Outdoor Concrete Tanks Research Articles

Alternate Day Feeding as a Cost-effective Strategy for Tank Culture of the Pacific Shortfin Eel Anguilla bicolor pacifica

There is a growing interest in the aquaculture of tropical anguillid eels as an export commodity. However, studies on feeding strategies, and the present demand to reduce feed costs need to be addressed to ensure the economic viability of eel farming. In this study, the effects of daily (DF) and alternate day (ADF) feeding on growth, feed utilization, body composition, blood chemistry, liver and intestinal morphology, and economic viability in the Pacific shortfin eel Anguilla bicolor pacifica were examined. Each feeding group of 30 elvers (166.25 ± 16.23 g mean initial wt) were randomly stocked in triplicate 4 m3 outdoor concrete tanks. These were fed for 155 d with formulated eel powder diet (49.77% crude protein; 10.21% crude lipid) made into a paste. Growth and survival were not significantly different between the two feeding groups. However, feed efficiency was improved in the ADF group, with significantly higher protein efficiency ratio (0.63) than in the DF group (0.39). Feed conversion ratio (FCR) was lower in ADF (3.85) than in the DF group (6.44), resulting in a 40% reduction in total feed consumption. Biometric indices, body proximate composition, and blood chemistry were not significantly affected. Likewise, liver and intestinal morphology showed no apparent alterations between groups. Partial costs-and-returns analysis showed that ADF yielded higher net profit and profit index. These results suggest that feeding on alternate days promote compensatory growth, better feed utilization, and normal physiological condition of A. bicolor pacifica, and reduce feed cost in the rearing process. Therefore, alternate day feeding should be promoted as a sound feed management strategy in the tank culture of tropical anguillid eels.

The Dietary Mixture of Betaine, Lactic Acid Bacteria, and Exogenous Digestive Enzymes Enhanced the Growth Performance, Intestinal Health, and Immunity of Nile Tilapia (Oreochromis niloticus) Grown in Outdoor Concrete Tanks

Abstract It has been illustrated that using mixtures of feed additives is more efficient than using individual additives in aquaculture. Hence, this study aimed to study a dietary mixture of betaine, lactic acid bacteria, and exogenous digestive enzymes (BLE) on the growth performance, digestion capacity, intestinal health, and blood indices of Nile tilapia reared outdoors in concrete tanks. Five diets were prepared where the basal diets were mixed with BLE at 0, 0.25, 0.5, 0.75, and 1%. After 90 days, the growth performance of Nile tilapia fed BLE was markedly enhanced in fish fed 0.25 and 0.5% of BLE, while the feed conversion ratio (FCR) was reduced (P<0.05). The lipase activity was significantly higher in tilapia fed BLE at 0.25, 0.5, and 0.75% than 0 and 1%. The amylase activity was meaningfully increased by 0.5% of BLE than 0, 0.25, 0.75, and 1%. The protease activity was significantly higher in tilapia fed BLE at 0.25 and 0.5 than 0, 0.75, and 1% (P<0.05). The intestine of fish fed on BLE showed an increase in intestinal villi density. The villi length, width, and the number of goblet cells were markedly higher in the anterior, middle, and posterior segments of the intestines of tilapia fed BLE than in the control group (P<0.05). Further, fish fed BLE had higher intestinal morphometry indices and count of goblet cells than the control. Significantly fish fed 0.25, and 0.5% of BLE had higher hemoglobulin, and hematocrit levels than fish fed 0, 0.75, and 1%. While, fish fed 0.5% had higher red blood cells than fish fed the remaining BLE levels (P<0.05). On the other hand, no marked effects for BLE supplementation were seen on the alanine aminotransferase (ALT), aspartate aminotransferase (AST), total protein, albumin, globulin, creatinine, uric acid, and urea. The regression analysis showed that the maximum dose of BLE supplementation to achieve the highest final weight and the lowest FCR is 0.46% and 0.42%, respectively.

Plant traits and environment: floating leaf blade production and turnover of Nymphoides peltata (S.G. Gmel.) O. Kuntze (Menyanthaceae).

