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 user 2006-11-03 at 1:09:00 pm Views: 43
  • #16721

    ‘Only 50 years left’ for sea fish
    will be virtually nothing left to fish from the seas by the middle of
    the century if current trends continue, according to a major scientific
    study.Stocks have collapsed in nearly one-third of sea fisheries, and
    the rate of decline is accelerating.Writing in the journal Science, the
    international team of researchers says fishery decline is closely tied
    to a broader loss of marine biodiversity.

    But a greater use of protected areas could safeguard existing stocks.
    way we use the oceans is that we hope and assume there will always be
    another species to exploit after we’ve completely gone through the last
    one,” said research leader Boris Worm, from Dalhousie University in
    Canada.”What we’re highlighting is there is a finite number of stocks;
    we have gone through one-third, and we are going to get through the
    rest,” he told the BBC News website.Steve Palumbi, from Stanford
    University in California, one of the other scientists on the project,
    added: “Unless we fundamentally change the way we manage all the ocean
    species together, as working ecosystems, then this century is the last
    century of wild seafood.”

    Spanning the seas
    This is a vast
    piece of research, incorporating scientists from many institutions in
    Europe and the Americas, and drawing on four distinctly different kinds
    of data.Catch records from the open sea give a picture of declining
    fish stocks.In 2003, 29% of open sea fisheries were in a state of
    collapse, defined as a decline to less than 10% of their original
    yield.Bigger vessels, better nets, and new technology for spotting fish
    are not bringing the world’s fleets bigger returns – in fact, the
    global catch fell by 13% between 1994 and 2003.Historical records from
    coastal zones in North America, Europe and Australia also show
    declining yields, in step with declining species diversity; these are
    yields not just of fish, but of other kinds of seafood too.Zones of
    biodiversity loss also tended to see more beach closures, more blooms
    of potentially harmful algae, and more coastal flooding.Experiments
    performed in small, relatively contained ecosystems show that
    reductions in diversity tend to bring reductions in the size and
    robustness of local fish stocks. This implies that loss of biodiversity
    is driving the declines in fish stocks seen in the large-scale
    studies.The final part of the jigsaw is data from areas where fishing
    has been banned or heavily restricted.These show that protection brings
    back biodiversity within the zone, and restores populations of fish
    just outside.”The image I use to explain why biodiversity is so
    important is that marine life is a bit like a house of cards,” said Dr
    Worm.”All parts of it are integral to the structure; if you remove
    parts, particularly at the bottom, it’s detrimental to everything on
    top and threatens the whole structure.”And we’re learning that in the
    oceans, species are very strongly linked to each other – probably more
    so than on land.”

    Protected interest
    What the study does not
    do is attribute damage to individual activities such as over-fishing,
    pollution or habitat loss; instead it paints a picture of the
    cumulative harm done across the board.Even so, a key implication of the
    research is that more of the oceans should be protected.But the extent
    of protection is not the only issue, according to Carl Gustaf Lundin,
    head of the global marine programme at IUCN, the World Conservation
    Union.”The benefits of marine-protected areas are quite clear in a few
    cases; there’s no doubt that protecting areas leads to a lot more fish
    and larger fish, and less vulnerability,” he said.”But you also have to
    have good management of marine parks and good management of fisheries.
    Clearly, fishing should not wreck the ecosystem, bottom trawling being
    a good example of something which does wreck the ecosystem.”But, he
    said, the concept of protecting fish stocks by protecting biodiversity
    does make sense.”This is a good compelling case; we should protect
    biodiversity, and it does pay off even in simple monetary terms through
    fisheries yield.”Protecting stocks demands the political will to act on
    scientific advice – something which Boris Worm finds lacking in Europe,
    where politicians have ignored recommendations to halt the iconic North
    Sea cod fishery year after year.Without a ban, scientists fear the
    North Sea stocks could follow the Grand Banks cod of eastern Canada
    into apparently terminal decline.”I’m just amazed, it’s very
    irrational,” he said.”You have scientific consensus and nothing moves.
    It’s a sad example; and what happened in Canada should be such a
    warning, because now it’s collapsed it’s not coming back.”

    1. Experiments show that reducing the diversity of an ecosystem lowers the abundance of fish
    Historical records show extensive loss of biodiversity along coasts
    since 1800, with the collapse of about 40% of species. About one-third
    of once viable coastal fisheries are now useless
    3. Catch records
    from the open ocean show widespread decline of fisheries since 1950
    with the rate of decline increasing. In 2003, 29% of fisheries were
    collapsed. Biodiverse regions’ stocks fare better
    4. Marine reserves
    and no-catch zones bring an average 23% improvement in biodiversity and
    an increase in fish stocks around the protected area.