Hi, I'm doing a report on the whale net website and I have a few questions.
One specifically about harbor seals. "What are scientists trying to learn
about Harbor Seals?" and Why is it importat to study marine mammals in the
wild? What impact do they have on human life? I'm really interested in the
marine mammal world. I'm hoping you could help me out
We are finding that whales are a good indicator of the health of the seas.
Whales (especially toothed whales such as sperm or killer whales) are top
order predators, meaning that they eat the large fish which eat the smaller
fish and so on down the food chain to the primary producers. In all, they
top about seven levels of prey items, as do humans. The oceans have been
contaminated by human-created chemicals. Because these chemicals are not
found in nature, animals have not had time to adapt to break them down.
Instead, they accumulate in the fats of animals. When a predator eats a
prey item, it ingests all of the toxins that that animal has ingested
through its lifetime. It is estimated that the levels of toxins in animals
increases tenfold for every step in the food chain, so a whale (or human)
eating at the top can ingest 10 million times the toxins that the first
animal ingested. These chemicals are also passed from mammal mother to
child through the fats in her milk, so young animals start out in life with
approximately the same level of toxins in their bodies as their mothers had.
In the US, we consider anything with 50 parts per million of organohalogens
(a toxicant) to be toxic waste. Beluga whales in the St. Lawrence river
have been found with 6900 parts per million in their bodies and must be
disposed of carefully.
As we learn more about whales, we also learn more about our oceans and the
threats we humans are posing to life in the oceans and to ourselves.
In regards to the harbor porpoise I suggest that you go to WhaleNet's
species/classification pages at
http://whale.wheelock.edu/whalenet-stuff/classifications.html. Here you can
find out what kinds of research are being conducted on harbor porpoises. I
believe there are many studies on the interactions between harbor porpoises
and coastal fishing practices like gill netting etc.
Thank you for your question and good luck on your project.
(Encompassing the Whale Conservation Inst. & the Voyage of the Odyssey)
191 Weston Road, Lincoln, MA 01773
781-259-0423 x 14 fax: 781-259-0288
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