Bycatch

In recent years increasing numbers of dolphins and whales have been washed up dead on the beaches of southwestern England and Wales. The numbers peak in the winter months and show a direct correlation with the activities of large offshore fishing fleets. In addition post mortems carried out on the dead animals indicate that their injuries and death are almost always consistent with pelagic bycatch. This is a sanitised term meaning that they are incidental and unintentional victims of huge modern trawlers, often operating in pairs, which tow extremely large nets between them scooping up everything in the water column between the surface and the sea bed. The intended catch is the shoals of oily fish such as bass and mackerel which are found in the Channel and Western Approaches at this time of year.

The fishing fleets that run these huge and indiscriminate trawling operations are French and Scottish and a Newlyn-based boat. The Danish and Dutch are involved in midwater trawling for mackerel. There are a number of reasons why bass pair and midwater trawling is so devastating:

  *  The speed at which the trawl is pulled through the water, an average of 6 - 8 knots.
  *  The trawlers themselves are huge with very powerful engines.
  *  The mesh size at the mouth of the trawl is 8 metres or larger (and can be up to 16 metres).
      Dolphins are unable to feel any water pressure or resistance on their bodies until they
      are much deeper in the net where the mesh size is smaller.
  *  The headline (the top of the trawl mouth) is on the surface and extends all the way to the
      sea bed. Nothing escapes.
  *  The length of time the trawl is towed, 8 hours or more.

Beam trawlers and scallop dredgers report trawling up increasingly large numbers of rotting carcases and skulls in their usual catches. These are mostly from common dolphins. It is clear that the common dolphin population is suffering the highest losses as they are also the most frequent corpses washed up along the coasts.

It is known that it is common for 20-30 animals to be caught at the same time. It is clear that the fishing industry attempts to distance itself from the deaths by throwing the dolphins overboard in the hope that they will sink. Most do, but the estimated 1% which come ashore as corpses bear the evidence of their fate. Animals have washed up with rope still tied around the tail stock, sometimes in pairs, left after they were winched overboard. Some have been punctured in the region of the heart and lungs to aid sinking, in at least one case post mortem evidence shows this was done while the dolphin was still alive and it subsequently bled to death in the sea. Other attempts to hide the evidence include cutting the heads off, and slicing the bodies into sections. These too washed ashore.

Some of the larger and slower moving victims may simply blunder into the nets but it is likely that dolphins and killer whales for instance are actively feeding on the trapped shoals of fish. While the nets are being towed (often for 8 or more hours) the dolphins probably swim in and out without much trouble. It is most likely that they are trapped when the net is hauled in. Their death must be an agonising one, asphyxiating as they are unable to reach the surface to breath. Damage to the head and beaks results from crushing as the net is constricted. Their bodies are lacerated by the spines of the fish they are tumbled with in the trawl and sometimes the spines are found embedded in the skin.

Any piece of discarded fishing gear is potentially lethal. If anything of this nature is noticed along the coast it should be safely disposed of away from the sea. Remember that whatever came in on the tide can wash out again on the next tide. Winter storms are particularly productive of such rubbish. If the mass of netting and rope is too large to remove personally then efforts should be made to secure it so it doesnít wash out on the next tide (donít take personal safety risks), and the local council should be informed to arrange removal.

It is not just active fishing gear that causes injury and death at sea. The most lingering and painful deaths are caused by discarded gear. Drifting lengths of rope, monofilament line and pieces of netting frequently become entangled around all manner of marine creatures from whales and turtles to seabirds and fish.

Such deaths are horribly slow as the tangled lines prevent normal movement and feeding, and relentlessly tighten around the victim. It can take months before the debilitated animal finally dies.

© Brixham Coast WatchTelephone: 07712 587799Website by Big Bird Design.


A washed up Common dolphin


. . . and another


. . . and another


Enormous Dutch boats off our coast


Humpback whale calf with rope
wrapped around its body


Discarded netting