Browsing by Author "Gunawardane, N.D.P."

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Capturing indigenous knowledge in fishing communities of beach seine fishery of Chilaw, Sri Lanka from introducing a co management strategy
(2014) Gunawardane, N.D.P.
Capturing local knowledge of beach seine fishers in the north-western province of Sri Lanka
(Sri Lanka Association for Fisheries and Aquatic Resources, 2016) Gunawardane, N.D.P.; Amarasinghe, U.S.
Morphometric differences observed between two populations of Clarias brachysoma, an endemic, edible freshwater fish of Sri Lanka
(University of Kelaniya, 2006) Gunawardane, N.D.P.; Hettiarachchi, M.
Clarias brachysoma is an endemic, edible, freshwater fish found in Sri Lanka. Several species of Clarias in other parts of the world are considered as suitable candidates for aquaculture. Clarias brachysoma also is a popular edible fish, however, it is not cultured in Sri Lanka mainly due to unavailability of seed for stocking. In trying to develop a breeding programme for Clarias brachysoma, preliminary studies were carried out to find out the size at maturity in order to select a suitable broodstock. Here, some significant morphometric differences were observed in samples of Clarias brachysoma collected from two river basins of Sri Lanka. Samples of fish were obtained from Madu Ganga River Basin (Balapitiya) and Dadugam Oya River Basin (JaEla) in December 2005 to July 2006 and were maintained separately. Each fish in each sample was euthansiated following the standard procedure. Before observing the gonads for maturity, morphometric and meristic characteristics such as length measurements of the body parts and ray counts of fins were recorded for each individual. All the data from two sets of fish samples were tested for normality and then were compared using two sample T-Test and Principle Component Analysis (PCA). Significant differences of the measurements of body weight, total length, standard length, width of the body, length of the caudal fin, head measurements such as pre-dorsal length, head shield length, length of barbles and height of the body were observed for the two samples (P< 0.05). Significant differences were not recorded for meristic data (P> 0.05). However the clear separations were obtained from the PCA score plot of the first two principal component axes. Calculated length weight relationships were also different from each other for the two sets of samples. In the present analysis of morphometric data it clearly indicated that there were significant morphological differences in the two sets of samples of Clarias brachysoma collected from Madu Ganga River Basin and Dadugam Oya River Basin. It would be interesting to carry out DNA analysis to see whether the morphological differences are due to heritable dissimilarities.
Validation of logbook catch records in offshore fishing vessels of Sri Lanka using VMS data.
(4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Gunawardane, N.D.P.; De Croos, M. D. S. T.; Amarasinghe, U.S.
Accurate information on fishing position is a timely need in the offshore fisheries, especially for preventing illegal, unregulated and unreported (IUU) fishing. Vessel monitoring system (VMS) is recognized as one of the effective mechanisms for validating the fishing positions of fishing vessels provided by logbook system. In the present study, an attempt is made for developing an approach to identify and validate the fishing locations of offshore vessels in Sri Lanka using VMS data. VMS data based on the speed, distance and angle filters were adopted to identify the fishing locations. Here, the best angle of the zig-zag shapes recorded in the cruise tracks of VMS was determined as < 15o using the flooding data of VMS. Similarly, speed level of <3 knots was identified as the possible speed of fishing. Distance gaps of fishing locations were recorded and converted to distance buffers. Data from 1291 multiday vessels, operated from 21 fisheries harbors of Sri Lanka from May 2017 to April 2018 were analyzed in the present study. Predicted fishing locations based on VMS data were compared with fishing data of log sheets reported by skippers were compared using paired t-test. Results of the analysis showed that fishing occasions predicted using the speed and course angle of VMS alerts had a good agreement (p<0.05) with the fishing locations reported by fishers. However, potential cruise occasions showed significant deviation from log-book records. Although the time differences of the locations of the two monitoring systems were > 4 hrs, most of the matched locations were recorded within 24 hrs. This may be due to the practice of skippers, who only record their fishing locations only once a day, which was found to be insufficient for reliable reporting. While the current manual logbook system is recognized as appropriate to comply with the enforcement and management needs, there is a need to adopt more appropriate method of reporting catch data by fishermen. Present analysis indicated that the use of VMS data provided an alternative approach for reporting fishing locations of offshore vessels with sufficient accuracy. Need for further improvement of the data recording system representing fishing duration, and species composition is discussed for preventing IUU fishing by offshore fishing vessels.