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Shark Info   (10-15-1999)



Circling around alleged victims

Shark Info

  Main article:

Shark Behavior: Circling around alleged victims

Dr. E. K. Ritter

  Article 1:

What do you know about shark brains and noses?

Dr. J. F Morrisey

  Article 2:

Film Review: Deep Blue Sea

Shark Info

  Article 3:

Annual Shark Congress in Pennsylvania

Shark Info

  Article 4:

Weak shark protection

Shark Info

  Fact Sheet:

Bull Sharks

Dr. E. K. Ritter

Annual Shark Congress in Pennsylvania

Report by Shark Info

This year's AES Congress (American Elasmobranch Society) took place between June 14 and 20 in Pennsylvania, USA, and was supported by the ASIH (the American Society of Ichthyologists and Herpetologists). Research studies on sharks were presented on four days of the Congress. Main themes included biochemical research, analysis of fishing tactics and general research into shark breeding grounds. Scientists from the U.S., Brazil, Japan, France, England, Mexico, Spain, Australia and Sweden were present. Dr. E. K. Ritter attended on behalf of Shark Info and the Shark Foundation. We will address some of the themes presented in more detail in some of the following issues.

Nurseries and breeding grounds

This theme was the subject of several presentations. A joint study known under the name COASTSPAN (Cooperative Atlantic States Shark Pupping and Nursery Survey) and conducted by several American institutes and work groups deserves special review. During the study more than 770 sharks were caught and tagged within a year. The most frequently caught species included sandbank sharks (Carcharhinus plumbeus), bull sharks (C. leucas), Spinner sharks (C. brevipinna) and Atlantic sharp-nosed sharks (Rhizoprionodon terraenovae). The objective of the investigation was to find the locations of shark species. Between 70 and 80% of all shark species bear their young in coastal regions. Destroying these zones through pollution, building developments or other changes can lead to the loss of these areas as breeding grounds and nurseries. This would force female sharks to bear their young in deeper waters, thus exposing their pups to predators. Finding out where certain shark species swim to bear their young is thus important.

Other presentations addressing the same themes indicate that young sharks tagged with radio transmitters have a relatively limited habitat. This recognition would indicate the need to define close seasons for these areas which would ban boat traffic and other water-related activities (also see SI 2 / 99"Jeopardized Nurseries").

Within the same framework it was demonstrated that certain shark species probably have a considerably larger area of distribution than assumed so far, not only geographically but also with regard to ocean depth. This knowledge stems from the NOAA (National Oceanographic and Atmospheric Association) which conducts annual catches and the respective taggings.

Methods to prevent poaching

A very remarkable piece of work was submitted by scientists from Nova Southeastern University. They generated a method to quickly identify certain shark species based on the application of small tissue probes. Much time and research had gone into finding such an identification method since more and more shark species are protected or submitted to catch quotas. Often, however, the identification process would break down in harbors or in the hands of dealers because the animals were usually processed on the high seas, leaving only fins or processed bodies (without heads or fins) which can no longer be identified by lay people. This new technique permits checkpoints to identify individual species without specific knowledge on sharks.

Peripheral themes

Presentations on palaentology (extinct sharks and their evolution), behavior or shark systems were barely represented. One piece of work addressed the evolution of the "hammer" native to "hammerhead" sharks and their size compared to the currently eight known hammerhead shark species. Another study discussed the difference in teeth between the white sharks (Carcharodon carcharias) and the extinct giant white sharks (Carcharocles megalodon), often only referred to as the megalodon. This particular piece of work indicated that the two species could only be remotely related and that the megalodon cannot be considered the predecessor of the white shark (see SI 1 / 98 " Carcharocles megalodon - a potential predecessor of Carcharodon carcharias?).

The only presentations on shark behavior were made by Dr. Erich K. Ritter and dealt with such aspects as domination within and between species, threatening gestures of blacktip sharks (Carcharhinus limbatus) and their origin.

May be published only by indicating the source: Shark Info



last change: 06-04-2016 11:48