Surveying the younger age grows of saithe - experiences from a small scale acoustic survey at the coast of western Finnmark

Abstract

The small saithe (1- and 2- group) is mainly distributed in fairly shallow areas close to the Norwegian coast from Rogaland to eastern Finnmark. It is known to occur quite regularily at certain localities. It is usually schooling, at least in daylight. Thus, by using a small vessel equipped with an echo sounder it is usually easy to detect. This paper discuss the possibilities of acoustic surveying a fixed number of known "saithe localities" to obtain a yearclass index. Hypothesis regarding the distribution pattern and fish behaviour are presented, and the cosequences for the reliability of a survey index are discussed. Absolute estimates seem unrealistic, because a large proportion of the most important areas can not be surveyed even with a small vessel. Results from a survey in western Finnmark during early August 1993 are presented and discussed. The results indicate that in these areas the 1- group tended to stay rather close to the shore, while the 2- group showed a more favourable distribution. At the lower limit of its vertical distribution range it showed some overlap with the 3- group.