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Notes: Diel feeding patterns and daily food rations of five cyprinids Amblypharyngodon melettinus, Barbus chola, B. dorsalis, B. filamentosus and Rasbora daniconius in two Sri Lankan reservoirs were studied based on diel surveys using an iterative method, MAXIMS. A. melettinus and B. chola had single peaks of feeding whereas diel feeding patterns with two peaks occurred in the other three species. Daily food rations varied seasonally and with size of fish. The iterative technique used is reliably applicable for quantifying daily rations, and provides a means of linking trophic levels in natural populations of fish.

Notes: Food intake, growth and food conversion of young, O-group herring were studied at two temperatures and feeding regimes over a period of 19 weeks. The food intake of fish fed to satiation twice daily showed considerable variation. Food intake per fish at 14.5° C was about three times that at 6.5° C, and was generally much higher than in most other species of fish studied. The mean increase in wet weight over the 19-week period was 0.581 g/week at 14.5° C and 0.236 g/week at 6.5° C in fish fed to satiation and 0.094 g/week at 6.2° C and a ration of 1.3% of the body weight. Growth depensation was found to occur even in fish fed to satiation. The changes in specific growth rate, that is the percentage increase in weight/day, showed similar trends at different temperatures and food regimes. The mean conversion efficiency of fish on a ration of 1.3% at 6.2° C was higher than that of fish fed until satiation, at 14.5 and 6.5° C. The conversion efficiency of fish fed to satiation at 14.5° C showed a distinct decrease with increasing weight while at 6.5° C such a clear trend was not observed. In general, the conversion efficiency of young herring were found to be much lower than that of most other species studied. The weight exponent of the quantitative relationship between food intake and body weight at 14.5° C was 0.744. The total metabolic expenditure at 14.5° C, calculated using Winberg's (1956) ‘utilization coefficient, gave a weight exponent of 0.773.

Notes: A production model is presented for semi-intensive freshwater crayfish culture ponds incorporating detrital forage. The conceptual model is developed from five submodels of trophic-dynamic interactions within the pond ecosystem. The model includes microbially enhanced detrital forage (MEDF) produced from plant matter grown in the pond as a significant component of nutrition. The model is proposed as an aid to understanding pond-based aquaculture techniques that rely upon manipulating the characteristics of MEDF. The significance of MEDF as a source of nutrition in aquaculture is discussed.

Notes: Abstract. The fishery of Parakrama Samudra, an ancient man-made lake of 2662 ha in Sri Lanka (8°-10°N; 80°-82°E), as in most other man-made reservoirs in the island, is dominated by the exotic cichlid Sarotherodon mossambicus (Peters), introduced in 1952. The fluctuations in catch per unit/fisherman over the period 1960 to 1982 are shown to be dependent on the yearly fluctuations in the water-level, the changes in the water-level effects being manifested in the fishery after a period of 3 years. The above results were arrived at by auto-correlation analysis of yearly catch per unit effort against the fluctuation of the water level at the main sluice. The changes in yield in a particular year are correlated to the changes in the water level and are described by the equation;〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:1355557X:ARE265:ARE_265_mu1"/〉where Y= yield in kg fisherman-1 month-1 in year t and X= fluctuations in the water-level in year t - 3. The available growth rates in natural and semi-natural impoundments also indicate that the size at which S. mossambicus enter the fishery in Parakrama Samudra corresponds to their size in the third year of life (age 2+). The significance of the above observations is discussed on the basis of available knowledge on the reproductive cycle and the nesting requirements of S. mossambicus which are achieved when significant fluctuations in the reservoir level take place by making available optimal water depths in areas with a suitable substratum. The possible use of the above criteria as a management measure is also briefly discussed in the light of possible irrigational and fisheries conflicts in the utilization of the reservoir resources.

