Where are all the coral trout?

Abstract

Marine scientists have been looking at methods for counting fishes underwater for some decades and the Marine Park Authority held a number of workshops in the late seventies and early eighties to develop techniques for counting coral trout. They also found that after training using wooden trout models a diver could make a good estimate of the length of any coral trout seen. We used a method that involved two divers searching for trout along 50 metre long by 20 metre wide survey transects so we could get an estimate of the number of coral trout living in a 1000 square metre area of reef. To cover as big a depth range as possible we ran the 50 metre fiberglass surveyors tape that defined each transect down the reef slope from the edge of the reef flat. On most reefs the transect ended in about 15 metres of water but on some shallow reefs the end of the tape was only at 8 or 10 metres depth and on the steep slopes of some outer reefs we reached depths between 20 and 30 metres.