A television and photographic survey of megafaunal abundance in Central Sognefjorden, Western Norway

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Abstract
The abundance of megafauna was estimated at two locations in Sognefjorden, western Norway, using television and still photography. The analyses revealed differences between the methods as well as between the two locations, the central trough (water depth about 1250 m) and H0yangsfjorden (water depth about 290 m), a shallow side arm of Sognefjorden. Density estimates from the photographs were generally higher than from the videos. The elevation of the camera also influenced the estimates, a shorter bottom distance leading to higher numbers. The predominant animals at both locations were decapod crustacens of the genus Munida: M. sarsi in Høyangsfjorden and M. tenuimana in the central trough. Megafaunal density appeared much higher in the central trough, but the results were probably obscured by the burrowing behaviour of decapods in Høyangsfjorden. The high dominance of a decapod crustacean in deep Sognefjorden is in contrast to observations from similar depths at the continental slopes and resembles depths shallower than 1000 m at these ‘normal’ deep-sea environments.