Report by Shark Info
One enormous problem encountered in trying to protect selected shark
species is the lack of knowledge on the migratory behavior of
individual species. During their migrations, sharks pay no attention
to political boundaries, while unfortunately catch and usage
regulations of these animals do.
In this study the migratory behavior of six whale sharks in the Sulu
Sea region was registered by satellite telemetry between 7 to 128
days. Each of the animals swam a distance of 4,567 km, i.e. 8,025
km, crossing several political boundaries in their migrations. The
acquired data proves the need to regulate the economy and the
protection of whale sharks multilaterally, or at least on a regional
Source: Movements of whale sharks (Rhincodon typus) in
South-east Asian waters as determined
by satellite telemetry (2002). Journal of Zoology 257 pp 111-115.
The Dry Tortugas Region of the Florida Keys represents a very
important area for the reproduction of nurse sharks where many of
the animals have been observed. Using molecular biological methods
the paternity of 32 descendants of one mother animal were examined.
Results showed that the young pups had at least four different
fathers. This multiple paternity strategy most likely increases the
genetic diversity of a population on a short-time basis which in
turn appears to be most valuable for species with limited migratory
Source: Multiple paternity in the nurse shark,
Ginglymostoma cirratum (2002). Environmental
Biology of Fishes 63 pp 347-351.
Determining the age of long-living pelagic sharks is particularly
difficult. It is known that sharks take up radioactive material in
their food chain and partially store it in various tissues. This is
true for porbeagle sharks (Lamna nasus) who store it in their
cartilaginous vertebrate tissue. Such deposits lead to measurable
growth rings or bands which are characteristic for a certain time
period time, similar to those of trees which reflect the relevant
The growth rings found in animals from the 60s corresponded with
animals found later on and thus made it possible to calibrate the
growth rings of porbeagle sharks up to at least the age of 26.
Source: Bomb dating and age determination of large pelagic sharks (2002) Canadian Journal of
Fisheries & Aquatic Sciences 59 pp 450-455.
Registering species is difficult, even for specialists. On the one
hand some species are so rare that even sighting them may be purely
accidental, making it just as accidental for the relevant specialist
to even find out about it. On the other hand, species can resemble
each other to such a degree that they can be assessed as being a
variation of one single, so-called cryptic species.
As concerns the above-mentioned species from West Australia,
Parascyllium sparsimaculatum (meaning the sparsely or weakly spotted), the differences to the next similar species ascertained through
morphological measurements are proven and cannot easily be
recognized without mathematical aids. Up until now only three
specimens of this species have been scientifically registered and
published as such. The authors provide an identification key which
includes and comprises those species in the group which can be
confused with each other.
Source: A new parascylliid species, Parascyllium sparsimaculatum, from Western Australiua
(Elasmobranchii: Orectolobiformes). Ichthyological Research, 2002, 49, pp 15-20.
May be published only by indicating the source: Shark Info