M.Phil. Supervision

Density and diversity of commercially captured Holothurians in North-East coastal region of Sri Lanka K. Veronika1*, U. Edrisinghe2, K. Sivashanthini3 and A.R.S.B. Athauda4 1 Marine Environment Protection Authority, Colombo, Sri Lanka 2 Postgraduate Institute of Agriculture, University of Peradeniya, Sri Lanka 3 Department of Fisheries, University of Jaffna, Sri Lanka 4 Department of Animal Science, University of Peradeniya, Sri Lanka *kveronika.8@gmail.com The present study was conducted with the aim of documenting the species composition and analyse the diversity indices for commercially captured holothurian species. The investigation was carried out from January 2015 to December 2016 at five study sites namely; Viyaparimuli, Munnai, Challai, Puthumattalan and Peppearippiddy. Holothurians were collected within random transects areas of 2 m width and 100 m length. Holothurian species were identified up to species level based on the morphological characters and spicule preparation. A total of seven species belong to the Order Aspidochirotida and two each representing Family Holothuriidae and Family Stichopodidae were identified. They were Holoturia atra, H. leucospilota, Stichopus horrens, S. herrmanni, Bohadschia marmorata, H. spinifera and S. naso. Among them B. marmorata was the dominant species contributing 48.3 % of the population. The highest abundance was of B. marmorata (0.5 ind.100 m-2) and the total species abundance recorded as 1.33 ind.100 m-2. The holothurian diversity was moderate and steady state condition with two dominant species in Peppearippiddy. Community of holothurians consisted of two groups in which the similarity was higher in first cluster ranged from 10-85%. The principal differences was due to the presence of B. marmorata and H. spinifera contributed for more than 50 % of the sites in cluster 1 (Challai, Puthumattalan and Peppearippiddy). The information and observations in this study will be of use in formulating management policies for the holothurian fishery for its sustainable exploitation in North-East coastal waters of Sri Lanka. Keywords: Bohadschia marmorata, Density and Diversity, Holothurians

Macrobrachium rosenbergii, a giant freshwater prawn, was newly introduced to Puthumurippu medium perennial reservoir in Kilinochchi district in June 2016 with the stocking of 100,000 post larvae (PL 15) with the aim of improving livelihood of the fishermen by diversifying species in the reservoir. Return of M. rosenbergii was found to be high with a recapture rate of 2.5 % and return on investment of 360.6 % within one year study period. Income from harvesting M. rosenbergii improved the livelihood of fishers by increasing their income and interest in fisheries. Furthermore, the total yield increased with the increase in fishing effort during the study period. In addition, it was observed that male M. rosenbergii had a significantly high mass and growth rate compared to females on average. The results of this study indicated that M. rosenbergii stocking program was a cost effective and a successful venture in the development of livelihood of fishing community and fisheries production of the Puthumurippu reservoir.

Factors influencing M. rosenbergii catches in Vavunikulam, Muthayankattu, Puthumurippu, Kalmadu and Muhathankulam perennial reservoirs in Northern Province, Sri Lanka were studied. Catch data were collected at the landing sites from the gillnets of the fishers. Individual weight and total number were taken. Since catch of M. rosenbergii get affected simultaneously by reservoir morphometry, fishing intensity, stocking density, rainfall, gear specification, species composition and water quality parameters, a multiple regression analysis was carried out. Comparison of reservoirs based on the studied parameters were used in multidimensional scaling (MDS). Pearson's correlation coefficient indicated a strong positive correlation between stocking density, gear specification, species composition and fishing intensity. In all the five reservoirs, fish yield was dominated by regularly stocked species, which composed of 71.9-99.8% of the total yield. Every reservoir possessed unique characteristics, and the recommendations had to be reservoir-specific. It was observed that the significantly higher fishing pressure had been applied on the bottom area mainly targeting for M. rosenbergii due to higher market value. A modified gillnet should be designed for M. rosenbergii fishing. It was also found necessary to develop a rational stocking program and limit fishing pressure in breeding and nursery grounds of the other fish populations, which would ensure sustenance of natural populations. Through detailed studies recommendations in respect of stocking and optimum effort levels for each reservoir have to be developed.

NARA-2014 Publication

Owing to the spectacular colouration, fish species of the genus Rasboroides have a substantial economic value in the aquarium trade of the world. All the species of Rasboroides categorized as threatened fishes. The studies revealed that some species of the genus Rasboroides are having a stable population in the South-western wet zone of Sri Lanka. Osteology of these important species was studied and the findings further support the recently described or re-described species within the genus. One of the important characters of the genus is danionin notch which was only observed in R. pallidus. This character is always observed in related Cyprinid genera Devario. The presence of danionin notch in R.pallidus is mystifying since it is independently found in two different tribes of subfamily Danioninae. Further studies ought to reveal the status of this character within the Danioninae.