Shrouded by the sea. The animal welfare implications of cetacean bycatch in fisheries a summary document

Transcription

1 Shrouded by the sea The animal welfare implications of cetacean bycatch in fisheries a summary document

2 It is estimated that more than 300,000 cetaceans die every year as a result of getting caught incidentally in fishing gear.

3 Shrouded by the sea The animal welfare implications of cetacean bycatch in fisheries a summary document Introduction Worldwide, it is estimated that more than 300,000 cetaceans (whales, dolphins and porpoises) die every year as a result of getting caught incidentally in fishing gear. These deaths are known to be a problem in terms of conservation; placing unsustainable pressures on already vulnerable populations of animals. Some entire species such as the tiny vaquita, Maui s dolphin and the North Atlantic right whale are being pushed literally to the brink of extinction by fisheries bycatch. What has not been recognised is the significance of this problem in terms of the welfare of each animal that suffers the fate of getting caught in fishing gear. Most victims die directly as a result of such interactions but the duration of this ordeal can vary considerably between species. Equally, the nature of the bycatch process varies with different types of fishing gear. Typically, however, animals suffer multiple injuries from the trauma of being caught or their efforts to escape, ranging from cuts and bruises to amputations and fractures. Some survive the capture but then endure protracted suffering from the injuries they sustain. This summary presents the main findings of a new technical report* that documents the results of a detailed review of the injuries recorded in whales, dolphins and porpoises that have been bycaught in fishing gear and assesses their significance in terms of the welfare of the animals. Uniquely, it includes analysis of the injuries recorded in bycaught cetaceans in one of the most comprehensive data sets available, the UK s database of stranded cetacean post mortems undertaken for Department for Environment, Food and Rural Affairs (the Poseidon database). The report further reviews the policy and legislation relevant to the bycatch of cetaceans and the animal welfare standards adopted in other sectors such as livestock slaughter. The results of this review expose the inadequacy of current provisions to address the animal welfare implications of cetacean bycatch. Given the vast number of dolphins, porpoises and whales that are affected, the bycatch of cetaceans in fisheries amounts to a major animal welfare problem that has gone largely unnoticed shrouded by the sea. * The Animal Welfare Implications of Cetacean Deaths in Fisheries (2008). C.D. Soulsbury, G. Iossa & S. Harris. School of Biological Sciences, University of Bristol.

4 The scale of the threat - how cetaceans get caught The fact that dolphins, porpoises and whales get caught accidentally in fishing gear should come as no surprise, given the scale and intensity of modern fishing activity and the fact that this occurs across great swathes of cetacean habitat. What is perhaps more surprising is the sheer number of animals that are affected by fisheries bycatch, the geographical extent of the problem and the range of different fishing gears involved. The number of cetaceans bycaught in fisheries globally during the early 1990s has been estimated at between 275,000 to 470,000 per year. These estimates are based on figures from relatively well studied fisheries in the United States, that were extrapolated to the vast areas of the world where there is scant information on fishing effort, let alone cetacean catches. The researchers emphasise that this scarcity of data means that their figures probably underestimate the true scale of the problem. The pattern that emerged is that the vast majority of mortalities are dolphins and porpoises and that the majority of these occur in gillnet fisheries. This is a function of the fact that high rates of bycatch are known to occur in gillnets, and that gillnets are the most widespread form of fishing used worldwide, especially in developing countries and in coastal waters where the risk of dolphin and porpoise catches is particularly high. However, it is apparent that many other gear types are responsible for cetacean bycatch. Dolphins are caught in substantial numbers in a range of pelagic trawl and purse-seine fisheries and also on long-lines. Some large whales are particularly at risk of entanglement in the rope lines attached to static nets, pots and traps, often towing the gear away with them so they may never be recorded. While the process of capture varies between different fishing gears, what is common is that, as intelligent, air-breathing mammals, once caught individuals go through a desperate struggle to escape, often incurring severe injuries, before most, that do not escape, probably die through asphyxiation.

