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An 8-week feeding trial was carried out to determine the effect of increasing dietary palm oil levels on African catfish juvenile growth and nutrient utilization. Six isonitrogenous diets were formulated to contain 0.5% to 15% crude palm oil with dietary lipid levels ranging from 5% to 20%. Growth performance and protein utilization efficiency of African catfish responded in a positive manner to palm oil addition up to 9% (diet 14% lipid). No further improvement in growth was observed with higher levels of palm oil in the diets, and lower survival was observed with inclusion of 15% palm oil (diet 20% lipid). Whole-body lipid content increased when fish were fed with increasing levels of dietary lipid. Under our experimental conditions, the best growth rate and nutrient utilization were observed with the inclusion of 9% crude palm oil in the diets for African catfish. [ABSTRACT FROM PUBLISHER]

This paper addresses the economic trade-offs associated with stocking varying sizes of fingerlings and stockers either purchased or produced on farm in catfish growout. A mixed integer-programming model of catfish growout was developed that included seven fingerling, six stocker, and eight foodfish production activities as well as options to purchase and sell fingerlings, stockers, and foodfish. Results showed that profits are maximized on farms of 102 ha and larger by adopting a three-phase production system that includes a stocker phase. On farms smaller than 102 ha, profits are maximized by understocking 17.5-cm fingerlings in multiple-batch. The choice of stocking fingerlings or stockers depended on the efficiency of the stocker production phase; at stocker FCRs of 2.4 or above or survivals less than 40%, stocking fingerlings in multiple-batch was more profitable than the three-phase system with stockers. Additional research is needed to develop farm-level datasets of the variability in key stocker production parameters to expand this model to explicitly evaluate the effect of risk on optimal management strategies. [ABSTRACT FROM AUTHOR]

Nursery rearing of an endangered fish, Labeo gonius (Ham.) was studied in relation to varying stocking densities in earthen ponds. The experiment was conducted for 8 weeks in nine nursery ponds having an area of 0.012 ha with an average depth of 1 m. Four-day-old hatchling stocked at 0.6 million/ha was designated as treatment-1 (T1), 0.8 million/ha as treatment-2 (T2) and 1.0 million/ha as treatment-3 (T3), respectively. At stocking, all hatchlings were of same age group with a mean length and weight of 0.66 ± 0.08 cm and 0.001 ± 0.0001 g, respectively. Hatchlings in all the experimental ponds were given wheat flour for the first 7 days, finely ground mustard oilcake lot the next 7 days and a mixture of rice bran, and mustard oilcake (1 : 1) for days 15 to 56. The rate of feeding was 20 kg/million hatchling/day for the first two weeks. 25 kg for the second two weeks, 30 kg for the third two weeks and 35 kg for the fourth two weeks. The physicochemical parameters of water and plankton were monitored simultaneously and were within the acceptable range for fish culture. Growth parameters (final weight, final length, weight gain length gain and specific growth rate) and survival of fingerlings were significantly higher in T1 (0.6 million hatchling/ha) than those in T2 (0.8 million/ha) and T3 (1.0 million/ha), respectively. Feed conversion ratio (FCR) was significantly lower in T1 followed by T2 and T3 in that order. The estimated gross and net productions of fingerlings were significantly higher in T1 than in T2 and T3, respectively. Significantly higher number of fingerlings was produced in T3 than those in T2 and T1, Despite this, consistently higher net benefits were obtained from T1 than from T3 and T2. Overall, highest growth, survival, production and benefits were obtained from T1 where stocking density of hatchlings was 0.6 million/ha. Hence, of the treatments evaluated, stocking density of 0.6 million hatchling/ha appears to be the most efficient stocking density for rearing of L. gonius fingerlings in earthen nursery ponds. [ABSTRACT FROM AUTHOR]

Some producers of channel catfish, Ictalurus punctatus, fingerlings stock sac fry in nursery ponds as early as two days after hatching to reduce hatchery operating costs associated with the traditional practice of feeding swim-up fry for 7-10 days prior to stocking. It is not known if the reduced costs associated with the elimination of hatchery feeding of swim-up fry are countered by reduced production of fingerlings from ponds stocked with unfed sac fry. This study was conducted to determine if stocking catfish fry two days after hatch (unfed sac fry) or 10 days after hatch (hatchery-fed swim-up fry) had significant effects on the subsequent production of fingerlings and the profitability of a fingerling production operation under practical production conditions. In two consecutive years, catfish fry were stocked in 0.08-ha ponds in the spring of the year and harvested about six months later. Sac fry were stocked at a density (mean±SD of both years) of 24,953±2,876/ ha; swim-up fry at a density of 31,473±9,260/ha. Fry were fed a 45%- protein mash for several weeks after stocking and then a 38%-protein crumble for the remainder of the production trial each year. There were no statistically significant (P > 0.05) differences in yield (sac fry, 40±39 kg/pond; swim-up fry, 30±17 kg/pond), number harvested (sac fry, 2,521±2,720 fish/ha; swim-up fry, 1,988±3,059 fish/ha), or survival (sac fry, 10±11%; swim-up fry, 6±9%) of fingerling catfish stocked as either sac fry or swim-up fry. Total annual savings were estimated to be $17,636 (1% of total specified expenses) for a medium-sized hatchery that produced sac fry, compared with a hatchery that produced and fed swim-up fry. Fry survival was a critical factor influencing revenue. In this study, feeding catfish swim-up fry in the hatchery for seven days prior to stocking in ponds for grow-out to fingerling size provided no benefit, in terms of fish survival or the quantity of fingerlings produced, when compared with fingerling yields from ponds stocked with two-day old (unfed) sac fry. Thus, hatchery feeding of swim-up fry may be an uneconomical practice that might be effectively replaced by the stocking of sac fry within 48 hours of hatching. Additional research is needed to determine if the results obtained in this study can be expected to occur under a wider range of production conditions before recommendations on the stocking of catfish sac fry are developed. [ABSTRACT FROM PUBLISHER]