BackgroundNymphaeid macrophytes, rooting in the sediment of water bodies and characterized by floating leaves, play an important role in wetland ecosystems. The present research deals with the effects of limited space, limited nutrient availability, water temperature and an unexpected inundation on the production, turnover and plasticity of floating leaves of the globally widespread species Nymphoides peltata (Fringed waterlily).MethodsThe effects of these environmental conditions were studied in two plots in outdoor concrete tanks (CT1, CT2, mesocosms simulating occurrence in small ponds) and in two plots in the floodplain oxbow lake Bemmelse Strang (BS1, BS2). Plot CT1 was situated in a stand coexisting with helophytes, plot CT2 in a monospecific stand, plot BS1 in the center and plot BS2 at the open water border of a monospecific stand. All floating leaf blades within the plots were marked at appearance at the water surface and subsequently length, width and damage of each leaf and maximum and minimum water temperatures were measured bi-weekly. Area and biomass of leaf blades were calculated based on leaf length and width and were used to calculate turnover rates and production.ResultsThe growth period started in May and ended mid-October with continuous production of floating leaves during nearly the whole vegetation period. In the tanks the water level was very stable, but the lake underwent an inundation by river water, causing a sudden loss of existing leaves. Considering environmental conditions and based on the assumed ranking from low to high nutrient availability, the ranking of the plots was CT1, CT2, BS1, BS2. This order was found for maximum leaf life span and maximum leaf length, and the reverse order was found for number of leaves, new leaves per day and duration of the vegetation period. Turnover rates appeared to be relatively similar for plots CT1, CT2 and BS1, but for the deeper border plot BS2 lower ratios were found. These results indicate that increased enclosure with expected nutrient limitation causes (1) the production of high numbers of small leaves with larger totals for leaf area and biomass, (2) a shift towards increased sexual reproduction by the production of more flowering stem leaves.

The effects of dietary oregano essential oil on the growth performance, intestinal health, immune, and antioxidative responses of Nile tilapia under acute heat stress

Climatic changes are impacting the aquaculture industry and result in low productivity and high economic loss. Herein, we evaluated the long-term acute heat stress on the productivity and performances of Nile tilapia and the ameliorative role of oregano essential oil. Fish were raised in outdoor concrete tanks during the summer season under high water temperature (32 °C) and fed four test diets supplemented with oregano essential oil at 0, 0.25, 0.5, and 1 g/kg for eight weeks. The final weight, weight gain, and specific growth rate were markedly enhanced (P < 0.05) by 0.5 and 1 g oregano essential oil/kg diet. Nevertheless, the feed conversion ratio was reduced by oregano essential oil (P < 0.05). The foregut, midgut, and hindgut of the intestines of fish-fed oregano essential oil showed apparent branching of villi and increased villi length and width, with the highest being in fish treated with a 1 g/kg diet (P < 0.05). The activities of aspartate aminotransferase and alanine aminotransferase were markedly reduced (P < 0.05) in Nile tilapia fed 0.5 and 1 g oregano essential oil/kg. At the same time, the total protein, albumin, and globulin levels were higher (P < 0.05) in fish-fed oregano essential oil than in the control. The superoxide dismutase, catalase, phagocytic index, and lysozyme activity were meaningfully increased (P < 0.05) in Nile tilapia fed oregano essential oil and raised under acute heat stress. The concentration of malondialdehyde and relative expression of heat shock protein 70 (HSP70) were markedly decreased (P < 0.05) in fish treated with oregano essential oil, with the lowest level in fish fed 1 g/kg. In conclusion, dietary oregano essential oil relieved the impacts of heat stress on Nile tilapia by increasing the growth performance, regulating the blood biochemical traits, improving the immune and antioxidative responses.

Influence of water exchange rates on fingerling production in Indian major carps in large outdoor concrete tanks

Influence of varied water exchange (total of 0%, 40%, 60%, 80% and 100% in four phases during three months) on fingerling production of Indian major carps-catla, rohu and mrigal under polyculture was evaluated in large outdoor concrete tanks (50 m2). Rearing density of 30 fry m−3 was used. Survival in the control tanks reduced during the 2nd month unlike the treatments, attributed to lack of water exchange in the tanks. While no marked variation in water quality was observed among the control and treatments, graded water exchange led to proportionate improvement in the fingerling performance in terms of survival and growth in the treatments. Harvested total lengths of fingerlings were similar in all, irrespective of varied exchange levels. Although no significant variation in net weight gain (NWG) and specific growth rate (SGR) were observed among the treatments during 1st and 2nd months of rearing in any of the species, these attributes increased significantly during 3rd month with higher water exchange in treatments. The harvested body weight (HBW) also increased significantly with increased exchange level. However, survival, HBW, NWG and SGR remained similar in all species between the 80% and 100% water exchange levels. Treatment with 80% water exchange had higher water productivity in terms of number and biomass production of fingerlings per unit (m−3) of TWU and CWU for which, the study recommended 80% to be the ideal total water exchange required for fingerling production of IMC in concrete tanks.

