Recent Submissions

  • Reservoir fishery resources of south-east Asia

    Fernando, C.H.; Furtado, J.I. (1975)
    Although the reservoir area in south-east Asia is considerable, the fish production is low in the majority of reservoirs. Although high fish production has been recorded in a number of reservoirs in Sri Lanka and Indonesia, high fish production in reservoirs has with few exceptions resulted from the introduction of typical lake species from Africa. Addition of further lake fish species especially into deeper reservoirs will probably increase present fish yields. Diversification of the lake fish fauna can be achieved by introduction of species indigenous to the region like Etroplus suratensis. In this introduction of fish species, three points may be noted with specific reference to Tilapia spp.: (a) Lakes without indigenous cyprinids show marked fluctuation in fish catch with the introduction of Tilapia, and this could be stabilised by the introduction of predators and more diverse species. (b) Lakes with a moderate diversity of fish fauna show a high stabilised production with the introduction of Tilapia, presumably because of the effect of predator pressure on excessive Tilapia breeding. (c) Lowland lakes with a rich diversity of indigenous fish species colonising lakes may not require the introduction of Tilapia. Introduction of invertebrates into reservoirs in south east-Asia has not been done deliberately so far. However, the experience in other parts of the world, notably the Soviet Union, indicates that such introductions are likely to prove beneficial and to increase fish production. The potential for a considerable increase in fish production from reservoirs exists in south-east Asia. Proper management is likely to cost less than what is required for fish culture. Rural areas are likely to benefit most from increased fish production in reservoirs, and this might be a way to provide cheap protein where it is most urgently needed.
  • Taxonomic study of the cephalopods, particularly the Teuthoidea (squids) and Sepoidea [i.e. Sepioidea] (cuttlefish) in the water around Sri Lanka

    Perera, N.M.P.J. (1975)
    A preliminary taxonomic study of the local cephalopods has been undertaken. 8 spp have been identified, and a key to the Sepioidea and Teuthoidea of the Ceylon seas is presented. The spp identified are described and illustrated, with notes on distinctive characters, and on distribution
  • An analysis of the experimental pole and line fishery conducted around Sri Lanka by Nichiro Fishing Company of Japan

    Sivasubramaniam, K. (1975)
    Under a joint agreement the Government of Sri Lanka and the Nichiro Fishing Company of Japan have undertaken an experimental pole and line fishery around Sri Lanka with a view to determining the feasibility of establishing a joint commercial venture. 3 Japanese vessels conducted trials during the period March 1973-October 1974. Details of the vessels and cruises are given. A variety of fish were tried as bait, and the selection of appropriate bait is discussed. Catches and catch and effort statistics are presented, with tables showing distribution of the tuna. The results of the trials were below expectations, and are in part attributed to bait availability, and unfavorable weather conditions. Seasonal variation of the type of fishery is suggested in order to take account of this, and it is concluded that a fishery based on 45/50 ft combined pole and line and drift net fishing vessels might prove feasible.
  • Purse seining for small pelagic fish around Sri Lanka

    Joseph, B.D.L. (1975)
    An attempt has been made to study skipjack (Katsuwonus pelamis) live bait availability and other small pelagic fish, their seasonal variations with respect to distribution, species and size composition. Exploratory surveys made use of echo sounding and lookout during the day, and light attraction at night. Percentage composition of spp caught at each station is tabulated. Seasonal variations are discussed and monthly variations in some important groups are plotted. Size composition, especially for Sardinella spp, is considered. The availability of 'red bait' would not be adequate to support an extended pole and line fishery for skipjack. The daytime fishing methods were not considered to have been especially successful, and the choice of gear and method of capture is discussed. It is suggested that the present fishery could be improved by the adoption of ring nets by local fishermen in place of the present purse seines when catching bait.
  • Vertical temperature structure of 250 m. water layer around Sri Lanka at the tail-end of the north-east monsoon

    Samarasinghe, J.R. de S. (1975)
    Data collected during cruises of the Hoyo Maru in Jan-Mar 1975 are analysed. Data is tabulated to show vertical temp profile, surface water temp and temp gradient. Each of these features is discussed. Thermoclines are shown to be established off the coast of India, their depth varying according to time of year. Upwelling off the Cochin coast is discussed. This occurs during Oct-Nov. Surface temp is considerably influenced by the north-east monsoon. The 'clockwise current' (or 'transparent current) characterised by high salinity, high transparency, and rich nutrient conchs, and which prevails in Jan-May brings oceanic water into the Bay of Bengal and sweeps along the Ceylon coast.
  • Cultivation of Gracilaria lichenoides in Puttalam Lagoon

