Subject: marine food webs

Nancy Stevick (Nancy.Stevick@btinternet.com)
Wed, 26 May 1999 22:09:14 +0100

On  26 May 1999 01:13, Jennifer Hoffen wrote:


>Dear Ms. Stevick,
> I am amazed with all of the wonderful things you have done with
>whales and other marine life.  I am a freshman in high school and I was
>wondering if you know anything about food pyramids, chains, or webs of the
>ocean.  Any information would be greatly appreciated.


Jennifer,

Marine food webs are very complex and difficult to explain in simple terms.
For example, think of the food chain associated with an individual marine
mammal species such as the minke whale.  They feed on euphausiid shrimp
(krill), copepods, sand eel, salmon, capelin, mackerel, cod, coalfish,
whiting, sprat, wolffish, dogfish, pollack, haddock and herring.  Each of
these prey species, in turn, have a food web of their own which you would
need to associate with the minke whale's food web.  As you can see, it
becomes much more complex than simply saying that phytoplankton are eaten by
zooplankton which are fed upon by small fish, which are fed upon by larger
fish, etc.

I would encourage you to contact David Lavigne, 3 Paisley Street, P.O. Box
515, Guelph, Ontario, N1H 6K9.  Many Canadian fishermen and government
officials believe that seals are primarily responsible for the decline of
cod stocks.  Lavigne worked out a food web for cod and seals which shows
that it is impossible to prove that seals alone are the prime culprits.
There are simply too many other prey and predator species involved in the
process.  This web illustrates the complexity of the issue of food webs very
eloquently.

I did not have much luck searching the Internet for good sites on marine
food webs.  Here are a few that might be useful for you.  They tend to deal
with fisheries issues.  You might have better luck choosing a single marine
species and working out a food web just for that particular species.


 http://www.cgiar.org/ICLARM/fishbase/trophic/Default.htm

 http://www.sciencenews.org/sn_arc98/2_7_98/fob1.htm

 http://www.stockton.edu/~cromartw/ecoprinciples/28foodch.htm

Good luck with your research.  If you have more specific questions, please
feel free to send another e-mail.

Nancy