Some reproductive characteristics of endangered Caspian Lamprey (<Emphasis Type="Italic">Caspiomyzon wagneri</Emphasis> Kessler, 1870) in the Shirud River southern Caspian Sea,Iran

Migration and reproduction of the Caspian Lamprey, Caspiomyzon wagneri, in the Shirud River were investigated during late-March to early-May at water temperatures ranging from 11 to 21.25°C. We examined the effect of water temperature on timing of spawning migrations. There was a significant negative relationship between temperature and intensive migration of Caspian Lamprey (p < 0.05). The most intensive migration of lampreys was at night (21:00–3:00 h) and when the water temperatures averaged 16°C (34.43%). The overall sex ratio (male to female) was 1.07 to 1. The individual absolute fecundity was 31 ‘758–51’ 198 eggs (mean±SD—41,924 ± 5,382). The egg diameter was 0.780–1.151 (0.92 ± 0.081) mm. The individual relative fecundity varies from 80.3 to 148.1 (107.2 ± 15.1) eggs per 1 mm of length and from 260.8 to 677.4 (397.6 ± 93) eggs per 1 g of weight. The gonadosomatic index (GSI) of females was 5.83–31.44 (11.22 ± 4.30).