House of Commons - Environment, Food and Rural Affairs

Select Committee on Environment, Food and Rural Affairs Third Report

2 Extent of the cetacean by-catch problem

6. It is difficult—if not impossible—to reach definitive conclusions about present rates of by-catch, on the basis of the evidence currently available. Two main groups of data are required: reasonably accurate estimates of the size of cetacean populations and reasonably accurate estimates of the numbers killed as a result of by-catch.

Population estimates

7. Estimates of the populations of small cetaceans in the waters around the UK appear to involve a wide margin of error. Defra's strategy document explains that:

Firstly, we are not confident of the geographical limits of any biological population of these species and secondly, there is usually a wide margin of error within the abundance estimates. The mobility of small cetaceans is such that they have been recorded in waters away from the core of their ranges … The wide margin of error with the population estimates emphasises the need to take a precautionary approach when developing proposals to reduce the impact of by-catch on the population.[3]

In this inquiry, we are particularly interested in the populations of the harbour porpoise, the bottlenose dolphin and the common dolphin.

Harbour porpoise

8. Defra estimates that the total UK continental shelf (including territorial waters) population of harbour porpoise to be in the order of 150,000 individuals.[4] The strategy document describes the harbour porpoise as widely distributed in all continental shelf waters around the UK, "with the exception of the southern North Sea and the English Channel where there has been an apparent reduction of numbers".[5] The Joint Nature Conservation Committee (JNCC) agrees with this estimate, but adds that numbers of porpoises present in UK waters vary seasonally, and more animals are likely to pass through UK waters than are present at any one time.[6]

Bottlenose dolphin

9. Bottlenose dolphins appear to spend much of their time inshore.[7] Defra estimates that there are between 300 to 500 individuals in UK inshore waters.[8] The JNCC estimates that there are probably fewer than 300 individuals in UK inshore waters.[9] Groups of bottlenose dolphins are semi-resident in two main areas of UK territorial waters: Cardigan Bay, off Wales, and the Moray Firth, off Scotland.[10] Smaller groups are found in inshore waters off south Dorset and around Cornwall, amongst other areas. The JNCC comments that the species was "formerly more widespread, especially in the southern North Sea and English Channel … and has certainly declined in range".[11] Nick Tregenza told us that the bottlenose dolphin population off south-west England could be critically endangered if even one dolphin were caught.[12]

Common dolphin

10. The population estimate referred to in Defra's consultation paper is 75,449 individuals, on the basis of a 1994 survey that covered the Celtic Sea and parts of the North Sea.[13] The species is described as abundant and widely distributed in the eastern north Atlantic and in UK waters, and common in the western approaches to the English Channel and the Celtic Sea.[14] Nick Tregenza comments that "little is known of the geographical extent of the population from which 'our' common dolphins come".[15]

By-catch estimates

11. Estimates of the numbers of cetaceans killed as a result of by-catch are imprecise. There are several reasons for this. It is probable that only some of the cetaceans that die as a result of by-catch are washed ashore; the remaining carcasses either sink or decompose at sea.[16] Whether a dead animal is washed ashore is dependent on the distance of the fishery from the shore, the depth of water in which the fishery takes place and the prevailing weather and sea conditions over a period of time. Of by-catch that is washed ashore, only some comes ashore on the UK coast, and it is likely that not all of that is recorded. There are reports of cetaceans that show signs of having died as a result of by-catch coming ashore in France and the Channel Islands.[17] The Wildlife Trusts states that, in 2002, over a period of ten days, more than 300 dolphins and porpoises were washed ashore on France's Atlantic coast and that the majority of these animals showed signs of having been caught in fishing nets.[18]

12. Of by-catch that is washed ashore on the UK coast, only some animals are able to be autopsied to ascertain their cause of death—many specimens are too decayed. For example, on the Cornwall coast, 33 harbour porpoise and seven common dolphin strandings were recorded between 1 January and 14 January 2004. Of these, only 17 harbour porpoises and two common dolphins were sent for post-mortem.[19]

13. Defra is responsible for collecting the post-mortem data. Between 1990 and 2002, by-catch was the most common cause of mortality for harbour porpoises (156, representing 30% of established causes of death) and for common dolphins (176, representing 66% of established causes of death) at post-mortem.[20] In 2002, the most recent year for which data has been properly analysed, 655 cetacean strandings were reported. Of the 189 able to be examined at autopsy, 29 of the 119 harbour porpoises examined and 29 of the 44 common dolphins examined were diagnosed as having died as a result of by-catch. Preliminary data for 1 January 2003 to 30 September 2003 indicates 653 reported cetacean strandings, including 247 harbour porpoises, 173 common dolphins and 6 bottlenose dolphins.[21]

14. A further difficulty is that the exact proportion of fishing effort carried out by the UK fleet as a proportion of the overall fishing effort appears either to be unknown or only a rough estimate.[22] Even if sufficient data could be gathered by on-board observers to enable a reasonably accurate estimate of the numbers of cetaceans caught by UK-registered vessels, it would still not be clear what proportion of overall by-catch that estimate represented. In addition, there is no indication of the scale of cetacean by-catch in industrial fishing.

