The underwater observation of fish communities and fish populations. Methods and problems

Abstract

Following the symposium held in June 1984 at Port Cros, the methods of underwater observation of fish communities and populations are critically reviewed. Particular emphasis is laid upon the possible causes of bias, and the ways of circumventing them. Given some necessary precautions and adequate training, and within definite limits, underwater observations and counts can produce highly reliable results, not obtainable by « blind » techniques. Some examples are given, based upon the personal experiences of the participants, both in the Mediterranean and the Indo-Pacifi