Artificial reproduction of Anguilla anguilla: evaluation of biometrics characteristics of a population from Valle Campo Lagoon, Comacchio (Italy)

One of the major problems in artificial eel reproduction is identification of broodstock with high performance reproductive characteristics. The aim of this study was to study population characteristics and the reproductive potential of eels (Anguilla anguilla) located in Valle Campo valley (Comacchio, Italy). A total of 200 eels/period (spring–summer and autumn–winter) were measured to obtain an external indicator of their maturation state. Morphometric parameters were used to calculate condition factor (K), eye index (EI) and pectoral fin length index (PFLI). Silver index analyses showed the lack of silver males and of fully mature females. Most represented females were yellow females at stage II. Silver females represented 27.9% of the population. Seasonal analysis shows how temperature reduction favoured the presence of silver females versus yellow females. Statistical analysis of EI, cranial (CI), PFLI and gonadosomatic (GSI) indexes showed that significant differences were found for EI, CI, PFLI and GSI between yellow and silver eels. No significant difference was found between stage III and IV silver eels, while a significant difference for EI was found between stage I and II yellow eels and for IC at stage II with respect to all other stages. The present study defined how Valle Campo could present environmental and trophic conditions which could favour precocious development of a population of silver females with a noticeable reproductive potential, to be used in open sea release or in artificial reproduction programmes. On the contrary, the valley seems to present unfavourable conditions for both development and sexual maturation of male eels.