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ABSTRACT: Investigations of shark habitat use and foragingecology have been hampered by inaccuracies inherent inmany current methods. Although catch rates and acoustictelemetry may be appropriate for studying habitat use at abroad geographic scale, they are often not adequate for finescale determination of habitat use. Also, these techniquescannot provide data on how sharks behave in different habitats or on feeding behavior or social interactions. In this paper,we present a method that allows analysis of shark habitat useusing an attached underwater video camera with an integrated time-depth recorder ('Crittercam'), which providesaccurate, and continuous habitat use data on a fine geographic scale, as well as a record of shark behavior. Deployments on tiger sharks that were tracked simultaneously (n =22) show that habitat use estimates of individual sharks maydiffer between Crittercam and acoustic tracking data. However, average habitat use measured by acoustic tracking maybe accurate if sample sizes are large.

In this lab you will study the anatomy of the shark. Humans are fascinated by sharks. We are at once repulsed and attracted to these predators. We fear them, often unneccessarily, because they are so at home in an environment in which we are so ungainly. They are fishes that are highly adapted to the ocean environment and their movements are a study in grace. They have survived for millenia in a form which is as successful now as it was when dinosaurs walked the Earth.

The shark's liver makes up as much as 25 % to 30% of the entire body mass of the animal. Squalene is a natural compound that all animals produce. It is a hydrocarbon and triterpine and...

Fish of five species of deep-sea squaloids (Centrophorus squamosus, Centroscymnus coelolepis, Dalatias licha, Deania calcea and Etmopterus princeps) and one-deep sea holocephalan (Hydrolagus affinis) were all found to float when brought to the surface and placed in surface or laboratory sea water. However, by taking account of the effects of salinity, temperature and pressure differences between this sea water and that in which the animals lived, it is shown that all these animals must have been very close to neutral buoyancy at the bottom of the sea. Every one of these fish had an enormous oily liver and the lift which this gave almost exactly compensated for the weight in sea water of the rest of the animal. These livers contained large amounts of the hydrocarbon squalene which is not a convenient material to have as a metabolic reserve but which, with its low specific gravity (0· 86), is particularly suited to give lift, being 80% more effective per unit weight for this purpose than cod-liver oil. It is calculated that because of this unusual oil such fish not only obtain the lift needed for neutral buoyancy more economically in terms of the weight of oil required, but also in terms of the metabolic energy which has to be used to provide the oil-store responsible for buoyancy. It is argued that these fish must carefully regulate the oil content of their livers so as always to balance exactly the weight in sea water of their other tissues. The mechanism whereby they do this is not known.

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