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O. Niloticus (o + niloticu)
Selected AbstractsGrowth of juvenile tilapia, Oreochromis niloticus L. from Lakes Zwai, Langeno and Chamo (Ethiopian rift valley) based on otolith microincrement analysisECOLOGY OF FRESHWATER FISH, Issue 3 2000D. Admassu Abstract , Age and growth of juvenile tilapia, Oreochromis niloticus, from Lakes Zwai, Langeno and Chamo (Ethiopia) were studied from microincrements in otoliths. Growth in length was best described by the Gompertz model. Average growth rate of the fish was most rapid in Lake Chamo (0.39 mm,·,day,1, 1.14%,·,day,1), intermediate in Lake Zwai (0.20 mm,·,day,1, 0.72%,·,day,1) and slowest in Lake Langeno (0.16 mm,·,day,1, 0.62%,·,day,1). Similarly, back-calculation from otolith increment widths gave growth rates of 0.28 to 0.43 mm,·,day,1, 0.15 to 0.32 mm,·,day,1 and 0.11 to 0.28 mm,·,day,1 for Chamo, Zwai and Langeno fish, respectively. In addition, Fulton's condition factor was largest for Chamo tilapia and smallest for Langeno tilapia; the difference between fish from Langeno and Zwai was small. Rapid growth of juvenile O. niloticus in Lake Chamo was attributed to warm temperature and better food quality., [source] Genotoxicity testing of the herbicide trifluralin and its commercial formulation Treflan using the piscine micronucleus testENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 6 2008Serpil Könen Abstract In this study, the genotoxic effects of a widely used herbicide, trifluralin, and its commercial formulation, Treflan, were evaluated using the micronucleus test in a commercially important fish species, Oreochromis niloticus (Nile Tilapia). Fish were exposed to 1, 5, and 10 ,g/L doses of trifluralin and Treflan for 3, 6, and 9 days under laboratory conditions. Ethylmethanesulfonate, at a single dose of 10 mg/L, was used as positive control. Micronuclei were evaluated on the peripheral erythrocytes. Both Treflan and trifluralin treatments significantly increased the micronucleus frequencies in peripheral erythrocytes of O. niloticus. Furthermore, the genotoxicity of the active ingredient, trifluralin, was observed to be higher than that of the commercial formulation Treflan. Our results indicate that herbicide trifluralin has genotoxic potential in fish. Environ. Mol. Mutagen., 2008. © 2008 Wiley-Liss, Inc. [source] Cadmium tolerance in the Nile tilapia (Oreochromis niloticus) following acute exposure: Assessment of some ionoregulatory parametersENVIRONMENTAL TOXICOLOGY, Issue 1 2006Sofia Garcia-Santos Abstract The Nile tilapia (Oreochromis niloticus) can tolerate very high levels of waterborne cadmium. It has one of the highest 96 h LC50 recorded for a freshwater teleost fish (14.8 mg/L Cd; hardness 50 mg/L CaCO3). Cadmium is known to perturb ion balance in teleost fishes. However, in an acute time course experiment, plasma Na+ concentrations were unaffected, and plasma Ca2+ values only decreased after 96 h exposure in a dose-independent manner. Branchial Na+/K+ -ATPase activity and ,-subunit protein level expression in crude gill homogenates were not affected by Cd exposure during this period. Branchial chloride cell numbers, identified as Na+/K+ -ATPase immunoreactive cells using immunohistochemistry, decreased 24 h after exposure but recovered thereafter. Histopathological changes did not follow a consistent pattern of variation with exposure time, and the alterations noted in gill epithelium were basically nonspecific to cadmium. Because of its tolerance, it can be concluded that the tilapia O. niloticus would not be a suitable test organism to evaluate sublethal toxicity of cadmium and the realistic impact of this pollutant in the environment. However, it certainly could contribute significantly to our understanding of the toxic mechanism of cadmium exposure in aquatic organisms. This is the first work to investigate the effect of waterborne pollutants on Na+/K+ -ATPase ,-subunit protein expression in fish gills. