From: ray@tsw.UUCP (Ray Izumi)
Newsgroups: rec.scuba
Subject: Re: Sharks: Search and destroy???  (listen up!)
Date: 20 Nov 92 15:29:02 GMT
Organization: The System Works, Redmond, WA

In article <1992Nov20.034615.10362@reed.edu> pbray@sloth.Reed.Edu (Peter Bray) writes:
>
>	Actually tiger sharks are assumed to have a nil effect on  
                                  ^^^^^^^
Assumed by whom? Do you have a source for this statement?

>population dynamics in the food chain due to their relative rarity and  
>vast territory ranges (anywhere in the ocean).  Furthermore, as you should  
>know, there is little predation on the tiger shark except by other tiger  
>sharks and whites. Statistically the tiger shark is the most dangerous  
                    ^^^^^^^^^^^^^
Once again, do you have some supporting documentation for this? There are
many dangerous critters in the oceans. Statistically, considering such
things as confidence limits, I would guess that this statement is entirely
unsupportable. It is easy to be misled by statistics if you don't understand
the mathematical rigors involved.

>aquatic animal to man.  Yes, we do not own the ocean; but since we have  
>the ability to minimize some of the dangerous aspects of the sea I do not  
>really see the debate. 

So, following this logic (reductio ad absurdum), we should eliminate every
oceanic animal (why limit ourselves - let's go after poisonous seaweeds too!)
that might conceivably harm any human who happens to get in it's way. For
instance, let's get rid of all clams, since they can harbor red tide toxins.
Atlantic Bluefish can be very nasty too, so they must go. Etc., etc.

> Conservation biology is seriously flawed in this  
>respect since controlling wide spread growth of tiger shark population is  
>a boon to all other species including the other large predators (white  
>etc.).

Whenever I hear an argument like this one, I think of the implications of
chaos theory, which basically says that a very small change in initial
conditions can lead to very large and essentially unpredictable changes
down the road. And our history of meddling with ecological systems can
offer many excellent examples. So it seems logical and prudent that we
should think long and hard before we tamper with any complex ecological
system.

>	Actually tiger sharks do pose a great threat to scuba divers.  The  
>orienting ability of the shark is not chiefly governed by thrashing  
>surface swimmers (or fish); but depends on many aspects, such as the  
>gellike substance (lorenzii) in the nose of the shark that detects minute  
                    ^^^^^^^^
You are referring to the ampulae of Lorenzini.

>pressure undulations in the sea water.  Unlike other sharks, which circle  
 ^^^^^^^^^^^^^^^^^^^^
The ampulae of Lorenzini detect variations in an electrical field.

>in the past.  The tiger shark WILL attack scuba divers.  It does not have  

Any shark, and many other animals, WILL attack scuba divers. Let's try to
keep a little perspective here.

> something about the mako being essential to the food chain...

So the mako is essential, but the tiger is not. I didn't realize that
biology had reached a state where we can precisely determine the relative
usefulness of every species.

>slaughtered for no apparent reason except for some wealthy Japanese  
>business men to make 10$/pound from the dorsal fins to make shark fin  
>soup.
>
For once I agree with you.
-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Ray Izumi, The System Works, Redmond, WA     206-823-4685      uunet!tsw!ray
"Put the pillow over your head, scream and cry - the garbage is coming!"
           - New York City Commissioner of Sanitation
Newsgroups: rec.scuba