5 The damage - what injuries are sustained? Cetaceans suffer an extensive range of injuries as a result of bycatch. The cause of some of these is fairly self-evident, but the process that animals go through during and after capture in fishing gear is largely a matter of speculation. While some controlled experiments have been conducted to record the response of harbour porpoises in particular to becoming tangled in netting, it has proved extremely difficult to monitor the bycatch process in situ in operational fisheries. Even where it is practicable, the ethical implications of observing, without intervention, a sentient animal s confinement and struggle to the point of death would be considerable. There is now a well-established catalogue of injuries that are typically seen in bycaught animals, although it can be difficult to establish whether some damage may have occurred after death. Bycaught dolphins, whales and porpoises commonly suffer cuts and abrasions to the skin. This results from the scraping or incision of rope, netting or twine into the skin as the animal tries to escape. Animals that get caught in very fine and loosely set gillnets, apparently twist or writhe, causing the netting to become more tangled and to tighten around them. Porpoises are particularly prone to capture in gillnetting and often have a characteristic ring incised round the head reflecting the mesh size of the net involved. Cuts are also common round the fins and tail flukes that become snagged in the netting that then tightens as the animal struggles. In extreme cases, fins and flukes are totally or partially amputated by this effect. Dolphins that have been hooked on longlines have also been observed with deep incisions to the body and also with a partially or completely severed dorsal fin caused by the tension of the line as the animal tries to pull away from it. Large whales such as North Atlantic right whales that become entangled in the ropes attached to fixed nets and traps have been found with severe lacerations deep into the blubber and even into bones. As these animals are powerful enough to tow the gear away with them, the rope continues to tighten and cut into their body over time. Bycaught dolphins are commonly recorded with broken teeth, beaks or jaws. These injuries are particularly associated with animals that have been caught in trawl nets which, as towed gear, are relatively taught and resistant. These animals are trapped within the net rather than entangled and in trying to find an escape route they appear to try to push their way through the meshes with such force that fractures occur. Bycaught dolphins also suffer extreme internal injuries. These include bruising, torn muscles, internal haemorrhaging (bleeding), congestion of organs such as the liver, kidneys and spleen and punctured and collapsed lungs. The processes that lead to these internal injuries are a matter of conjecture. However, the muscular tears and haemorrhaging that are frequently recorded are consistent with extreme struggling or thrashing as the animal tries to escape the net or convulses before death.

6 The damage - what injuries are sustained? Finally, it is not uncommon to find deep penetrating wounds on the bodies of dolphins and porpoises that have been bycaught. These include stab wounds and cut open body cavity. It is assumed that these wounds are the result of the animal being gaffed when it is removed from the net or moved around the deck, or a deliberate attempt to make the body sink and thus avoid detection. Bycaught animals have also been recorded with severe blunt trauma injuries such as fractured skulls that appear to have been caused by animals being dropped on deck or passing through hauling gear. While it is assumed that the majority of animals are dead before these extreme injuries occur, it cannot be stated with any certainty that all animals are dead or even insensible at the time. External injuries recorded in post mortem data from UK bycaught cetaceans (97 harbour porpoises and 80 common dolphins) 29.4% net marks (tail flukes/tailstock) 15.6% net marks (dorsal fin) 23.0% net marks (head/beak) 17.0% broken teeth Injuries found in UK bycatch victims The incidence of these various injuries in a sample of animals (97 harbour porpoises, 80 common dolphins) that were diagnosed as having died from bycatch in the UK s cetacean strandings post mortem database (Poseidon) is shown opposite. 7.4% net marks (body) 24.5% net marks (pectoral fins) 24.2% broken maxille/mandible

7 The damage - what injuries are sustained? Internal injuries recorded in post mortem data from UK bycaught cetaceans (97 harbour porpoises and 80 common dolphins) 65.4% visceral congestion, typically liver, kidneys, spleen and adrenals 6.6% haemorrhaging or muscle tears to thoracic or intercostal regions 39.0% haemorrhaging thoracic rete mirabile Peri-scapular (12.1%) or subscapular (8.8%) haemorrhaging or muscle tears 18.1% haemorrhaging or tears to longissimus dorsii muscle 15.4% haemorrhaging to sub-mandibular or sub- cranial regions These injuries may be considered relatively trivial in the context of animals that suffer death by asphyxiation. However, many of the injuries are severe and would in other circumstances be regarded as extremely distressing. They may be endured for a protracted period of minutes that it can take the animal to die. In the case of animals that escape entrapment, they may suffer the pain and debilitation of such injuries for days, months or even longer.

8 Death How do bycaught cetaceans die? Cetaceans that are caught and restrained underwater by fishing gear usually die of asphyxiation. Whales, dolphins and porpoises do not have the irresistible, involuntary response to inhale that causes humans and other terrestrial mammals to breathe in water and drown. Instead, they can hold their breath literally until they die from lack of oxygen (hypoxia). Typically, the airways of a bycaught cetacean contain a characteristic blood-stained froth and the lungs and heart show damage that is caused by hypoxia. This includes changes to the fibre structure in heart tissue and swelling, haemorrhage and rupture in the lung tissue. While it is not clear whether these pathological changes are themselves painful or stressful, there is evidence that the changes seen in heart tissue are caused by massive releases of enzymes that are produced in response to stress. Given the high cognitive abilities of cetaceans, it is very likely that they find this process highly stressful. up to 8 minutes, minke whales up to 13 minutes, whereas sperm whales the champions of deep diving can stay underwater for up to 73 minutes. Some animals escape their entrapment and live on with the injuries they sustained in the process. It is impossible to quantify how widespread this occurrence is, or how long animals survive after their ordeal but plenty of live cetaceans have been recorded with specific debilitating injuries that can reasonably be assumed to have been caused by fishing gear. In the case of large whales, suffering can be particularly prolonged as the animals may be powerful enough to reach the surface while still entangled and thus continue to breathe for some time until they become too weakened. Most extremely, whales can tow fishing gear away with them. In the case of North Atlantic right whales, animals have survived for months with ropes progressively cutting into their bodies and causing gradual and extremely painful debilitation until they eventually die. How long does the suffering last? How long the process lasts is difficult to ascertain. It will vary with the nature of the entrapment, for instance whether an animal is caught at the beginning or end of a dive, and also how it responds; animals that struggle vigorously are likely to use up their oxygen reserves more quickly than those that don t. Fundamentally, though, different species have very different capacities to remain under water, which provide at least a theoretical limit to how long they may suffer before dying. Small cetaceans such as harbour porpoises can dive for up to 5.5 minutes, bottlenose dolphins for The wider impact The entrapment and subsequent death of cetaceans is also likely to affect the welfare of remaining family and group members. Dolphins are highly social and the suffering of one individual is likely to cause distress to others. The death of an individual may also result in the loss of knowledge or experience that could diminish the wellbeing of the group. Calves in particular are likely to suffer if their mothers are killed in this way, both psychologically from the direct experience and physically from the loss of care and protection, leading to starvation or reduced survival chances over time.

