Subject: Re: undersea colonization

Greg Early (
Fri, 06 Nov 1998 13:34:44 -0500

At 09:32 PM 10/20/98 -0700, you wrote:
>Dear Mr. Early,
>	I am writing a "scenario" about the troubles a dolphin pod may face due
>to pollution and overfishing, set 40 years into the future. What might
>happen if a dolphin ate a toxic fish? How are people trying to stop
>pollution and overfishing? Do you think it will work? Please write back.
>Thank you in advance for your help.
>			Sincerely,
>			Jill Murdoch 
>			6th grader


First apologies for not getting back to you sooner.  Fish can be toxic in a
couple of ways.  First the fish may just be toxic itself (some types of
puffer fish are poisonous for people, and I would assume dolphins to eat).
Secondly, fish can pick up toxins that occur naturally, generally through
the food they eat.  This is , in fact what we think happened to the
humpback whale in the picture of me on WhaleNet.  We think these whales
were feeding on some fish that became unusually toxic from eating other
fish that had eaten a small toxic single celled plant.  These single celled
plants grow naturally in the ocean, although they may "bloom" more when
exposed to freshwater and nutrient rich runoff from rivers (so people may
play an indirect part in this as well).

The third way would be from man made chemicals that get into the ocean.
The good news is that people are more aware of many of the worst things and
have been working to limit the amount that goes into the ocean.  The bad
news is that some of these things still get into the ocean, and some do not
go away very readily.

Although you would think that man made chemicals have been shown to do the
most damage, there is still quite a bit of controversy about how much harm
they do (and have done).  We do know that dolphins and whales tend to pick
up these chemicals through their food.  What we do not know so clearly is
how much trouble they can cause.

As for over fishing.  It is a complex problem, because while many areas are
or have been over fished, fish are very important food for people (some of
which have little other choice for food).  Also, stopping fishing in an
area that has been over fished does not always mean that the fish will come
back the way you want.  Mostly, because people can have such a big effect
on fish populations, I think we need to learn better ways to both fish and
leave enough fish for the rest of the ecosystem.



Greg Early
Edgerton Research Laboratory				
New England Aquarium
Central Wharf
Boston, Mass 02110
617-973-5246 (phone)
617-723-6207 (FAX)