The success on pre-mating molt of immature female mud crab (Scylla tranquebarica) reared at different depth in concrete tank

Cannibalism is one of the obstacles event in the mud crab breeding program. Placement of the prospective broods communally in a container waiting for coupling and mating to occur naturally often leads to fights each other that cause limb defects and even death. Fail in providing optimal environmental conditions in a controlled container also often results in prolonged period of premating-molt and spawning. This study aims to prepare female mud crab broods separately from males placed at different depth in the water column to see the success of premating-molt and mating process. The early inter-molt phase of immature female crabs that heading premating-molt stage were randomly selected from crab sellers in the local market with the following initial data: CW 100 ± 3.4 mm, CL 65.6 ± 2.5 mm, and BW 154.2 ± 16.6 g. Each of 30 available crabs was inserted in separate crab-box after then 10 crab-box placed at each different depth of 0, 70 and 140 cm respectively in an outdoor concrete tank. At the same time, three male broodstock weighing >350g were placed individually in a 0.5 ton fiberglass tank in the hatchery building. The newly molted female in crab-box were immediately transferred to the male tank to mate. The response to growth, molting time, molting frequency, success of mating and spawning to the depth treatment were recorded during the study. The results showed that the rearing of crabs at different depths did not show any significant differences (P>0.05) in growth and molting time, but the molting frequency and survival rate at 70 cm depth were better than other depth treatment.

Evaluation of three forms of feed on growth and survival of rohu Labeo rohita (Hamilton, 1822) juveniles reared in outdoor tanks

A feeding trial for 90 days duration was conducted to study the efficacy of three forms of feed (dough, sinking and floating feeds) on growth performance and survival of rohu Labeo rohita (Hammilton, 1822) juveniles. Four hundred and fifty fingerlings (average weight 8.7±0.7 g, average length 9.68±0.37 cm) were randomly distributed into nine large outdoor concrete tanks (50 m2 ), grouped into three treatments with three replicates each. Three forms of diet designated as T1 (dough feed), T2 (sinking pellets) and T3 (floating pellets), prepared from the same quantity of ingredients, were fed at 8% of biomass twice a day. The results revealed significantly higher weight gain, specific growth rate (SGR) and lower feed conversion ratio (FCR) in sinking pellet fed group (p 0.05). Though rohu is known to feed from column to bottom zones, the present results revealed better efficacy of sinking pellet over dough or floating form to improve the growth performance of the species during juvenile rearing. Keywords: Condition factor, Feed form, Growth, Labeo rohita, Water quality, Yield

Role of fertilization, supplementary feeding and aeration in water quality changes and fry growth in intensive outdoor nursing of fringed lipped carpLabeo fimbriatus(Bloch)

A 30-day nursery trial was conducted to study the contribution of fertilizers, feed and aeration on the growth performance of fringed lipped carp, Labeo fimbriatus fry. Twelve large outdoor concrete tanks (10 m x 5 m x 1.2 m each) provided with 15 cm soil base were divided into three treatment groups. The three treatments received varied input combinations such as: only fertilizer (T-1); fertilizer + supplementary feed (T-2); and fertilizer + supplementary feed + aeration (T-3). Each tank was stocked at 1000 spawn m−3. After 30 days of rearing, the addition of supplementary feeding (T-2) recorded an 18% increase in the production of fry by number and 5.35-fold increase by biomass than T-1. However, additional aeration in T-3 resulted in 14.8, 31.4 and 44.0% increase in survival, fry yield (in number) and biomass than those in T-2, respectively, signifying potential advantage of aeration during intensive nursery rearing phase. Aeration also helped to maintain good water quality and sustain higher biomass. The absence of supplementary feeding (T-1) in such high-density nursery rearing led to starvation stress and caused poor fry performance in terms of growth and survival. The study further reinstated that added inputs in the form of supplementary feeding and aeration reduced such stress, ensured better environmental conditions and fry performance and also increased the profit margin during high-density nursery rearing.

