Behaviour of Pacific Cod (Gadus macrocephalous) and Environmental Parameters during Winter in Jinhae Bay by Acoustic Telemetry

Abstract

Pacific cod are fished on their spawning grounds, therefore, it is important to evaluate whether particular spawning sources are more critical than others in sustaining the productivity of fished populations. Four wild male cod (WC1 to WC4) were captured by a pound net. The fish were tagged using surgical method with acoustic transmitters including a pressure. Average total length and weight of tagged fish was 62.5cm (±4.36) and 2,152.5g (±129.34), respectively. The four tagged cod were manually tracked for 2-6 hours. The swimming depth of WC1 and 2 were below 5 m, whereas, WC3 and 4 swam close to the seabed. WC2 average swimming speed was 0.60 TL /s and showed high site fidelity. The average swimming speed of WC1, WC3 and WC4 were 1.11, 2.34 and 1.32 TL/s respectively. Total acoustic signal detection for WC2 was 5.1 hr whereas for WC1, 3 and 4 signal ranged from 1.6 hr to 2.2 hr. In this study the four tagged cod moved south- eastward in the bay near the coast of Geoje-do. Temperature is the main factor in the movement of WC. Optimum temperature and salinity was found to be in the range of 7.8-8.4oC and 33.4-33.6 psu respectively.