Hybrid Fingerlings Research Articles

The effect of feeding black soldier fly larvae on growth performance, protein, and fat content of red hybrid tilapia (Oreochromis spp.).

In the aquaculture industry, the crucial goal is to minimize production costs, especially feeding costs, without significant side effects. Black soldier fly larva (BSFL) is a locally available, eco-friendly, and sustainable source that is high in crude protein (42% dry matter [DM]) and fat (35% DM). This study aimed to determine the growth performance along with the composition of crude fat and protein in red hybrid fingerlings after the addition of BSFL into the diet. A total of 120 fingerlings of uniform size (mean initial weight of 1.46 ± 0.06 g) were randomly assigned to one of four groups (n = 10) (A, B, C, and D) per tank (1 m × 2 m × 1 m). For 21 days, Group A (control group) was fed with 100% commercial diet; Group B was fed with 90% commercial fish diet + 10% BSFL; Group C was fed with 80% commercial fish diet + 20% BSFL; and Group D was fed with 70% commercial fish diet + 30% BSFL. Feed efficiency, growth performance, and proximate composition analysis were performed on the fish. The results displayed that the group with the highest BSFL percentage had a greater effect on protein and fat composition than the control group. The proximate composition analysis of fish-fed diet revealed that an increase in the level of BSFL inclusion increases the protein content in the fish. In comparison to the other groups, the experimental diet with 30% BSFL inclusion has the highest levels of crude protein (80.30% DM) and fat (2.90% DM). It is concluded that incorporating BSFL into a commercial diet for red hybrid tilapia fingerlings increased crude protein and fat composition, providing an alternative protein and fat source in fish diets.

Пластические и меристические признаки гибрида «ленбел» (F1 Acipenser baerii × Huso huso) в условиях культивирования

The hybrid of sturgeon "lenbel" (F1 ♀ Acipenser baerii × ♂ Huso huso) was studied by conventional methods for a complex of plastic and meristic signs.
 It was found that only the horizontal diameter of the eye (O), the greatest height of the head (HC), the distance from the end of the rostrum to the base of the middle antennae (rc) and to the cartilaginous arch of the mouth (rr), the width of the snout at the cartilaginous arch of the mouth (SRr), the width of the mouth (SO) and the width of the break of the lower lip (il) for hybrid and beluga, and the width of the lower lip break (il) and the width of the snout at the base of the middle antennae (SRc) for hybrid and Siberian sturgeon have a transgression index of less than 67%, and can be used to identify the hybrid form. The beluga fingerlings were largely consolidated, and therefore united into a single cluster. Siberian sturgeon and hybrid also form two clearly differentiated clusters, but the intra-group divergence of the hybrid is slightly higher than that of the original forms. In hybrid fingerlings, relative plastic and meristic signs are not related to body size and remain constant during the growing period, that is, they may be specific to it. It is shown that some head measurements can be used for confident identification of the hybrid.

Genetic variability of Edwardsiella piscicida isolates from Mississippi catfish aquaculture with an assessment of virulence in channel and channel × blue hybrid catfish.

The bacterium Edwardsiella piscicida causes significant losses in global aquaculture, particularly channel (Ictalurus punctatus)×blue (I.furcatus) hybrid catfish cultured in the south-eastern United States. Emergence of E.piscicida in hybrid catfish is worrisome given current industry trends towards increased hybrid production. The project objectives were to assess intraspecific genetic variability of E.piscicida isolates recovered from diseased channel and hybrid catfish in Mississippi; and determine virulence associations among genetic variants. Repetitive extragenic palindromic sequence-based PCR (rep-PCR) using ERIC I and II primers was used to screen 158 E.piscicida diagnostic case isolates. A subsample of 39 E.piscicida isolates, representing predominant rep-PCR profiles, was further characterized using BOX and (GTG)5 rep-PCR primers, virulence gene assessment and multilocus sequence analysis (MLSA) targeting housekeeping genes gyrb, pgi and phoU. The MLSA provided greater resolution than rep-PCR, revealing 5 discrete phylogroups that correlated similarly with virulence gene profiles. Virulence assessments using E.piscicida representatives from each MLSA group resulted in 14-day cumulative mortality ranging from 22% to 54% and 63 to 72% in channel and hybrid fingerlings, respectively. Across all phylogroups, mortality was higher in hybrid catfish (p<.05), supporting previous work indicating E.piscicida is an emerging threat to hybrid catfish aquaculture in the south-eastern United States.

