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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 "Tiburón". 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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