Freshwater Earthen Ponds Research Articles

Monogamous hybridization of Nile tilapia (Oreochromis niloticus) with Mozambique tilapia (O. mossambicus) results in unprecedented all-female F1 hybrid

Tilapiine breeding success is season-dependent, with very rare exceptions. The female (f) to male (m) ratio differences showed significant variations in fruitful breeding. Furthermore, the female-to-male ratio in any hybridization protocol involving reciprocal crosses may be the most influential factor in determining breeding seasonality. The innate genetic traits of tilapia, a prominent contributor to global aquaculture production, enable them to easily adapt to a wide range of aquatic environments, rendering them suitable for domestication. The study aimed to determine the breeding timeframe of Nile tilapia (Oreochromis niloticus, N) through interspecific monogamous/two-parent reciprocal crossing with Mozambique tilapia (O. mossambicus, M). Considering preselected genotypic characteristics by PrlLK microsatellite marker, different combinations of hybrid reciprocal crosses were performed in breeding hapa (3 × 3 × 3 cubic feet) inside an indoor plastered cemented tank and then in an outdoor earthen pond facility. Total 11 parental pairs were attempted to propagate inside a cemented tank with (9 pairs) and without (2 pairs) hapa during early April to mid-June. Unfortunately, the trials failed to produce any successful breeding within the schedule. Among those 11 pairs, 6 pairs were Nf × Mm and 5 pairs were Mf × Nm cross. In the earthen pond inside hapa, a total of 18 pairs were attempted where seven breeding successes were reported without demonstrating any dependency for hybridizations over cross types or genotypes and for individuals over sex or species. Successful breeding were reported from the month of May to November. There were few overlapping months of successful breeding for different grouping categories. During the successful breeding period, there were no successful outcomes in both August and October. An inadvertent all-female F1 generation was observed for Mf × Nm crosses, while the reciprocal cross Nf × Mm produced an F1 generation with a nearly 1:1 female to male ratio. The F1 sex ratios exhibited a significant reliance on parental genotypic combinations (p = 5.4e-11). The success stories from different cross combinations would help to frame the breeding protocol for future research. More precisely, for arranging a breeding schedule in freshwater earthen ponds inside hapa for a monogamous/two-parent hybrid cross the study light a close insight.

Biocontrol of Oreochromis mossambicus Population by Chitala chitala (Hamilton, 1822) in a Composite Carp Culture System of Purulia District in West Bengal, India

Aims: Pond-based carp production in the Purulia district in West Bengal, India is confronted with several challenges. This study aimed to establish an alternative semi-intensive carp production method for the district by addressing an endemic challenge i.e. recruitment of O. mossambicus, through an endangered (EN) and native predatory fish, Chitala chitala.
 Study Design: Present study has been conducted on two numbers of perennial water resources with 1 ha effective area; where annual production of Indian Major Carps (IMC) and impact of O. mossambicus and C. chitala on the same culture system have been compared.
 Place and Duration of Study: This study was conducted in farm conditions from 2018 to 2020, in two freshwater earthen ponds, Gosai Bundh (N23.47737/E86.79032) and Bara Notun Bundh (N23°46439/E86°65080), at Uluberia village under Kashipur Block of Purulia district in West Bengal, India.
 Methodology: Stocking density of Indian Major Carp (IMC) fingerlings was maintained at 8000 numbers (4:3:3 ratio of catla : rohu : mrigala) per ha (T1). After getting contaminated by O. mossambicus, wild C. chitala juveniles have been introduced in the similar facility (T2). Results of T1 and T2 were compared with control pond (C) containing IMC only. Recruitment of O. mossambicus and growth performance of C. chitala and IMCs determined periodically and annually.
 Results: Increasing growth of C. chitala showed contrasting impact over O. mossambicus fry recruitment. Survival percentage of C. chitala remains high in T2. While, poorest growth performance of IMCs have been observed in T1. Among IMC’s C. catla showed best survivality in every experimental ponds.
 Conclusion: Excessive recruitment of the O. mossambicus population can be controlled by C. chitala in a pond-based IMC culture system.

Growth, production and feed conversion performance of the gurami sago (Osphronemus goramy Lacepède, 1801) strain in different aquaculture systems.