Growth and survival of Ripon barbel (Barbus altianalis) larvae and juveniles fed five experimental diets in captivity

Mass production of quality seed is vital for commercial culture and requires prior knowledge of appropriate larval diets and their utilization. Four experiments were sequentially conducted at different periods to evaluate the effect of live and a processed microdiet on growth and survival of Barbus altianalis larvae and juveniles. Larvae were fed exclusively on live prey (Moina and Artemia nauplii), microdiet (57 % Crude Protein), decapsulated Artemia cysts and in combination (Moina + microdiet). The effect on growth was further evaluated in subsequent juvenile trial by co-feeding. Green water effect on larval growth was also evaluated. In the final experiment, 15 day old larvae were raised in fertilized outdoor concrete tanks. Results indicated that each diet affected larval growth significantly different (P < 0.05) with the combination diet (152.05 ± 2.51mg) and decapsulated Artemia (141.14 ± 2.43 mg) performing better than microdiet, Moina and Artemia nauplii in that order. In subsequent juvenile experiment, larvae originally fed decapsulated Artemia (510.13 ± 11.93 mg) and those fed a mixed diet (500.20 ± 11.8 mg) performed better than other diets. Ontogenetic pattern of amylase, lipase and protease activity identified larvae maturation age at 14–21 Days after hatching (DAH) (14.93 ± 0.36–31.5 ± 0.61 mg) with the combination diet. When larvae at 15 DAH were nursed in outdoor tanks, final survival and growth performance increased to 95.3 % and 1112 ± 42.70 mg compared to the indoor nursing at 90.9 % and 355.33 ± 6.44 mg respectively by 75 DAH. Therefore we recommend that any microdiet manipulations and or outdoor nursing be done during or after this period. Microalgae had no direct effect on larval growth (P > 0.05). In this study, larvae were confirmed to utilize the microdiet from exogenous stage but co-feeding produced best average weight (152.05 ± 2.51mg), specific growth rates (4.06 ± 0.19) and survival (90.9 %). This study provided guiding strategies for improved rearing of B. altianalis fingerlings in captivity.

Optimising water requirement for nursery rearing of rohu Labeo rohita (Hamilton, 1822) in large outdoor concrete tanks: influence of water depth on seed performance

A study was conducted to find the optimum water depth requirement for nursery rearing of rohu Labeo rohita (Hamilton, 1822). Nine concrete tanks of 50 m2 each (10 x 5 x 1.2 m) were grouped into three treatments T1, T2 and T3 and were filled upto 1.0, 0.75 and 0.5 m water depths, respectively. Each tank was stocked with 0.5 lakh hatchery produced spawn and reared for 20 days. The study revealed significant influence of water depth on growth and survival of fry (p&lt;0.05). Though the final length of fry did not differ among the treatments (p&gt;0.05), T3 with 0.5 m water depth showed significantly lower survival, final body weight and specific growth rate than the other two treatments (p&lt;0.05), whereas tanks with 1.0 and 0.75 m water depths showed almost similar survival, final weight and SGR (p&gt;0.05). Assessment of water use for production of every 1000 fry revealed significant reduction in total water use (TWU) with decreased water depth (p&lt;0.05), while the consumptive water use (CWU) in terms of water exchange and replenishment did not differ between water depth treatments of 1.0 and 0.75 m. The results of the study indicate 0.75 m to be the ideal water depth with better water use efficiency for fry production of the species.

Evaluation of different water exchange regimes for optimizing growth and production of koi carp, Cyprinus carpio in tanks

The effect of different water exchange regimes on the growth and survival of koi carp, Cyprinus carpio in tanks provided with the supply of exogenous zooplankton as the food was investigated. Fish larvae (0.15±0.012g) were stocked in outdoor concrete tanks at 0.5 fish/l (T1 and T2); 1.0 fish/l (T3 and T4); and 1.5 fish/l (T5 and T6) and cultured for three months. The water exchange rate was 10% once daily in T1, T3 and T5 and twice daily in T2, T4 and T6. Values of dissolved oxygen were highest in T2, followed by T4, T1, T6, T3 and T5. The T5 treatment showed the highest concentrations of conductivity, NH 4 -N, NO 2 -N, NO 3 -N, PO 4 -P, and bicarbonate alkalinity, which were significantly higher than the other treatments. The final body weight of C. carpio ranged from 4.01 to 8.22g in the different treatments. At harvest, maximum weight gain was achieved in the T2, followed by T4, T1, T6, T3 and T5 in descending order. There was a significant difference in the survival of koi carp among the treatments, ranging from 56.43% (T5) to 96.32% (T2). The percentage and number of fish exceeding a total weight of 5g were estimated from the size-frequency distribution at the end of the study and was significantly higher in T6 ( P <0.05) than other treatments. From the present study, a daily water exchange of 20% could support higher stocking densities of koi carp in tanks and result in high productivity, measured in terms of the number of marketable fish.

