1,000 whales in the period 1987–2007 could have caused the population to decline. Also the Eastern sub-Index Areas may be most relevant to the Faroese harvest, and there is little evidence of decline in either the 3 or 5 Survey Eastern Index Area.
The fact that the population has been subject to approximately the same level of harvest for at least 300 years, with apparently little change in availability (Hátún and Gaard 2010), also suggests that the Faroese harvest is likely not causing the stock to decline in numbers. In 1997, NAMMCO concluded that the drive hunt was sustainable (NAMMCO 1998c).
The effect of catches of pilot whales in the Faroe Islands depend critically about the geographic range of the population, which is affected by these catches (ICES 1996, figure below). If the whales come from the Mid-Atlantic Ridge-Iceland Area (A+B+C) or the area covered by the NASS 1989 (A+B+C+D) sighting survey, then catches over the last 150 years have hardly any impact on the population trajectory. However the qualitative effect of the catches is very different if they have come from a population with a geographic range the size of the Rockall-Iceland Area (A+B) or the Faroese Islands Area (A).
Areas to which the abundance estimates used in the ICES 1996 population trajectory runs apply.
Faroe Islands Area = A
Rockall - Iceland Area = A + B
Mid-Atlantic Ridge - Faroes Area = A + B + C
NASS-1989 = A + B + C + D
Although the stock delineation of pilot whales remains uncertain, non-genetic evidence (pollutant concentrations and parasite burdens, see above) indicate that there is likely more than one stock subject to harvesting in the Faroe Islands (ICES 1996, NAMMCO 1998b) and that Faroese harvesting is not concentrated on a small resident population. The satellite tagging data also show that pilot whales caught off the Faroes moved well beyond the Faroe Islands Area. Indeed the satellite tagging data from 2012 indicate that the whales moved well beyond the Mid-Atlantic Ridge Area (A+B+C below), as well as beyond the 3-NASS survey Eastern index region.
A = Faroe Islands Area, A+B = Rockall - Iceland Area, A+B+C = Mid-Atlantic Ridge - Faroes Area, A+B+C+D = NASS-1989
The abundance of pilot whales in the population contributing to the catch required to sustain an annual catch of 678 animals (the average annual Faroese catch 1997–2011) is between 50,000 and 80,000 whales (with a precision equivalent to that of the last sightings survey in 2007) (NAMMCO 2013). The population in the Eastern index area, which is smaller than the range of the population affected by the catch, is alone over 100,000 pilot whales. That said, further research and better surveys are required to determine if the apparent negative trend in pilot whale abundance is a real phenomenon, due to annual fluctuations in distribution or some other causes.
The average annual catch of long-finned pilot whales in West Greenland during 1993–2007 was 126 whales. The aerial TNASS 2007 survey off west Greenland yielded an abundance of 7,440 pliot whales (95% CI = 3,014–18,367), but only partly covered the potential pilot whale habitat, as aggregations of pilot whales were encountered at the western edge of the survey area (Guldborg Hansen and Heide-Jørgensen 2013). The NAMMCO Scientific Committee (2013) suggested that a sustainable harvest level of pilot whales taken from this abundance would be between 50–70 whales per year. However, it seems likely that the size of the stock subject to the Greenlandic hunting is larger than that revealed by the survey. In addition, the summer aggregation in West Greenland cannot be considered an isolated stock. Instead, it is likely connected to pilot whales along Labrador and at Newfoundland, and the occurrence and abundance in West Greenland is probably influenced by the sea temperature regimes in the area (Fullard et al. 2000). For these reasons the stock status of West Greenland pilot whales remains uncertain.
The 2011 US assessment (Waring et al. 2012) concluded that the status of long-finned pilot whales in the U.S. Atlantic EEZ was unknown. There were insufficient data to determine population trends for this species. The total U.S. fishery-related mortality and serious injury for long-finned pilot whales was unknown, since it was not possible to partition mortality estimates between the long-finned and short-finned pilot whales. However, this mortality was most likely not less than 10% of the calculated PBR (Potential Biological Removal) and therefore could not be considered to be insignificant and approaching zero mortality and serious injury rate. Therefore, it was recommended that the stock should be considered a strategic stock. However, the inability to partition mortality estimates between the two pilot whale species limited the ability to adequately assess the status of the long-finned pilot whale stock.
Pilot whales were subject to an intensive drive fishery in Newfoundland from 1947 to 1972, and this fishery apparently reduced the stock to very low levels (Mercer 1975, Hay 1982, Nelson and Lien 1996). Abundance at the onset of the fishery was likely about 60,000 animals (Mercer 1975). Hay (1982) conducted in 1980 an aerial survey in eastern Newfoundland and southeastern Labrador waters, and estimated 13,167 whales (95% CI = 6,731-19,602, not corrected for diving whales or whales missed by observers).
Nelson and Lien (1996) concluded that the population had likely not yet recovered to its pre-exploitation size. This seems confirmed by the results of the 2007 Canadian T-NASS survey (Lawson and Gosselin 2009), which provided a full coverage of the Atlantic Canadian coast and yielded an abundance estimate of 5,612 (95% CI = 3,020–10,867, not corrected for availability and perception biases).
Pilot whales are likely one of the most abundant odontocetes in the North Atlantic. The harvesting of pilot whales that continues today in the Faroe Islands has proven sustainable over a period of more than 400 years. In 1997, NAMMCO concluded that the drive hunt was sustainable (NAMMCO 1998c). The population off Newfoundland is likely slowly recovering after a period of excessive harvesting.
In some other areas, bycatch of pilot whales in fisheries continues, but apparently at relatively low levels. While there is no indication at present that pilot whales are being affected by contaminants, their occupation of a relatively high trophic level and the high level of contaminants observed does make them susceptible to this threat.
The apparent reduction of pilot whale abundance in the NASS index areas, which includes the hunting area around the Faroes, as well as the level of the catch in West Greenland compared to the population abundance available, should however be of concern. Better information on the abundance and trends in abundance of pilot whales is required to ensure the long-term sustainability of these harvests. In addition, further information on stock delineation, and geographical range of any stock components found, would improve the ability to design and carry out effective surveys for this species. In the light of the new genetic information, the recent tagging data, as well as the upcoming 2015 NASS survey and likely the 2016 European Sightings Survey, a new assessment would be warranted when the new abundance data become available.
North Atlantic long-finned pilot whales. Photo: P. Jean
Long-finned pilot whales are currently listed on Appendix II of the CITES. CITES is a legally-binding multilateral environmental agreement that aims to ensure that international trade does not threaten the survival of species in the wild. Both Greenland and the Faroes are signatories to the convention through Denmark. A listing on Appendix II means that an export permit shall only be granted when the Scientific Authority of the State of export has advised that such export will not be detrimental to the survival of the species in the wild. There is however no export of pilot whale products from Greenland or the Faroes, except for a very small non-commercial export of meat and blubber for family consumption.
IUCN classify long-finned pilot whales, treated as one species, as Data Deficient, with the following justification: There is evidence that long-finned pilot whales may comprise a complex of two or more species. Because additional data should resolve this taxonomic uncertainty, the current species is listed as Data Deficient. Threats that could cause widespread declines include high levels of anthropogenic sound, especially from military sonar and seismic surveys, and bycatch. Primary threats that could cause widespread declines include entanglement in fisheries and competition with squid fisheries. The combination of possible declines driven by these factors is believed sufficient that a 30% global reduction over three generations (72 years; Taylor et al. 2007) cannot be ruled out (criterion A) (Taylor et al. 2008).