Lake-Based Nursery Rearing of Nile Tilapia (Oreochromis niloticus) Fingerlings in Nylon Hapas: Effects of Stocking Density on Growth, Survival and Profitability

The inadequate supply of tilapia fingerling is a major limitation to cage culture development in Ghana. Lake-based hapa systems are very efficient in nursing fingerlings although the process can be tricky due to inherent effects of stocking densities and environmental factors. This study aimed at assessing the growth, survival and profitability of Nile tilapia (Oreochromis niloticus) fingerlings of the Akosombo strain reared in nine 1 m3 Lake-based hapas at different densities. Each hapa was stocked with 2.12 ± 0.14 g sex-reversed tilapia fingerlings at varying stocking densities of 400 fish/m3, 800 fish/m3 and 1200 fish/m3 serving as treatments T1, T2 and T3 respectively. Each treatment was replicated thrice. Bi-weekly samplings were done and water quality parameters were measured. After the experiment, analysis of variance showed significant differences (p

Replacement of Fish Meal with Graded Levels of Earthworm Meal in the Diet of Fingerlings： Effect on Feed and Growth Parameters

The study was aimed at evaluating growth response of Heteroclarias fingerlings fed diet in which fish meal was substituted with graded levels of earthworm meal. The replacement levels were 0.00%, 25%, 50%, 75% and 100% designated as Eo, E25, Es0, E75 and El00, respectively. Fingerlings used for the work were obtained through artificial insemination of brood stock （purchased from local farmers） with ovaprim in the laboratory. The resulting fry were reared and fed with cultured plankton for 2 weeks followed by 100% fish meal for another two weeks. Thereafter sixteen fingerlings weighing 4.73 g and measuring 6.512 mm standard length （on the average） were starved over night and reared in five indoors tanks （0.8 ~ 0.5 ~ 0.5 m） in duplicate for eight weeks. Fingerlings were fed on graded earthworm meals of 40% protein twice daily at 08：00 and 16：00. The highest mean weight （6.77 g）, specific growth rate （0.86） and protein efficiency ratio （0.6） were obtained at 50% replacement level. Also, Food conversion ratio was the highest at 50% substitution level and lowest at 0.00% substitution, indicating that fingerlings use earthworm containing meal more efficiently. Furthermore, cost benefit analysis revealed that the profit index for 50% inclusion of earthworm meal was the highest （1.71） and the highest net profit of N374.32 （circa $2.3） was achieved at this level. Water quality parameters observed were within tolerable values for the fingerlings well being. Consequently, farmers are advised to use 50% earthworm meal in place of fish meal for formulation of Heteroclarias fingerlings diet. This will drastically reduce production cost, increase farmers profit and enhance the biological value of our menu.

Production Cost of Heterobranchus longifilis (Valenciennes, 1840) Fingerlings in the Ponds Fertilized with Poultry Droppings

This study aims to evaluate the production cost of Heterobranchus longifilis larvae reared in fertilized fish ponds. Experiment was carried out in two fish ponds. Each fish pond was filled with 200 liters of water and fertilized with dry poultry droppings (dose: 0.6 g.L-1) and zooplankton was inoculated with 83±13 individuals/L. Six days after inoculation of zooplankton, larvae of H. longifilis of 2 days after post-hatching were directly introduced into ponds with 300 individuals/m3. These larvae used exclusively zooplankton during the first 7 days. From the 8th day, larvae were fed with Coppens feed until 30 days. At the end, the survival rates were ranged between 58.33% and 56.67%. Final mean weights were brought up to all the ponds and were notsignificantly different (p > 0.05). The production costs ranged between 2.55 FCFA and 2.60 FCFA per fingerling with ratio production cost/weight gain around 0.80 FCFA/g in each pond. Then, this production system of fingerlings in fertilized ponds is very efficient and could be popularized in the rural fish farms.

Determine the Optimal Density of Nile Tilapia (<i>Oreochromis niloticus</i>) Fingerlings Cultured in Floating Cages