Growth performance of pengba, Osteobrama belangeri (Valenciennes, 1844) and water quality changes during fingerling rearing with varied stocking density in large outdoor concrete tanks

Fingerling rearing of pengba, Osteobrama belangeri, was conducted at varied densities for 90 days in 12 outdoor concrete tanks (10 m × 5 m × 1 m). The tanks, grouped into four triplicated treatments, were stocked with fry at 20, 30, 40 and 50 fry m-3; and designated as control, T-1, T-2 and T-3 respectively. Tanks were filled up to 90 cm depth. Evaporation loss compensated fortnightly. Fish sampling and monitoring of water quality parameters done at fortnight intervals. Survival varied between 71.5% and 84.0% in treatments. Both survival and total length significantly reduced with increasing densities from control to T-2 (p < .05), while no differences were observed between T-2 and T-3 (p > .05). Similarly, significant reductions in final body weight and specific growth rate were observed with increased densities and these values further reduced in T-3 than T-2 (p < .05). Such results corroborated the inverse relationship between stocking density and growth. Gross biomass yields in two higher densities (T-2 and T-3), despite their lower survivals, were significantly higher than the two lower densities. The numbers of fingerlings harvested were 35, 74 and 112% higher than the control in T-1, T-2 and T-3 respectively. The lowest size obtained even at the highest density (T-3) was of 7.0 ± 1.0 cm and 3.99 ± 0.17 g, which can be considered as ideal grow-out stocking size of pengba. Therefore, the study showed feasibility of stocking up to 50 fry m-3 for rearing from fry to fingerling stage. However, the other lower densities may be used in case of requirement of larger fingerlings.

EFFECT OF WONDERFUL KOLA SEED MEAL (Buccholzia coriacea) ON GROWTH, MASCULINIZING POTENCY AND GONAD GROSS MORPHOLOGY OF THE NILE TILAPIA (Oreochromis niloticus, LINNAEUS 1758)

This study was aimed to investigate the effect of Buchholcia coriacea on the masculinization of Oreochromis niloticus. Five days old mixed sex of O. niloticus (mean weight 0.2g, mean length 0.45mm) were subjected to powdered B. coriacea seeds meal (BSM) at 0, 2, 4, 6, 8, 10g/kg twice daily for 1 month in an indoor experimental plastic basin capacity (50cm in diameter and 30cm deep) in duplicates with a total of six treatments in a complete randomized design. After which there were later fed with a normal diet in an outdoor concrete tank of size 1m3 for another one month. One way ANOVA and LSD were used to analyze the experimental data. The result obtained in this study showed that fish fed with 4g/kg BSM powdered BSM had the highest number (83.33%) of males which was significantly higher (p&lt;0.05) compared to all other treatments categories. The highest survival rate (100%) was recorded in fish fed with 6g/kg BSM. The highest mean length, mean weight and weight gain observed are 0.488mm, 4.68g, and 4.65g respectively. The result of the histology showed that B. coriacea altered the sex of O. niloticus due to the presence of a hormone called dopamine in the kola. Conclusively, B. coriacea showed potential reproduction control in Oreochromis niloticus.

Changes in gonad of Nile Tilapia (&lt;i&gt;Oreochromis niloticus&lt;/i&gt;) fed with crude extract of guava (&lt;i&gt;Psidium guajava&lt;/i&gt; Linnaeus) leaves

