The probability of cod (Gadus morhua) and ling (Molva molva) to encounter gillnets based on in situ fish movements

Abstract

The probability of cod (Gadus morhua) and ling (Molva molva) to encounter a fleet of four gillnets (110m) set within a fixed survey area of 600x600 m2 and soaked for a period of 12 h (1800-0600 hrs) is calculated on the basis of in situ observations of fish movement and random simulated start positions and setting directions of a fleet of gillnets. The movements of cod and ling, which were tagged by allowing them to voluntarily swallow bait-wrapped transmitters close to the sea bed, were studied by means of a stationary positioning system. The expected number of encounters per fish for the fleet of gillnets varied between 0.127 and 0.626 for cod and 0.077 and 0.614 for ling with a fish density of three fish per 0,1 (n.mile)^2 .