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Accidental by-catch: birds, mammals and turtles

Indicator Fact Sheet (Deprecated)
Topics: ,

Assessment made on  01 May 2004

Generic metadata


Water Water (Primary theme)

DPSIR: Impact


Indicator codes
  • FISH 005
Geographic coverage:

Policy issue:  What is the impact of fisheries on habitats, benthos, mammals, birds, and turtles?

Key messages

  • The rate of accidental by-catch of turtles, mammals and birds in the Mediterranean and North Seas demonstrate a negative impact of fisheries on the marine ecosystem.

  • The rate of accidental catch of turtles, mammals and birds in the Western Mediterranean increased between 1999-2000 by 90, 130 and 140 % respectively.

  • The rate of accidental catch of porpoises in the North Sea has remained stable for the period 1990-1997


Key assessment

Cetaceans are often the non-target victims of the fishing industry as, being relatively large, they easily become entangled in fishing nets. In the Celtic Sea, it has been estimated that about 6% of the porpoise population is killed in bottom-set gillnets1. This, according to the International Whaling Commission, is unsustainable (rates above 1% of abundance may not be sustainable and rates higher than 2 % threaten unsustainability). Nevertheless the rate is lower than the 7% rate observed in the mid-1990s.

Current mortality rates of striped dolphins (Stenella coeruleoalba) in the Mediterranean have been considered potentially unsustainable by the International Whaling Commission. Driftnets pose the major threat and the imposed ban in their use at the beginning of 2002 is hoped to aid the recovery of the population.

Data on bird mortality rates in the Mediterranean exist only for the Western Mediterranean, the Spanish fleet being the only one to operate longlines. Cory's shearwater ( Calonectris diomeda) appears to be affected the most with catch rates in 2000 to unsustainable rates ( Cooper et al., 2000) and data from Greece and Malta support this susceptibility.

Turtles in the Mediterranean (Loggerhead (Carreta carreta), Green (Chelonia mydas) and Leatherback (Dermochelys coriacea) are classified as endangered species with fisheries their most serious threat. More than 60 000 are caught annually and mortality rates range from 10 - 50 % (Lee and Poland, 1998). Surface longlines and driftnets pose the major threat although bottom trawls and gillnets are also responsible.

Entanglemet in static fishing gear and abandoned nets (ghost fishing) cause a serious impact on monk seal (Monachus monachus) in the Mediterranean, a population suffering rapid decline despite the fact they are listed as critically endagered species and the only acceptable level of fishing related mortality is in the region of 0 %


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