Background: Giant gourami ( Osphronemus goramy, Osphronemidae), belonging to gurami sago strain, is an important economic fish species that was newly released for domestication in 2018 in Indonesia. The present study aimed to determine the growth, production and feed conversion efficiency of gurami sago strain in different aquaculture systems. Methods: A mean of 240 juveniles were stocked (initial weight mean, 54.53 g and length 13.88 cm) into concrete ponds, floating net cages and earthen freshwater ponds (12 m 3) with three replicates of each. The juveniles were fed a floating commercial pellet diet containing 30% crude protein and 5% crude lipids. Feed was supplied at 3% of fish biomass per day throughout the 90 days of the experiment. The research was conducted in the area surrounding Lake Maninjau of Indonesia. Results: After 90 days, the mean weight of fish reared in concrete ponds was 166.86 g, floating net cages was 179.51 g and earthen freshwater ponds was 149.89 g. The mean final biomass was 37.64 kg for concrete ponds, 41.27 kg for floating net cages, and 33.72 kg for earthen freshwater ponds. The specific growth rates (%/day) for concrete ponds, floating net cages and earthen freshwater ponds were 0.67, 0.75 and 0.62, respectively. The feed conversion rates were 1.45 for concrete ponds, 1.30 for floating net cages and 1.87 for earthen freshwater ponds. The net yields (kg m -3) were 2.05 for concrete ponds, 2.27 for floating net cages, and 1.73 for earthen freshwater ponds. The exponents (b) of the length-weight relationship were calculated for concrete ponds (1.0146), floating net cages (1.2641), and earthen freshwater ponds (1.0056). Conclusion: The study showed that the growth performance, production and feed conversion efficiency of the gurami sago strain were the best found in floating net cages and considered a new aquaculture system in the future.

Growth, production and feed conversion performance of the gurami sago (Osphronemus goramy Lacepède, 1801) strain in different aquaculture systems

Background: Giant gourami (Osphronemus goramy, Osphronemidae), belonging to the gurami sago strain, is an important economic fish species that was newly released for domestication in 2018 in Indonesia. The present study aimed to determine the growth, production and feed conversion efficiency of gurami sago strain in different aquaculture systems. Methods: A mean of 240 juveniles were stocked (mean, 54.53 g and 13.88 cm) into concrete ponds, floating net cages and earthen freshwater ponds (12 m3) with three replicates of each. The juveniles were fed a floating commercial pellet diet containing 30% crude protein and 5% crude lipids. Feed was supplied at 3% of fish biomass per day throughout the 90 days of the experiment. The research was conducted in the area surrounding Lake Maninjau of West Sumatera Province, Indonesia. Results: After 90 days, the mean weight of fish reared in concrete ponds was 166.86 g, floating net cages was 179.51 g and earthen freshwater ponds was 149.89 g. The mean final biomass was 37.64 kg for concrete ponds, 41.27 kg for floating net cages, and 33.72 kg for earthen freshwater ponds. The specific growth rates (%/day) for concrete ponds, floating net cages and earthen freshwater ponds were 0.67, 0.75 and 0.62, respectively. The feed conversion rates were 1.45 for concrete ponds, 1.30 for floating net cages and 1.87 for earthen freshwater ponds. The net yields (kg mˉ3) were 2.05 for concrete ponds, 2.27 for floating net cages, and 1.73 for earthen freshwater ponds. The exponents (b) of the length–weight relationship were calculated for concrete ponds (1.0146), floating net cages (1.2641), and earthen freshwater ponds (1.0056). Conclusion: The study showed that the growth performance, production and feed conversion efficiency of the gurami sago strain could be considered a new candidate strain for floating net cage aquaculture in the future.