9 Collateral damage what is tolerable in the name of food production? It is not possible to conceive of a form of terrestrial commercial meat production where the incidental killing of hundreds of thousands of sentient mammals would be tolerated in any form, let alone by the extremely inhumane processes described here. However, this is what happens in the production of some fish. To put the times to death assumed for bycaught cetaceans in context, animal welfare standards have been adopted in other sectors that identify limits for the time it takes animals to die. For instance, it is a requirement in the UK and many other parts of the world that animals that are slaughtered commercially for meat must not be subjected to avoidable pain or suffering at the time of death. They must be rendered immediately insensible and thus have to be stunned or anaesthetised before killing. Many standards also require death to be instantaneous. Estimating the time it takes for bycaught cetaceans to die is largely a matter of theoretical deduction. However, the estimates suggest that many cetaceans are subjected to periods of suffering far longer than would be considered morally acceptable in commercial meat production. Large whales that become entangled can suffer extreme pain and distress for very prolonged periods.

10 Legal protection? The safeguards - what protection do cetaceans have? Whales, dolphins and porpoises are protected in many parts of the world by legislation such as the Marine Mammal Protection Act in the USA and the Habitats Directive in the EU. The purpose of such legislation is generally to reduce negative impacts on the conservation status of species. Although such reductions in bycatch, if achieved, would help to ameliorate the scale of the welfare problem, the legislation is not designed to address the impacts on the welfare of the individual animals concerned. Therefore, except in the case of the most endangered populations or species, a certain level of bycatch is deemed to be sustainable and therefore, implicitly, acceptable. Most countries have animal welfare legislation that prohibits causing pain and suffering to animals, such as the Wild Mammals (Protection) Act (1996) in the UK or the Animal Welfare Act (1999) in New Zealand. Some legislation even prohibits killing animals specifically by drowning. However, it is generally the intentional or wilful causing of suffering that is prohibited, which means that suffering that is caused as an incidental result of otherwise lawful activities, such as fishing, is not covered by current welfare legislation. There is general acknowledgement that it is unacceptable to cause pain and suffering or the prolonged or stressful death of animals and this is reflected in legislation and guidelines governing other sectors of human interaction with animals, such as livestock slaughter and trapping. It is remarkable that the welfare of highly intelligent mammals incidentally but predictably caught or killed by the otherwise highly regulated fishing industry is not covered by legislation or apparently even considered.

11 Conclusions The bycatch of whales, dolphins and porpoises in fisheries, while unintended and usually highly unwelcome, tends to be regarded by fishers and authorities alike as unavoidable, or at best, as an issue to be reduced to a level that is sustainable in population terms. However, cetacean mortality in fishing gear is an important animal welfare issue as animals frequently suffer multiple and severe injuries during a stressful and protracted death. The scale of the issue, affecting hundreds of thousands of animals each year means that it is also a welfare problem of major proportions that has barely been acknowledged until now. Indeed, existing legislation entirely fails to address the whole issue of animal suffering that is not caused intentionally, but is nevertheless a predictable outcome of a wide range of fishing operations in many parts of the world. It is arguable that if the capture and death of these large intelligent mammals occurred in this manner on land, rather than out of sight in the depths of the sea, the international community would have taken far stronger and far swifter action to bring an end to this problem. Governments and regulatory authorities with responsibilities for both animal welfare and fisheries, at national, regional and international levels must act urgently and decisively to end the unacceptable suffering that is associated with cetacean bycatch in fisheries. To this end, they must: > recognise the major significance of the animal welfare issues presented by the bycatch of cetaceans and the need, therefore, not just to reduce bycatch to sustainable levels but to strive to eliminate it entirely; > revise without delay their policies and legislation to reflect the need to regulate better those fisheries practices where cetacean bycatch can be prevented by mitigating measures, and to outlaw those where it cannot; and > urgently step up their implementation and enforcement of these measures and to monitor their efficacy.

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