Performance of defatted black soldier fly pre-pupae meal as fishmeal replacement in the diet of lemon fin barb hybrid fingerlings

This study was conducted to determine the optimal level of defatted black soldier fly pre-pupae (BSFP), Hermetia illucens as a fishmeal replacement in lemon fin barb hybrid diet. Triplicate groups of fish (1.52 ± 0.01 g) were fed twice a day until apparent satiation with five iso-nitrogenous (30 %) and isocaloric (17 kJ g−1) diets containing varying BSFP levels ranging from 0 to 100 % for 8 weeks. No mortality was found during this study. BSFP level used in the diets were significantly affected the growth response of the barb hybrid. The growth performance of fish such as body weight gain and specific growth rate improved up to 75 % BSFP and decreased above this level, while feed conversion ratio and daily feed intake were not affected by BSFP levels. Body protein and lipid contents of the barb hybrid were significantly affected by dietary replacement levels. The protein retention decreased and lipid retention increased when the BSFP level increased, while the carbohydrate retention was extremely low. The most abundant of essential amino acids in the whole body of lemon fin barb hybrid was valine while glutamic acid was the abundant non-essential amino acids. No pathological changes were observed among all dietary fed groups. The present study suggested that fishmeal could be replaced up to 75 % or 2.5 % fishmeal was still required in the lemon fin barb hybrid diet.

Hybrid grouper in Vietnamese aquaculture: Production approaches and profitability of a promising new crop

Grouper aquaculture is a rapidly growing and dynamic industry within Vietnamese aquaculture and an important source of local employment and income generation. Information on the state of current production practices and profitability for specific crops across different geographic locations and stages of production is difficult to obtain. This research contributes to wider efforts to address this knowledge gap by providing indicative findings on current market characteristics, production practice, and profitability of a ‘new’ aquaculture crop in Vietnam: Hybrid grouper (E. lanceolatus X E. fuscoguttatus). Participants in the study identified Hybrid grouper as the most important crop for grow out farms and the second most important crop for nursery farms due to strong market demand and sales prices, fast growth rate, and higher survival compared to other grouper crops. Research utilised a survey of 12 grouper farms in the Northern (Hai Phong) and Central (Khanh Hoa) provinces of Vietnam in mid-2018 to determine indicative financial production characteristics and gross margins (annual net sales revenue minus cost of goods sold) of nursery, cage, and pond enterprises that currently culture Hybrid grouper. Farmers indicated that the Hybrid grouper industry was segmented into three distinct phases of production: spawning, larval rearing and grow out. Few grouper farmers specialise in more than one area. Farmers in both study regions reported that Hybrid grouper were desirable due to the strong market demand and high sale prices, fast growth rate, and higher survival compared to other grouper crops. Farms had different economic characteristics between region and type, major differences were seen in the species cultured, number of people employed and age of farms. All farms interviewed generated annual net sales revenue exceeded the cost of goods sold. Earthen pond farms in Central Vietnam generated a median gross margin of US$ 8741 per year, Central region nurseries US$ 8059, and Northern Sea cage farms US$ 4562. Relative importance, calculated by contribution to total farm income, indicated that Hybrid grouper is the most important crop for grow out farms in both regions and second most important for nursery farms. Central region grow out farms generate higher gross margins than Northern Sea cage farms, which is a result of Central region grouper growing faster, having higher survival rates, and selling for more per kg than those grown out in the Northern region. The main changes to the industry since 2010 have been the introduction of Hybrid grouper as a new crop, the increase in average grouper sale price, and the move to full life-cycle aquaculture. Average sale price for grouper has increased from US$ 7.7–9.6/kg (adjusted to 2019 US$) to US$ 9–15/kg. The findings indicate that the most significant constraints to the growth and diversification of the grouper aquaculture industry in Vietnam are the limited availability of Hybrid fingerlings due to difficulties in larval rearing, and increases in feed costs due to a lack of domestic feed suppliers. Notwithstanding these constraints, the higher gross margins of Hybrid grouper relative to other financially viable grouper crops suggests continued, albeit moderated, growth of grouper aquaculture in Vietnam.

