نوع مقاله : مقاله پژوهشی
1 گروه شیلات، دانشکده کشاورزی و منابع طبیعی، دانشگاه گنبدکاووس، گنبدکاووس، ایران.
2 مرکز بازسازی و حفاظت از ذخایر ژنتیکی ماهیان استخوانی گلستان، بندر ترکمن، ایران.
عنوان مقاله [English]
The used Caspian roach broodstocks for semi-natural propagations are collected from the Gorgan river estuary during February-March every year and transported to the fisheries center of the stock enhancement and conservation of genetic stocks of Caspian bony fishes. Sampling of Caspian roach broodkstcoks for this study perforemed for 5 successiv years duing 2014 to 2018. Total length and weight of the broodstocks ranged from 21 to 32.5 cm and from 45.60 to 423.50 g, respectively. The largest mean value of lengths and weights were observed in February-March 2014, and the smallest in February-March 2018. Age of broodstocks ranged between 3+ and 9+. Abundance of ages and sexes were different between years. Feamles had positive allometry in all years, while that of males ranged 2.65 and 3.05 indicating mainly negative allometric pattern. Different instanteneus growth rates were observed during five years, indicating presence of strong and/or weak ages and/or cohorts in the studied populations. Condition factor of the females were larger than that of males in all periods. The results showed that L-infinity of males ranged from 26.49 to 38.53 cm, and that of females from 32.45 to 41.97 cm, k-coefficient ranged between 0.12 and 0.24 (year-1) for males and between 0.11 to 0.21 (year-1) for females, and t0 of males ranged from -0.21 to -0.34 (year), and that of females from -0.39 to -0.99 (year).