Glass eel (Anguilla anguilla) recruitment to the river Lis: Ingress dynamics in relation to oceanographic processes in the western Iberian margin and shelf

다국어 초록 (Multilingual Abstract)

To provide new information on the ingress dynamics of glass eels at the Portuguese coast, the study analyzes catch per unit effort (CPUE) data from river Lis, biometric data from recruits in basins of western Portugal and meteo‐oceanographic data from the Iberian margin and shelf. Biometric data of glass eels in western Portugal are congruent with the latitudinal size gradient of leptocephali in oceanic surveys and show clear seasonality, with longest and heaviest individuals arriving from October to December. Generalized additive models fitted to CPUEs from two experimental fishing periods (1996–1997 and 2013–2014) show that availability of glass eels to the sampling gear was inversely related to lunar phase and sea wave height. CPUE was lowest from May to September, increased towards the end of the year and peaked in February–March, when recruits were almost 40% lighter than autumn arrivals. Commercial CPUE during the 1989–1990 fishing season was significantly higher than experimental fishing data in 1996–1997. Higher variance and smaller sample size in 2013–2014 prevent conclusive interdecadal comparisons. Finally, CPUE was significantly higher during the prevalence of northward current flow off western Portugal and during strong cross‐shelf westerly winds. Findings support the suggestion that eel recruitment in Portugal occurs mainly by leptocephali travelling along the Azores Current, deflected northwards through the Iberian Poleward Current, with river ingress, and possibly oceanic metamorphosis, modulated by seasonal dynamics in coastal hydrology and shelf/upper margin oceanography.