SEX STRUCTURE, RECRUITMENT RATE, AND SIZE OF MATURING SPECIMENS OF EUROPEAN EEL (ANGUILLA ANGUILLA (L.)) IN A POPULATION FROM LAKES IN NORTHEASTERN POLAND
Stanisław Robak
The Stanisław Sakowicz Inland Fisheries Institute in Olsztyn, Poland
ABSTRACT. Studies of the sex structure and recruitment rates of silver eels from a population occurring in natural conditions in a large lake complex were conducted in the 1985-1990 period based on a sample of 6998 specimens. The fish were caught in 60 connected lakes with a combined surface area of 300 km2 using box traps, cross traps, stownets on stakes and electric fishing. It was determined that the share of males in the eel population occurring in the lakes was barely 1.03%, and in the group of fish with body lengths (Lt) of up to 46.0 cm it was 3.17%. Silver and yellow eels were noted among both males and females. The share of silver eels increased from 0 to 100% in the body length categories from 39.0 to 46.0 cm among males and from 47.5 to 95.0 cm among females. In both instances, the dependence of the share of silver eels on the total length of the body was described with linear regression with a high correlation coefficient and high regression significance (P < 0.05). The studies indicated that in the lakes of northeastern Poland, which are located within a large complex that is permanently connected, the share of males is small and the recruitment of silver eels from this group occurs within a narrower and lower size range than it does in females.
Keywords: EUROPEAN EEL (ANGUILLA ANGUILLA), GROWTH POTENTIAL, SEXUAL MATURATION
CORRESPONDING AUTHOR:
Dr Stanisław Robak, Instytut Rybactwa Śródlądowego, Zakład Ichtiologii, ul. Oczapowskiego 10, 10-719 Olsztyn, Tel./Fax: +48 89 5241072, +48 89 5240505; e-mail: robak@infish.com.pl