Studies on Deep Sea Benthic Fishes using Baited Camera Landers:
New Insights 500-10,000m depth.
Oceanlab, University of Aberdeen, Newburgh, Aberdeenshire, AB41 6A, UK.
Autonomous landers have emerged as a potent method for study of active deep sea fishes which are otherwise too dispersed to sample and at depths too deep to be routinely sampled by trawls and other fishing gears. An experimental protocol has been evolved in which a bait (ca. 0.5kg) suspended within the field of view of downward-looking camera is deployed on the sea floor and observations are made of times of arrival of fishes which can then be identified, measured and counted. Making assumptions about the rate of dispersal of food odour on bottom currents and approach speeds of attracted fishes it is possible to calculate the local population density of the dominant species of fishes. Using length-weight relationships estimates of biomass are possible. We also developed acoustic transmitters that are ingested by fishes which can then be following during their movements across the sea floor. Results for species, times of arrivals and population densities from 500m to 10000 depth are also presented. There is a global trend of increase in arrival time and decrease in population density with depth range.