Reproduction, length-weight relationship and condition of sardine, Sardina pilchardus (Walbaum, 1792), in the eastern Middle Adriatic Sea (Croatia)

Background and Purpose: The reproductive cycle of sardine, Sardina pilchardus (Walb.), from offshore (Dugi otok) and inshore waters (Virsko more) of Mid Adriatic Sea was studied to gain information on spawning period, sex ratio, length-weight relationship and condition of this most commercially important fish species in the Adriatic Sea. Materials and Methods: A total of 1,219 sardine specimens were collected from monthly random samples of purse seine catches realized in the Mid Adriatic Sea during the March 2004 – February 2005 period. Fish were measured and weighed. Sex was determined and gonad maturity stage was assessed. Gonadosomatic index (GSI) was calculated by expressing the monthly gonad weight as a proportion of the total body weight. The length (LT)–weight (W) relationship was determined (logW=log a+b log LT) as well as the monthly fish condition, using Fulton’s equation (K=100 W/ LT 3). Results and Conclusions: The total length of sardine ranged from 13.0 to 19.0 cm and the mass ranged from 16.72 to 51.45 g. Sex ratio was different from 1:1; males predominated (a/b=1.2). The reproductive activity period was from October to May, coinciding with the most developed stages of gonads as well as with the highest gonad weights and gonadosomatic indices. The length-weight relationship of sardine was described by the expression: W=0.026 LT2.5538 (r2=0.697). Fulton’s condition factor showed greater values in sardine samples from the inshore waters (Virsko more, K=0.8205) than those from the offshore waters (Dugi Otok,K=0.7317).