Publikationsdatum:
2021-05-19
Beschreibung:
Through most of the last century, three endemic kilka species supported major commercial species in the Caspian Sea. It is clear that catches and abundance of all species have changed. Recent changes in the Caspian
Sea ecosystem have occurred as a consequence of ecological change caused by the invasive ctenophore (Mnemiopsis leidyi). In this investigation which had been done in commercial catch regions during 2002-2004, in addition of biological characteristics survey such as species composition, length, weight, age, sex ratios and maturity stages; catch and catch per unit effort also were analyzed. During the years 2002-2004 the annual catches of kilka varied between 15000-25000 mt and CPUE varied between 1.077-1.474 mt (vessel×night). The frequency of anchovy kilka declined from 69.5% in 2002 to 26.9% in 2004. During the years 2002, 2003 and 2004 the frequency of common kilka were 30.4%, 48.9% and 71.9%, respectively. During this period the frequency of bigeye kilka was negligible. The average fork length of anchovy kilka increased from 100.4 mm in 2002 to 105.0 mm in 2004 and the average weight were 6.4 g and 8.4 g, respectively. The average fork length of common kilka increased from 87.0 mm in 2002 to 93.8 mm in 2004 and the average weight were 5.2 g and 7.4 g, respectively. Anchovy kilka spawn in spring and autumn but mass spawning anchovy occurred in autumn.
Spawning of common kilka occurred in spring and early summer. In the age compositions of anchovy kilka, age 3 was the largest age group during 2002 and 2003 (55.3% and 52.1%, respectively). In 2004, age 4 predominated (42.5%). For common kilka, ages 3 and 4 predominated (representing 67.2, 62.0 and 69.1% of catches, respectively). According to CPUE and biological characteristics, after the appearance of ctenophore in the Caspian Sea, the abundance and biomass of bigeye and anchovy kilka collapsed.
Beschreibung:
Iranian Fisheries Science Research Institute
Beschreibung:
Published
Schlagwort(e):
Commercial
;
Ecological
;
Biological
;
kilka
;
Species
;
Ecosystem
;
Mnemiopsis leidyi
;
Survey
;
Length
;
Age
;
Sex ratios
;
Weight
;
Maturity
;
CPUE
;
Anchovy Kilka
;
Spawning
;
Bigeye kilka
Repository-Name:
AquaDocs
Materialart:
Report
,
Refereed
Format:
49pp.
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