Harbour porpoise

15. By-catch of harbour porpoises occurs predominantly in the Celtic Sea and in the North Sea. We note the comment of the Natural Environment Research Council (NERC) that the greatest numbers of animals being taken in UK fisheries are harbour porpoises and that "present levels of porpoise by-catch are probably not sustainable in some areas".[23]

16. In the Celtic Sea, observations between 1992 and 1994 of the bottom-set gill net fishery for hake estimated that some 2,200 harbour porpoises were killed annually as a result of by-catch.[24] This figure was estimated to represent 6.2% of the local population; the actual figure may in fact be higher, as some animals may drop out of the nets undetected and several sections of the fishing fleet, such as vessels under 15 metres in length, were not surveyed.[25] The National Federation of Fishermen's Organisations (NFFO) told us that, since 1994, there has been a "very dramatic reduction" in the size of the hake fleet, from about 50 to about 12 vessels: it therefore submitted that annual harbour porpoise by-catch is probably now about 2% of the local population.[26]

17. In the North Sea, annual by-catch of harbour porpoises in bottom-set gill net fisheries laid by Danish vessels alone has been estimated to average 5,591 porpoises or 3.3% of the local population between 1987 and 2001.[27] The UK fleet has been estimated to be responsible for by-catch of approximately 1,000 animals in 1995, reducing to around 600 in 2000.[28] Defra describes Norway as also having a significant take of fish from bottom-set gill net fisheries in the North Sea and, therefore, presumably also being responsible for cetacean by-catch.[29]

18. The JNCC states that, if these numbers are placed in a population context, "it is likely that the by-catch [in UK fisheries] to the south-west on the Celtic shelf is taking a higher proportion of the population than the by-catch [in UK fisheries] in the North Sea".[30] Of course, as the JNCC points out, in both cases other nations are also catching harbour porpoises from the same population as are the UK fisheries. In the case of the North Sea, Danish fisheries have been observed, and by-catch assessed. The JNCC considers that observations of gill net fisheries of other nations to the south-west of the UK "have probably been inadequate".[31]

Bottlenose dolphin

19. No bottlenose dolphins are recorded as having been stranded in Defra's autopsy data. However, both The Wildlife Trusts and Nick Tregenza raised concerns about the potential danger posed to the bottlenose population in the south-west by inshore bottom-set gill nets.[32] Mr Tregenza told us that bottlenose dolphins have been known to be caught in nets in Scotland, Ireland and Wales.[33] He considers that by-catch of a bottlenose dolphin is unlikely to be identified in England, for a number of reasons, including the fact that there is a very low rate of fishermen spontaneously reporting by-catch and the fact that the dolphins are comparatively large and heavy, and so would be likely to drop out of the net or be cut out of it, outboard.[34]

Common dolphin

20. We received few estimates of the numbers of common dolphins killed as a result of by-catch. However, in February 2002, the then Minister for Fisheries, Elliot Morley MP, said that he believed up to 50 dolphins a day were being killed in the pelagic trawl fishery for sea bass.[35]

21. Estimates of the proportion of the common dolphin population killed as a result of by-catch are difficult to make, although the Wildlife Trusts estimated that by-catch of common dolphins in the sea bass fishery represented between 2% and 3.5% of the local population.[36] This is due to the lack of knowledge about the size of common dolphin populations off the UK coast.

22. Despite this, it is clear that by-catch of common dolphins occurs predominantly in the seas off south-west England during the winter months.[37] Defra's preliminary data shows that, for the period from 1 January 2003 to 30 September 2003, numbers of harbour porpoises stranded remained fairly constant throughout. However, significantly higher numbers of dolphins were recorded stranded in the winter months, between 1 January and 31 March: 132 common dolphins were recorded stranded in this period, compared to only 41 in the six months between 1 April and 30 September. Of the 132 common dolphins stranded between January and March, 25 were sent for post-mortem, 23 of which were stranded on the south-west English coast. Of these 23, by-catch was listed as a cause of death for 17.[38]

23. Common dolphin by-catch appears to be continuing at comparable levels during winter 2003-04. Linda Hingley states that, in December 2003, she counted 25 dolphins washed ashore on the South Devon coast. All ten or 12 of the dolphins able to be sent for post-mortem were found to have died as a result of by-catch.[39] Nick Tregenza states that, in the first two weeks of January 2004, seven common dolphins were washed ashore on the Cornish coast.[40]

Other species of dolphin

24. The statements above about the common dolphin are likely to apply to other species of dolphin. In UK waters, the common dolphin is much more abundant than other species, and therefore constitutes the majority of recorded strandings, and all by-catch observed on board fishing vessels. However, Defra refers to a number of other cetaceans that are present in UK waters, including the white-beaked dolphin, the Atlantic white-sided dolphin, Risso's dolphin and the striped dolphin.

25. There is some evidence of these other species being caught in or adjacent to UK waters. The Whale and Dolphin Conservation Society refers to a Dutch study of pelagic trawl fisheries for mackerel and horse mackerel, conducted in the early 1990s, which recorded by-catch of small cetaceans including the Atlantic white-sided dolphin and white-beaked dolphins.[41] Defra refers to a study of a pair-trawl for tuna, conducted by the Republic of Ireland in 1998 and 1999, which recorded by-catch of the Atlantic white-sided dolphin and the striped dolphin.[42]

3 Department of Environment, Food and Rural Affairs, UK small cetacean by-catch response strategy, March 2003, para 8 ("Defra strategy") Back

4 Defra strategy, para 9 Back

5 Defra strategy, para 9 Back

6 http://www.jncc.gov.uk/Publications/JNCC312/ Back

7 Nick Tregenza commented that "two distinct forms are suspected, one living close to the coast and one offshore"; Ev 10 and Q 42. Back

8 Defra strategy, para 12 Back

9 http://www.jncc.gov.uk/Publications/JNCC312/ Back

10 Both these areas are candidate Special Areas of Conservation (SACs); see paragraphs 39 to 42. Back

11 http://www.jncc.gov.uk/ProtectedSites/SACselection/ Back