Trials to wean golden perch, Macquaria ambigua ambigua, were conducted using two commercially-available prepared diets. Co-feeding with brine shrimp, Artemia salina, nauplii or abrupt transition to the prepared diets, were compared. Golden perch fingerlings (25-30mmtotal length) were most successfully weaned onto prepared diets using frozen ice blocks made of brine shrimp and commercial diet crumbles, with a 77% weaning rate. The weaning period was over ten days, with the volume of crumble to Artemia slurry in ice blocks increasing by 10% every day. Co-feeding was essential to successful weaning (>71%), as an abrupt transition from Artemia to crumble diet resulted in a high rate of failure to wean(< 52%), and subsequent starvation. However, growth of fish that successfully weaned in the abrupt weaning treatment was equal to that of those which underwent the gradual, co-feeding weaning treatment. This weaning strategy may be used for commercial aquaculture production of this species. [ABSTRACT FROM PUBLISHER]

The objective of this study was to evaluate different salt concentrations in the treatment of Ichthyophthirius multifiliis. Silver catfish, Rhamdia quelen, fingerlings infected with I. multifiliis were submitted to four sodium chloride concentrations (g/L): 0, 1, 2, and 4 for 23 days. In a second experiment, fingerlings were maintained with 4 g/L salt, but for 45 days. Treatments with 2 and 4 g/L salt significantly increased fingerling survival compared with 0 and 1 g/L, and survival was significantly correlated with salt concentrations. In the second experiment, fish maintained at 4 g/L salt showed a gradual reduction of “white spots” and survival was 100%. Therefore, salt offers an alternative for treatment of silver catfish fingerlings infected with I. multifiliis. [ABSTRACT FROM PUBLISHER]

Production of fingerlings from very small fry depends upon an initial high concentration of rotifers followed by high densities of crustacean zooplankton. High fertilization rates lead to increased zooplankton production but often cause poor water quality conditions that aeration may alleviate. This study was designed to determine the effects of constant, nocturnal, and no aeration on water quality, primary productivity, and standing crops of phytoplankton and zooplankton in heavily fertilized nursery-size ponds that contained no fish. Four 0.04-ha ponds were aerated continually; four ponds were aerated only at night with a 372-W (1/2 hp) paddlewheel aerator; and four ponds were not aerated. For 21 days after they were filled on July 21, 1999, the ponds received 1,224 kg/ha rice bran and 581kg/ha liquid 9-27-0 fertilizer. Water quality variables, primary production, chlorophyll-a and zooplankton were sampled daily. Constant aeration resulted in several conditions more conducive to survival of fish fry, such as higher zooplankton densities, more moderate temperatures, and safer dissolved oxygen levels than did nocturnal aeration or no aeration. However, the development of a higher standing crop of phytoplankton and higher total ammonia concentrations in the turbulent, constantly aerated ponds resulted in higher un-ionized ammonia levels that were not favorable to survival and growth of fry. The high concentrations of zooplankton that developed in the aerated ponds have good potential for cropping to inoculate other ponds or to provide live foods for tank culture of zooplanktivorous fish. [ABSTRACT FROM PUBLISHER]

A pond production trial was conducted to compare yield, growth, feed conversion ratio, costs, and economic risk of producing catfish, Ictalurus punctatus, fingerlings with thinning. Catfish fry were stocked at 625,000 fry/ha, thinned when they reached 5.6 cm total length, and re-stocked at either 291,500/ha, 145,750/ha, or 70,000/ha. Mean weight (g) and length (cm) at harvest decreased as a logarithmic function of stocking rate (y = 191.236 2 14.128[ln X]; R2 = 0.86 for weight and y = 46.831 2 2.781[ln X]; R2 = 0.88 for length), while yield increased linearly (y = 962 + 0.00812X; R2 = 0.57) with stocking rate. There was no significant difference in survival, feed conversion ratio, or condition of the fish due to the stocking treatments. The significantly higher yield of fingerlings at the higher densities resulted in lower costs per fingerling, per kilogram, and per centimeter. The risk analysis showed little risk of incurring cost per centimeter higher than commercial rates. Additional research is needed to quantify the economic benefit of understocking larger fingerlings in catfish growout ponds and to compare relative costs and benefits of on-farm production of various sizes of fingerlings for understocking in growout ponds. [ABSTRACT FROM PUBLISHER]