Age and growth of yellow eels, Anguilla anguilla, in the estuary of the Guadalquivir river (south‐west Spain)

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Abstract
A total of 1068 eels were examined from a population located in the Guadalquivir river estuary (37°N, 6°25′W). Maximum ages recorded were 4 + (males) and 7+ (females), and maximum lengths were 39‐1 cm (males) and 54.1 cm (females). No growth was recorded between November and April, most occurring in May and, to a lesser extent, in June‐October. Females grew to be larger than males. A classification analysis, based on 17 different European eel populations revealed that populations in brackish waters grew faster than those in fresh waters, but latitude also had an influence. Length‐weight relationships obtained for three eel categories (males, females and undifferentiated) were used to estimate relative condition: condition cycles were similar between sexes, with increases in autumn and decreases in winter. There were monthly fluctuations in the sex ratio, and females dominated significantly in the combined catch (234 males/276 females).