    Sivapalan, A. (1975)
    A brief description is given of experimental rearing of the red alga G. lichenoides using a coir net frame method. Frames of 1x1 m were made and tied to bamboo poles which were planted in water; the frame was fixed at a level about 1 ft below the water level. 2 cm fragments were used as propagating material. Plants were found to grow more luxuriantly and were more greenish than using other methods, and in addition were free from extraneous matter such as sand. The regeneration time of the plant is low, and it reaches marketable size in 3-4 months.
  • De-scummer for beche-de-mer processing

    Sachithananthan, K.; Natesan, P.; Alagaratnam, C.; Thevathasan, A.; Philip, L.B. (1975)
    An improved method for processing sea cucumber (beche-de-mer) is described. Details of a machine named de-scummer are presented. The traditional method for preparation is discussed, and the new method outlined; this involves burying boiled sea cucumber in clean sand contained in cement pits for periods of 6-8 h. The animals are then transferred to the de-scummer for mechanical treatment and are boiled again. After this they are dried.
  • Antibacterial properties of some marine algae of Sri Lanka

    Sachithananthan, K.; Sivapalan, A. (1975)
    The authors report on the antibacterial activity of 11 algae, green, brown and red. Prepared extracts were tested, and varying degrees of activity were exhibited. Most activity was shown by Ulva fasciata, Sargassum cervicone and Halimeda macroloba.
  • A preliminary study on the keeping quality of locally produced marine and freshwater salted dried fish

    Goonewardene, I.S.R.; Etoh, S. (1980)
    Experiments were conducted on the storage life of salted dried fish from both freshwater and marine species. It was found that the storage life of salted dried products from the 2 freshwater species tested (Ompok bimaculatus and Labeo dussumieri) is much longer than that of the 2 marine species (Gonialosa manminna and Chorinemus lysan), i.e., 51 days.
  • Increase of storage shelf life of locally produced salted/dried fish by redrying and/or packeting

    Etoh, S.; Goonewardene, I.S.R. (1980)
    Experiments were undertaken to prolong the storage life of salted/dried fish by re-drying and/or packing. The storage life under normal conditions is 51 days; re-drying the fish at 50°C for 12 hours extends the storage life only by 7 days. However, re-drying and packing gizzard shad (Gonialosa manminna ) in polyethylene maintains the fish in excellent conditions for well over 87 days. The use of air tight bags for storing good quality salted dried fish is recommended.
  • Storage life of silverbelly (Leiognathus sp.) with delayed icing

    Jayaweera, V.; Villadsen, A.; De Silva, T.; De Alwis, D.; Jansen, M.A.B. (1980)
    Silver belly (leiognathus splendens) caught in September spoiled faster than the fish caught in May. This could be due to seasonal changes. For silver belly, Total Volatile Base (TVB) value could be used as a measure of spoilage. At the beginning of spoilage TVB value is between 30-40 mg. N/100g sample. The main spoilage for silver belly appears to start between 6 and 8 hours (at 28° C-30°C) after landing on board. Therefore it is not necessary to ice silverbelly immediately; it seems to be sufficient if icing can be done within 6 hours of landing on board.
  • Improved chemical methods for extraction of fin rays from shark fins

    Jayawardena, K.M. (1980)
    A survey was undertaken of methods available for the extraction of fin rays from shark fins. The development of new, quicker and easier methods of processing is presented.
  • Studies on the preparation of fish silage. 4. Economics of production

    Aagaard, J; Disney, J.G.; Jayawardena, K.M.; Poulter, R.G. (1980)
    Economic aspects of producing liquid and dried silage from silver belly (Leiognathus splendens) in Sri Lanka are considered. A discounted cash flow analysis for the production of a dried fish silage/rice bran product suitable for use in compounded poultry feeds shows that the internal rate of return for a 10-year project would be between 34-77% and for a 5-year project between 26-73%. Thus it is concluded that the project would be extremely profitable.
  • Keeping quality of imported dried fish

