A Study of Stock Status and Size at Maturity of Dasyatis Zugei (Pale-Edged Stingray) in Gulf of Mannar (Mannar District)
No Thumbnail Available
Date
2014
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Uva Wellassa University of Sri Lanka
Abstract
Dasyatis zugei is one of the major non-target species caught in the bottom-set crab nets used for catching blue swimming crab (Portunus pelagicus) in Gulf of Mannar. This study aims to determine stock status, the length—weight relationship and size at maturity. In total 1,404 individuals were collected from crab nets in two landing sites; Vankalai and Thalvupadu in Gulf of Mannar during the period of September - November, 2018. Disc Width-WD of all the individuals were measured to the nearest mm, body weight was weighed to the nearest gram and sex was determined. The state of maturity of gonads of females was identified through dissection and macroscopic examination of ovaries. Mean ova diameter significantly varied among females, according to the different maturity stages (P<0.05). Sex ratio in the catch was 1:1.35 (M: F). Disc width of males ranged from 85-260 mm with a mean of 175.43±22.42 and females ranged from 110-220 mm with a mean of 167.27±17.55. The Disc width-weight relationship was analyzed by Simple Linear Regression using log transformed data and it showed Log W = -0.5923 +
2.364 log W D for male and Log W = -3.497 + 2.599 log WD for female. The results show negative allometric growth (b<3) for D. zugei. There was no significant statistical difference (P>0.05) in male and female regression co-efficient. The size at first maturity
=
was 166.5 mm for female D. zugei. Embryos were found only in females > 160 mm of WD. The maximum fecundity was three embryos per female and the stock status of D. zugei was determined as above limit reference point (Spawning potential ratio as 21%) but not in a state of sustainable utilization. This study reports the first findings on length-
weight relationship and size at maturity of D. zugei in Sri Lankan waters.
Keywords: Dasyatis zugei, Size at maturity, Stock status, Length-weight relationship, Non-target species
Description
Keywords
Aquatic Resources Technology Degree Programme ( AQT)