Tilapia is fraught with the problem of prolific breeding which usually leads to stunt growth thus making the fish undesirable for consumers. A56-days study was done to investigate the antifertility potential of P. guajava leaves extract on Oreochromis niloticus gonad, the sub-lethal concentrations were earlier reported to inhibit reproduction in the fish species. Oreochromis niloticus of mean weight 29.30±2.02-31.79±3.11 were divided into 6 groups replicated three times. Fishes were stocked in outdoor concrete tanks supplied with 450 litres of water. Six experimental diets (35% crude protein) containing varying sub-lethal concentrations of P. guajava leaf crude extract (0.0, 0.5, 1.0, 2.0, 4.0 and 8.0gkg -1 diets) were formulated (representing O, A, B, C, D and E respectively; O serve as the control). The ovary and testis of fish fed control diet showed normal ovarian tissues and normal distribution of the testicular tissues. Mild atresia and reproduction in the oocytes were observed in the ovaries as the concentration of the crude extract increased from 0.5- 8.0gkg -1 , while in the testes mild to severe atrophy and cystic seminiferous tubules were observed. This study infers that, for sustainable growth of Tilapia culture, P. guajava could be used to solve the problem of prolific breeding, thus energy used in reproduction can be converted to growth. Keywords: Crude extracts, atresia, atrophy, Psidium guajava Linnaeus and guava

Haematology and gonad histology of Oreochromis niloticus (Linnaeus, 1758) fed Carica papaya seed meal

This research investigated the effect of Pawpaw (Carica papaya) seed meal (PSM) on haematological parameters and gonad histology of Oreochromis niloticus (Linnaeus, 1758). Freshly hatched fry of O. niloticus were fed blended commercial diet (35%CP) mixed with varying levels of PSM (0, 2, 4, 6 and 8gkg-1) for 28days in fifteen aquarium tanks (30×30×20cm3). Resultant fingerlings were maintained in outdoor concrete tanks (1×1×1m3) for 140days till they gained an average weight of 30g. Haematological analysis and gonad histology was done to determent the effect of the PSM on the fish. Haematological changes observed in this study did not revealed detrimental effect of feeding of PSM. However, histological evaluation of the gonads showed various degrees of deformities and tends to increase in severity as the levels of PMS increased. It was concluded that PSM might not affect the health status of the Nile tilapia but lead to sterility of the fish.

SURVIVAL RATE AND GROWTH OF JUVENILE SANDFISH (Holothuria scabra) IN VARIOUS REARING CONDITIONS

Techniques for producing Holothuria scabra or sandfish sea cucumbers from aquaculture have been developed rapidly in the recent years to address the issues of decreasing sandfish population and increasing market demand. During the process of culturing H. scabra, the early stages of sandfish (i.e. larvae and juveniles) are the most critical of the development. Therefore, the Research and Development Division of the Marine Bio Industry – LIPI conducted a study to assess the growth performance of juvenile H. scabra ultured in four different rearing conditions: (i) indoor concrete tank, (ii) indoor fiberglass tank, (iii) outdoor concrete tank with 1 mm hapa mesh, and (iv) outdoor concrete tank with 3 mm hapa mesh. Each of the rearing condition was set with an initial juvenile density of 15 juveniles per tank with a mean initial weight of 14 g, and fed ad libitum with a mixed feed consisting of Enhalus acoroides sea grass, Pennisetum purpureum napier and cow manure. The experiments were conducted for 20 weeks between April 26 - September 23, 2013. After the experimental period, juveniles reared in the outdoor concrete tank with 1 mm mesh show the best performance with respect to their survival rate (48.89 ± 3.85 %),mean final weight (22.07 ± 1.01 g), final biomass (162.05 ± 18.17 g) and specific growth rate (0.15 ± 0.03% per day). Further studies that combine rearing conditions with different bottom substrates as well as investigating the effect of light are needed to optimize the production of H. scabra from aquaculture.

SURVIVAL RATE AND GROWTH OF JUVENILE SANDFISH (Holothuria scabra) IN VARIOUS REARING CONDITIONS

Techniques for producing Holothuria scabra or sandfish sea cucumbers from aquaculture have been developed rapidly in the recent years to address the issues of decreasing sandfish population and increasing market demand. During the process of culturing H. scabra, the early stages of sandfish (i.e. larvae and juveniles) are the most critical of the development. Therefore, the Research and Development Division of the Marine Bio Industry – LIPI conducted a study to assess the growth performance of juvenile H. scabra ultured in four different rearing conditions: (i) indoor concrete tank, (ii) indoor fiberglass tank, (iii) outdoor concrete tank with 1 mm hapa mesh, and (iv) outdoor concrete tank with 3 mm hapa mesh. Each of the rearing condition was set with an initial juvenile density of 15 juveniles per tank with a mean initial weight of 14 g, and fed ad libitum with a mixed feed consisting of Enhalus acoroides sea grass, Pennisetum purpureum napier and cow manure. The experiments were conducted for 20 weeks between April 26 - September 23, 2013. After the experimental period, juveniles reared in the outdoor concrete tank with 1 mm mesh show the best performance with respect to their survival rate (48.89 ± 3.85 %),mean final weight (22.07 ± 1.01 g), final biomass (162.05 ± 18.17 g) and specific growth rate (0.15 ± 0.03% per day). Further studies that combine rearing conditions with different bottom substrates as well as investigating the effect of light are needed to optimize the production of H. scabra from aquaculture.

