Effect of stocking density on the growth of Thai pangas, Pangasius sutchi (Fowler) in net cage fed on formulated diet

A three month long experiment was conducted to observe the effect of stocking density on the growth of Pangasius sutchi in net cages. The size of each cage was 1m³.The three stocking densities used were 40, 50 and 60 fishes/m³ and designated as treatment T1, T2 and T3 respectively. Each treatment had three replicates. All the fishes were of same age group having mean length and weight of 7.13 ± 1.37 cm and 2.46 ± 0.12 g respectively. The fish in all the net cages were fed a diet containing 34% protein. The result of the study showed that fish in the treatment T1 stocked at the rate of 40 fish/m³ resulted the best individual weight gain followed by T2 and T3 respectively. The specific growth rate (SGR) ranged between 3.51 and 3.09, the food conversion ratio (FCR) values ranged between 1.73 and 2.04 with treatment T1 resulting the lowest FCR. The protein efficiency ratios (PER) values were 1.69, 1.16 and 1.43 for treatment T1, T2 and T3 respectively. There was no significant (P>0.05) variation among the survival rates of fish which ranged between 92 and 95%. The net productions in different treatments were 2189, 2343, and 2283g for treatment T1, T2 and T3 respectively. The result of the present study indicated that the best individual growth of P. sutchi was obtained at a density of 40 fish/m³ but the highest total production was obtained at a stocking density of 50 fish/m³ in net cages.

Post-larval production of Macrobrachium rosenbergii using mass-cultured live food organisms

Macrobrachium rosenbergii post-larvae were produced in 1992 and 1993 using Artemia nauplii and cultured zooplankton Brachionus plicatilis (rotifier), Apocyclops dengizicus (copepod) and Moina sp. (cladoceran) supplemented with chopped Tubifex worms. In 1992 (first trial) two experiments were carried out under water temperature range of 24.5 to 28°C and 26.0 to 28.5 °C respectively and corresponding post-larval production was 5.6% and 86.3%. The duration of experiments was 58 and 40 days. During second trial in 1993 water temperature varied between 25.0 to 27.0°C. At the end of 59 days the post-larvae were found to be 44% of the total number of larvae stocked on the first day.

Microbiological quality of some iced fishes of Imphal market, Manipur

Imphal is the main marketing centre of fish in Manipur. As fish production of the state is not sufficient to meet the demands, about 120 metric tons of iced fishes are annually brought from other states and sold in this market. Microbiological quality of iced Wallago attu, Labeo rohita, L. gonius and Aorichthy aor in respect of total fungal count (TFC), total plate count of bacteria (TPC), Most Probable Number (MPN) of coliforms, Streptococci, Staphylococcus, Salmonella and Escherichia coli in four tissues (skin, muscle, gill and intestine) were analysed. In all cases, the counts were highest in the gills and lowest in the muscles. The values of TFC, TPC, coliforms, Streptococci and Staphylococci were 0-10³/g 10(sup)6-10⁸/g, 2-α/g, 10-10⁵/g, 10-10⁵/g respectively. E. coli and Salmonella were not detected in any of the samples while the ice used in the preservation contained 10⁵-10⁷ of TPC per gram. The microbiological qualities of the iced fishes of Imphal market were adjudged poor. The extremely high counts of bacteria might be due to (1) poor quality and left over fishes being packed, (2) contact with contaminated ice and (3) repeated thawing and freezing during the process of marketing and transportation.

Some aspects of the biology of Tachysurus tenuispinis Day from Veraval

The regression coefficients in length-weight relationship of males and females of Tachysurus tenuispinis differ significantly. The relative condition factor was calculated for females in relation to various lengths and months. The sex ratio in the catch varied widely in the different months. The number of eggs ranged from 72 to 89 for the fish of length 394 to 570 mm. Empty stomachs occurred in a very high percentage (63.5%) of the total stomachs examined. This is a bottom carnivorous feeder. The main food items found in the guts in order of preference were crustaceans, polychaetes, molluscs, fishes and echinoderms.

The effect of feeding rate on the growth, food conversion and protein efficiency of silver dollar, Metynnis schreitmulleri (AHL), fry

A 30-day experiment was conducted to determine the effects of varying feeding rates on the growth of fry of silver dollar, Metynnis schreitmulleri (Ahl). Silver dollar fry with an average initial body weight of 1.100 ± 0.029 g were collected from a local fish breeder and fed a diet (35% protein and 6% fat) at the rate of 3, 6 and 9% of body weight per day in two equal meals. Per cent weight gain increased from 54.54 to 118.18 with increased feeding rates, which were significantly different (p<0.05) from each other. The highest specific growth rate was obtained in the fry fed at 9% body weight per day. In another study for 30 days, the effects of feeding frequency on growth, feed conversion and protein efficiency of silver dollar fry were evaluated. Groups of silver dollar fry with an initial individual weight of 0.700 ± 0.019 g were offered feed continuously for 24 hours during the day or night at different time intervals with varying meal sizes. The night time feeding with two meals gave the lowest weight and length gains (0.985 g and 0.30 cm). The growth rates of fish fed during day with three equal-sized meals are significantly (p<0.05) higher (4.66%) than the other treatments.