Biological filtration properties of selected herbs in an aquaponic system

This study was conducted to determine the biological filtration capabilities of some culinary herbs co‐cultured with lemon fin barb hybrid in a nutrient film technique (NFT) recirculating aquaponic system. Lemon fin barb hybrid (Hypsibarbus wetmorei ♂ × Barbonymus gonionotus ♀) fingerlings were stocked in twelve 2‐tonne fibreglass tanks at 25 fish per tank and co‐cultured with Chinese celery (Apium graveolens var. secalinum Alef.), coriander (Coriandrum sativum) and peppermint (Mentha × piperita) for seven weeks. The impacts of the waste generated by the fish on the water quality, the filtration capability of the herbs and the ability of fish and herbs to retain nutrients (NPK) were also estimated. All the herbs showed water purifying potentials to varying degrees as significantly lower levels of nitrogenous compounds (NH₃‐N, NO₃‐N, NO₂‐N) were observed after the herbal filtration. The plant growth seemed to be affected by their ability to absorb nutrients and consequently purify the culture medium. Interestingly, the lemon fin barb hybrid also showed significant differences in terms of weight gain, but the nutrient retention among fish treatments was not statistically different. The plants absorbed less phosphorus and potassium than the fish. After computing for the total system percentage of NPK recovered, nitrogen was the most retained nutrient. The peppermint showed superiority in terms of gross biomass and water purifying potential compared to the Chinese celery and coriander.

Growth Performance of Heteroclarias Hybrid Fingerlings Fed Watermelon Seed Meal as a Replacement for Soybean Meal

Growth Performance of Heteroclarias Hybrid Fingerlings Fed Watermelon Seed Meal as a Replacement for Soybean Meal

Induced spawning, survival and growth of an African catfish hybrid (female &lt;i&gt;Clarias gariepinus&lt;i&gt; and male &lt;i&gt;Clarias anguillaris&lt;/i&gt;) fingerlings relative to their parental species in the mount Cameroon region

Clarias is a good candidate for aquaculture in Cameroon because of its high economic value but getting hardy and fast growing Clarias seed have been a major problem to fish farmers, especially in the Mount Cameroon Region. The objectives of this work are: to present the results of the experiments where a new Clarias hybrid fry/fingerlings will be reared simultaneously with the fry/fingerlings produced from pure parental species crosses in order to provide a critical assessment of the growth performance and survival rate of the hybrid fingerlings relative to those of the both parental species. Interspecies hybrids were produced by artificial insemination of the African catfish, pure C. gariepinus females X pure C. anguillaris males. The results revealed that the growth performance of the hybrid fingerlings relative to both parental species was most rapid in the second month and a high survival rate of 85.5 % was recorded. The absolute density estimated (at 95 % confidence limits) showed that the hybrid fingerlings of two mature female pure C. gariepinus (1kg/fish) and one mature male C. anguillaris (1 kg/fish) was 10,471 ± 126 fingerlings. This result is the first recorded success in the survival and growth of African catfish hybrid fingerlings relative to their parental species in the Mount Cameroon Region.Key words: Performance, aquaculture, hardy, interspecies hybrids, environmental

Channel catfish Ictalurus punctatus strain comparison for induced ovulation in the early spawning season to produce channel catfish ♀ × blue catfish I. furcatus ♂ hybrid catfish embryos

The channel catfish (Ictalurus punctatus) ♀×blue catfish (Ictalurus furcatus) ♂ hybrid catfish has superior performance in respect to survival, growth rate, feed conversion, low dissolved oxygen, and fillet yields compared to its parent species. Currently the demand for hybrid fingerlings is greater than available supply. Selective breeding for early spawning could extend the spawning season to partially address this problem. Under commercial conditions and using natural open pond spawning, the Thompson line of channel catfish spawns earlier at its location than other strains at their home farms. Over a 4-year period the Thompson line was compared to the Kansas strain and AR line for fry production in the early spawning season using induced spawning with luteinizing hormone-releasing hormone analogue implants to induce ovulation, followed by hand stripping, and in vitro fertilization techniques. Relative reproductive performance was variable among years, but in general, fry output of the three strains was similar and relatively high, with the 3-year average of both Thompson and Kansas strains being approximately 2500fry/kg. The observed fry output of Thompson was about 15% higher than that for Kansas, which was not significantly different because of the high variation among years. The early spawning of the Thompson line appears to be due to an environmental effect, related to genotype-environment interactions or natural spawning and response to induced spawning are actually two different traits. Strains of more northerly origin might be evaluated to achieve the goal of better response to early induced spawning.