The Extent of Manure Removal from Storages and Its Impact on Gaseous Emissions.

Manure remaining in storage due to incomplete removal is a source of microbial inoculum that may affect methane (CH), nitrous oxide (NO), and ammonia (NH) emissions during subsequent storage. Manure removal was studied by loading fresh manure into outdoor concrete tanks (10.6 m) that contained previously stored manure (inoculum) at six levels (0, 5, 10, 15, 20, and 25%, with 0% representing an empty tank). Emissions were continuously measured for 6-mo storage periods (warm and cold seasons) using flow-through chambers. Fluxes during the warm season (average manure temperature at 80 cm depth, = 17°C) were 25 times higher for CH, 20 times higher for NO, and 2.9 times higher for NH compared with the cold season ( = 4°C). Cumulative CH emissions increased linearly with the level of added inoculum in the cold season ( = 0.98). A similar linear increase was observed in the warm season from 0 to 20% inoculum ( = 0.91), after which a decrease in emissions was observed at 25%. Reducing inoculum from 15 to 5% reduced CH emissions by 26% in the warm season and 45% in the cold season. There was no clear effect of inoculum on NO and NH emissions, suggesting that complete manure storage emptying does not alter their emissions.

Assessment of cotton-seed (&lt;i&gt;Gossypium&lt;/i&gt; species) meal as ingredient in the diet of &lt;i&gt;Clarias gariepinus&lt;/i&gt; juveniles

The effect of feeding graded levels of cotton GossypiumSpp . seed meal as an inclusion in the diet of Clariasgariepinus juveniles for growth performance was analysed in comparison with the conventional commercial fish feed. Six experimental rations formulated were cotton-seed Gossypium spp . meal replaced fish meal at graded levels of 20%, 30%, 40% 50%, and 100% and were fed to Clarias gariepinus juveniles for 56 days. The experiment was conducted in six outdoor concrete tanks in the Department of Biological Sciences Garden, Ahmadu Bello University, Zaria, Nigeria. Data for each parameter were subjected to Analysis of Variance (ANOVA) and the means for various experimental diets were compared for significant differences at 0.05% level of inclusion. The results showed that fish fed with diet contained 20% cottonseed meal (D 1 ) gave the best Body Weight Gain (81.28g), Specific Growth Rate (2.23), and Condition Factor (1.49), while diet contained 30% cottonseed meal (D 2 ) gave the least Weight Gain (49.67g), Specific Growth Rate (1.58) Conversion Ratio (3.64) and Condition factor (0.79). The results were significantly different (p<0.05) for both growth and feed utilization parameters. Therefore, cotton-seed meal can be used as a replacement for fish meal at 20% level of inclusion. The results established significant reduction in production cost while optimal production is achieved. Keywords : Cotton-seed ( Gossypium species ), Diet, Growth performance, Clarias gariepinus juveniles

Preliminary Report on the use of Androgen for the Production of All-male &lt;i&gt;Oreochromis niloticus&lt;/i&gt;

Fresh hatchlings of Oreochromis niloticus was fed with 17 α methyltestosterone (MT) at 30 µg/g diet for 28 days. Comparative analysis of hormone treated fish with non hormone treated fish indicated improved growth in the former by 44.3% in six months of rearing in outdoor concrete tanks. In both indoor and outdoor rearing conditions, hormone treatment did not have any negative significant effect on survival. Sex ratio in the hormone treated group was 12 males: 1female, and 1.5 males: 1 female in the untreated group. There is a significant difference in the expected 1:1 ratio of sexes in MT treated group which indicated that sex reversal of genetic females to males was successful using 17 α methyltestosterone at 30 µg/g diet for 28 days.