Studies on Growth Characteristics of Siganus species
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Date
2019
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Fisheries College and Research Institute, Thoothukudi, Tamilnadu Dr.J.Jayalalitha Fisheries University
Abstract
This study was undertaken to document the Population biology, Growth and Mortality characteristic of Siganus species under controlled condition. Fish specimens were collected fortnightly during July 2018 to June 2019 from Threspuram, Fishing harbour, Inigo nagar and newharbour. A total of 8245 samples were encountered during the study which includes S. canaliculatus, S. javus, S. lineatus, S. fuscescens and S. stellatus.
For stock assessment, length frequency data were collected at fortnightly intervals for studying the length-weight relationship, growth patterns, recruitment pattern, using the FiSAT computer software. The annual catch of S. canaliculatus, S. javus, and S. lineatus showed year round occurrence along Gulf of Mannar. The estimated life span of S. canaliculatus, S. javus and S. lineatus was estimated as 3 years and 4 years and 3.5 yearsrespectively. The K value for S. canaliculatus was low (0.27) because of slow growth and for S. javusand S. lineatusit was high 0.57 and 0.52 respectively. The estimated total instantaneous mortality (Z) of S. canaliculatus, S. javus and S. lineatus were 0.59, 0.58 and 0.56 respectively. Recruitment of S. canaliculatus, S. javus and S. lineatus was recorded throughout the year with single peak. The Virtual Population Analysis revealed that fishing pressure was high during the below the length group of 18 to 25 cm for S. canaliculatus. For S. javus and S.lineatus natural mortality was low upto 16cm. Based on the relationship between exploitation ratio and yield per recruit of S. canaliculatus, S. javus and S. lineatus it could be inferred that this species is moderately exploited.During the study period new occurence of Siganus fuscescens was observed from Gulf of Mannar Region S. canaliculatus, S. javus and S. lineatusform good fishery of Siganus groups in Thoothukudi coast of Gulf of Mannar, These species are exploited mainly by trawlers.
Live Siganus fishes were collected and acclimatized for further studies at Shore Lab Field Research Facility (SRFF). Initial experimental trial was conducted with mixed Siganus species and better growth and survival was obtained in S. canaliculatusand S. lineatus.The specific Growth rate was 3.52 + 0.01 g for S. lineatusand 3.45 + 0.02 g for S. canaliculatus. The estimated FCR value was 1.2 and survival was 82.5%. There is no significant difference between the value obtained from the Organosomatic index of initial and final values of the fishes. The results indicates that there is an improvement in the growth of the Siganus lineatusstocked under controlled condition and better growth was obtained at less and medium stocking density of 5 and 10 nos /m3.