Sarmin Akther
Department of Zoology, University of Rajshahi, Rajshahi, Bangladesh
Maksuda Akhter
Department of Zoology, University of Rajshahi, Rajshahi, Bangladesh
Mosharrof Hossain
Department of Zoology, University of Rajshahi, Rajshahi, Bangladesh
Gangetic Mystus, Fish biology, Length-weight relationship, Condition factor, Rajshahi University
Rajshahi City Corporation
Animal Health and Management
A total 300 specimens (110 male and 190 female) of each of different sized Mystus tengra and Mystus cavasius were collected from local market, Shaheb Baza, Rajshahi New Market and Binodpur Bazar of Rajshahi City Corporation areas during September 2010 to February 2011. Sexes were separated on the basis of body shape, genital papilla and coloration. Females were identified by visually the base of the round genital structure which had a round protrusion; the abdominal region was always broader and longer and darkens color than the male. However, the male, genital papilla was a soft, elongated structure, broad at the base and gradually tapering towards the end. The tip of the papilla was beyond the base of the first anal fin, the body was elongated, and the color was light in comparison with that of the female. Finally, a semi-circle incision was used to open the body cavity and sex was assessed. All the specimens were carried in the laboratory of Fisheries, Department of Zoology, University of Rajshahi for further study. In the laboratory, the total length and standard length of the fish were measured in the nearest mm by means of a measuring board and their weights were recorded in the nearest grams by a sensitive pan balance (Model No. CT, 1200-S, USA). The collected specimen were washed under tap water and preserved in 5% formalin in individual plastic jars for morphometric and meristic study. Some amount of 5% formalin was also injected into the gut to prevent further digestion. A magnifying glass was used to count the fin rays and dorsal spines. Total length (TL), Standard length (SL), 1st dorsal length (DL1), 2nd dorsal length (DL2), pectoral length (PL), pectoral length (PL), pelvic length (PVL), anus length (ANL), anal length (AL), and total weight (TW) were recorded. Co-efficient of condition factor (K) was also calculated according to the researcher [13, 14] in this study was presented in the Table 3, 4 and 5. The length-weight relationships of the two species were calculated from the logarithmic formula described [14] and other statistical analyses were calculated by SPSS (statistical packages for social science). Length-weight relationship was calculates by following formula, W= aLn [where, W, weight; L, length; a, constant equivalent; n, another constant to be calculated empirically]. The value of ‘a’ and ‘n’ was calculated in log form as, Log a = ∑Log TW ×∑logTL2 ∑logTL × ∑(logTL×logTW) / N×∑logTL2 ?(∑logTL)2 . n = ∑logTWN×loga / ∑logTL, [where n, indicates the number of specimens]. Condition factor was calculated as; here we used observed value (K0) and calculated value (Kc). Formulae, TW=KTL3 which was written as, K= TW/TL3 [where TW total weight in grams and TL is the total length in mm and K factor was written as, K=TW×105 /TL3 . Relative condition factor was determined by using the following formula, Kn=TW/aLn or, Kn= TW/ [where TW, observed total weight, , calculated total weight].
Journal of Entomology and Zoology Studies 2017; 5(2): 979-982
Journal