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 33,46, 2006. [source] Culture-based fisheries in non-perennial reservoirs in Sri Lanka: production and relative performance of stocked speciesFISHERIES MANAGEMENT & ECOLOGY, Issue 4 2005W. M. H. K. WIJENAYAKE Abstract, In Sri Lanka, there is a great potential for the development of culture-based fisheries because of the availability of around 12 000 non-perennial reservoirs in the dry zone (<187 cm annual rainfall) of the island. These reservoirs fill during the north-east monsoonal period in October to December and almost completely dry up during August to October. As these non-perennial reservoirs are highly productive, hatchery-reared fish fingerlings can be stocked to develop culture-based fisheries during the water retention period of 7,9 months. The present study was conducted in 32 non-perennial reservoirs in five administrative districts in Sri Lanka. These reservoirs were stocked with fingerlings of Indian (catla Catla catla Hamilton and rohu Labeo rohita Hamilton) and Chinese (bighead carp Aristichthys nobilis Richardson) major carps, common carp Cyprinus carpio L., genetically improved farmed tilapia (GIFT) strain of Nile tilapia, Oreochromis niloticus (L.) and post-larvae of giant freshwater prawn, Macrobrachium rosenbergii De Man, at three different species combinations and overall stocking densities (SD) ranging from 218 to 3902 fingerlings ha,1, during the 2002,2003 culture cycle. Of the 32 reservoirs stocked, reliable data on harvest were obtained from 25 reservoirs. Fish yield ranged from 53 to 1801 kg ha,1 and the yields of non-perennial reservoirs in southern region were significantly (P < 0.05) higher than those in the northern region. Naturally-recruited snakehead species contributed the catches in northern reservoirs. Fish yield was curvilinearly related to reservoir area (P < 0.05), and a negative second order relationship was evident between SD and yield (P < 0.05). Chlorophyll- a and fish yield exhibited a positive second order relationship (P < 0.01). Bighead carp yield impacted positively on the total yield (P < 0.05), whereas snakehead yield impact was negative. Bighead carp, common carp and rohu appear suitable for poly-culture in non-perennial reservoirs. GIFT strain O. niloticus had the lowest specific growth rate among stocked species and freshwater prawn had a low return. [source] Partial compensatory growth in hybrid tilapia Oreochromis mossambicus × O. niloticus following food deprivationJOURNAL OF APPLIED ICHTHYOLOGY, Issue 5 2005Y. Wang Summary The capacity of hybrid tilapia Oreochromis mossambicus × O. niloticus [23.2 ± 0.2 g (mean ± SE)] to show compensatory growth was assessed in an 8-week experiment. Fish were deprived of feed for 1, 2 and 4 weeks, and then fed to satiation for 4 weeks; fish fed to satiation during the experiment served as control. Water temperature gradually declined from 28.1 to 25.5°C throughout the experiment. Specific growth rate (SGR) decreased with progressive food deprivation. At the end of deprivation, body weight was lower in the deprived fish than in the control. Fish deprived for 4 weeks exhibited lower contents of lipids and energy in whole body, and higher moisture content and ratio of protein to energy (P/E) than those of the control; they also consumed feed faster than the control when normal feeding was resumed. All deprived fish showed higher food intake (FI) than that of the control during re-alimentation; however, enhanced SGR was only observed in the fish deprived for 4 weeks. There were no significant differences in digestibility of protein and energy, food efficiency (FE) or energy retention efficiency between the control and deprived fish. At the end of re-alimentation, deprived fish failed to catch up in body weight with the control, while content of moisture, lipids and energy, and P/E in whole body of the deprived fish did not significantly differ from that of the control. The results of the experiment revealed that the hybrid tilapia reared in freshwater showed partial capacity for compensatory growth following food deprivation of 4 weeks, and that growth compensation was due mainly to increased FI, rather than to improved FE. [source] PROPOSED NEW COLOR RETENTION METHOD FOR TILAPIA FILLETS (O. NILOTICUS, × O. AUREUS,) BY EUTHANATIZING WITH REDUCED CARBON MONOXIDEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 5 2008LAIHAO LI ABSTRACT The conditions of color retention for tilapia fillets (O. niloticus, × O. aureus,) treated by euthanatizing with