Whales, dolphins and fishing

The biggest killer of whales and dolphins across the world is the fishing net. Every year, hundreds of individuals wash up dead on shores around the world. Some of their bodies bear the tell-tail marks of having been caught in nets but their bodies represent only a tiny fraction of the thousands that die out at sea – the rest simply disappear without trace. There is no ocean where this is not a serious issue but the extent of the threat, the species concerned and the fisheries that are primarily involved vary from place to place.

The incidental capture, or ‘bycatch’, of non-target species - including marine mammals, birds, turtles, fish and other species - in fisheries is recognised to be a major problem in many parts of the world.

Worldwide it has been estimated that 300,000 cetaceans (whales, dolphins and porpoises) are killed in nets each year and bycatch is acknowledged to be a serious threat to the conservation of cetaceans in some regions, including – for example - the north-east Atlantic region and Baltic Sea. The cetacean species caught in the greatest numbers in the north-east Atlantic are probably the common dolphin and the harbour porpoise but any removals from the small coastal bottlenose dolphin populations may be of particular concern from a conservation perspective as there are so few animals in the first place. The vaquita in the Gulf of California is critically endangered and its survival is threatened by fishing activities in this region.

High levels of common dolphin bycatch have been recorded in pelagic trawl fisheries such as the UK sea bass pair trawl fishery and the Irish albacore pair trawl fishery but other fisheries may also be taking a toll. For many years the large numbers of bycaught dolphins that have stranded mainly in the winter on French and adjacent English coasts, have indicated a high mortality out at sea in this region.courtesy of freedigitalphotos.net

The harbour porpoise seems particularly vulnerable to being taken in bottom-set gillnet fisheries and, given its already endangered status in the Baltic, there are currently grave concerns about its survival there and also, increasingly, in the neighbouring Kattegat, where the main threat, again, seems to come from fishing.

WDC campaigns to reduce and, where possible, eliminate the impacts of destructive fishing practices. Our studies strive to find out more about vulnerable whale, dolphin and porpoise populations and illustrate the impact that such fishing practices have on them. This is vital if we are to expose and eliminate these threats.

We have recently sponsored and published a unique study which looked at the welfare implications for cetaceans captured in nets. Our report ‘Shrouded by the Sea’ based on research by the University of Bristol, reveals the harrowing details of how many whales and dolphins slowly meet their death, many suffering extreme injuries in what can be a very drawn out underwater struggle.

Most dolphins trapped underwater by fishing gear die of asphyxiation. While the time it takes for the animals to die in this way varies, it is likely that many are subjected to a longer period of suffering and stress than would be considered morally acceptable. Whales and dolphins can hold their breath for long periods of time. The smallest porpoise can remain underwater for over five minutes between breaths, and sperm whales can dive for over an hour between surfacing. The damage seen on bycaught animals shows that many of them struggle desperately to escape from their entrapment, sustaining horrific injuries in the process.

WDCS colleagues investigate the death of common dolphins in bycatchThe severe injuries regularly seen in bycaught whales and dolphins are evidence of the suffering victims go through. Rope and netting often cause cuts and abrasions to the skin, tightening as the animal struggles and cutting deeper into the flesh. In extreme cases, fins and tail flukes can be totally or partially amputated by the tightening nets. Bodies of bycaught dolphins are commonly recorded as having broken teeth, beaks or jaws and extreme internal injuries.

Large whales that become entangled in fishing gear have been found with severe lacerations deep into their blubber and even into their bones. As these animals are powerful enough to swim away and pull the gear with them, the rope continues to tighten and cut into their body over time, often resulting in a slow and painful death.

WDC is calling for governments and regulatory bodies to act urgently and decisively to end this unacceptable suffering of whales and dolphins. This will require changes to the way fish are caught and even closure of fisheries where there is no effective or practicable way of preventing the incidental capture of whales and dolphins.

Click here to see a summary copy of the report ‘Shrouded  by the Sea’.

Click here for the full background study by Carl D. Soulsbury, Graziella Iossa and Stephen Harris of the School of Biological Sciences, University of Bristol, which examines information collated in the UK Government’s database of cetacean post mortems ‘The Animal Welfare Implications of Cetacean Deaths in Fisheries’ (Poseidon).

Dolphins and Fisheries in the English Channel

Little is known about cetacean communities in the Western Approaches of the English Channel during winter. Very few studies have been carried out despite the fact that the conservation status of the common dolphin in this region has been of great concern for many years because this species is subject to a high level of bycatch in fisheries.

For many years the Western Approaches have been intensively trawled by pelagic fisheries during the winter and early spring from October to May. These fishing activities coincide with relatively high levels of cetacean strandings. In some winters several hundred corpses of short-beaked common dolphins have washed ashore in south west England, many clearly having died through capture in fishing nets. In many cases the external damage has been identified as being consistent with death in small-meshed mobile gear such as trawl netting.

During the winters of 2004 and 2005, WDCS and Greenpeace carried out a cetacean survey in the Western Approaches of the English Channel with the main aim of collecting more information on the little-studied cetaceans that occur in these waters at this time of year.

You can read the results of the investigation in the report here: Cetaceans and pelagic trawl fisheries in the western approaches of the English Channel summary report of the 2004-2005 WDCS/Greenpeace winter surveys: a WDCS science report.

You can read the WDCS full report on bycatch in the whole north-east Atlantic region here “The Net Effect - a review of cetacean bycatch in pelagic trawls and other fisheries in the northeast Atlantic ” review of cetacean bycatch in pelagic trawls

And an update to this review here: “The Price of Fish”.