Studies on the growth and mortality of invasive Oreochromis niloticus (Linnaeus, 1758) in sub-tropical river Yamuna, part of Gangetic River System, India

Abstract

Growth parameters, mortality, growth performance index and exploitation ratio of the Oreochromis niloticus were assessed based on the length-frequency data collected fortnightly from the Allahabad stretch of the Yamuna, India during September 2011 to August 2013. The size of the catch ranged between 70 and 495 mm total length (TL). The data was analyzed in the ELEFAN-I (Electronic Length Frequency Analysis) module in FiSAT software. The asymptotic length (L∞) and growth coefficient (K ) were estimated as 562 mm TL and 0.58 year-1, respectively. The total mortality (Z), natural mortality (M) and fishing mortality (F) coefficients were 3.74, 1.015 and 2.725 yr-1, respectively. The growth coefficient index (ø’) was calculated as 3.26. The exploitation ratio (E) was worked out as 0.667, indicated that the stock was slightly overexploited. The estimated growth (Total Length) at the end of I, II and III years were 247, 386 and 463 mm TL, respectively. The observed multi-year survivorship based on the length frequency data from the river Yamuna in O. niloticus suggested that it has successfully established in the non-native environment and is rapidly spreading in other tributaries of the river Ganga. The recruitment pattern was observed to be continuous throughout the year with several micro-cohorts with two overlapping peaks of unequal pulse strengths. The estimated MSY for this species in the Allahabad stretch of the river Yamuna was 27.13 t. This study can form an important base for future research work in the management of this invasive species in the Gangetic river system in India. Not Available