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.
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
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.
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.
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