Publication Date:
2021-05-19
Description:
During the past decades the environmental status of the Caspian Sea has changed. Therefore, study on the biological structure such as: age, growth, Lm50%, feeding of fishes is necessary. In the present study the biological characteristics of some commercial important species including kilka, kutum, golden grey mullet and carp were studied during 2006-2010.
Kutum, golden grey mullet and carp predominated in the catch composition of bonyfishes, representing 61.3, 29.6 and 7.6% of the total catch. The average fork lengths of kutum, golden grey mullet and carp were 38.4, 32.7 and 36.7 cm, and weights were 784.5, 411.0 and 977.0 g, respectively. The values of b in length-weight relationships were 3.02 and 2.97 for kutum and golden grey mullet indicating an isometric growth. The value b for carp was 2.89, indicating an allomertic growth.
The maximum age of three species was 12 years. Von Bertalanffy growth equations were estimated as:
for kutum:
for golden grey mullet:
and for carp:
The sex ratio of three species showed that females were dominant. Spawning migratory of kutum was started in March. The gonadosomatic index value of kutum peaked in March and April.
The spawning season of carp expended from March to August. The gonadosomatic index value of golden grey mullet peaked in September and then declined in November and December. Absolute fecundity of kutum, golden grey mullet and carp were 64400, 700800 and 131000 eggs, respectively. Length maturity (Lm50%) of three species were 39.07, 28.4 and 31.6 cm, respectively.
The highest feeding intensity (Gastrosomatic index=GSI) for females and males were 313.9 ± 65.9 and 350.7±103.7 in October; and the lowest value of GSI were 19.4 ±59.2 and 144.1±85.04 in March, respectively. There are significant different between GSI with male and female in difference months (P〈0.05). Main prey mature of Kutum was Cerastoderma lamarki; Gastropoda and Balanus were subordinate, and Crab, Hypanis, Fish (Neogobous sp.) Algae, egg, and scale were random preys. Planktone groups comprise to Exuviaella, Nitzchia, Osillatoria, Synedra, Nematoda, Navicolla, Diatoma, Rholcosphenia were preys juvenile of Kutum. Based on ISI (Important species index), Cerastoderma lamarki and Balanus were dominant species in feeding of Kutum. The percent of empty stomach and prey dominant evaluated during different seasons by specific formula result showed that in Cyprinus carpio prey Molluscs was dominated and specific food items.
Empty stomachs in winter and spring were higher and lower, respectively. The results showed that catch of kilka decreased from 22300 mt in 2006 to 16700 mt in 2008, but the CPUE increased from 1.7 mt (Vessel×Night) to 2.5 mt, due to decrease of effort, respectively. The length frequency of three species of kilka is close and the juvenile fish did not see in catch. The age frequency had the same situation as fish lower than 2 years was not in the samples of anchovy and bigeye kilka.
The parameters of the von Bertalanffy growth curve were:
For common kilka: L =136.5 cm, K=0.249 yr-1 and t0= -1.89 yr-1
For bigeye kilka: L =148. cm, K=0.346 yr-1 and t0= -1.123 yr-1
And for anchovy kilka: L =131.7 cm, K=0.375 yr-1 and t0= -1.243 yr-1 The exploitation rate of anhovy, bigeye and common kilka were 0.51, 0.58 and 0.6, respectively. The highest of GSI for common and bigeye was recorded in May and March, respectively. For anchovy kilka it was in July and November. Main prey of anchovy and common kilka was Acartia tonsa and for bigeye kilka it was Cypris balanus. We concluded that the ecological problems caused by Mnemiopsis leidyi as well as overfishing have been collapsed kilka stocks, particularly anchovy. Therefore, sustainable fisheries management and conservation biodiversity in the Caspian Sea are real challenges now.
Description:
Iranian Fisheries Science Research Institute
Description:
Published
Keywords:
Commercial
;
Growth
;
Species
;
Kilka kutum
;
Bonyfish
;
Sex ratio
;
Spawning
;
Gonadosomatic
;
Maturity
;
GSI
;
Hypanis
;
Neogobous sp.
;
Algae
;
Nitzchia
;
Cyprinus carpio
;
Diatoma
;
Clupeidae
;
Rutilus frisi kutum
;
Liza auratus
;
Chalchalburnus chalcoides
;
Vimba vimba
;
Abramis brama
;
Sander lucioperca
;
Liza saliens
;
Fish
Repository Name:
AquaDocs
Type:
Report
,
Refereed
Format:
98pp.
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