Growth, production and feed conversion performance of the gurami sago (Osphronemus goramy Lacepède, 1801) strain in different aquaculture systems

Background: Giant gourami ( Osphronemus goramy, Osphronemidae), belonging to gurami sago strain, is an important economic fish species that was newly released for domestication in 2018 in Indonesia. The present study aimed to determine the growth, production and feed conversion efficiency of gurami sago strain in different aquaculture systems. Methods: A mean of 240 juveniles were stocked (initial weight mean, 54.53 g and length 13.88 cm) into concrete ponds, floating net cages and earthen freshwater ponds (12 m 3) with three replicates of each. The juveniles were fed a floating commercial pellet diet containing 30% crude protein and 5% crude lipids. Feed was supplied at 3% of fish biomass per day throughout the 90 days of the experiment. The research was conducted in the area surrounding Lake Maninjau of Indonesia. Results: After 90 days, the mean weight of fish reared in concrete ponds was 166.86 g, floating net cages was 179.51 g and earthen freshwater ponds was 149.89 g. The mean final biomass was 37.64 kg for concrete ponds, 41.27 kg for floating net cages, and 33.72 kg for earthen freshwater ponds. The specific growth rates (%/day) for concrete ponds, floating net cages and earthen freshwater ponds were 0.67, 0.75 and 0.62, respectively. The feed conversion rates were 1.45 for concrete ponds, 1.30 for floating net cages and 1.87 for earthen freshwater ponds. The net yields (kg m ˉ3) were 2.05 for concrete ponds, 2.27 for floating net cages, and 1.73 for earthen freshwater ponds. The exponents (b) of the length–weight relationship were calculated for concrete ponds (1.0146), floating net cages (1.2641), and earthen freshwater ponds (1.0056). Conclusion: The study showed that the growth performance, production and feed conversion efficiency of the gurami sago strain were the best found in floating net cages and considered a new aquaculture system in the future.

Fillet Quality of Asian Seabass Lates calcarifer (Bloch, 1790) Grown in Monoculture and Coculture Systems in Freshwater Earthen-ponds

Fillet Quality of Asian Seabass Lates calcarifer (Bloch, 1790) Grown in Monoculture and Coculture Systems in Freshwater Earthen-ponds

Growth, production and feed conversion performance of the gurami sago (Osphronemus goramy Lacepède, 1801) strain in different aquaculture systems

Background: Giant gourami (Osphronemus goramy, Osphronemidae), belonging to the gurami sago strain, is an important economic fish species that was newly released for domestication in 2018 in Indonesia. The present study aimed to determine the growth, production and feed conversion efficiency of gurami sago strain in different aquaculture systems. Methods: A mean of 240 juveniles were stocked (mean, 54.53 g and 13.88 cm) into concrete ponds, floating net cages and earthen freshwater ponds (12 m3) with three replicates of each. The juveniles were fed a floating commercial pellet diet containing 30% crude protein and 5% crude lipids. Feed was supplied at 3% of fish biomass per day throughout the 90 days of the experiment. The research was conducted in the area surrounding Lake Maninjau of West Sumatera Province, Indonesia. Results: After 90 days, the mean weight of fish reared in concrete ponds was 166.86 g, floating net cages was 179.51 g and earthen freshwater ponds was 149.89 g. The mean final biomass was 37.64 kg for concrete ponds, 41.27 kg for floating net cages, and 33.72 kg for earthen freshwater ponds. The specific growth rates (%/day) for concrete ponds, floating net cages and earthen freshwater ponds were 0.67, 0.75 and 0.62, respectively. The feed conversion rates were 1.45 for concrete ponds, 1.30 for floating net cages and 1.87 for earthen freshwater ponds. The net yields (kg mˉ3) were 2.05 for concrete ponds, 2.27 for floating net cages, and 1.73 for earthen freshwater ponds. The exponents (b) of the length–weight relationship were calculated for concrete ponds (1.0146), floating net cages (1.2641), and earthen freshwater ponds (1.0056). Conclusion: The study showed that the growth performance, production and feed conversion efficiency of the gurami sago strain could be considered a new candidate strain for floating net cage aquaculture in the future.