reduced carbon monoxide (CO) were investigated. Live tilapias were first exposed to water saturated with CO. After a certain amount of CO-saturated water had been pumped through the gills, the tilapias were timely picked out and killed following the industry guidelines. The color value of fillets was measured by colorimeter to evaluate the color retention. The results showed that (1) temperature did not have a significant effect on the color of the fillets; (2) the optimal conditions were a ratio of 3:1, v/w between water and fish, a CO flow rate of 80 mL/min and 10 min CO injection followed by 5 min air exposure. Under these conditions, a higher a*value (redness 19.44) and a better sensory evaluation value (4.8) were obtained; and (3) the proposed method shortened processing time by 30,35 min, reduced the frequency of sterilization to only once, significantly lowered microbial counts from 82.33 × 102 to 56.33 × 102 and reduced the CO requirement 25-fold, which has significant occupation, health, safety, and environmental implications. PRACTICAL APPLICATIONS Color retention for tilapias is conventionally accomplished by treating fillets with CO. Recently, euthanatizing tilapias with CO has been assumed to be an effective way to shorten processing time and to lessen product handling process. Many factories have been searching for a way to solve the problem of color retention for tilapias or other red muscle treatment, but there has been a lack of information on how euthanasia affects fish quality, especially red muscle color. The objective of this experiment was to explore the application of the new method. [source] Spawning and recruitment patterns of major fish species in Bontanga Reservoir, Ghana, West AfricaLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2010Kwadwo Kwarfo-Apegyah Abstract The spawning and recruitment patterns of the major Cichlid fish species, including Hemichromis fasciatus, Oreochromis niloticus, Sarotherodon galilaeus, Tilapia zillii and other species, Auchenoglanis occidentalis, Brycinus nurse, Clarias gariepinus and Marcusenius senegalensis were studied for 24 months in Bontanga Reservoir, Ghana, using length-based fish stock assessment approaches. The species spawned throughout the year, with two spawning pulses described as major and minor spawning seasons. The major spawning season occurred from March to September for the Cichlids, and from May to September for the other species. The minor spawning season, indicative of extended spawning, occurred from October to March for all the fish stocks. Fish spawning began with the onset of the rains in April/May, peaking by June/July, before the rainfall peak in August for all the fish stocks studied. Recruitment was found to occur throughout the year, with major and minor pulses coinciding with the major and minor spawning seasons. Accordingly, the most appropriate time for a possible closed fishing period appears to be from June to August, 1 month after the start of, and before the end of, the rains. The estimated mean standard length (Lm) for first time spawners of A. occidentalis, B. nurse, C. gariepinus and H. faciatus were 11.7, 12.7, 2.7 and 7.5 cm respectively. The estimated maturity,length ratio of 0.4 and 0.2 for O. niloticus, S. galilaeus and T. zillii were lower than the known 0.7 for normal growth, suggesting the tilapias matured faster, and at a smaller size, in the reservoir. Apparent sexual precocity associated with early maturity, year-round spawning and recruitment were some important adaptations found to have sustained the reservoir fisheries, even during high fishing pressures. For conservation and sustainable exploitation of the fisheries, instituting a closed fishing season, mesh size regulations, withdrawal rights and a community-based fishery management system are recommended. [source] Management of the Nile tilapia (Oreochromis niloticus (L.)) fishery in the Kenyan portion of Lake Victoria, in light of changes in its life history and ecologyLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2008M. Njiru Abstract This study reports on the population parameters, catch distribution and feeding ecology of Nile tilapia (Oreochromis niloticus) from bottom trawls and commercial catches obtained in the Kenyan