    Goonewardene, I.S.R.; Etoh, S. (1980)
    All imported salted, dried fish samples tested had a salt content below 30% and above 12% and hence met requirements of the proposed standard. Also samples without quality cut tested had a greater salt content than that with quality cut. This indicates that salt contributes to protecting dried fish and hence may be endorsed by sensory evaluation to a certain extent. Samples with quality cut had more moisture than that without quality cut. But all samples with and without quality cut had a moisture content greater than 35% which is the maximum moisture content for such species specified in the standard. Microbiological testing for total counts and Coliform contents too showed that good quality dried fish had counts greater than that specified in the standard. The different species of fish tested had varying lengths of shelf life. But on an average the shelf life of dried fish could be prolonged for about 12 days by re-drying at 45°C for 6 hours, i.e., re-drying at these temperatures without subsequent packing in polythene bags may not be practical for prolonging the storage life of salted/dried fish.
  • Studies on the preparation of fish silage. 1. Effect of quality of raw material and type of acid

    Jayawardena, K.M.; Villadsen, A.; Guneratne, Q.; Aagaard, J.; Poulter, R.G. (1980)
    An experiment was undertaken in which silver bellies (Leiognathus splendens) of different quality were used to produce silages using different concentrations of hydrochloric acid and formic acid. The quality and storage life of the various preparations are reported. Silages which keep for at least 30 days can be produced from silver belly held for 3 or 12 hours at 28°C by: 1) reducing the pH by addition of hydrochloric acid; 2) adding 0.5% formic acid and reducing the pH to 3.5 with hydrochloric acid; or 3) adding 2.5% formic acid.
  • A survey of process hygiene in the Sri Lankan prawn industry. 3. Critical control points

    Sumner, J.L.; Goonewardene, I.S.R.; Fonseka, T.S.G. (1980)
    Of fifteen processing plants surveyed in Sri Lanka, only five were found to have a prawn process which was adequately controlled. Most common process faults were: inadequate chilling of prawns after a wash in 30°C, mains water, the use of large blocks of ice to cool prawns, and high ratios of prawns to ice. There was also ample scope for cross-contamination of the processed prawns.
  • Studies on the preparation of fish silage. 2. Rate of liquefaction in different parts of silver belly

    Jayawardena, K.M.; Poulter, R.G. (1980)
    An experiment was undertaken to determine from which part of silver belly (Leiognathus splendens) carcasses originate the autolytic enzymes responsible for liquefaction of silage. Findings show that it is important to leave head and viscera present in order to get a satisfactory liquefaction in silage prepared from silver belly using 3.5% formic acid. The storage life of silage produced from various parts of the fish carcasses is also discussed.
  • Studies on the preparation of fish silage. 3. Dried silage products

    Jayawardena, K.M.; Guneratne, Q.; Villadsen, A.; Poulter, R.G. (1980)
    An investigation was undertaken on the production of dried products from silver belly (Leiognathus splendens) silage mixed with plant filter materials. Silages produced using hydrochloric acid and/or formic acid when mixed with rice bran or maize meal and dried, yielded powders having an acceptable appearance and a pleasant odour, which are suitable for use in compounded chicken feeds.
  • Use of length-weight relationship in grading processed beche-de-mer

    Siddeek, M.S.M.; Sachithananthan, K. (1979)
    Holothurians, belonging to the species Holothuria scabra, have been collected by diver-fishermen and processed for export. There is an active fishery for these animals in Palk Bay and Gulf of Mannar, off the north-western coast of Sri Lanka. The absence of standardized method of grading has led to unwarranted variation in sale prices and sometimes in loss of foreign exchange in Sri Lanka. In this paper an attempt is made to present a method to grade processed beche-de-mer by using the lenght-weight relationship.
  • A survey of process hygiene in the Sri Lankan prawn industry. 1. Hygiene status of raw materials and products

    Sumner, J.L.; Goonewardene, I.S.R.; Fonseka, T.S.G. (1980)
    A survey of processing hygiene in the Sri Lankan prawn industry has shown that the incoming raw material has extremely high bacterial loadings; about 50% of samples analysed had a total count in excess of 10,000,000/g. Although beheading reduces the count, ineffective temperature control during processing means that the final total count of raw, shell-on, P.U.D. and P.A.D. prawns, as well as cooked prawns, is in excess of 1,000,000/g. - the maximum level specified by many importing countries.

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