Potentials of integrated multi-trophic aquaculture (IMTA) in freshwater ponds in Bangladesh

An experimental study was carried out for a period of six months to assess the potential of integrated multi-trophic aquaculture (IMTA) in earthen freshwater ponds. Nine earthen ponds (40 m2 each) were randomly assigned to three treatments in triplicate. Carps and stinging catfish; carps, stinging catfish, and snails; and carps, stinging catfish, snails, and water spinach as IMTA, were assigned to T1, T2, and T3, respectively. The stocking densities were: carps: 20,000 fingerlings ha−1 at a ratio of 3: 1: 2: 2 for catla: silver carp: rohu: mrigal; stinging catfish: 24,700 fingerlings ha−1 in cage-in-pond for all treatments; and snails: 62 kg ha−1 in T2 and T3. The carps were fed with supplementary feed, a mixture of rice bran and wheat bran (1: 1) at the rate of 3–5% of fish biomass; the stinging catfish with commercial feed for the first 45 days, and snail-mixed pelleted feed for the rest of the experimental period, at the rate of 5–25% of body weight. The highest survival, particularly of silver carp, mrigal, and stinging catfish was found in T3, i.e., in IMTA ponds. The weight gain of silver carp, rohu, and stinging catfish was the highest in IMTA ponds. The highest yields of the carps and stinging catfish in cage-in-ponds were obtained in IMTA ponds. The production of snails and water spinach in IMTA ponds contributed to the biomitigation process of organic and inorganic waste, keeping the water quality within suitable conditions for fish culture.

Composition and Abundance of Benthic Macro-invertebrates in Freshwater Earthen Ponds of Noakhali District, Bangladesh

The composition and abundance of benthic macro-invertebrates in freshwater fish ponds of Noakhali region were analyzed for a period of six month (December-May, 2012). Experimental ponds were categorized as culture, household and derelict and samples were drawn every week during the entire study period using an Eckman grab with dimension of 15.2×15.2×15.2 cm. A total of 10 major groups/taxa were identified viz.; Polychaetes, Oligochaetes, Gastropods, Amphipods, Bivalve, Diptera, Crab, Isopods, Prawn larvae and Copepod. Total macro-benthos abundance was recorded 1555.54, 1466.66 and 2177.79 ind. / m2 respectively in culture, household and derelict ponds. Oligochaetes were found dominant (49 -75%) in all the experimental ponds. Density of Oligochaetes was recorded 888.89, 1088.89 and 1066.67 ind. /m2 respectively in culture, household and derelict ponds. The overall composition of macro-benthos was Polychaetes (9.19%), Oligochaetes (58.56%), Gastropods (19.23%), Amphipods (3.85%), Bivalvia (1.50%), Diptera (1%), Crab (0.43%), Isopods (0.43%), Prawn larvae (0.21%) and Copepods (0.85%). The present study reveals that macrobenthic fauna and their density are variable among the freshwater ponds. The obtained information can be used for further analysis of seasonal variation of macrobenthos, conserve biodiversity and seasonal change of water quality parameter of freshwater ponds.

Genetic improvement of tilapias in China: Genetic parameters and selection responses in growth, survival and external color traits of red tilapia (Oreochromis spp.) after four generations of multi-trait selection

Genetic parameters and selection responses were obtained for growth, survival and external color traits of Progift red tilapia (Oreochromis spp.) in China after four generations of multi-trait selection to increase all traits except black spots, which should, ideally, be eliminated from the breeding population. Red tilapia from four Asian and four South-American hatchery stocks were used to compose a synthetic breeding population. About 45,000 tagged fingerlings representing 610 full-sib families in five generations were tested in freshwater earthen ponds, freshwater floating cages and brackish water tanks in Hainan Province of China. About 30,000 fish were recorded at the expected time of sexual maturation (170days) and at harvest (250days) to estimate genetic parameters. Heritability (h2) estimate for body weight was 0.42±0.03 when analyzing all harvest data, while h2 of survival was 0.05±0.01 and 0.09±0.12, respectively, when estimated on the observed and underlying scales. The h2 of external color traits at harvest was 0.24±0.04, 0.51±0.03 and 0.14±0.02, respectively, for black spots, pigmented area and skin/scale color. Including all data, effects common to full-sibs other than additive genetic effects (c2) accounted for 3–5%, 2–3% and 5–13%, respectively, of the total phenotypic variance for body weight, survival and external color traits. Genetic correlations between observations at expected time of sexual maturation and at harvest were generally high in magnitude (0.9–1.0) for all recorded traits except black spots (0.78±0.06). The genetic correlation between growth in freshwater earthen ponds and floating cages was very high (0.92±0.06), while that between freshwater earthen ponds and brackish water tanks (0.33±0.14) suggests considerable genotype by environment interaction. The genetic correlation between growth and survival was favorable (0.42±0.11), while those between growth and black spots (0.28±0.09), pigmented area (−0.25±0.06) and skin/scale color (−0.09±0.07) were all unfavorable. Breeding candidates in G0–G3 were all ranked according to selection indices including individual breeding values for growth (recorded as body weight at harvest) and color traits, while those for G2 also included family breeding values for survival. A genetic trend analysis based on all grow-out data predicted an accumulated selection response of 175g larger harvest weight (2.13 phenotypic standard deviation units) and an average selection response relative to each parent generation of 12.3%, using the LS mean of the G0 as a base line for the comparison. Similar genetic trend analyses predicted accumulated selection responses of 5.0%-units higher survival rate, 0.6 scores less black spots, 0.9 scores larger pigmented area and 0.1 scores better skin/scale color on scales of 5, 6 and 6 scores, respectively. The average inbreeding coefficient (F) was 1.5% in the G4 generation. It is concluded that the ongoing selective breeding of red tilapia in China has resulted in considerable genetic improvements of growth (59% larger body weight at harvest), survival and external color traits after four generations of multi-trait selection.