Effect of Paternal Blue Catfish Strain Effects on Hatchery Fry Production and Performance of Channel Catfish × Blue Catfish F1 Hybrid Fry Production and Fingerling Performance Under Commercial Conditions

AbstractThis study examined the influence of strain of sire on hybrid catfish embryo production and performance of fingerlings under commercial conditions. Four hundred 4‐year‐old female Gold Kist strain Channel Catfish Ictalurus punctatus were induced to spawn in eight spawning trials. The stripped eggs were fertilized with the sperm of either D&amp;B or Rio Grande Blue Catfish I. furcatus to produce D&amp;B or Rio Grande hybrid catfish embryos. Testes weight (g/kg body weight [BW]) was higher in Rio Grande (1.98 ± 0.28 g/kg BW) than in D&amp;B (1.02 ± 0.12 g/kg BW) Blue Catfish males. Hatching parameters between Rio Grande and D&amp;B hybrids did not differ. Approximately 100,000 hybrid catfish fry produced from each spawning trial were stocked in an individual 0.4‐ha pond to raise fingerlings. Four ponds of D&amp;B and four ponds of Rio Grande hybrids were stocked in eight ponds of identical conditions at the same time. The mean individual BW of D&amp;B hybrid fingerlings (38.5 g) was higher than that of Rio Grande hybrid fingerlings (32.5 g) at 9 months of age. Mean survival (99.3%), production (8,875 kg/ha), and feed conversion (1.14) of D&amp;B hybrid catfish fingerlings were superior to Rio Grande hybrid catfish fingerling survival (92.1%), production (7,664 kg/ha), and feed conversion (1.23), the catfish being raised in replicated earthen ponds under farm conditions. While the D&amp;B strain of sire improved the performance of hybrid catfish fingerlings, it had minimal influence on hybrid catfish fry production.

No Evidence for Intercohort Cannibalism in Mixed‐Size Cultures of Food‐Size and Fingerling Channel Catfish × Blue Catfish Hybrids Grown in Ponds

AbstractFemale Channel Catfish Ictalurus punctatus × male Blue Catfish I. furcatus hybrids are normally harvested by seining single‐batch pond or split‐pond production systems in fall or winter. Ponds are typically restocked with fingerlings without draining. There is concern that without completely draining the pond after harvest, food‐size hybrids that escape seining may cannibalize restocked fingerlings. The purpose of this study was to determine if such hybrid fingerlings stocked after the fall harvest would be cannibalized by the larger carryover fish during winter or the following growing season. Three 0.04‐ha ponds were each stocked on November 25, 2013, with 100 food‐size hybrid catfish averaging 1.07 kg. Those three ponds and an additional three ponds were then stocked on November 27, 2013, with 300 hybrid catfish fingerlings averaging 14.8 g. The fish were not fed over winter. Mean survival of the fingerlings after 4 months at 91.9% and 92.9% was not significantly different between treatments. Survival of the food‐size fish was 99.7%. Four ponds stocked with fingerling and food‐size hybrids and an additional four ponds stocked with just fingerlings in April 2014 were harvested in October. Survival of the fingerlings was not significantly different between ponds with (88.8%) and without (90.3%) food‐size fish. We found no significant intercohort cannibalism by food‐size hybrid catfish on understocked fingerlings either overwinter or during the following growing season.

Effects of Stocking Density on Production Traits of Channel Catfish×Blue Catfish Hybrids

