FISHERY AND POPULATION DYNAMICS OF CASPIAN KUTUM, Rutilus frisii kutum (CYPRINIDAE), IN THE CASPIAN SEA
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Date
2010-10
Authors
BANDPEI, MOHAMMADALI AFRAEI
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Abstract
The Caspian Sea is the largest enclosed body of water in the world. The
water is slightly brackish. The aim of project was to determine length at maturity
(Lm5o%), evaluate of feeding items, investigation some ofbiological aspects included
in sex ratio, growth and age structure, instantaneous mortality coefficient, maximum
sustainable yield (MSY) and break-even point of Rutilus frisii kutum in southern part
of the Caspian Sea. Specimens of Kutum were collected from the catches obtained
from 131 sample sites along the Iranian coast of the Caspian Sea.
The minimum and maximum fork length and weight was 21cm and 58cm
with mean 38.4±6.4 em; 104 and 2450 g with mean 775.2±382.5 g, respectively. The
sex ratio of males to females was 0.65: 1 (males: females). The condition factor in
Guilan was more than Mazandaran and Golestan provinces. The length at maturity
(Lm5o%) of Kutum obtained was 39.1cm. The minimum and maximum absolute
fecundity varied from 15,713 to 130,737 eggs with mean 69,961.7±3,836.4. The
reproduction phase was extended from February to April, peak in March, with the
highest average values 5.52 for males and the highest value was 17.00 for the
females in April. Due to males' migration from sea to river occurred sooner than that
of the females.
The diet consisted of different prey items, bivalves representing the most
important prey group (59%), and followed by Cerastoderma lamarki (57%). The
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instantaneous natural mortality rate was estimated M= 0.46 i 1
• Based on total
instantaneous mortality coefficient (Z) frcm the seasonalized length-converted catch
curve, F (the instantaneous fishing mortality coefficient) as 0.82 i 1 through the
relationship: F=Z-M, and giving a current exploitation rate E (=FIZ) as 0.64 i 1
. The
length-at-first capture and age-at-first capture was obtained Lc =36.8 em and 3.92
years, respectively.
The Maximum sustainable yield (MSY) based on cohort analysis for Kutum
resulted MSY=20,004 tonnes with biomass B of 51,937 tonnes. The selection ogive
procedure gave the following summary: Emax=0.76, Eo.t=0.65 and Eo.s=0.39. Yield
per recruit analysis suggests that the stock of this species has a moderately
exploitated at E=0.64. Kutum contributed about 76% of total sell bony fish in south
of the Caspian Sea and total income of Kutum sell were estimated US$30,415,998.
The income of the fishermen through selling of Rutilus frisii kutum from total bony
fish income was 74% for Guilan, 85.8% for Mazandaran, and 26% for Golestan
provinces. Therefore, R. f kutum plays a significant role in fishermen's income in
southern coasts of the Caspian Sea. The break-even point of Kutum obtained with
mean 19,220±5,364.5 for Guilan, 18,843±4,989.2 for Mazandaran, and
10,677±1,358.2 for Golestan provinces, which coincided with the fishing effort,
catch ratio, number of fishing cooperatives, and number oflabour.
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Keywords
FISHERY AND POPULATION DYNAMICS OF CASPIAN KUTUM,