Genetic improvement of tilapias in China: Genetic parameters and selection responses in growth, pond survival and cold-water tolerance of blue tilapia (Oreochromis aureus) after four generations of multi-trait selection

Genetic parameters and selection responses were obtained for growth, pond survival and cold-water tolerance of Progift blue tilapia (Oreochromis aureus) in China after four generations of multi-trait selection. Blue tilapia from four Chinese hatchery stocks and one from Vietnam were used to compose a synthetic breeding population. About 31,000 tagged fingerlings representing 519 full-sib families in five generations were tested in freshwater earthen ponds in Hainan Province of China. Individual body weights were recorded on 11,000 fish at the expected time of sexual maturation and 22,000 at harvest to estimate genetic parameters for growth rate. An additional 5000 tagged fingerlings representing all families in G3 and G4 were challenged to estimate genetic parameters for cold-water tolerance. Heritability (h2) estimates for body weight were relatively stable across time of recordings and generations, and was of similar magnitude (0.40±0.04) when analyzing all harvest data. The h2 of pond survival was considerably lower (0.05±0.01 and 0.08±0.11), while that of cold-water tolerance was intermediate (0.20±0.04 and 0.30±0.31) when estimated on the observed and underlying scales. Including all data, effects common to full-sibs other than additive genetic effects (c2) accounted for 7% and 1%, respectively, of the total phenotypic variance for body weight at harvest and the two survival traits. Genetic correlation between growth recorded at expected time of sexual maturation and at harvest was very high (0.99±0.01). The genetic correlation between growth and pond survival was positive (0.15±0.08), while that between growth and cold-water tolerance was not significantly different from zero (0.02±0.12). Breeding candidates in the base population (G0) were ranked according to their individual breeding values for growth (recorded as body weight at harvest), while those in later generations (G1–G3) were ranked according to a selection index including individual breeding values for growth and family breeding values for survival traits. A genetic trend analysis based on all grow-out data predicted an accumulated selection response of 168g (2.16 phenotypic standard deviation units) and an average selection response of 14.0% per generation of selection when using the LS mean of the G0 as a base line for the comparison. Genetic trend analyses of survival data predicted accumulated selection responses of 8.4 and 1.2%-units higher survival rates in earthen ponds and cold-water challenge tests, respectively. The average inbreeding coefficient (F) was estimated to be 2.1% in the G4 generation. The results are discussed in a practical context of adapting selective breeding technology to a new aquaculture species and it is concluded that the ongoing selective breeding of blue tilapia in China has resulted in considerable genetic improvements of both growth (about 70% larger body weight at harvest) and pond survival after four generations of multi-trait selection.