AbstractChannel Catfish Ictalurus punctatus × Blue Catfish I. furcatus hybrid fingerlings (mean weight, 47 g) were stocked in 0.4‐ha ponds at densities of 7,425, 12,375, 17,325, 22,275, and 27,225 fish/ha in three replicate earthen ponds for each density. Fish were fed a 28% protein diet to apparent satiation once daily. Ponds were equipped with electric paddlewheel aerators (12.5 hp/ha) that were turned on when dissolved oxygen (DO) levels reached &lt;5.0 mg/L; additional aeration was provided by power‐takeoff tractor‐driven paddlewheels at DO &lt; 2.5 mg/L. Feeding was terminated at the end of October and fish were harvested and weighed. Stocking density had no significant effect on feed conversion (overall average, 1.97), survival (≥93% in all treatments), or processing yield (carcass yield = 66.2%, shank fillet yield = 34.8%, nugget yield = 10.5%). Harvest weight was not significantly different between 7,425 and 22,275 fish/ha (average, 0.85 kg) but was less at 27,225 fish/ha (0.72 kg). Net production increased significantly with increased density from 7,425 to 22,275 fish/ha but was not different between 22,275 and 27,225 fish/ha. Percentage of submarketable fish (&lt;0.45 kg) was not significantly different from pond densities of 7,425 through 22,275 fish/ha (average, 2.3%), but was higher at 27,225 fish/ha (8.8%). Aeration hours increased and minimum DO levels decreased significantly as stocking density increased. The smaller average weight at 27,225 fish/ha may have been due to fish behavior associated with crowding, lack of equal access to feed, or degraded water quality. However, past research has demonstrated a “threshold” relationship between minimum DO levels and catfish feeding and growth. Data from this study indicate a similar DO threshold–growth relationship, suggesting the observed effect of density on growth may have been at least partially due to minimum DO levels being below that needed for optimal growth at 27,225 fish/ha.

Growth and Feed utilization of Catfish Hybrid (Heterobranchus longifilis x Clarias gariepinus ) Fingerlings fed practical diets

The effects of four practical diets (3 commercial and one locally prepared) on growth, feed utilization and survival of catfish hybrid ( Heterobranchus longifilis x Clarias gariepinus ) fingerlings were compared in plastic aquaria in triplicates for 56days. Diets differed in crude protein (CP) and digestible energy as follows: Commercial Diet 1 (39.73% CP, 3911.8Kcal/kg), Diet 2 (34.50% CP, 3926.8Kcal/kg), Diet 3 (45.37%, 3883.6Kcal/kg) and local Diet 4 (40.34% CP, 3861.8Kcal/kg). Observations made indicated higher performance in weight and percent weight gain (2.299g, 411%), specific growth rate (0.78% day -1 ), condition factor (0.96), feed conversion ratio (2.67) and protein efficiency ratio (10.73) for fingerlings fed Diet 3 than other diets. Commercial Diet 2 appeared to perform least among the test diets. Fish survival was high and varied between 76.7% (Diet 4) and 96.7% (Diet 1). These results demonstrated that catfish hybrid fingerlings can be successfully reared in aquaria with good feed conversion, growth and high survival on commercially or locally prepared diets with 45.37% CP and adequate energy.

Evaluating different additive levels of yeast, Saccharomyces cerevisiae, on the growth and production performances of a hybrid of two populations of Egyptian African catfish, Clarias gariepinus

A breeding and feeding experiment was undertaken to study the performances of the hybrid of two Egyptian populations of African catfish Clarias gariepinus, El-Manzalah catfish (MCF) characterized by the tolerance against poor water quality and the ease to be farmed in captivity and El-Qanater catfish (QCF) characterized by rapid growth and high quality flesh. Crosses of these two populations (MCF♀ × QCF♂) were carried out in El-Gamalia hatchery, El-Manzalah, Egypt, during spring. When the mean body weight of African catfish hybrid fingerlings has reached 24.34 ± 1.38 g (mean ± SD) they were transferred to cages (112 m 3) with a stocking density of 50 fish/m 3 suspended in lake El-Manzalah. Fish were fed a formulated diet containing approximately 31% (analyzed value) crude protein and cultured for 214 days. Four levels of dried brewer's yeast, Saccharomyces cerevisiae, (DY) were used as feed additives at levels of 0.0, 1.0, 1.5 and 2.0% in diets. Results showed that, adding high level of DY, 2%, recorded highest final body weight (913.26 g), growth rate (4.72 g/fish/day), total production (47.5 kg/m 3) and profit per cage (52.21%) after 186 days. The study demonstrates that DY inclusion in the feeds of hybrid cat fish was significant. However, finding the optimal inclusion level of DY still needs more investigation of higher DY levels than 2%. The overall data of the present study has confirmed that catfish hybrid showed better parameters than the parents in respect of growth rate, survival percentage and feed efficiency. Moreover, hybrid catfish had a significantly highest production, 47.5 kg/m 3.

