Frontiers in Marine Science (Nov 2015)
Eel population dynamic and habitat relationships in the European southern tip.
Abstract
The European eel (Anguilla anguilla) stock has decreased by 1% from the overall population size in 1980. Consequently, Eel Managements Plans (EMPs) have been carried out across Europe in order to increase the population to a 40% minimum of the considered original. In Spain, each autonomous region has set different measures. This study shows the first data on eel population dynamic and habitat relationships in the most southern region in Europe. Monthly sampling has been performed in the Guadiaro River during 2014 and 2015. Two different but continuous stretches were set, with three daily replicates and 50 fyke-nets each. Capture-recapture analysis was performed for two groups (individuals 300 mm of total length) using PIT-tags in the field and population dynamic indicators. Examples include; survival rate, density and temporal migration, these were modeled by a Robust design method. Habitat data was collected using both field and laboratory registers and main predictors were detected by multivariate regression model with capture per unit of effort (CPUE) as the only response variable. Annual survival was estimated to be 0.68 and 0.67 for individuals that are 300 mm, respectively. Density estimates ranged from 0.046 to 0.090 eels/m2 on individuals 300 mm. With an average range of 113 m, movement was measured for recaptured individuals, finding significant differences according to fish length. Environmental variables related to major rainfall previous to sampling were shown as the main predictor accounting for 88% of the CPUE. According to our previous results, the eel population in the most southern region in Europe shows similar averages in dynamic population indicators compared to other European areas. On the other hand, no environmental predictors showed major influence on catchability, except for, those related to previous abundant rainfalls.
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