The objective of the study was to determine the optimal density of fingerlings of the Nile tilapia (Oreochromis niloticus) culture in floating cages with respect to growth performance and to know the effect of temperature on growth during the winter period. Tilapia fingerlings (mean weight 8.5 ± 0.36 g) were stocked at densities of 120, 180 and 360 fish/m3 for 10 weeks. During culture, fish were fed a diet contains 35% protein made of peanut seed, cottonseed, wheat bran, and Sorghum. The results showed that the increase in fish density reduced the final weight of the fish. The percentage of the fish weight increased and reached 111% ± 1.45% in the lowest fish density (120 fish/m3), 79% ± 1.87% in the medium density (240 fish/m3), and 63% ± 2.03% of high fish density (360 fish/m3), therefore the daily growth rate was better in the lowest density. The rate of food conversion ratio was also better in the lowest density with 2.17 ± 0.33, followed by the medium density with 2.79 ± 0.28 and then the highest density with 3.09 ± 0.21. However, the total production in the cage increased with increasing fish density, and the return to the cost of food was better with higher fish density. According to various performance evaluation criteria, it can be concluded that the medium density 240 fish/m3 is the best for growing Nile tilapia fingerlings in floating cages. It was observed that the growth rates of the three treatments were low due to the decrease in water temperature in most of the study period, which may indicate the useless of culture in cages in the winter season.

Effects of Pawpaw Seed Powder as an Additive on Growth of Catfish Fingerlings Reared in an Indoor Tanks

Since the demand of African Catfish （Clarias gariepinus） is on increase there is need to increase its production so as to meet the protein requirement of the populace. An investigation was conducted for six weeks feeding trial to determine the performance of African catfish （Clarias gariepinus） fingerlings feed diets containing varying replacement level of fish meal with pawpaw seed powder meal （Carica papaya）. Fingerlings of Clarias gariepinus were subjected to five different dietary treatments with varying levels of pawpaw seed powder meal. The diets I-V contained 0, 20%, 40%, 60% and 80% replacement levels, respectively. The experiment was carded out in an 80 litres circular plastic bowls, the treatments were in triplicate. Each bowl contained 12 fingerlings. Feeding was done at 3% body weight per day and fishes were weighed every week. Growth parameters such as specific growth rate （SGR）, weight gained （WG）, food conversion ratio （FCR）, protein efficiency ratio （PER） and mortality were determined. Therefore, it could be concluded that fish meal could be replaced up to 80% with pawpaw seed powder meal in the diet of Clarias gariepinus fingerlings to encourage growth, while at 40% pawpaw seed powder meal inclusion mortality was reduced.

Factors Associated with Increased Walleye Production in Lined Compared to Earthen-Substrate Ponds

Walleye (Sander vitreus) fingerling production can be enhanced when the pond substrate is altered from earthen soils to an exposed liner;however, few differences in water chemistry, prey densities, and food habits have been identified that could potentially explain this production difference. Lack of an explanation led to further comparison of walleye fingerling culture between substrate types during 2016. Two ponds of each type were stocked with 1- to 3-day-old walleye fry, but lined ponds received an additional 104,166 fry/ha and were stocked 1 or 2 days later than earthen ponds (May 10). Walleyes in lined ponds achieved a growth advantage on May 31 (+2.5 mm) and on June 6 (+3.3 mm), but lengths were not significantly different at harvest (June 15). Lined ponds increased walleye yield and number 1.8-fold while not reducing individual fish size at harvest compared to earthen ponds. Walleye food habits were generally similar between pond types with a greater number of zooplankton being consumed through June 6 followed by an increase in larval chironomid consumption at harvest (June 15). After May 30, lined ponds exhibited lower dissolved oxygen and higher ammonia-nitrogen concentrations even though earthen ponds received additional (157 kg/ha) alfalfa (Medicago sativa) meal fertilizer. Also, at this time pH declined abruptly and remained below 8.2 in lined ponds. Moreover, the enhanced production in lined ponds coincided with walleyes that exhibited an increased pelagic (δ13C) signature during the culture period (2‰ to 3.3‰ more negative). Efforts to improve production in earthen-substrate ponds should focus on increasing the pelagic signature of the food web through fertilization strategies which increase ammonia-nitrogen (≈0.3 mg/L) and decrease dissolved oxygen (≈6.5 mg/L) while maintaining a pH between 8.0 and 8.2 during the second half of the rearing interval.

Rearing Test of Ictalurus punctatus in Cold Plateau Zone

Three ponds with the areas of 800, 1 000 and 1 000 m2 were settled in Yambajan aquaculture base for rearing test of Ictalurus punctatus in plateau zone. The results showed that as 30 000 fries were released, 19 830 fingerlings of 1. punctatus were obtained after 270 d rearing, with the average body length of 21.2 cm, the average body weight of 216.5 g, the survival rate of 66.1%, and the fingerling harvest of 4 293.2 kg. Thus, it is effective and feasible to rear I. punctatus with residual heat resources of power plants in cold plateau zone.