Relative Production Performance and Cost of Food Fish Production from Fingerlings of Channel-Blue F1 Hybrids, Ictalurus punctatus-Ictalurus furcatus, and NWAC-103 Channel Catfish, I. punctatus

Production studies comparing hybrid catfish (channel-blue), Ictalurus punctatus–Ictalurus furcatus, with NWAC-103 channel catfish strains have produced conflicting results depending on the size of fingerling stocked and maternal genetic inheritance. Generally, the strain with larger fingerlings at stocking tended to grow better than strains with smaller fingerlings at stocking. A production trial was conducted at the University of Arkansas Pine Bluff research station to compare production characteristics and costs of hybrid catfish and NWAC-103 strains with similar stocking sizes of fingerlings and similar maternal inheritance. Ten 0.10-ha earthen ponds were stocked with 15,000 precision-graded fingerlings/ha (15–20 cm total length) of either channel-blue hybrid catfish or NWAC-103 channel catfish with five replicates of each treatment on April 14, 2006. There were no significant differences in growth, yield, survival, dress-out yield, seinability, and mean daily feed fed. The mean feed conversion ratio was significantly lower for the channel-blue hybrid catfish, but NWAC-103 channel catfish were more uniform in size at harvest. A partial budget analysis showed that, while the hybrids converted feed more efficiently, the benefit of the reduced cost of feed was less than the additional cost of the hybrid fingerlings. Thus, under the conditions of this study, it was more profitable to raise NWAC-103 channel catfish.

The Effects of Proliferative Gill Disease on the Blood Physiology of Channel Catfish, Blue Catfish, and Channel Catfish × Blue Catfish Hybrid Fingerlings

AbstractThis study was conducted to gain a better understanding of the effect of exposure to the myxozoan Henneguya ictaluri (the agent of proliferative gill disease [PGD]) on host physiology by measuring the variation in selected blood characteristics in three differently affected host taxa (channel catfish Ictalurus punctatus, blue catfish I. furcatus, and blue catfish × channel catfish hybrid fingerlings). Forty‐five fish of each host taxon were exposed to PGD, and 10 fish of each host taxon were sampled at 24, 96, and 168 h. Fish were weighed, blood was collected and analyzed for a suite of physiological variables, and wet mount preparations of gill clips were examined grossly for the presence of cartilage breaks. The results of this study are consistent with the current knowledge regarding H. ictaluri infections in blue catfish, channel catfish, and blue catfish × channel catfish hybrids. Chondrocytic lysis was observed in channel catfish and hybrid catfish at 96 and 168 h but was not observed in blue catfish. There was an observed reduction in oxygen partial pressure (pO2) and an increase in carbon dioxide partial pressure (pCO2) at 96 h in the blood of channel catfish and hybrid catfish, but these changes were not exhibited by blue catfish. For all species, pH decreased as lactate concentrations increased. The lack of physiological changes and the absence of H. ictaluri sporozoites and DNA in gill tissue lead us to speculate that H. ictaluri is unable to establish infection in blue catfish. Current research investigating the mechanisms of infection and portals of parasite entry into blue catfish, channel catfish, and blue catfish × channel catfish hybrids is underway to better elucidate the defenses employed by blue catfish against H. ictaluri.

Bio-flocs technology application in over-wintering of tilapia

A 50-day experiment was conducted to investigate the effectiveness of the bio-flocs technology for maintaining good water quality in over-wintering ponds for tilapia hybrid fingerlings ( Oreochromis niloticus × Oreochromis aureus). To preserve adequate water temperatures in the ponds, they were covered with polyethylene sheets and the water exchange rate was minimized to increase pond water temperature. To avoid water quality deterioration, starch was added to the ponds to stimulate the formation of bio-flocs. Temperature in the covered ponds could easily be controlled and was 0.4–4.9 °C higher than the influent water. Adjusting the C/N ratio in the ponds by adding starch or increasing the amount of carbohydrates added through the feed limited the presence of inorganic nitrogen species when the C/N was about 20, even at high stocking densities of 20 kg/m 3 at harvest. Fish survival levels were excellent, being 97 ± 6% for 100 g fish and 80 ± 4% for 50 g fish. Moreover, at harvest the condition of the fish was good in all ponds with a fish condition factor of 2.1–2.3. Overall, these findings can help to overcome over-wintering problems, particularly mass mortality of fish due to low temperatures in the ponds.