Genetic improvement of tilapias in China: Genetic parameters and selection responses in growth of Nile tilapia ( Oreochromis niloticus) after six generations of multi-trait selection for growth and fillet yield

Genetic parameters and selection responses were obtained for growth of Progift Nile tilapia ( Oreochromis niloticus) in China after six generations of multi-trait selection. About 64,000 tagged fingerlings representing 787 full-sib families in seven generations of Nile tilapia originating from the GIFT breed were tested in freshwater earthen ponds, floating cages in reservoirs and a brackish water earthen pond in Guangdong and Hainan Provinces of China. Individual body weight was recorded on 25,000 of these at the expected time of sexual maturation and 50,000 at harvest to estimate genetic parameters for growth rate. Heritability (h 2) estimates for body weight showed large variation in magnitude (0.00–0.52) when analyzing data from each test environment and generation separately. Estimates obtained in floating cages and a brackish water pond was comparable or lower in magnitude than those obtained in freshwater earthen ponds. The h 2 estimates for body weight at harvest became more stable (range 0.13–0.20) when data from previous generations were included in the analysis. Including all data, the effect common to full-sibs (c 2) accounted for 10% of the total phenotypic variance for body weight at harvest. Genetic correlation between growth recorded at expected time of sexual maturation and at harvest was 0.8, but seemed to decrease in later generations. The genetic correlations between growth in freshwater earthen ponds and other test environments were of similar magnitude. Breeding candidates in the base population (G 0) were ranked according to their individual breeding values for growth (recorded as body weight at harvest), while those in later generations (G 1–G 5) were ranked according to a selection index including individual breeding values for growth and family breeding values for fillet yield. The selection response for growth was, on average, 11.4% per generation of selection (range 7.4–18.7%) when estimated based on control groups representing the parental generations. A genetic trend analysis based on all data (h 2 = 0.20, c 2 = 0.10) predicted an accumulated selection response of more than 200 g and an average selection response of 8.0% per generation of selection when using the LS mean of the G 0 as a base line for the comparison. The average inbreeding coefficient (F) was estimated to be 5.0% after six generations of selection. The results are discussed in a practical context of developing selective breeding programs for tilapias and it is concluded that the ongoing selective breeding of Nile tilapia in China has resulted in considerable genetic improvement of growth (60–90% larger body weight at harvest) after six generations of multi-trait selection.

Capacity for thermal acclimation and winter mortality of sea bass Dicentrarchus labrax in freshwater earthen ponds

Some fish species exhibit a biochemical response to low winter temperatures. For example, after a period of cold acclimation, an increase in enzyme activity occurs. This can result in at least partial compensation in the rate of biochemical reactions of aerobic metabolism. Sea bass (Dicentrarchus labrax L. 1758) is a commercially important fish for the Mediterranean mariculture industry, which can grow satisfactorily in both freshwater (FW) and seawater (SW) conditions. The purpose of the present work was to evaluate the survival and growth of sea bass in FW earthen ponds. The experiment was initiated in September 2003 in order to avoid the water temperature highs during spring–summer and allow several weeks for acclimation before the winter temperature lows. Fish growth occurred for several months, but by the end of December 2003, ambient water temperature reached levels below 5°C and mass mortality occurred. The capacity of sea bass for thermal compensation was evaluated by monitoring the activity of cytochrome c oxidase (CCO) of red axial muscle. The activity of CCO initially increased from 6.4 (±0.98) in September (ambient water temperature 19°C) to 10.4 (±1.49) in October (ambient temperature 15.4°C), but decreased again to 8.8 (±1.45) in November (ambient temperature 12.3°C). A similar trend was exhibited by the glycolytic enzyme lactate dehydrogenase in white muscle. The results do not indicate a capacity of thermal acclimation in FW ponds with low temperature (<13°C) for sea bass. Evidently, seasonally extremely low temperature is a challenge for the production of sea bass.

Bacterial microflora of the african catfish (&lt;i&gt;Clarias gariepinus&lt;/i&gt;) juveniles raised under fish cum pig integrated farming system in freshwater earthen ponds during the dry season.

