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Shark Info 3 / 01   (09-15-2001)

Author

  Intro:

Accident analysis as a measure for active shark protection

Shark Info

  Main article:

Accident analysis as a measure for active shark protection

Dr. E. K. Ritter

  Article 1:

Is fear of sharks justified?

Nihal Özkara

  Article 2:

Annual Meeting of the American Elasmobranch Society (AES)

Jürg Brunnschweiler

  Article 3:

Meaningful usage or overexploitation?

Harald Gay

  Fact Sheet:

Mackerel Sharks

Dr. E. K. Ritter


Annual Meeting of the American Elasmobranch Society (AES)

By Jürg Brunnschweiler

This year's 17th Meeting of the American Elasmobranch Society (AES) from July 5 to 10 was held for the second time since 1999 in the State College of Pennsylvania, USA, in the scope of the annual meeting of the American Society of Ichthyologists and Herpetologists. Approximately 450 scientists attended the meeting, the majority from the U.S., and presented their research results on the biology of sharks, bony fish, amphibians and reptiles.

During the AES meeting, sessions and symposia were held on such themes as fishery and fish populations, behavior and ecology, immunology, biochemistry and physiology as well as the cultural presentation of sharks in art.

The purpose of such presentations is to present and discuss the research projects and findings of scientists from other institutes and universities. Often the results and conclusions are only mentioned in passing, while more emphasis is placed on presenting the methods and working techniques used to gather the data, a procedure which can be very significant, especially for those who work with sharks. As was shown again this year, it is still very hard to collect data on sharks in their natural environmental for scientific purposes. The exchange of ideas can thus provide valuable tips on possible difficulties.
In this regard and similar to past years, the importance attached to the so-called "tracking" method was obvious. With this method sharks are caught and equipped with various types of transmitters which send out signals which are received with special equipment on the water's surface, e.g. from a boat. In this way sharks can be observed as to when, where and how deep they swim. Such movement patterns can provide valuable indications on a shark's behavioral patterns as well as his daily and annual locations, i.e. migrations. The results of numerous projects based on this method have been impressive with regard to the amount of data collected, although in most cases a scientifically relevant conclusion was missing. The value of such studies thus remains questionable unless results are put into the context of ecological behavior.

Nevertheless, in some cases this tracking method can really deliver valuable data on the biology and behavior of sharks, for example on species which live in great depths of water or in cold waters and which are difficult for biologists to observe directly. One example is a study performed on Greenland sharks Somniosus microcephalus which live in deep waters underneath the Arctic ice. Practically no information is available on their behavior. U.S. scientists succeeded in following six Greenland sharks for 5.5 to 31.4 hours by means of acoustic transmitters. The results of these observations appear to indicate that these sharks swim out of deep into shallow waters during the night, perhaps in search of food. Greenland sharks feed at least partially on marine mammals living in shallow waters.

Very few scientists present studies in which sharks were directly observed in their natural habitat, although these would be the most valuable in helping to achieve the objective of understanding the various aspects of a shark's behavior more comprehensively. Two biologists who researched the mating behavior of nurse sharks Ginglymostoma cirratum around the Florida Keys show how impressive and informative such observations can be. For several years they filmed these sharks as they were mating. Their repeated observations enabled them to identify ten behavior patterns in connection with their reproduction which, when analyzed, impressively showed that sharks have an extremely multifacetted mating repertoire. Nevertheless, the fact that such past observations on mating behavior were made almost exclusively with nurse sharks prevents an objective estimate of what the described behavior means for other shark species. One of the biggest challenges for shark biologists is thus to observe and analyze the mating behavior of other species and compare these with already existing research findings.

This year two symposia were held which are worth mentioning. The first was titled "Nonfisheries- related human impact on elasmobranchs" and dealt with man-made influences and disturbances on shark populations. Such disturbances are frequent and complex. Take, for example, South Africa and its Aliwal Shoal area - a famous diving area for the observation of numerous sand tiger sharks Carcharias taurus. A stationary underwater camera was installed in the vicinity of an underwater cave used by sand tiger sharks as a resting place. Sharks can perceive weak electrical fields with their special sensoric organs and most likely are even attracted by such fields. As it turned out, an increasing number of scuba divers who were aware of this haven for many sand tiger sharks began to dive more frequently to the cave. This resulted in several incidents with these sharks who are known for being harmless animals. But the sharks were continually and increasingly disturbed by the divers until they finally disappeared from the area. In addition to investigating the influence of the direct presence of scuba divers, a study is now being made to ascertain how strongly sharks are attracted to electrical underwater apparatus and possibly negatively influenced by them.

Additionally touched upon potential disturbances for shark populations are poisonous substances and food which people dump into the area. While the first is unquestioned and at most leads to problems with the quantitative registration of such pollution, the feeding of sharks is often connected with diving tourism and gives rise to discussions. The spokesmen mutually agreed that the extensive usage of food as bait to attract sharks can change their behavior. On the other hand this method is also useful in collecting scientific data on sharks, and often it is the only way of observing them in sufficient number. Another aspect of touristic shark feedings which deserves mentioning is the educative effect it has on divers as a result of encounters with sharks in their natural environment. All in all, a positive picture with some reservations was presented and agreement was reached that shark feedings and the resulting effects on their behavior must be researched more precisely by the scientific community.

The second symposium bore the title "From icons to art: the cultural significance of sharks and man". This remarkable series of lectures left room for contributions which are usually rare at such events. For once shark biology became secondary, replaced by contributions on the meaning and presentation of sharks by the old Greeks or on the origin of the English word "shark" and the Spanish word "Tiburn". Worthy of mention was a talk on the symbolism of freshwater sharks and sawfish in northern Australian aboriginal societies. In a captivating manner the lecturer pointed out the role these animals play in religious symbolism and how, even today, they are worshipped as the creators of the various river systems in northern Australia. Contrary to our western culture, these societies advocate their protection because they consider sharks and rays important for the maintenance and functioning of the ocean ecosystem.

* Jürg Brunnschweiler, Project Manager, Green Marine, Miami, FL

May be published only by indicating the source: Shark Info / Jürg Brunnschweiler



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