tailieunhanh - Reproductive biology of the marbled goby, Pomatoschistus marmoratus (Pisces, Gobiidae), in a northern Aegean estuarine system (Greece)

Several sexuality education programs have been evaluated, and many include a combination of abstinence messages for sexually inexperienced teens and messages about contraceptive use for sexually experienced teens. Slightly more than half of these programs show some positive impacts on reproductive health outcomes for at least some populations (Aarons et al., 2000; Eisen, Zellman & McAlister, 1990; Kirby, 2001; Thomas et al., 1992). Several HIV education programs were evaluated and slightly more than half of them show some positive impacts on sexual activity and contraceptive use for at least some populations (St. Lawrence et al., 1995; Jemmott III,. | Folia Zool. - 58 4 447-456 2009 Reproductive biology of the marbled goby Pomatoschistus marmoratus Pisces Gobiidae in a northern Aegean estuarine system Greece Emmanuil T. KOUTRAKIS1 and Athanassios C. TSIKLIRAS2 1 Fisheries Research Institute National Agricultural Research Foundation Nea Peramos 640 07 Kavala Greece e-mail manosk@ 2 Department of Ichthyology and Aquatic Environment University of Thessaly 38446 Nea Ionia Volos Greece Received 19 February 2007 Accepted 29 May 2009 Abstract. The reproductive biology of the marbled goby Pomatoschistus marmoratus Risso 1810 was studied in the Strymon River estuarine system northern Greece between September 1997 and August 1999. Samplings were conducted on a monthly basis at the mouth of the river using a bag seine net and overall a total of 4 563 individuals were collected. The total length of males ranged between and cm and that of females between and cm while that of unsexed individuals ranged between and cm. Sex ratio was 1 in favour of the females and statistically different from unity. The spawning of the species was extended occurring between February and May. Mean absolute fecundity F was 1 386 SE 8 oocytes and showed a significant positive exponential relationship with total length F 92 and total weight F 1351TW 83 of the fish. The relative fecundity ranged between 878 and 3 444 oocytes g of total weight. Mean size at first maturity was estimated at cm for the females and cm for the males. Key words sex ratio fecundity spawning maturity Introduction The attraction of marine and freshwater fish species to estuaries and coastal lagoons distinguished estuarine habitats as important transition zones connecting the freshwaters with the sea. Although lagoon and estuarine habitats are important feeding grounds for fishes fishes do not use lagoons for spawning except for very few exceptions see K o u t r a k i s et al. 2005 . Indeed the majority of fish .