Page 21

Sharks - Free Sample

Complex Social Behavior The front of the cephalofoil is kidney shaped and has a notch in the middle. The short, inner nos-tril does not extend to the center of the front edge of the head (unlike the smooth hammerhead shark). The base of the anal fin is longer than the base of the second dorsal fin. The end of the second dorsal fin is elongated, extending to the base of the tail. Large schools of up to 500 female sharks of all ages have been observed aggregating over sea-mounts off the Gulf of California. The sharks exhibit complex social behavior and communicate with at least nine different movement patterns to gain the highest social position, which is in the middle of the school. The schools disband at night. The sharks leave the seamounts, focusing on 20 km long hunting trips, later returning in the morn-ing hours to circle around "their" seamount. The sharks orientate themselves according to the geomagnetic fingerprint of welled lava on the ocean floor during their daily excursions. For the sharks, these disruptions of the geomagnetic field appear to be the equivalent of city limit and exit signs on our highways. Females reach maturity at a length of 2.5 meters and a weight of about 80 kg. The fish give birth after 9-12 months. Up to 38 embryos are initially nourished by a yolk sac during the gestation pe-riod. Three to four months before birth, the now empty yolk sac interdigitates with the lining of the mother shark's placenta and the babies are then fed directly by the mother. The females take a year off after birth to rebuild energy stores. Scalloped hammerhead sharks are also known to react in emergencies: Pregnant females caught by anglers repeatedly release embryos during their last fight hooked on the gaff, but these are often too small to survive. Scalloped hammerhead sharks can reach a length of 4.3 m and a weight of 152,4 kg, as well as an age of 35 years or more. The shark is common only off Eastern Australia. The International Union for Conservation of Nature and Natural Resources (IUCN) added it to their Red List in 2009, classifying it as globally endangered. 77


Sharks - Free Sample
To see the actual publication please follow the link above