Some biological survey of the Clupeonella engrauliformis (anchovy-like Kilka) in Guilan coastal region, the south-west of Caspian Sea, in 1996-97

According to a survey in 1996, among three species of kilka, living in the South-West of Caspian Sea, anchovy-like kilka composes 90.3% of total kilka catch. In all seasons of a year, anchovy-like kilka, in the second stage of gonadal maturation, shows higher abundance in the catch, compared with other maturation stages. This indicates anchovy-like kilka shows more positive phototaxis, at the beginning of its sexual maturation. Sex ratio shows females dominancy is 54.8-60, 7-75.9 and 82 percent in spring, summer, autumn and winter respectively. The average length of this fish in the four seasons with above order were 98.6±10.8, 97.7±10.3, 99.6±10.6, 100.1 ± 10.6 and the mean weight were 8.24±1.1, 7.5±1.7, 7.3±1.96 and 6.9±1.56 gr. The age composition of anchovy caught on spring in 1997 ranged between 2-5 years old and the dominate group was 3-year-old. The K value and infinite length calculated 0.27 and 147.8 mm respectively. No significant differences were observed between male and female concerning fat reserve and feeding intensity

Ionic regulation ability in Rutilus frisii kutum fingerlings during sea water adaptation.

Experiments were conducted to determine the effects of weight on the ionic regulation ability of reared Rutilus frisii kutum fingerlings during adaptation to the seawater and downstream migration. Accordingly, the ionic regulation ability of Cl-, K+, Na+ and Mg2+ in kutum fingerlings with weights of 1, 3, 5 and 7 g in three different salinities, that is 13‰ (the Caspian Sea salinity), 7‰ (estuarine area) and fresh water (as control, 0.3-0.5‰), were assessed. The blood samples were provided before being transferred as control (fresh water) and during adaptation to the sea and estuary water in a period of up to 336 h by a pooling method. The measurements of ions were carried out for blood serum Na+ and K+ and alsoplasma Cl-1 and Mg2+ by photometric methods. This investigation showed that ionic regulatory ability of kutum fingerlings depends on their weights. Results of ionic changes during the duration of 336 h (14 days) proved that unlike kutum fingerling with weights of 3, 5 and 7 g, the ionic regulation system in 1 g fingerlings were not able to expel excess ions. Further 1 g kutum were not physiologically ready (smolt) for downstream migration

Population dynamics and stock assessment of common kilka (Clupeonella cultriventris caspia) in Iranian waters of the Caspian Sea

This paper examines the changes in the population biology and biomass of common kilka (Clupeonella cultriventris caspia) in the Iranian waters of the Caspian Sea from 1995-2004. For most years during this 10-year period, we estimated the age structure of the catch, length-weight relationship, von Bertalanffy growth parameters, condition factor, sex ratios, maturity stages determined from ovarian analysis, natural and fishing mortality, age at first capture and biomass. Growth parameters were estimated as L∞=132mm, K=0.259/yr, t0=-1.285/yr. The instantaneous coefficient of natural mortality was estimated at 0.506/yr and the instantaneous coefficient of fishing mortality varied during the 10-year period between 0.125/yr to 1.487/yr. Biomass of the common kilka increased from about 16,000mt in 1995 to more than 41,000mt in year of 2002. This increase in common kilka was simultaneous with a sharp decline in anchovy kilka, changes in zooplankton abundance and composition, and especially increase in zooplankton species used by common kilka. We concluded that at the present time, the stock of common kilka is being over-fished