SUMMARY

Regression analysis was used to estimate the dependence of CPUE and average weight of bigeye on the temperature of surface water, the temperature of water at hook depth, the depth of the hook and the depth of thermocline. Hydrological data, catch and effort data and length/weight data were collected during four cruises of the Polish longliner WIECZNO from 1981 to1985. The vessel operated in the Central Atlantic (37oN-09oS and 15oW-38oW). A total of 220 sets were analysed. Bigeye tuna was represented in 59 % of sets. The daily CPUE of bigeye ranged up to 620 kg/1000 hooks in different years. The average length and weight of bigeye was 130 cm and 45.5 kg respectively. Since standard longlines with 5-hook baskets were used, the prevailing depth range for bigeye was 60-100 metres. The most efficient water temperature at hook depth was 12-16o C. Statistically significant dependencies were found between CPUE and hook depth, CPUE and the depth of thermocline and CPUE and surface temperature. The dependence between average weight of fish and water temperature at hook depth was also significant. RÉSUMÉ L’analyse de régression a été utilisée pour estimer la dépendance de la CPUE et du poid