ASPETTI DELLA BIOLOGIA ED ANALISI DEL CICLO RIPRODUTTIVO DI GOBIO BENACENSIS (POLLINI, 1816) NEL NORDEST ITALIA BIOLOGY ASPECTS OF GOBIO BENACENSIS (POLLINI, 1816) IN NORTHEAST ITALY

The aim of the present work is to study the biology and the reproductive cycle of the Italian gudgeon Gobio benacensis, which is included as “endangered” (EN) in the IUCN Redlist, due to the endangered status, information could be useful for the correct management of the species and for the scheduling of focused conservation plans. Analyses were carried out within a watercourse included in the Isonzo River Basin (Reca Stream, Northeast Italy) and regarded 86 specimen collected during April 2016 in order to assess population consistence and structure, and 77 specimens collected monthly and bimonthly between April 2016 and February 2017 to investigate the reproductive cycle. Regression between total length (TL) and body weight (W) obtained for males (W=0,1253TL2,8770) 54 2 and females (W=0,1555TL2,7554) were analyzed using the ANCOVA and did not show significant differences. Mean values of the gonadosomatic index (GSI) ranged from 0,61±0,49 and 1,75±0,58 for males and from 1,02±0,88 and 14,15±2,80 for females. Hepatosomatic index (HIS) showed ranges between 0,05±0,02 and 2,68±1,26 for males and between 0,25±0,19 e 1,75±0,58 for females. Analyses of ovaries and testicles, firstly performed for this species, allowed to identify maturation stages. The results show that G. benacensis females repeatedly spawn during the reproductive period between April and June and that males prolonged reproductive activity until August.