THE REPRODUCTION BIOLOGY OF BARBUS ESOCINUS IN DEZ DAM RESERVIOR

This study was carried out from April 1999 to March 2000 in Dez dam reservoir located at North Khouzestanprovince. From the total number of 607 specimen of collected fish, 267 and 64 were males and females respectively, and276 specimen were immature. Samples were caught by hooks and gill nets. Length range of females was 156-1350 mm and their weight range was 31.7-26500 g. Males ranged 183-1065mm in length and 48-12208g in weight. The males showed more ranges in length and weight comparing to females. The spawning period is very short and occuring in spring after flooding of the river and increase in the reservoir water level. This species is a total spawner and eggs are release in upstream regions and reservoir shallow waters on bottoms gravels. Spawning occurs in 24°C. Fecundity was intermediate. Sex ratio was 4.2:1.0 (male/female). Males show a faster maturation. According to the ratio of gut length to the body length, it seems to be an omnivorous species, but all samples were found to have fish in their stomachs (100%). Feeding intensity was higher in males. Annual growth is slow and asymptomatic length is more than 2m. Relative growth in weight is not in accordance with growth in length for various length groups, and relative growth in weight is increased with increasing of fish length. Growth of this species is positive allometric type. Various length groups were observed in examined specimens. It I seems that it has a longer reproductive life comparing to its pre-maturation life. Relative fatness is higher in females