With the aim of determining the reproductive characteristics and mating periods specific to Syngnathus acus, a study was carried out from December 2001 to November 2002 in the Camalti Lagoon (Izmir Bay, Aegean Sea). Study material consisted of 605 individuals that were captured using a beach seine in areas with vegetation. 43% (n=261) of the captured individuals were female, 25% (n=154) were male and 31% (n=190) were juveniles that were not sexually mature. The female-male ratio was 1:0.58. Mean total length values in females and males were 113.1 and 111.4 mm, respectively. The abundance of females carrying oocytes and of pregnant males of the species was observed between March-August 2002, coinciding with the period of relatively warmer water temperatures in that year. Gonadosomatic index (GSI %) analyses of females found that the reproductive period was between March-September. The relationship of egg/embryo number with total length in pregnant males and the total length-batch fecundity relation in females was statistically insignificant. We found that there were three groups of oocytes in the ovaries of females. Average oocyte diameter varied between 0.4-1.8 mm (developing 0.4-0.5mm, 0.7-0.8mm and 1-1.8mm hydrated oocyte group); thus, there were three spawning events during a year. The ratios of annual fecundity (mean: 65) and partial fecundity (mean: 28) data support this result (three spawning a year). Average hydrated oocyte number of females was 28, average egg number in the pouch of a male was 24, and average embryo number was 31. Average egg diameter in pregnant males was 1.42 mm (min:1, max:1.85); average length value of pre-larva and post-larvae was 8.91 ram, (min:3, max:14.29) and 13.29 mm (min: 9.71 max:15.29).