Notes: Abstract. The applicability of mixed feeding schedules using low-and high-protein diets was evaluated by three on-farm field trials conducted in fertilized earthen ponds. Rohu, Labeo rohita (Hamilton), and common carp, Cyprinus carpio L., were used in the first two trials, and catla. Catla catla (Hamilton-Buchanan), was also included in the third trial. The concept of a mixed feeding schedule was tested using a 1:1 rice bran-groundnut meal cake mixture, a commonly used feed in Indian carp culture.In a mixed feeding schedule, two feeds are used alternately, each for a predetermined number of days. In the present study, one of three such mixed feeding schedules was used in conjunction with one of two control diets. The control diets were rice bran (diet A) or a mixture of rice bran-groundnut meal cake (diet B). The mixed feeding schedules tested were: 1A/1B, 1A/2B and 1A/3B (numerals indicate number of days diet A or B was offered continuously). Diet A (rice bran only) induced significantly poor growth in all treatments. Interestingly, growth in the mixed feeding schedules was generally equal or superior to that when fish were fed with diet B. Growth efficiency indicators such as SGR. FCR and PER were found to be good for fish maintained on certain mixed schedules. Savings of 15–31% protein and 10–20% of the feed cost were achieved with the various schedules, the highest saving being achieved with the 1A/1B schedule. Nitrogen retention was higher in fish treated with mixed schedules. The results demonstrated the usefulness of mixed schedules in reducing nitrogen input, output and feed costs.

Notes: In this paper the results of a study conducted on the culture-based fisheries in small (ranging from 2 to 160 ha), farmer-managed reservoirs in YenBai and ThaiNguyen Provinces in the northern highland region of Vietnam, for the production cycles of 1997/98, 98/99 and 99/00 are presented. The small reservoirs are leased to small farmers by the provincial authorities for fishery activities, and all lessees adopt culture-based fisheries when fingerlings of grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix), bighead carp (Aristichthys nobilis), common carp (Cyprinus carpio) and mrigal (Cirrihinus mrigala) are stocked between March and mid-April each year and harvested, using large seine nets, after approximately 11–12 months. The mean yields from reservoirs in YenBai and ThaiNguyen Provinces in 97/98, 98/99 and 99/00 production cycles were 251, 332 and 253, and 331, 372 and 210 kg ha−1 respectively. There were major differences in the fish productivity in the reservoirs in the two Provinces, and in a reservoir between culture cycles. The stocking strategies appeared to be rather ad hoc, being determined by the availability of seed stock and the financial status of the lessees. Accordingly, there was no apparent consistent trend in the improvement of yields from the culture-based fishery practice throughout the growth cycles. The fish yields in reservoirs in each Province were significantly related to reservoir area (exponentially) and to mean weight of stocked fish and conductivity (logarithmically). Of the stocked fish, the highest returns were obtained with mrigal and bighead carp, which collectively contributed 〉 50% to the harvest. The return from common carp was the lowest. The mean growth rate of grass carp (2.7 g day−1), followed by bighead carp (2.0 g day−1) was the highest in reservoirs in YenBai Province, bighead carp (4.0 g day−1) followed by grass carp (3.2 g day−1) was the highest in ThaiNguyen Province. The seed stocked on average accounted for 65% and 48% of the total operating costs in YenBai and ThaiNguyen Provinces, and the mean cost:benefit ratio of the culture-based fishery in the two Provinces was 0.35 and 0.37 respectively. The culture-based fishery on average contributed about 28% to the gross income of a farmer lessee.