portion of Lake Victoria during 1997,2006. The population parameters were analysed using the FAO-ICLARM stock assessment tool (FISAT). The fish biomass and the food ingested by the fish were estimated using the swept area and point methods, respectively. Immature fish comprised ,70% of the total fish population. The asymptotic length, maximum weight, maximum age, exploitation rate (E) and length at 50% maturity of Nile tilapia have decreased, whereas the growth curvature and fishing mortality have increased. The commercial catches increased from 13.93 t in 1997, to 23.70 t in 1999, decreasing thereafter to 18.73 t in 2005. The bottom trawl catches increased from 46.90 kg ha,1 in 1997, to 401.48 kg ha,1 in 2000, decreasing thereafter to 15.57 kg ha,1 in 2006. The major food items ingested by the fish were algae, insects and other fish. Population parameters, and the catch and diet of O. niloticus, have changed over the years in Lake Victoria. The population characteristics suggest a population under stress, attributable to intense catch exploitation. Even under intense exploitation (E = 0.68), however, the mature fish constituted ,30% of the population. The commercial catches are still high, indicating a very resilient fishery. Nevertheless, despite this resilience, the future of Oreochromis fishery is threatened by increased fishing capacity in the lake, and there is need to re-evaluate the effectiveness of current fishery management measures, with the goal of possibly adopting new measures. Enactment of new fishery policies also should provide for co-management to enhance the management process. Furthermore, there is a need to reduce fishing capacity and illegal fishing methods, and to seek alternative livelihoods for lake fishers and other stakeholders. [source] Amino acid availability and protein digestibility of several protein sources for Nile tilapia, Oreochromis niloticusAQUACULTURE NUTRITION, Issue 5 2008I.G. GUIMARÃES Abstract Apparent amino acid availability coefficients and protein digestibility of four animal products [fish meal (FM), meat and bone meal (MBM), poultry by-product and feather meal] and four plant protein-rich products [soybean meal (SBM), cottonseed meal-28, cottonseed meal-38 and corn gluten meal (CGM)] were determined for Nile tilapia, Oreochromis niloticus. Ingredients were incorporated to a practical reference diet at a 7 : 3 ratio (70% of reference diet and 30% of test ingredient). Chromic oxide was used as external digestibility marker. Among animal products poultry by-product meal (PBM; 89.7%) and FM (88.6%) presented the highest apparent protein digestibility (APD) while MBM (78.4%) and feather meal (78.5%) presented the lowest APD. Among plant protein-rich products CGM (91.4%) and SBM (92.4%) presented the highest APD values while cottonseed meal-28 presented the lowest APD (78.6%). Average apparent amino acid availability of feed ingredients was similar to protein digestibility with 92.3%, 89.6%, 73.4%, 80.7%, 88.9%, 84.4%, 91.2% and 79.7% values for SBM, CGM, cottonseed meal-28 and 38, FM, MBM, PBM and feather meal respectively. These results indicate that O. niloticus is able to utilize efficiently different feedstuffs. [source] Growth, salinity tolerance and microsatellite analysis of the F2 reciprocal hybrids of Oreochromis niloticus×Sarotherodon galilaeus at different salinitiesAQUACULTURE RESEARCH, Issue 9 2010Biao Yan Abstract Oreochromisniloticus (O), the sixth generation of Genetic Improvement of Farmed Tilapia, shows rapid growth but poor salt tolerance, while Sarotherodon galilaeus (S) exhibits opposite traits. To combine the traits, F1 progeny was obtained through artificial fertilization. Fertile F1 produced F2 by natural spawning. The mean survival times, the median survival time (ST50) or the survival rate of hybrids was greater than O. niloticus in a gradual or an acute salinity change. Plasma osmolarity, [Na+] and [Cl,] of the hybrids fluctuated in 32 g L,1 water during a 24-h period, but eventually reached levels similar to fish in freshwater. O. niloticus,×S. galilaeus, (OS F2) or S. galilaeus,×O. niloticus, (SO F2) showed the fastest growth at 22.5 g L,1, equal to about 78.2% or 69.7% of O. niloticus at 0 and 3.87 or 3.45 times that of S. galilaeus at their