The bacterial microflora of a fish cum pig integrated farming system was examined during the dry season months of November to March. Clarias gariepinus fingerlings of 9.2g mean weight were stocked at a density of 5 fingerling m-2 in three freshwater earthen ponds of 200m2 surface area each that were fed 175gm-1 fresh pig manure as the major nutrient source till they reached juveniles of 341.6g mean weight within the period. Standard methods of bacterial identification and confirmation were conducted on fish organs such as the fin, skin, gill, intestine, liver as well as the original pig manure resource, pond water and pond sediment to determine microbial quality. The gram negative bacteria identified were Citrobacter, Escherichia, Yersinia, Campylobacter, Enterobacter, Serratia, Pseudomonas, Klebsiella, Proteus, Aeromonas, Vibrio and an Unidentified gram negative bacterium while the gram positive bacteria were Lactobacillus, Corynbacterium, Listeria, Streptococcus, Bacillus, Staphylococcus and Nocardia. The highest heterotrophic plate count of 1.40x1015cfug-1 was obtained from pig manure samples, 1.58x1013cfug-1 for the pond sediment but 1.20x108 cfug-1 for the pond water. For the fish organs, mean plate count for the skin was 4.20x109cfug-1 in contrast with 2.30x1012cfug-1 for the intestine, 1.40x1010cfug-1 for the gill, 3.30x109cfug-1 for the fin while the lowest tissue count of 3.50x105 was obtained for the fish liver. While there was no general physical presentation of dermal lesions, the gill tissues were necrosis with haemorrhage of intestinal mucosa. The bacteria of economic and health importance encountered in this study were from varied sources, but the pig manure was the main source of Kliebsiella and Proteus while the pond water was the source of Nocardia and the unidentified gram negative bacterium. It was recommended that alternative means of improving fish pond fertility be exploited. Keywords: Bacteria, Clarias gariepinus, Juvenile, Pig manure, Fish pond, Dry Season Nigerian Journal of Fisheries Vol. 4 (2) 2007: pp. 91-104

Biochemical composition of zooplankton community grown in freshwater earthen ponds: Nutritional implication in nursery rearing of fish larvae and early juveniles

This study was conducted to obtain a database describing the nutritional value of freshwater mixed zooplankton that are widely used for larval and grow-out rearing of freshwater fish. The macro and micronutrient composition of mixed zooplankton samples collected from 6 fertilized earthen ponds were analysed for protein, lipid, carbohydrate, ash and these ranged from 73–79%, 10.79–14.55%, 3–4.79% and 3.20–10.07%, respectively on a dry matter (DM) basis. Amino acid profile showed the presence of all the ten essential amino acids with low level of methionine. The content of saturated fatty acids (SAFA), mono unsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) ranged from 64–81%, 7–15% and 6–20% of total fatty acids, respectively. The predominant fatty acids were SAFA (16:0), MUFA (18:1n-9), PUFA viz. linoleic acid (LA 18:2 n-6) and linolenic acid (LNA 18:3 n-3). Among the vitamins, ascorbic acid (15–40.01 μg/gDM) was less than the requirement of fish especially for larvae, vitamin-A (13.61–63.95 μg/g DM) and vitamin-E (218–348μg/g DM) were more than the requirement of fish. Mineral and trace element content showed the presence of P, Ca, Fe, Cu, Zn and Mn. Seasonal variation of all biochemical components was evaluated in the study. Vitamin E had strong co-relation (r1=0.72; r2=0.88; r3=0.83; r4=0.86; r5=0.36 and r6=0.88) with seasonal variation in lipid content of zooplankton of different ponds and varied inversely with that of rising temperature. Enzyme content from the mixed zooplankton of different ponds showed availability of protease (6.21–7.92 μg leucine/ mg protein/h), lipase (25.82–39.1 μg α-naphthol/mg protein/h) and amylase (100–226.1 μg maltose/mg protein/h), which could be used as an exogenous source of digestive enzymes for fish and shellfish during ontogenesis. Absence of l-gulonolactone γ-oxidase activity confirmed the incapability of these zooplankton to synthesize ascorbic acid (AA) de novo. The average dry weight in zooplankton in different ponds was 1.2–4.2 mg/l and different species present in these ponds were Moina (Moina dubia), Daphnia (Daphnia lumholtzi, Daphnia carinata); Cyclops (Mesocyclops hyalimus, Mesocyclops leuckarti); Diaptomus (Heliodiaptomus viddus, Neodiaptomus handeli); Rotifer (Brachionus). These results indicate that the biochemical composition and subsequently the nutritional value of these planktonic organisms are not only genetically determined but also influenced by its maturity stage and type of ingested food. These data may be helpful for reference purpose and for formulated feed preparation accessing the nutritional potentiality of these freshwater zooplankton in the nursery rearing of freshwater fish larvae and early juveniles.

