Subject: sharks and nature's balance

Dagmar Fertl (
Mon, 04 Oct 1999 08:20:28 PDT

I am an avid diver and I have dove with sharks like jaque Qeusto? But I dont 
like big sharks,I recently had a real close call with a giant bull shark. I 
dont think we should kill of all sharks but if you could explain to me the 
ramifications of killing sharks to the eco system.  I feel that pollution 
and over fishing  would also have a tremendous impact.  Do we really need 
sharks? Like I said I wouldnt want to eliminate sharks but every time i hear 
someone defending them I hear them say that it will throw of the balance of 
nature.  Back to the Human Factor concerned diver, fisherman, Sportsman JC 

Thanks for your question about sharks and their role in the ecosystem. Our 
concern about other species is not only our recognition of their intrinsic 
importance (e.g., we feel some sort of special tie or relationship to 
them...people usually identify with 'cute' animals like dolphins and whales, 
fuzzy seals, etc.).  We depend on many animals (like sharks) for food and 
medicine (some people say that sharks can cure cancer), etc.

Basically, balance of nature means looking at biological diversity - the 
numbers of different species of plants, animals, etc. that occur. Every 
animal, etc. has a purpose for its being around. Conservation is not only 
important at a species level, but at a population level and a genetic level.

It seems that you would be in favor of removing large sharks because they 
scare you. But sharks provide an important service in the food web of the 
marine ecosystem...they are top-level predators (in many cases) and food for 
other large predators (like other sharks, killer whales, people, etc.).  Let 
me give you an example where removing large sharks had some interesting 
repercussions.  Removing large sharks off South Africa to protect human 
swimmers led to increases in the numbers of small sharks they eat, hence to 
reductions in other fishes on which the small sharks prey.  Those smaller 
fishes might well be fishes that humans are interested in targetting for 

Sharks are long-lived animals that take a while to become reproductively 
mature (kind of like whales and dolphins). This makes them very vulnerable 
to removal, because it takes a long time to replace them (versus something 
lower on the food chain that has a shorter life span and greater 
reproductive potential).

Basically, humans have a poor understanding still of how food webs work, so 
removing an animal has a domino effect that we don't fully comprehend.

Also, does one animal have some greater importance in regards to 'saving'? 
Why do we always hear about people wanting to save whales and dolphins, but 
not sharks? Because one is 'cuter' than the other? Because we're scared of 
one and not the other?

But back to your description of the bull shark. Those are very aggressive 
sharks, which are one of the bigger predators of dolphins. Glad you came out 
of that encounter favorably!

Hope the above answers your question ok.

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