BBC Fishing 'major threat' to turtles

[Guest guest]

>

>SCIENCE/NATURE

>

> * Fishing 'major threat' to turtles *

>Ocean longline fishing is a greater threat to

>turtles than previously believed, according to a

>study.

>Full story:

>http://news.bbc.co.uk/go/em/-/1/hi/sci/tech/5005548.stm

>

Fishing 'major threat' to turtles

By Richard Black

Environment Correspondent, BBC News website

 

 

The endangered loggerhead turtle may face a

greater threat than previously realised from

longline fishing.

 

Researchers found that many turtles spend

considerably longer in the open ocean, where

longline boats operate, than earlier studies had

indicated.

 

The boats aim to catch big predatory fish such

as tuna and marlin, but accidentally snare other

species including turtles and albatrosses.

 

The new research is published in the journal Current Biology.

 

Until now scientists have believed that young

turtles live in the open ocean, but change to a

coastal habitat when they reach a certain size.

 

But researchers working in Cape Verde found that

most adults nesting there retain their open water

behaviour, with the attendant risk posed by

longline boats.

 

" The bottom line is that we thought juveniles

experienced this risk out in the open ocean with

longline fisheries, " said Brendan Godley from the

University of Exeter.

 

" We thought that if you got them past that, then

unless they're being taken by inshore fisheries,

you're OK, " he told the BBC News website.

 

" But now you've got adults exposed to longline

fisheries, which is very worrying. "

 

Twin lives

 

Longline boats trail fishing lines tens of

kilometres long, with baited hooks at regular

intervals to catch some of the biggest and most

powerful fish in the oceans.

 

Sea birds and turtles are among the other creatures caught accidentally.

 

With several thousand longline boats in

operation, US scientist Larry Crowder has

calculated that 1.8m hooks are set each night,

and that a loggerhead turtle has about a 50%

chance of encountering one each year.

 

Loggerheads (Caretta caretta) are categorised

as Endangered on the internationally-recognised

Red List of Threatened Species.

 

In theory, the turtles should be safe from

longline vessels once they reach maturity, with

research indicating that at an age of about 15

and a length of about 50cm they swap open water

for a coastal environment.

 

" [The young ones] venture out into the open

ocean, and that's thought to be because they hide

in the open - the shore environment is the worst

place to be for predatory fish, " said Dr Godley.

 

" Then, we thought, they would grow to a size

where if they come near to the shore they can

deal with it, diving to 20 or 30 feet (six to 10

metres) [to hide from predators]. We always

thought they moved into the inshore environment

because the food supply is more reliable. "

 

Using satellite transmitters placed on the

turtles to follow their movements - a technique

pioneered by the conservation group

seaturtle.org, which co-funded the research - the

team found that most of the adults did not make

this switch.

 

Most of the adult loggerheads swam in open water

A minority journeyed to more fertile inshore feeding grounds

Bigger individuals did, while smaller ones stayed away from the shore.

 

This means, the researchers say, that attempts

to conserve them will have to focus even more

closely on longline boats.

 

Bird conservation groups have developed a set of

simple measures which they say can substantially

reduce the annual bycatch of albatross, thought

to number about 100,000.

 

These include trailing streamers behind the

boats to scare birds away, weighting hooks so

they stay below the surface, and fishing at night.

 

A similar set of measures to discourage

loggerheads may not be so easy to develop, though

keeping hooks deeper than the turtles usually

dive may be one option, as may using

blue-coloured bait, which they do not see as

easily.

 

Richard.Black-INTERNET

 

Story from BBC NEWS:

http://news.bbc.co.uk/go/pr/fr/-/1/hi/sci/tech/5005548.stm

 

Published: 2006/05/23 14:23:25 GMT

 

© BBC MMVI

 

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