نوع مقاله : مقاله پژوهشی
نویسندگان
1 ساری
2 انزلی
چکیده
کلیدواژهها
عنوان مقاله [English]
نویسندگان [English]
Kilka, a pelagic fish feeding on zooplanktons, are the most abundant fish genus in the Caspian Sea. There are three species of the fish living in the Sea including anchovy (Clupeonella engrauliformes), bigeye (C. grimmi) and common kilka (C. cultriventris). All three species live in the coastal waters of the Sea and comprise part of the commercial catch in the area. The relative frequency of the bigeye ranked second after anchovy over the years 1990-1991 with 6.84% increasing to 12.6% and 21.7% over the years 1997-1998 and decreasing in the subsequent years. We studied biological characteristics of the bigeye kilka over the years 1997-2001 in three fishing regions Amirabad, Babolsar and Anzali.
In winter and earlier spring of each year, mature bigeye kilka ready to spawn were always present in the catch. The mean fork length of the fish increased from 95.87mm in 1997 to 105mm in 2000 and decreased to 102.3mm afterwards. Over the same time period, the fork length range became wider with specimens in the upper length classes representing most of the catch. We found that males were always dominant during our study comprising 60 to 90% of the catch. The caught fish consisted of six age classes 1+ to 6+. During the years 1998 to 1999, the age Classes 1+ to 3+ comprised more than 90% of the catch. In the year 2000, we observed a decrease in the age classes 1+ and 2+ and an increase in the age classes 4+, to 5+ compared to that of the previous years. In the year 2001, the age classes 3+ and 4+ decreased and the age classes 5+ and 6+ increased. In recent years, the relative frequency of the bigeye kilka has decreased as a result of the attack by the Mnemiopsis leidyi, but fork length range of the fish has increased and bigger and older fish are dominant in the catch.
کلیدواژهها [English]
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