Notes: Three major carp species, viz. catla Catla catla (Hamilton-Buchanan), Labeo rohita (Hamilton) and mrigal Cirrhinus mrigala (Hamilton), are farmed in polyculture systems in the southern state of Andhra Pradesh (15–18°N, 77–80°E), India. A survey of 189 carp farms was undertaken, and principal component analysis was used to assess the relationship(s) between farm inputs and fish yield. Model results exhibited a strong relationship of yield with the stocking density of all three major carp species (rohu, catla and mrigal). Similarly, buffalo manure, poultry droppings and groundnut oil cake, representing use of major organic fertilizers, also contributed to high yields. Also, supply of supplementary feed ingredients, such as groundnut cake, cottonseed meal, deoiled bran and sunflower meal, and additives in the feed, such as salt and mineral mix, had a positive influence on the yield. The management inputs that influenced the yield were rate of water exchange, frequency of medication and age and mean weight of fingerlings at stocking. Furthermore, the analysis indicated that older ponds were more productive. It was observed that inorganic fertilizers and a few feed ingredients have a secondary and/or a tertiary role in the system, indirectly influencing production. Intrinsic variables, such as age of the farmer and literacy rate, were linked with the less important components, suggesting that the socio-economic variables had a less prominent role in influencing the yields once a production decision was made.

Notes: Apparent dry matter and protein digestibility coefficients (DMD and PD, respectively) were determined using several different marker compounds [Cr2O3, ash, crude fibre (CF), hydrolysis resistant ash (HRA) and hydrolysis resistant organic matter (HROM)] for nine different pelleted diets fed to adult Australian freshwater crayfish, Cherax destructor Clark. For a soybean-meal-based diet (Soy-60), HRA resulted in the highest DMD and PD coefficients (98.6 and 99.6%, respectively), while the lowest values were obtained by using CF (DMD, 74.3%; PD, 91.6%). For the series of diets tested, digestibility coefficients determined using Cr2O3 were significantly higher than those obtained using ash or CF, and lower than those obtained using HRA and HROM. Using ash as the marker resulted in a mean reduction in DMD and PD of 12.4% and 5.5%, respectively, compared to Cr2O3. On average, coefficients obtained using CF were 11.8% and 4.2% lower, respectively, than the values obtained using Cr2O3- Despite an overall reduction in the digestibility coefficients estimated using ash, the ash-ratio technique provided a reasonable estimate of nutrient digestibility for some diets. Based on the ease and speed of determination, it is proposed that dietary ash is suitable for use as a digestibility marker in field situations.

Notes: There is expanding interest in the culture of the Australian shortfin eel Anguilla australis Richardson; however, there is a lack of fundamental biology and husbandry information necessary to further develop an industry within Australia. The present study was undertaken to gain a preliminary understanding of basic husbandry requirements for rearing of juvenile A. australis (glass eels and elvers) in tanks and earthen ponds. Newly caught glass eels were successfully acclimated to culture conditions. During tank culture trials, specific growth rates (SGR) and survival rates ranged from −2.1 to 2.8% day−1 and 52% to 100% respectively. Glass eels weaned onto a commercial eel diet exhibited a significantly greater SGR and survival rate than those weaned onto a commercial trout diet. Glass eels weaned onto an eel diet over a 15-day period grew slightly faster than eels weaned over a 5-day period, but survival rates were not significantly different for each treatment. SGRs (up to 2.8% day−1) were significantly higher for glass eels fed at 9 and 12% day−1 than at 6% day−1. Stocking densities between 2.5 kg m−3 and 30 kg m−3 did not influence either SGR or survival rates. SGRs were significantly higher for glass eels cultured at 25 °C than at lower temperatures. During pond culture trials, SGRs and survival rates ranged from 1.36 to 1.65% day−1 and 39% to 77% respectively. The SGR and survival rates of juvenile eels stocked into ponds receiving supplementary feeding with a commercial eel diet were not significantly different to those of eels stocked into ponds that did not receive supplementary feeding.

Notes: Abstract. The reservoir fishery of China is essentially a post-1950 development. China has an estimated reservoir acreage of 2 × 106ha of which about 1.44 × 1O6ha is used for fisheries. The present reservoir fish production averages 214kg/ha/year and accounts for about 8-9% of the total inland fish production, which is around 4.0 × 1O6mt. The total reservoir fish production and production per unit area in China have been steadily increasing since 1980.The Cwhinese reservoir fishery is essentially a stock and capture fishery. The reservoir management practices and aspects of the present fishery are discussed. Those practices which are not found in the rest of Asia are highlighted.