Allometry and Condition factor of Whipfin Silverbiddy, Gerres filamentosus from Mangalore Coast, Karnataka, India

Abstract

Background: Gerrids under family Gerridae are important in contributing rich source of protein. Gerres species are economically important food in India. They take a good role in development and economic of Indian estuaries. In fish biology, knowledge of the length-weight data and condition factor (Kn) is an important tool. Gerres filamentosus is one of the economically important groups of fishes inhabiting Karnataka coast. It was selected as a candidate for the present study since the knowledge on length-weight data and condition factor will be helpful in mass culture and production of this species in Karnataka.Methods: The length-weight relationships and condition factor of 2020 specimens of fish, G. filamentosus from Mangalore, Karnataka, south west coast of India, were studied from July 2009 to June 2011. The length-weight relationship was found using parabolic equation. Analysis of co-variance was used to test the significant difference in estimates of “b” between sexes. The condition factor for individual fish was calculated using the formula Kn = Wo/Wc.Result: The relation between the total length (L) and total weight (TW) was described as LogTW = -1.7716 + 2.9511 Log L for females, Log TW = -1.7526 + 2.9364 LogL for males and LogTW = -1.8343 + 2.9720 LogL for indeterminate fishes. The highest and lowest condition factor (Kn) values in females was in December 2010 (1.1186) and September 2010 (0.8871), respectively. Similarly, the highest and lowest Kn values in male was in March 2011 (1.0630) and September 2010 (0.6977), respectively. The result of length-weight relationships could be used for fishery to approve appropriate regulations for sustainable fishery management. The present findings could also be useful for ecosystem modeling. In the present study, changes in Kn value may be in relation to some other reasons than reproductive cycle and feeding intensity.