Report of Catch Assessment Survey of Lake Albert – Albert Nile conducted in July 2012

A Catch Assessment Surveys (CAS) with the overall objective of generating information on the fish production and commercial value of the fisheries of Lake Albert and Albert Nile system was implemented by the National Fisheries Resources Research Institute (NAFIRRI) in collaboration with the Department of Fisheries Resources (DFR), Local Government staff (FOs) and BMU members at selected landing sites on Lake Albert (12 landing sites) and Albert Nile (26 landing sites) in July 2012. A total 622 and 313 boat days on Lake Albert and Albert Nile respectively were sampled for a period of 9 days. Results indicate an annual landing of 151,600 and 5,900 tonnes (t) of fish with an estimated beach value of 122.5 and 14 Billion (UShs) from Lake Albert and Albert Nile respectively. Over 80% of the catch from Lake Albert comprised the small pelagic species; Neobola bredoi (Muziri) and Brycinus nurse (Ragoogi) followed by Nile perch (6%). However, due to low market value of the small fishes and the high prices attached to Nile perch for industrial processing and export market, the contribution of the latter to beach value rose to 34% of the total. The contribution of the light fishery based on small pelagic species (B. nurse and N. bredoi) are insignificant on Albert Nile. Even if the small pelagic species may be present in the river system, a light fishery based on these two is yet to be developed. Proportionally, Albert Nile still remain a multispecies fishery with over 20 fish species harvested commercially. Interestingly, the Albert Nile fishery still remains primitive with simple crafts and gears (mainly dugout canoes, traps, and gillnets). This could suggest that the more developed the system becomes the higher the level of transformation in its fisheries leading to simplification, characterized by reduction in multispecies nature and dominance of few species. Illegal gears especially undersized gillnet of mesh size less than 4 inches were the most dominant in the Lake Albert and Albert Nile fisheries. They captured large quantities of immature fish particularly when used to target Nile perch, Bagrus, Nile tilapia, and large Barbus spp. Their impact when used to target the smaller species (Ragoogi, Angara & Ngasia) is yet to be evaluated. A specific study to analyze selectivity and impacts of these nets is a recommended. However, the dominance of 1.5” mesh sizes especially on Albert Nile to target Angara, Ngassia and Barbus, is definitely destructive to their fisheries and should be checked forthwith. In addition, there is an emerging fishing method locally referred to as “Salsio or Luzira” whereby fishers stay on the lake from 3 days up to 2 weeks without returning to the landing site. They carry with them food and salt for processing the catches on the lake, and in the case of Albert Nile on make shift shelters on islands and in the game park. They normally use gillnets of 3-3½ inch mesh size and caught mainly Nile perch & Bagrus (Pethi & Munama). On return they land several tons of fish. Most of these Catches are not captured in the estimates presented in our analyses since we target daily fishing boats. The possible impacts of this fishing method should be studied and appropriate action recommended.

Aquatic coleoptera and hemiptera taken at light in some Asian countries with a note on Sphaerodema (Hemiptera-Belostomatidae)

Aquatic insects are relatively common at artificial lights and are often taken in light traps operated for catching other insects. They are however seldom recorded. These records are however of importance in understanding their distribution and abundance. Aquatic Coleoptera and Hemiptera are of importance in fisheries because some of them are predators on small fish whilst others serve as food for fishes of all sizes. Some like the Corixidae are of special interest because they can utilize the bottom ooze which is abundant especially in small habitats. Fernando (1961a) gave a comprehensive bibliography of records at light. In the present paper a number of records are given from various parts of Asia, where in the past records were very few. They are based on collections made by the author and also on material in the Zoological Survey of India, Calcutta. Amongst specimens sent for study by the Bernice P. Bishop Museum, Honolulu, were a few specimens which had been recorded at light.

New species of Monogenoidea from fishes of Ceylon

During the stay of the vessel "Ob" (Soviet Antarctic Expedition) at Colombo, May, 1957, the author received from Dr. C. H. Fernando some specimens of different species of fishes from Ceylon, preserved in formalin, as a present for the Zoological Institute (Academy of Sciences of the U.S.S.R.) New species of Monogenoidea have been found when examining the gills of the fishes received and the present paper deals with their description. The material was preserved in strong formalin which highly condensed the tissues of the parasites. Therefore the details of the anatomical structure in most of the specimens could not be recognized even by means of phase-contrasting equipment. So the description is confined almost exclusively to the chitinoid armature of the haptor and copulatory organ. The terms and the measurements used in this paper are the same as those used previously (Gussev, 1955).