Long-Term Passive Integrated Transponders (PIT) Tag Retention in Juvenile Rainbow Trout and Brown Trout

Two hundred and forty-three juvenile rainbow trout Oncorhynchus mykiss ranging from 73 to 119 mm were implanted with 8, 9, or 10 mm Passive Integrated Transponder (PIT) tags, with tag retention and fish survival observed for 343 days. Similarly, 173 brown trout Salmo trutta ranging from 71 to 86 mm were implanted with 8 or 10 mm PIT tags and observed for 293 days. Over the entire duration of the study, rainbow trout ejected only six tags, while no tags were ejected from the brown trout. All of the rainbow trout tag ejections occurred before 50 days post-tagging. There was no significant difference in the length or weight of fish that ejected tags compared to those that retained tags. No fish died during the trials. These results indicate that rainbow trout and brown trout at the sizes used in this study can be safely implanted with, and subsequently retain, up to 10 mm PIT tags for durations of nearly one year.

Sustainable ifngerling production technique of endangeredLabeo calbasu (Hamilton, 1822) based on different protein levels in ponds

Objective:To conduct on sustainable fingerling production technique of endangered Labeo calbasu (Hamilton, 1822) (L. calbasu) based on different protein levels in ponds. Methods: The experiment was carried out under rearing pond in fish hatchery complex with three treatments group each having three replicates under department of fisheries, University of Rajshahi.L. calbasu were stocked at 41990/ha in T1, T2 and T3, respectively. The initial length ofL. calbasu in three treatments were (4.60 ± 0.10) cm and initial weights were (3.48 ± 0.01) g. Fishes were fed with 28%, 30%, 32% protein supplement for T1, T2, T3, respectively. The fishes were initially fed at 10% of body weight on 1st and 2nd fortnight. Then it was decreased at 8% of body weight on 3rd and 4th fortnight. Finally in 5th fortnight they were fed 5% of body weight. The physico-chemical characteristics of pond water were measured fortnightly. Results: The mean final weight gain was found highest in T3 (40.87 ± 0.01) g which was significant compared to T1 and T2. SGR (% bwd–1) was found 2.83 ± 0.02 (T1), 3.04 ± 0.01 (T2) and 3.39 ± 0.01 (T3). The highest survival rate ofL. calbasu was found in T3 (90.00 ± 1.00) and the lowest was found in T1 (87.00 ± 1.00). The best FCR (1.54 ± 0.01) was observed in T3 fed with 32% protein supplement. The highest production was observed in T3 (1672.20 ± 16.96 kg/ha/75 days) and lowest was observed in T1(1055.50 ± 29.04 kg/ha/75 days). The highest net benefit was calculated in T3 (260663.00 ± 4326.88 tk.) and lowest was found in T1 (112831.00 ± 7383.66 tk.). The CBR was found 0.60 ± 0.04, 0.80 ± 0.02 and 1.16 ± 0.02 in T1, T2 and T3, respectively. There were significant differences in CBR values among the three treatments. Conclutions:In this study, growth parametersi.e., weight gain, SGR (% bwd–1), length gain, total yield were significantly (P < 0.05) improved in T3 treatment fed with 32% protein supplemented diets.

Low-cost mobile hatchery produced silver barb(Barbodes gonionotus)fingerling:it's growth and economic performance in intensive culture system

Objective:To explore the growth performance of low-cost mobile hatchery produced silver barb(Barbodes gonionotus)fingerling comparing with typical one,field laboratory complex hatchery.Methods:Assigning Treatment I and Treatment II stoked with low-cost mobile hatchery and field laboratory complex hatchery originated fingerling of silver barb in plastic circular tank.Results:The average weight gain(g/day)of fish was 0.18 and 0.16 g,length gain(cm/d)0.03 and 0.02,gross yield 0.09 and 0.08 kg/tank per month,net yield 0.03 and 0.01 kg/tank per month respectively in Treatment I and Treatment II.The growth of low-cost mobile hatchery produced silver barb was higher(P<0.05)although SGR(%/d)was 1.63 and 1.89 and FCR was 2.57 and 2.55 for Treatment I and Treatment II,correspondingly and survival was 100%in both cases.In case of economic efficiency,total operating cost were BDT 68.91 and 67.41,revenue BDT 107.35 and 89.30,net profit BDT 38.44 and 21.89 and BCR 1.55 and 1.32 respectively in low-cost mobile hatchery and field laboratory complex hatchery produced fishes.Conclusions:The fry from both origins showed more or less similar growth performance and none of them was superior.Considering the economic feasibility in both cases,it is assumed that the intensive culture of silver barb is possible at field level.