individual optimum growth. Growth in OS F2 was 12% faster than SO F2. Microsatellite analysis showed that F2 had more alleles, a higher polymorphism information content and greater observed and expected heterozygosity than O. or S. Population differentiation was not detected between F1 and F2. All the results indicated that F2 could be exploited for commercial production under saline conditions. [source] Effect of stocking density on the growth performance and yield of Nile tilapia [Oreochromis niloticus (L., 1758)] in a cage culture system in Lake Kuriftu, EthiopiaAQUACULTURE RESEARCH, Issue 13 2008Ashagrie Gibtan Abstract This research was conducted to investigate the effect of stocking density on the growth performance and yield of Oreochromis niloticus in cage culture in Lake Kuriftu. The treatments had stocking densities of 50 (50F), 100 (100F), 150 (150F), and 200 (200F) fish per m,3. All treatments were in duplicate. Juveniles with an average weight of 45. 76±0.25 g were stocked in the treatments. The fish were fed a composite mixture of mill sweeping, cotton seed, and Bora food complex at 2% of their body weight twice per day using feeding trays for 150 days in powdered form. The growth performance of O. niloticus was density dependent. The final mean weight of O. niloticus ranged 147.76±0.28,219.71±1.42 g and the mean daily weight gain was 0.69±0.01,1.15±0.02 g day,1. Fish held in cages with lower density were heavier than the ones held at higher densities, and showed higher weight gain and daily weight gain. The most effective stocking density, in terms of growth parameters, was 50 fish m,3. The gross yield (4.5,20.55 kg cage,1) showed a significant difference with increasing stocking density (P<0.05). Moreover, the apparent food conversion ratio (2.48,7.22) was significantly affected by stocking density (P<0.05). However, survival rate was not affected by stocking density (P>0.05). It can be concluded that the most effective stocking densities were at 50 fish m,3 cage for larger size fish demand in a short period and 200 fish m,3 for higher gross production with supplementary feed. [source] Incidence of conjoined twins in tilapia after thermal shock induction of polyploidyAQUACULTURE RESEARCH, Issue 5 2000M Owusu-Frimpong Conjoined twins (polyembryonic fish) were observed in batches of blue tilapia Oreochromis aureus (Steindachner) and Nile tilapia O. niloticus (L.) embryos incubated at 28 °C. Heat shock (41.8 °C) treatment of fertilized eggs for 3,4 min applied between 4 min and 27 min after fertilization increased the twinning rate by three or four times over that of unshocked eggs. Two basic morphological variations , ventrally or laterally conjoined twins , were observed. Twins did not survive beyond 21 days after hatching. The proportion of twins in heat-shocked egg batches of both species combined ranged from 0.32% to 0.40%. [source] Rapid invasion of a subtropical lake fishery in central Mozambique by Nile tilapia, Oreochromis niloticus (Pisces: Cichlidae)AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2008Olaf L.F. Weyl Abstract 1.Lake Chicamba, Mozambique (19°08,S; 33°08,E) is a large (116 km2) impoundment in the headwaters of the Buzi River system, which was invaded by Oreochromis niloticus in 1996 from a small (<0.3 km2) upstream reservoir. 2.Experimental and artisanal catch data showed no O. niloticus until January 1996; after this O. niloticus was recorded in up to 83% of experimental seine net catches, 33% of experimental gill net catches, 43% of boat angling and 23% of shore angling catches, and in 48% of artisanal gill net catches. 3.During the period January to March 1997, O. niloticus mean (upper, lower 95% confidence interval) yields in the artisanal fishery were 5.2 (3.6, 7.0) t month,1. 4.The rapid invasion of this lake illustrates the significant invasion threat that small point-sources of this species pose to southern African freshwater systems. 5.The study recommends: (1) that this species should not be used for aquaculture or fisheries enhancement in catchments that have not been invaded, and (2) that the eradication of potential point sources of O. niloticus in non-invaded catchment systems should be considered. 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