Maturation, reproduction and recruitment of the sand smelt, Atherina boyeri Risso, 1810 (Pisces:Atherinidae) in the estuary of Mala Neretva River (southeastern Adriatic, Croatia)

Characteristics of maturation and recruitment of the sand smelt, Atherina boyeri, from the Mala Neretva River estuary in the southeastern Adriatic, Croatia in 2001/2, are presented. The average gonadosomatic index (GSI) during a 12-month period was 1.59% for females and 2.1% for males. The highest value was in April, 5.4% for females and 4.7% for males. The smallest mature female was 5.2 cm total length. Fifty percent of the females were mature at 7.75 cm total length. New juveniles began to recruit in June and July and later appeared in fewer numbers. In general, the GSI was lower than in other sand smelt populations. The reasons are difficult to determine but might be partly explained by the high and unpredictable temperature and salinity variations in the researched area that have led to previously described disturbances of the sand smelt life cycle, as in feeding and a high incidence of spinal deformities.Original Abstract: Prikazane su karakteristike dozrijevanja i novacenja olige, Atherina boyeri na uscu Male Neretve, na srednjem dijelu istocne obale Jadrana, Hrvatska u 2001 i 2002. Prosjecni gonadosomatski indeks tijekom 12-mjesecnog razdoblja za zenke je iznosio 1,59%, a za muzjake 2,1%. Najveca vrijednost je bila u travnju, za zenke 5,4%, a za muzjake 4,7%. Najmanja zrela zenka je zabiljezena pri ukupnoj duzini 5,2 cm, a 50% zenki je bilo zrelo pri ukupnoj duzini 7,75 cm. Nova mladj se pocinje novaciti u lipnju i srpnju, a pojavljuje se i kasnije, ali u manjem broju. Vrijednosti GSI su uglavnom manje nego kod ostalih istrazivanih populacija olige. Tesko je zakljuciti koji je razlog, ali djelomicno se moze objasniti velikim i nepredvidljivim kolebanjima temperature i slanosti, kod kojih su vec opisani razliciti poremecaji zivotnog ciklusa olige na istrazivanom podrucju, u ishrani i visokoj ucestalosti deformacija kraljesnice.