| Recently we had a bit of a go at the Whale and Dolphin Conservation Society. We argued that divers would have a job harassing dolphins even if they wanted to. Now WDCS Director of Science Mark Simmonds has his say - it's only fair! |
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WHAT IS LIFE LIKE FOR DOLPHINS in the cold, polluted, net-strewn and over-fished waters of the UK?
With colleagues from the Whale and Dolphin Conservation Society, I have been working to find some practical methods to improve their situation. The diving community has usually been very supportive of initiatives to protect the dolphins, so I was surprised when one of my more moderate recommendations received a strong rebuke from Diver (Chasing Dolphins, July).
There are some 24 species of whales, dolphins and porpoises with ranges that include UK waters. Only two species are normally seen inshore. The big grey animals with sickle-shaped dorsal fins and prominent beaks are bottlenose dolphins (immortalised by Flipper). The smaller, far shyer, black-backed animals with triangular dorsal fins and blunt faces are harbour porpoises. These have largely disappeared from much of the South Coast, southern North Sea and Baltic.
The bottlenose now has only two resident populations - in Cardigan Bay, Wales, and the Moray Firth, Scotland.
A third, smaller group travels widely around the coasts of Devon and Cornwall.
Another large grey species, the Risso's dolphin, is seen occasionally off the Welsh coast and more commonly off Scotland. Other smaller species occasionally venture inshore, including the common, white-sided and white-beaked dolphins.
We still know little about any of these animals. The 130 or so Moray Firth dolphins are the best known but it has been calculated that they will be extinct in under 50 years. The others are likely to be in a similar situation.
Dead, stranded cetaceans are subject to full pathological study in the UK, and porpoises, tissues of which are most heavily polluted, have been shown to be the most prone to infectious disease.
The immunosuppressive effects of the pollutants that accumulate to very high levels in cetacean bodies are well-known, so this is no surprise. It is also apparent that a high and increasing number of porpoises are dying in fishing nets around the UK. In the Celtic Sea, set-bottom gill nets kill an estimated 6 per cent of local porpoises annually, about 2200 animals. In the North Sea, the same type of fishery takes almost 7000 porpoises a year.
Earlier this year, hundreds of mainly common dolphin bodies washed ashore on English and French coasts. Not all bodies wash up, so thousands probably died through winter . This has been going on for years. Huge, modern, fast-moving offshore trawlers seem to be to blame.
This is a cruel death. Caught in nets, dolphins and porpoises thrash around and mutilate themselves as they run out of oxygen over several minutes.
Typically, they suffocate rather than drown, clamping their blow-holes (the flap over their single nostril) shut to stop water entering their lungs.
For some years, the WDCS and other conservation groups have called on the Government to end these deaths. In July, the countries (including the UK) that are party to ASCOBANS (the Agreement for Small Cetaceans in the Baltic and North Seas) agreed to work with the European Commission to ensure its integration into the revised Common Fisheries Policy.
ASCOBANS also considered other threats. Diver in July suggested that fisheries were the main threat to dolphins. I agree. However, it was dismissive of the threat posed by disturbance, arguing that dolphins like to bow-ride and, anyway, can go anywhere in the sea to escape persecution. Here I disagree.
Dolphins stay in certain areas, even if only temporarily, because there are things there that they need, perhaps warmer water, favouring young calves, but most likely abundant or highly nutritious prey.
If they are forced out, such harassment will not kill them outright but might mean that they have lower energy stores, making them more vulnerable to disease, less able to survive periods when food is not plentiful and less able to reproduce.
But, surely, dolphins love boats? Yes, sometimes! At other times, if chased, they make evasive (and even defensive) manoeuvres, typically when young calves are present. These are slower and less agile and the nicks and scars on the backs and dorsal fins of live dolphins show that they are occasionally struck by boats. But can't they just dive away? No. Dolphins are creatures of the surface. Every few minutes they must come up to breathe. This is why fast modern water-craft (notably jetskis and RIBs) have been seen to "herd" and even corral them.
Porpoises and dolphins may also be physiologically stressed by human noise and continual boat attention. If they come to you, fine. Otherwise, stay away!
With so many threats to UK dolphins, sensible precautionary protective measures need to come into play swiftly. These include acting to control cetacean-deadly fishing activities, controlling marine pollution and reducing disturbance. The diving community - which knows the marine environment so well - can be very helpful in this.
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