~ Alan Hart ~

Alan is a marine biologist working for NIWA in New Zealand. His area of expertise and main focus is on the commercially important New Zealand fish species, mainly orange roughy and oreos. These species occur between the depths of 600 to 1200 metres on the slope, and on undersea hills offshore. They school in very large numbers in order to feed and spawn. Thus, they are able to be harvested easily by man. NIWA provides research to ensure that the numbers of fish caught do not exceed levels that are sustainable into the future.

Measuring the population size of animals that live so deep in the ocean provides many challenges. Various techniques are used in our research. Traditionally trawl surveys have provided estimates of the health of populations. This involves randomly trawling a net along the bottom within an area in which the species are known to occur. The results of this are used as a representative sample of the fish populations and multiplied up to provide an estimate of the overall population. More recent techniques involve the use of acoustic technology. Sound waves are emitted by a towed acoustic transmitter. These waves travel down through the water column and bounce back off any fish or other animals within the beam. A large school makes a large echo of sound to the acoustic receiver.

As a biologist, Alan tries to solve the problems by analysing the data gathered from measurements of acoustic backscatter: what species of fish are within the sound beam, where those fish are in the water column and what the fish's target strength is (how much sound does the fish reflect back). Being on this expedition is helpful in my research; apart from identifying the fish and animals encountered on the Giant Squid Expedition, I enjoy seeing many familiar fishes alive for the first time. It's fascinating to observe the behaviour of many of the fish, how far off the bottom they are and at what angle they are swimming. This gives us good clues for acoustic analysis; which fish are off the bottom and their angle of swimming which relates to their target strength. It has been a real privilege to see some of these deepwater fish and associated benthic animals.