Showing papers on "Nile tilapia published in 1994"

Supplemental Feeding of Tilapia in Fertilized Ponds

Abstract: The addition of feed to fertilized fish ponds was evaluated by adding feed alone, feed plus fertilizer, or fertilizer alone to nine ponds stocked with Nile tilapia Oreochromis niloticus. Two experiments were conducted. The first had 500 fish per 250 m2 pond in 3 treatments: ad-libitum feeding; fertilizer only; or fertilizer and ad-libitum feeding. The second experiment had 5 treatments with 750 fish per pond ad-libitum feed only; fertilizer only; or 0.25, 0.50, and 0.75 satiation ration plus fertilizer. Ponds in Thailand were maintained for 155–162 d, during which chemical and physical properties were monitored. In experiment 1 tilapia growth was highest in feed only ponds, and lowest in fertilizer only ponds. Net yield did not differ significantly among treatments, due to variation in survival. In experiment 2, tilapia growth was lowest in fertilizer only ponds, intermediate in 0.25 ration ponds, and highest in 0.50, 0.75, and ad-libitum ponds. The latter treatments were not significantly different. Multiple regressions for each experiment indicated only 47–87% of the variance in growth was explained by feed and fertilizer input, while 52–89% of the variance in yield was explained by those factors. For both experiments combined, 90.3% of the variance in growth was explained by feed input, fertilizer input, alkalinity, and total inorganic nitrogen concentration. For yield, R2 was 0.888 and the regression included feed input, pH, and number of low dissolved oxygen events. Experiment 1 appeared to approach carrying capacity near the end, while no reduction in growth occurred in experiment 2 at higher fish density and biomass. Reductions in growth in experiment 1 were not correlated with declining water quality late in the grow out. Combinations of feed and fertilizer were most efficient in growing tilapia to large size (500 g) compared to complete feeding or fertilizing alone.

Systematic granulomas caused by a rickettsia‐like organism in Nile tilapia, Oreochronuis niloticus (L.), from southern Taiwan

Abstract: . A rickettsia-like organism was observed in diseased Nile tilapia, Oreochronuis niloticus (L.), from southern Taiwan. Most affected fish were pale and lethargic with haemorrhages and ulcers on the skin. The most significant gross pathological changes were varying degrees of ascites, and enlargement of the spleen, kidney and liver. Marked white nodules (as ring-shaped foci), varying in size, were found in these organs. A Gram-negative, rickettsia-like organism (RLO) frequently appeared as inclusions or within host cell intra-cytoplasmic vacuoles. Fibrin thrombi, perivascular necrosis, chronic inflammatory cells with hypertrophy and RLO-laden cells were characteristic of the disease. White nodules induced in experimental fish were similar to naturally infected cases and RLOs were reisolated in tissue culture using a CHSE-214 cell line. This provides evidence that the systemic granulomas in Nile tilapia were caused by RLOs.

Water-soluble vitamin requirements of tilapia: ascorbic acid (vitamin C) requirement of Nile tilapia, Oreochromis niloticus (L.)

Abstract: . The quantitative dietary ascorbic acid requirements of fingerling Nile tilapia, Oreochromis niloticus L., were assessed by feeding seven diets containing graded supplements of this vitamin (0, 50, 75, 100, 125, 300 and 400mg/100g dry diet) to triplicate groups of fish for 12 weeks. Fish fed the diet devoid of ascorbic acid exhibited significantly (P < 0·01) poorer growth and higher condition factor. Food conversion and protein efficiency ratios were improved with increasing dietary ascorbic acid level up to 125mg/100g of dry diet. Protein utilization, haematocrit, haemoglobin level and tissue ascorbate concentrations were depressed in fish fed the ascorbic-acid-free diet. Tissue ascorbate concentrations, especially for liver, were highly correlated with dietary ascorbic acid level. Fish fed the ascorbic-acid-free diet exhibited deficiency signs including erratic and convulsive swimming, anorexia, lethargy, caudal fin erosion, skin haemorrhages and mortality. Based on the nutritional and pathological parameters investigated, the recommended dietary inclusion level is 125mg/100g dry diet, which is equivalent to a net requirement (after processing and storage) of 42mg/100g diet.

Fish as biocontrol agents in rice: the potential of common carp Cyprinus carpio (L.) and Nile tilapia Oreochromis niloticus (L.).

