S. S. De Silva

Mineral composition of some commercial fish feeds available in Europe

Abstract The concentrations of 14 mineral elements (Na, K, Ca, P, Mg, Fe, Zn, Cu, Mn, Co, Cr, Ni, Cd and Pb), together with pH, moisture, ash and NaCl content, were determined in 38 feeds commonly available in Europe for trout (starter, fingerling, grower, brood), salmon (starter, fingerling, grower), eel (grower), and larval fishes. Large differences in the mineral composition, particularly the trace elements Fe, Zn, Cu, Mn, Co and Pb, exist within and between the different feed categories tested. The results obtained are discussed in the context of available information on the dietary mineral requirements of these fish species.

Biology of juvenile grey mullet: a short review.

Abstract Grey mullet include a number of species belonging to the family Mugilidae and are a typically catadromous group of fish with a very wide geographical distribution. Mullet are an important group from the point of view of culture, particularly in the tropics. Aspects of the biology of the juvenile grey mullet, from the onset of metamorphosis to a length of 10 cm, are reviewed. Migration, growth in the natural environment, food and feeding habits, environmental tolerances, parasites, diseases and body composition of the juvenile grey mullet are discussed.

Performance of juvenile Oreochromis niloticus (L.) reared on diets containing cowpea, Vigna catiang, and black gram, Phaseolus mungo, seeds

Abstract Sixteen isocaloric diets containing one of three protein levels (20, 25 and 30%) were prepared by partially or totally replacing fish meal with seeds of the legume Vigna catiang (cowpea) and Phaseolus mungo (black gram). Oreochromis niloticus fingerlings (mean weight of 2.60±0.52 g) were fed the test diets twice daily to satiation over a 70-day period. Poor growth rates were noted when fish meal was completely replaced by each of the plant protein sources. Weight gain generally declined as the dietary level of legume seeds increased. Poor feed conversion was observed for fish fed diets with higher plant materials at 20% dietary protein. PER tended to increase with decreasing dietary protein level. Carcass lipid of fish fed 20% protein diets was increased significantly except for one group. It was noted that each of the tested legume seeds could replace about 33% of the fish meal in the test diets without any adverse effect on growth rate.

Reproductive strategies of some major fish species in Parakrama Samudra Reservoir and their possible impact on the ecosystem — a theoretical consideration

Available information and fresh evidence is presented to show that presently, commercially important indigenous cyprinid species such as Puntius sarana and Labeo dussumieri of the Parakrama Samudra reservoir as well as other species like P. dorsalis etc. which are known to constitute a significant fish biomass of the reservoir but commercially yet unexploited, are not likely to breed in the reservoir. Possible reasons for an apparent lack of breeding success in the reservoir are briefly discussed. In addition the possible effects of water level fluctuations in the reservoir on the nest building capability of the exotic cichlid. Sarotherodon mossambicus, which is the mainstay of the commercial fishery are discussed. It is postulated that a certain degree of fluctuation in the water level is essential for S. mossambicus to maintain its breeding success.

Habitat, associations and competition of eight Barbus (=Puntius) species (Pisces, Cyrinidae) indigenous to Sri Lanka

A detailed description of the typical habitats of 8 Barbus species of Sri Lanka is given. The distribution of their typical habitats over the various waters leads to the grouping of species in associations. Quantitative analysis of catching data corroborates these groupings. Food competition and competition for spawning grounds is discussed following the species associations.

Growth, food intake and evacuation rates of grass carp, Ctenopharyngodon idella fry

Abstract Grass carp fry ranging in weight from 9 mg to 300 mg were used in experiments to determine their response to diets of coconut meal and a 1:3 mixture, by weight, of coconut meal and zooplankton at 28 and 33°C. The food intake was generally higher in those fry maintained on the mixed diet at 33°C. The rate of growth was always found to be higher in those fry maintained on a mixed diet at 28°C. The rate of weight increase of fry expressed as a percentage of the initial body weight tended to decrease in fry maintained on a diet of coconut meal, whilst the reverse was observed for others. A maximum food conversion ratio of 1.29 was recorded for fry maintained on a mixed diet of coconut meal and zooplankton at 28°C. Fry of grass carp changed from an almost exclusively carnivorous to a herbivorous one at a length of 25–30 mm. The evacuation time was both temperature- and weight-dependent, decreasing with increasing weight at a particular temperature.

Changes in body condition and proximate composition with maturation in Puntius sarana and Sarotherodon mossambicus

Changes in body condition and moisture ‘protein’ total lipid and ash content of the musculature in Puntius sarana and Sarotherodon mossambicus with maturation was studied in individuals obtained from the commercial fishery of the Parakrama Samudra, an ancient man-made lake in Sri Lanka. In S. mossambicus the body condition declined, in both sexes, with increasing maturity whilst in P. sarana the body condition improved with maturation until Stages IV/V and declined after spawning.

The Identity of Puntius Melanampyx Singhala (Duncker, 1911) (Pisces, Cyprinidae)

It is shown that Puntius melanampyx singhala (Duncker, 1911) is identical to juvenile stages of P. filamentosus (Val., in Cuv. & Val., 1844). The taxonomic relationship between the latter species and P. melanampyx (Day, 1865) is briefly discussed. The argument of the present paper is not influenced if the generic name Barbus is adhered to instead of Puntius. Synonymy Barbus singhala Duncker, 1911: 263. Puntius singhala; Deraniyagala, 1930: 11. Puntius melanampyx singhala; Deraniyagala, 1949: 17. Puntius melanampyx sinhala; Deraniyagala, 1949: 4; 1952: 33; Munro, 1955: 43. Puntius filamentosus (Val., in Cuv. & Val., 1844).