Publication Abstract

Spatial and temporal variation in the size and age at maturity for the European eel (Anguilla anguilla).

Bevacqua, D., A.M. Walker*, Aprahamian, M. et al.

The study is an update of Vøllestad (1992). It brings together new data collected over the intervening years and made available to ICES / EIFAAC eel working group and from the EELIAD project (EU FP7; grant no. 212133). Data on size and age at maturity for male and female European eel (Anguilla anguilla) were gathered from 66 eel stocks belonging to 12 countries during the period 1936-2010. Mean length of female eel increased significantly with latitude (p<0.01), from 500 to 800 mm between 37-70⁰ latitude, there was no relationship between male size and latitude remaining constant at between 380-400 mm. Age at silvering, increased significantly (p<0.01) with latitude from 3 to 25 and 3 to 34 years for males and females, respectively. As consequence of variability in age and size at silvering, average growth rate (estimated as size/age) decreased significantly (p<0.01) with latitude for female and male eel.  These relationships were modeled to provide a predictive capability for size and age at maturity for those river systems where no or little data are available. Trends in silvering length with time in last 40 years were analysed for three catchments. Length at silvering in males increased in IJsselmeer (NL) and Girnock Burn (UK) (p < 0.01), but not in Burrishoole (IR) (p = 0.66). Silver eel females were not captured in Girnock Burn, those caught in Burrishoole show a significant increase in size in Burrishoole (p << 0.01) while in Ijsselmeer there was no increase in mean length over the time period (p= 0.07).