Significant changes in pelagic fish stocks of Clupeonella spp. in the south Caspian Sea
محل انتشار: مجله علوم شیلات ایران، دوره: 11، شماره: 3
سال انتشار: 1391
نوع سند: مقاله ژورنالی
زبان: انگلیسی
مشاهده: 114
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شناسه ملی سند علمی:
JR_JIFRO-11-3_009
تاریخ نمایه سازی: 22 اسفند 1400
چکیده مقاله:
The present study was carried out
during ۲۰۰۶-۲۰۰۷ along the southern Caspian Sea. The species composition showed that the common kilka, Clupeonella cultriventris caspia, is
dominant species with ۸۹% and then anchovy, C. engrauliformis, has shown only ۸.۷% while it was already dominant
species in the past decades. The overall results indicated that common kilka was
replaced with anchovy kilka as previous dominant kilka species due to invasion
of Mnemiopsis leidyi to the southern Caspian Sea. Anchovy suffered greatly from M. leidyi so
that the total catch dropped from ۹۵۰۰۰ mt in ۱۹۹۹ to less than ۲۰۰۰۰ mt in ۲۰۰۷. In our survey, ۱۴۱۵ fish
specimens were collected randomly, including ۲۲۱ anchovy, ۲۸۱ bigeye and ۹۱۳
common kilka. The mean length of anchovy was ۱۱۷.۸ ± ۰.۲۷ mm, while it was
about ۹۳.۰ mm during ۱۹۹۵ to ۱۹۹۸ before the invasion of M. leidyi. Analysis
of age classes indicated the mean age of ۴.۵ ± ۰.۰۴ years for anchovy, ۳.۶ ±
۰.۰۳ for common kilka and ۴.۶ ± ۰.۰۸ for big eye C. grimmi. According to the age and the length structure of the specimens in this
study, it could be concluded that in recent years, young fish population of
anchovy has been decreased in comparison with the last decade. The results
showed that some biological characteristics of kilka population were affected
by M. leidyi. Recently
fishing activities take place in shallow waters where schools of kilka are in
suitable density for fishing. According to our results,
ctenophore occupied the anchovy habitat where it was mainly more than ۵۰ m
depth. The fishing has moved to areas with depths less
than ۵۰ meters where it was the main reason to change in species composition.
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