whales and prey

From: Phil Clapham (pclapham@mercury.wh.whoi.edu)
Date: Thu Oct 21 2004 - 16:51:34 EDT

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    hi

    well, you certainly know how to hit the difficult questions! that
    question is the big one in whaling politics, because japan claims that
    whales take too many fish and therefore they're in compteition with human
    fisheries (and therefore need to be culled). none of this makes any
    sense; if it did, human fisheries should be doing really well right now
    after whaling greatly reduced populations of whales, but they're not.
    human overfishing by japan and others is the reason for declining fish
    stocks, not whales. and the biggest predators of fish are not whales, but
    other fish.

    anyway, there's no clear answer to your question. the whaling industry
    removed maybe 80% of the whales from the Antarctic in the 20th century
    (95% for some species like blue whales), and most of those animals fed on
    krill. with them gone, that should have prompted what's called
    "competitive release" - you get rid of one predator, and there's a lot
    more of the prey to go around for other species. this may have happened
    in the antarctic, where some other krill-eating critters became more
    abundant after whales were removed; but it's a VERY complicated ecosystem
    relationship and no one entirely agrees on the outcome.

    this probably doesn't help, but i'm afraid there's no straight answer!

    phil clapham

    -- 
    Phillip J. Clapham, Ph.D.
    Large Whale Biology Program
    Northeast Fisheries Science Center
    166 Water Street
    Woods Hole, MA 02543
    

    Tel (508) 495-2316 Fax (508) 495-2066

    > hey, its Amey again > i was just wondering if you could help me with something again. > ok the question is: > seals and blue whales are hunted for fur and blubber. if these species > were to become extinct, what effect would this have on the food web > (food web includes = killer whale, phytoplankton, birds, penguins, > fish, and krill) > > thank you for your time. im sorry bout troubling you. if you could > answer it i would be very greatful. > > cheers , amey



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