Abstract: Fish in rice fields pests in Asian rice farming systems, with special reference to the golden apple snail pomacea canaliculata general approach and methodology aquaria experiments field experiments the golden apple snail population ecology in rice-fish and rice monoculture - a modelling approach integrated evaluation of the results recommendations for future research programmes

Growth of control and androgen‐treated Nile tilapia, Oreochromis niloticus (L.), during treatment, nursery and grow‐out phases in tropical fish ponds

Abstract: . Masculinization of sexually undifferentiated tilapia fry is achieved by oral administration of the androgen 17-α methyltestosterone (MT). An anabolic response to androgen treatment of tilapia has been reported. Growth of control and MT-treated tilapia was evaluated during consecutive treatment, nursery, and grow-out phases under conditions approximating commercial, semi-intensive tilapia farms in Central America. Oreochromis niloticus (L.) fry were fed a 0 or 60 mg/kg MT diet for 28 days. Growth curves for control and MT-treated fish did not have significantly different slopes. Mean harvest fry weights were similar, averaging 0·1 g/fry for both treatments. Fry were subsequently stocked into 0·2-ha nursery ponds for 94 days growth. Slopes of control and MT-treated fish growth curves were not significantly different. Mean final individual weights did not differ significantly between treatments. Control fish did not deviate significantly from the1:1 male: female ratio, but MT-treated fish were 97% males. Control male and MT-treated male fingerlings were stocked for grow-out into 0·1-ha organically fertilized earthen ponds. No significant difference in growth was observed between control and MT-treated fish. Mean gross yields after 150 days and mean final individual weights were similar for both treatments.

Effects of starvation and feeding on tissue Nα -acetylhistidine levels in Nile tilapia Oreochromis niloticus

Abstract: The effects of long-term starvation and feeding on N α, -acetylhistidine (NAcH) levels in skeletal muscle, brain and lens of Nile tilapia Oreochromis niloticus were examined. A drastic decrease in NAcH level of skeletal muscle during starvation was observed. This compound disappeared from skeletal muscle of the fish after 8 weeks of starvation, and was completely restored to the pre-starvation level (4–5 μmol/g muscle) by the following 8 weeks of feeding. The activities of N -acetylhistidine deacetylase (NAcHDE) and histidine acetyltransferase (HISAT) were very weak, but detectable in skeletal muscle of the species. It is supposed that the change of the NAcH level in skeletal muscle during starvation and feeding appears as a result of the degradation by NAcHDE and of the synthesis by HISAT.

Commercial production and marketing of Nile tilapia (Oreochromis niloticus) fry in Chonburi and Chachoengsao provinces, Thailand

Abstract: Nile tilapia (Oreochromis niloticus) fry production and marketing in the provinces of Chonburi and Chachoengsao, Thailand are discussed, covering historical background, production methodology, transfer of technology to other region, and future trends.

Nitrogen models of lowland irrigated ecosystems with and without fish using Ecopath 2

Abstract: Results on higher N transfer efficiencies in all trophic levels in rice-fish model suggest the role of fish in ameliorating N utilization within the ecosystem. Higher throughput (or sum of all flows) in the rice-fish system than rice alone indicates that it had a higher capacity to produce and to capture N within the system. In both systems, the largest nutrient through put comes mainly from microbial biomass and also from rice, weeds and phytoplankton. Mixed trophic impact showed the negative impact of rice on phytoplankton, weeds, oligochaetes, zooplankton, microbiomass, tilapia, carp and detritus. This negative impact of rice on natural food of fish partly limits fish yields in rice-fish systems. Rice negatively affected soil microbial biomass indicating that crop intensification could lead to reduction of soil fertility. Nile tilapia and common carp did not enhance rice yields. Common carp had a negative impact on weeds while tilapia enhanced it. This result is attributed to the benthic feeding of carp and the surface feeding of tilapia. Mixed trophic impacts also showed the negative impact of carp on weeds, snails and insects which imply the usefulness of this fish species for biological pest control leading to less use of pesticide in rice production. Fish food organisms such as oligochaetes and zooplankton were negatively affected by carp. The models revealed selected interactions of rice and fish leading to a better understanding by both systems

The biology, ecology, population parameters and the fishery of the Nile tilapia, Oreochromis niloticus (L)

Abstract: Oreochromis niloticus (the Nile tilapia) and three other ti1apine species: Oreochromis leucostictus, Tilapia zi11ii and T. rendallii were introduced into Lakes Victoria, Kyoga and Nabugabo in 1950s and 1960s. The source and foci of the stockings are given by Welcomme (1966) but the origin of the stocked species was Lake Albert. The Nile tilapia was introduced as a management measure to relieve fishing pressure on the endemic tiapiines and, since it grows to a bigger size, to encourage a return to the use of larger mesh gill nets. Ti1apia zillii was introduced to fill a vacant ,niche of macrophytes which could not be utilised' by the other tilapiines. Tilapia rendallii, and possibly T. leucosticutus could been introduced into these lakes accidently as a consquence of one of the species being tried out for aquaculture. The Nile perch and Nile tilapia have since fully established themselves and presently dominate the commercial fisheries of Lakes Victoria and Kyoga. The original fisheries based on the endemic tilapiines O. escu1entus and o. variabilis have collapsed. It is hypothesized that the ecological and limnological changes that are observed in Lakes Victoria and Kyoga are due to a truncation of the original food webs of the two lakes. Under the changed conditions, O. niloticus to be either playing a stabilizing role or fuelling nutrient turnover in the lakes. Other testable hypotheses point to the possible role of predation by the Nile perch, change in regional climate and hydrology in the lake basins.