The incidental capture of small cetaceans in fishing gear, also known as by-catch, is thought be one of the most significant threats to populations worldwide. The entanglement of these animals in fishing nets is relatively common and since they cannot get to the surface to breathe, the animals if not released can eventually drown.
There are a number of cases where the by-catch of individuals from fishing gear has caused significant decline of specific populations. The Vaquita (Phocoena sinus), the smallest of all porpoises is endemic to the Sea of Cortez. It is now the world’s most critically endangered cetacean species with an estimated 150 individuals remaining. The decline is due to gillnet fisheries in which by-catch numbers are thought to occur higher than the birth rate of the species. It is predicted that if by-catch rates remain as they are today, extinction of the species could occur in as little as two years. Another well known case is the harbour porpoise (Phocoena phocoena) in the Baltic Sea where numbers have reduced rapidly due to by-catch. The problem of incidental capture also occurs at many parts of UK and Irish waters. For example, significant by-catch has been recorded for short beaked common dolphin (Delphinus delphis) and harbour porpoise in the Celtic Sea. High numbers of common dolphins, harbour porpoise and other species have been washed up off the Cornwall coastline in particular, over the years with injuries consistently linked to bycatch.
Recent examples have come from here in Wales. On the evening of the 23rd March a harbour porpoise was found alive and entangled very close to shore between Tresaith and Aberporth. The animal was so exhausted that it did not resist being handled by RNLI crew from Cardigan whilst they were releasing it from the net but luckily this porpoise was successfully released.
One month later a report came to SWF of an entangled porpoise which was sadly already dead. On the 24th April at Pensarn beach (Abergele) observers taking a stroll on the beach found an animal entangled in loose netting in shallow waters. Once they dragged the net out of the water they actually found a dead porpoise, tope shark, spotted dogfish, five mullet as well as a number of decomposed fish and a few live fish and crustaceans (that were released) all entangled in the net.
A number of measures have been introduced in past years to attempt to reduce rates of by-catch. These include fishing gear modification and the introduction of pingers, a device that acoustically deters cetaceans from the fishing gear. There have also been changes in fisheries policy such as implementation of no-take zones and by-catch monitoring programmes. Sadly many of these measures have been relatively unsuccessful.
On the 20th March 2010, a workshop to assess by-catch mitigation was held at the 24th annual conference of the European Cetacean Society (ECS) in Stralsund, Germany. The workshop was led by Dr. Peter Evans, SWF, Siemensma, and Stefan Bräger. The workshop was organized by ASCOBANS, ECS, with input from the European Commission (DG MARE) and North Sea Foundation aimed to report an up-to-date review of current mitigation measures and effectiveness with discussion on how to improve current strategies that will reduce by-catch in fisheries in Europe. Several key recommendations were reached:
1) Cooperative projects should be funded that bring together fishers, gear technologists and cetacean scientists to work on finding solutions for by-catch mitigation.
2) ASCOBANS parties should try to influence the revision of EC Regulation 812/2004 so that it:
a) covers significantly and adequately the fleets and fisheries having a high risk of by-catch in European waters
b) allows fishers (and other stakeholders) to participate fully and from the start in the development of the revision
c) sets targets that need to be met in each area, thus allowing fishers to find the most suitable solutions for their specific situations
d) calls for financial resources to be made available for the improvement of pingers, and research into alternative mitigation measures and alternative gear types
e) includes an adequate monitoring and support system to ensure that mitigation devices like pingers are maintained adequately and that their efficacy is checked
3) ASCOBANS parties should create incentives for the development of environmentally friendly, sustainable, fishing methods.
Further information on the events of the workshop can be seen here.
For details on ASCOBANS and mitigation measures for by-catch in Europe visit www.ascobans.org.