From: pbray@sloth.Reed.Edu (Peter Bray)
Newsgroups: rec.scuba
Subject: Re: Sharks: Search and destroy???  (listen up!)
Date: 20 Nov 92 03:46:15 GMT
Article-I.D.: reed.1992Nov20.034615.10362
Organization: Reed College, Portland, OR

In article <18NOV199221412504@trentu.ca> pstonge@trentu.ca (CMDR P.D.  
Keener) writes:
> 	On the other hand, what would the effects of a large scale tiger 
> shark kill be in that area, from an ecological point of view.  Clearly, 
> the population dynamics of that area would be affected - particularly if 
> this species of shark is a higher order carnivore.  The potential  
release 
> of predatory pressures on other organisms directly lower in the food  
chain 
> should be a matter of concern.  After all, what do these sharks normally 
> eat?  It follows that without these sharks, the population of these prey 
> items could skyrocket, outstripping the food available to them, causing 
> another peturbation.  And of the higher order carnivores (what eats  
these 
> sharks?).  Without the tiger shark as a prey item, what alternatives do 
> these other animals have?  We all know that natural systems have a great
> resiliancy for peturbations in population, but this only goes so far...   
Is 
> that mandated agency able to guarantee that a threat exists after all  
other
> possible steps have been taken to segregate the swimmers and the sharks?  
> Has that agency performed an environmental impact assessment with the  
help 
> of marine ecologists to ascertain the hazards involved with such a  
course of
> action?  I'd really like to know...


	Actually tiger sharks are assumed to have a nil effect on  
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  
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.  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.).
	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  
pressure undulations in the sea water.  Unlike other sharks, which circle  
their victims and attack repeatedly, the tiger shark is well-known for its  
sudden attacks on quietly swimming species.  While other smaller species  
pose only minimal threats to humans (blue tipped) the larger tiger sharks  
are by far the most dangerous.  There teeth are specifically serrated for  
cutting through tough protective skin.  It is only due to the relative  
rarity of this Chordata subset that has prevented more attacks on humans  
in the past.  The tiger shark WILL attack scuba divers.  It does not have  
a diet of preference.  You should know, further, that the tiger is never  
"full".  It continually eats and if its stomach fills up it disgourges  
itself by way of reverse peristalis.  
	If you want to talk about something barbarous why not talk about  
the senseless competetions they have in Hawaii each year when thousands of  
mako shark (now this shark is essential to the Hawaiian food chain) are  
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.




		Peter