Glass eel recruitment and exploitation in a South European estuary (Oria, Bay of Biscay)

Abstract

The size of the European eel population is below safe biological limits. To assess the status of the stock properly, it is necessary to increase the number of recruitment series based on scientific monitoring. In this study, the spatio-temporal variation in glass eel density in a South European Atlantic estuary, the Oria, has been examined using experimental fisheries and fishery data. Glass eel density was predicted using a mixed generalized additive model. Current and depth were selected as covariates and date as a random variable then extrapolated to the whole sampling point volume to obtain the daily recruitment (mean, 12.76 kg; range, 0-72.8 kg). The average seasonal daily recruitment and fishery data were combined to obtain the seasonal recruitment (mean, 1144 kg; range, 682-1593 kg) and exploitation rate (mean, 31.1\%; range, 6.2-48.7\%). The information of spatio-temporal dynamics in glass eel density gathered in this study will help to improve the design of a recruitment-monitoring scheme at the European level. The integration of glass eel fishery data and scientific estimates is crucial to obtain a recruitment index in the Bay of Biscay, the area with the largest glass eel recruitment in Europe.