Effect of stocking densities of grey mulle (Mugil cephalus) reared on natural food in monoculture earthen ponds on growth performance and total production with economical evaluation

rowth performance, total fish yield and economical evaluation of the grey mullet Mugil cephalus (L.) at different stocking densities were compared in monoculture system without any supplementary feeding. Four stocking densities at rate of 1050, 1400, 2100 and 4200 fish/feddan (0.42 ha) for treatments, T1, T2, T3 and T4 respectively, were carried out in eight freshwater earthen ponds. Ponds were fertilized with organic and inorganic fertilizers, (60 kg; chicken manure, 30 kg. super phosphate and 10.0kg urea per feddan biweekly). Results indicated that the main individual growth rate was highest for lower density and lowest for the higher density. Final body weight was 231.86, 182.82, 151.19 and 91.65 g /fish for T1, T2, T3 and T4 respectively, with significant difference (p<0.05). Final body length, SGR (%), RGR (%), daily weight gain, survival rate, condition factor, economic evaluation and sensitivity analysis were discussed. Total fish production values at the end of experimental period (180 days) were 233.7, 236.8, 273.0 and 313.9 kg. / feddan (0.42 ha.) for T1, T2, T3 and T4 respectively. It could be concluded that treatment (T1) that received the lowest stocking density at the rate of 1050 grey mullet Mugil cephalus fingerlings per feddan (0.42 ha.), without any supplementary food, and cultured for 180 days in monoculture system, had the highest net return and rate of return, followed by T2 and T3, which can reduce the risk for the farmer in the event of unexpected fall in market price or production or increasing of costs.

Effects of pond depth and water temperature on the growth, mortality and body composition of Nile tilapia, Oreochromis niloticus (L.)

The effects of varying water depths and temperature on the growth, feed utilization, mortality rates and body composition of Nile tilapia, Oreochromis niloticus (L.), were evaluated. Triplicate groups of 20 fish (mixed-sex) m-3 were stocked into 200-m2 freshwater earthen ponds maintaining four water depths: 50, 100, 200 and 300 cm. The fish were fed on commercial fish pellets (23% protein), twice a day for 10 months (May 1991-February 1992). Water temperatures ranged from 5 oC to 33 oC. Growth performance and survival were significantly affected by pond depth and water temperature. Fish weight gain was lowest (250 g per fish), feed conversion poorest (3.15), and mortality highest (41.5%) at 50 cm depth, whereas 100-200 cm depth produced the best growth rates at warm water temperatures (> 21 oC). At 100-200 cm depth, weight gain was significantly (P<0.001) increased to 348-362 g per fish, feed conversion improved to 2.53-2.59 (P<0.01) and mortality reduced to 21-27% (P<0.001). Fish growth was significantly reduced (P<0.001) below 21 oC. Below 10 oC, fish stopped feeding and developed severe stress, fungal infection and high mortality. However, mortality rate was significantly reduced at 300 cm depth. Body lipid and protein were sharply decreased (P<0.001) with decreasing water temperature and pond depth, whereas body ash showed irregular patterns.

Self-contained Upwelling System for Rearing Larval Fishes in the Laboratory

Abstract The design and operation of a rearing and salinity conversion system is described. This system was developed and successfully used to rear snook (Centropomus undecimalis) from artificially fertilized eggs for the first time. The system consists of a 300-L glass aquarium with a biological filter and four 8-L flow-through rearing chambers. The rearing chambers consist of acrylic tubing 20 cm in diameter, friction-fitted into vacuum-formed styrene funnels. Each chamber is individually plumbed to produce an up welling current by introducing water at the bottom and discharging it near the top. Eight screened openings cut into the acrylic tubing assure an even, gentle flow through the chambers. Snook were reared through the early larval stages in salt water and then converted to fresh water. As many as 35 snook per chamber were reared through the conversion process and stocked in earthen freshwater ponds. Use of this system enabled the evaluation of the foods, feeding behavior, and growth of larval sno...