Intergeneric Hybridization between Kutum, Rutilus frisii kutum, and Bream, Abramis brama orientalis, of the Caspian Sea

Abstract Artificial hybridization was performed between Rutilus frisii kutum and Abramis brama orientalis of the Caspian Sea. Synchronization of spawning of female broodstock of both species was induced by injection of carp pituitary extract. Reciprocal crossings between R. frisii kutum ♀×A. brama orientalis ♂ (RA) and A. brama orientalis ♀×R. frisii kutum ♂ (AR) produced viable hybrid larvae without any clear particular pre‐ or postzygotic isolation phenomena. RA and AR hybrid larvae were reared to fingerling stage with survival rates of 22.5 and 28% and average weight of 6.8 ± 0.17 g and 9.0 ± 0.79 g, respectively. A heterosis of 45% was calculated for weight at fingerling stage. RA and AR hybrid fingerlings were cultured in polyculture along with Chinese carps for 6–7 mo and reached an average weight of 190–195 g and 235–255 g, respectively. Karyotyping of these hybrids revealed a modal diploid number of 2n = 50 for both groups, which is similar to those of the parental species. Discriminant function analysis on 28 morphometric and meristic characteristics of two parental species as well as their hybrids could separate these groups at highly significant level (P &lt; 0.001). These results indicated an overall intermediate inheritance of the studied characters.

The effects of poultry dropping and cow dung on growth and feed utilization of &lt;i&gt; Heterobranchus longifilis x Clarias gariepiuns &lt;/i&gt; hybrid reared in concrete ponds

The effect of poultry and cow manures on growth and feed utilization of Heterobranchus longifilis (male) x Clarias gariepinus (female) hybrid fingerlings were monitored for fourteen weeks. The study was conducted at the fish farm of Michael Okpara University of Agriculture, Umudike. The one hundred and twenty fingerlings were subjected to three treatments. Two replicated ponds were fertilized with poultry droppings and cow dug while the third had no fertilizer (control). While there was no significant difference (p>0.05) in the Mean Total length (MTL) for the three treatments, the Mean Body weight (MBW), Specific Growth Rate, (SGR) Feed Conversion Efficiency (FCE) and Feed Conversion Ratio (FCR) showed significant differences (p Keywords : Effect, manures, growth, feed utilization, Heteroclarias, hybrid, fingerlings > Animal Production Research Advances Vol. 2 (4) 2006: pp. 253-257

Results of First Experiments on Application of Electrical Stimulation of Blue Catfish Testes for Production of Channel Catfish × Blue Catfish Hybrids

AbstractCommercial interest in production of F1 hybrids of female channel catfish Ictalurus punctatus × male blue catfish I. furcatus has increased dramatically. However, current production methods are unable to provide large numbers of hybrid fingerlings for commercial producers. Increasing the hatch rates of hybrid embryos will aid in making large‐scale hybrid production a feasible option for the catfish industry. The objectives of this study were to determine (1) whether electrical stimulation of excised testes of Rio Grande and D&amp;B strain blue catfish (Kincaid et al. 2000) produce changes in the motility rank, motility time, and concentration of spermatozoa and (2) whether differences exist between the fertilization rates for spermatozoa obtained from electrically stimulated testes and those from nonstimulated testes for the two strains. Testes were excised from the males of both strains and one testis was subjected to electrical stimulation. Spermatozoa were removed, counted, checked for motility ranking, and used to fertilize eggs. Electrical stimulation did not significantly affect motility rank, motility time, or spermatozoa concentration for either strain. The fertilization of channel catfish eggs was significantly higher for spermatozoa from electrically stimulated Rio Grande strain testes (93.0 ± 3.5%) than for those from nonstimulated testes (76.2 ± 16.8%). The fertilization rate was not significantly higher for spermatozoa from electrically stimulated testes in D&amp;B strain blue catfish. Hatch rate was not significantly different for eggs fertilized with spermatozoa from electrically stimulated testes in either strain. Modulation of voltage, amperage, and cycle times with larger sample sizes should be investigated further to determine whether a range of effects exists among the parameters measured and the intensity of stimulation.