Acoustic estimates of spawning cod in the Lofoten area in 1982 and 1983

Abstract

The main spawning grounds for Arctic cod, the Lofoten area, were covered by acoustic surveys 7 times in 1983 and 12 times in 1983 during the prespawning and spawning season. The results indicated a spawning stock in the area of approximately 80 million specimens in 1982. and 50 million spec-imens in 1983. These figures were less than half the estimated total spawning stock of Arctic cod these years. The acoustic data were analyzed in order to estimate the migration rate in and out of the Lofoten area during the surveying period. The results indicate that in 1983 spent cod started to leave the grounds in the middle of March, and that the fish flux in and out of the area is an important factor to be considered when evaluating the acoustic survey results. In general acoustic surveys will tend to underestimate the number of spawners Bn the area under such circumstances.