Publication Date:
2021-05-19
Description:
Coregonus lavaretus is one the important species of coregonidae family. It has adipose fin and the tail fin has a deep notch. The fish is special for fresh and cold north waters and are mainly found in north hemisphere and north of Europe, Asia and America. It feeds aquatic invertebrate and zooplanktons. The mentioned species has tasteful meat and supplies the major part of fish consumption. The big fishes meat is tasteful, low fat and has a cucumber like odorous characteristics and is mostly consumed in dried and smoked forms. Since this fish is important in inland fisheries and is releasable and developing in water sources of lakes behind dams has been considered and respect to purity of water resources behind dams. In the lake of Karaj dam has been considered as the only habitat and considered to have to low biological information from October to late march 2001 for 6 months totally 82 samples were caught and studied and through this way lack of fishing in the region by determining 11 stations, the samples were collected and grown, relation between length and weight, age and length, propagation, nutrition and fertility parameters were evaluated. Most of caught fishes are 4 to 5 year olds and 3 and 4 year olds. The 4 year olds males were majority and 5 and 6 year olds females formed the dominant group. Correlation relation between age and total length in both sexes (male and female) was very significant at 1% level, of course in females the correlation was around 100%. The weight and total length in males and females that was caught both had high correlation at 1%level; of course this correlation in females had been very stronger than males. % level related to gonad weight and sexual evolution stages of females. Gonad had correlation at 5 The most absolute fecundity had belonged to 5 year old female with 19120 ovules and the lowest to 4 year old breeder.
With 11496 ovules the most relative fecundity was 62.13% and belonged to 5 year old breeder and the lowest was 36.06% belonged to 4 year old breeder by increasing the quantity of ovules in breeders the sixth stage of sexual evolution the fecundity rate has been directly increased as well. % of Gonad weight was the most effective factor on absolute fecundity and according to (R2) more than 90 variations of breeders; absolute fecundity is claimable by their gonad weight. Among all traits, affecting gonad weight fecundity the breeders sexual evolution stage has been recognized the most effective factor on fish ovules diameter. Generally in oligotrophic aquatic resources they become mature before the age of 3 and in utroph aquatic resources and full of edible zooplanktons they become mature with 2 years of age. In respect to nutrition this fish eats a broad range of zooplanktons separated from surface to bed of water of dam lake and no kind of selection was seen there so that in different ecological condition it can differ appropriately to kind of foods available in different seasons so that in cold months (December to March) the food diet of this fish varies toward eating water bed living things such as tobifex.
Description:
Iranian Fisheries Science Research Institute
Description:
Published
Keywords:
Biological
;
Coregonus lavaretus
;
Species
;
Coregonidae
;
Aquatic
;
Zooplanktons
;
Fishes
;
Fisheries
;
Samples
;
Gonad
;
Evolution
;
Fecundity
;
Breeders
;
Zooplanktons
Repository Name:
AquaDocs
Type:
Report
,
Refereed
Format:
79pp.
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