~ 1746 ~ Journal of Entomology and Zoology Studies 2017; 5(4): 1746-1749 E-ISSN: 2320-7078 P-ISSN: 2349-6800 JEZS 2017; 5(4): 1746-1749 © 2017 JEZS Received: 15-05-2017 Accepted: 16-06-2017 Santhoshkumar S Department of Fisheries Biology and Resource Management, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi, Tamil Nadu, India CBT Rajagopalsamy Department of Aquaculture, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi, Tamil Nadu, India P Jawahar Department of Fisheries Biology and Resource Management, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi, Tamil Nadu, India N Jayakumar Department of Fisheries Biology and Resource Management, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi, Tamil Nadu, India P Pavinkumar Department of Fisheries Biology and Resource Management, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi, Tamil Nadu, India Correspondence Santhoshkumar S Department of Fisheries Biology and Resource Management, Fisheries College and Research Institute, Tamil Nadu Fisheries University, Thoothukudi, Tamil Nadu, India Growth and mortality characteristics of Otolithes ruber (Schneider, 1801) exploited off Thoothukudi Coast, Tamil Nadu Santhoshkumar S, CBT Rajagopalsamy, P Jawahar, N Jayakumar and P Pavinkumar Abstract A detailed analysis was undertaken to study the growth and mortality characteristics of the Otolithes ruber in Thoothukudi coast from July 2006 to June 2007. The growth parameters L∞, K and t0 were estimated as 37.28 cm, 0.27 and -0.58 respectively. The K value of O. ruber was relatively low which inferring slow growth rate of this tropical demersal fish species. The estimated total instantaneous mortality co-efficient (Z) of O. ruber was 2.45 and the fishing mortality co-efficient (F) was 1.74. The species are slightly over exploited in this region. Keywords: Growth, mortality, Otolithes ruber, Sciaenids, Thoothukudi Introduction Growth and mortality parameters are vital population dynamic tools to assess the stock in the aquatic ecosystem and it helps to formulate effective management measures to sustainably harvest the resource. Thoothukudi is one of the potential areas in Tamil Nadu coast and it covers the coastal length of 163.5 km in the Gulf of Mannar Marine biosphere. Ramanathapuram and Thoothukudi contribute major catches in the Gulf of Mannar region. In Thoothukudi, trawl nets are the most dominant fishing gear used to catch the demersal and pelagic fishes. Among the demersal fishery, sciaenid species are the most important group of fishes caught in bottom trawl net. Otolithes ruber contributes dominant catch among the sciaenid fishery next to Nibea maculata in Thoothukudi coast [1] . Though the growth and mortality parameters of several sciaenid species have been studied by many authors from different regions of India [2,3,4,5,6,7,8,9,10,11,12,13,14,15] , studies on population parameters from Tamil Nadu coast, particularly, from the Gulf of Mannar region are limited. Hence, the present study was undertaken to estimate the growth and mortality parameters of O. ruber exploited in Thoothukudi coast. Materials and methods The study was carried out for a period of 12 months from July 2006 to June 2007. Length frequency data of O. ruber were collected six times in a month to estimate the age, growth and mortality parameters. A total of 1,587 specimens of O. ruber were collected from the mechanised trawlers in Thoothukudi coast. Fishing grounds and study area of O. ruber in Thoothukudi coast is shown in Fig. 1. Age and growth of O. ruber was assessed using the FiSAT computer software [16] . The length frequency data were subjected to a modal progression analysis by splitting the modes using Bhattacharya’s analysis followed by linking of means. The K value was estimated using K scan. ELEFAN I module in FiSAT II software [17] was used to estimate the growth by using the following von Bertalanffy’s growth equation [18] . The equation is as follows, L t = L∞ * [1-exp {-K*(t-to)} ] Growth performance index (φ’) or phi-prime and t0 value were computed based on the calculated K and L∞ values obtained from the growth equation. The equation used to calculate phi-prime [19] is as follows,