A Preliminary study of the defensive spines of some Malayan freshwater fishes

The defensive spines of fifteen Malayan freshwater fishes have been studied morphologically. The classification of spines has been slightly modified from the previous work of Fernando and Fernando (1960). They are divided into simple, denticle-bearing and venom-carrying. The simple spines are further sub-divided into single and multiple and the denticle-bearing into Bagriid and Clariid types. The latter agree morphologically with the venom-carrying spines of previously studied forms and may be a degenerate condition. Simple spines occur singly in the Cyprinidae where they are found at the anterior end of the dorsal fin. A spine of similar structure occurs in the catfish Glyptothorax. In the families Anabantidae, Cichlidae and Mastacenbelidae simple spines occur as a series. Denticle-bearing spines occur in the catfishes (Order-Nematognathi). Those having denticles on one face occur in the Bagridae, Siluridae, Sisoridae, and Akysidae. They are referred to as Bagriid type. In the other type denticles occur on the anterior and posterior faces of the spine. They are referred to as Clariid type. None of the Malayan species studied had venom-carrying spines and they are unlikely to be found in the freshwater species. The functioning of the defensive mechanism whose morphological bases are spines is discussed and the relation between the size and habitat on the effectiveness of the spines is mentioned. The evolution of defensive spines is discussed briefly.

Distribution and length-weight relationship of tunas and tuna-like fishes around Ceylon

Tunas and tuna-like fishes have contributed considerably towards the increase in fish production from Ceylon's coastal waters, during the last five years and in this blood fish group lies a potential resource for a further increase in production. Consequently considerable attention is being paid to the study of these species. Length frequency sampling of these species are being carried out and quite often it becomes necessary to convert catch in terms of weight to catch in terms of number, when estimating apparent abundance of the stock. The length-weight relationship in addition to its usefulness in converting length frequency data to weight frequency data for such purpose is of general value to biologists and even to fishermen. The six species studied are yellowfin tuna (Thunnus alacares, Bonneterre), skipjack tuna (Katsuwonus pelamis, Linnaeus), mackerel tuna (Buthynnus affinis, Cantor), frigate mackerel (narrow corseleted Auxis thazard, Lacepede and broad corseleted A. rochie, Risso) and bonito (Saida orientalis, T&S).

Some freshwater mollusca from Ceylon with notes on their distribution and biology

Very few records of freshwater molluscs of Ceylon are available in several publications and although they are of importance as food for fishes and vectors of parasites we know little of their role in these capacities in Ceylon. The present paper is to be considered more as a pointer to the group than as a study of the freshwater molluscs of Ceylon. The author collected freshwater molluscs during surveys made for the study of systematics and distribution of various freshwater invertebrates. Material of freshwater molluscs purchased by the Museum in Leiden and labelled Ceylon was also seen by the author. The nomenclature used in this paper has been simplified by the omission of sub-generic and sub-specific names. The sub-generic divisions are dealt with critically for the Gastropoda by Wenz (1938-1944) and Zilch (1959-1960).

Seasonal variation in the distribution and availability of Carangids ("Paraw" and "Parati") in the Wadge Bank

The Wadge Bank has been exploited regularly by Ceylon based trawlers since 1955 (Sivalingam & Medcof 1957). The bank is about 4,000 sq. miles in extent (Malpas 1926) and is located south of Cape Comorin within the Continental Shelf of India (Fig. 1). Carangids are taken in large numbers during the months of the south west monsoon (Sivalingam 1966). The quantity, in which the Carangids are captured as shown by the fishing records, is large enough to influence the total catch from the bank during these months (Fig. 2). Carangids are held in high esteem as excellent quality food fishes and accordingly constitute a commercially important group. This paper records the results of a detailed examination of the past fishing records in respect of this group, based on the analysis of the catch and fishing effort for the years 1957 to 1962. The distribution pattern of this group of fish in the Wadge Bank is discussed.

Taxonomic notes on a collection of flying fishes from Ceylon waters

The present study reports another seven species of flying fishes and brings the total for Ceylon to fifteen. Eleven of these fifteen species are represented in the author's collection. A key based on Breader (1938) and Parin (1960) and descriptive notes for these eleven species are given in this paper.

Chemical analyses of some Ceylon fishes - 2

Sri Lanka is an island surrounded by the Indian Ocean. Many varieties of marine species of fishes are caught in waters surrounding the island. The catches vary from coast to coast with the monsoonal fluctuations. The island is geographically situated in the tropical latitudes of high rainfall. The topographical landscape presents a central cluster of peaks surrounded by vistas of plains. Hence inland water bodies rise and meander in different directions of the country resulting in heterogeneous habitats yielding a host of freshwater fishes. As the different types of marine and freshwater fishes are manifold, an investigation into the nature and constituents of various species from a chemical standpoint was initiated by Lantz and Gunasekera (1957). Their paper was with a view to rendering possible a better commercial utilization of fishes. The present work is an extension of the above with necessary deviations. Lantz and Gunasekera (1957) had published results of 30 species of Sri Lanka fishes. The present paper introduces results of 5 species and investigations are being continued to cover other species. Investigations appearing in this paper were on fish samples obtained from different sales points in Colombo.

Chemical analyses of some Ceylon fishes - 3

Chemical analyses of fishes found in Sri Lanka were initiated by Lantz and Gunasekera (1957), who presented data from examination of 30 different species of fishes. Later Peiris and Grero (1972) published the analysed data of 5 more species. The present paper continues the analyses and the results obtained from 10 more varieties of marine fishes are given.