Spawning performance and seed production from hybridization between Oreochromis spilurus and the GIFT strain of the Nile tilapia Oreochromis niloticus

This study compared the spawning performance of four crosses between the salt‐tolerant tilapia Oreochromis spilurus and the fast‐growing genetically improved farmed tilapia (GIFT) strain of the Nile tilapia Oreochromis niloticus: (1) O. spilurus♀×O. spilurus♂ (SS); (2) Nile ♀× Nile ♂ (NN); (3) Nile ♀×O. spilurus♂ (NS) and (4) O. spilurus♀× Nile ♂ (SN). In each cross, males and females having mean weights of 157 and 115 g, respectively were stocked in 0.43 m³ tanks at a male to female ratio of 1:3. Seeds (unhatched eggs, yolk‐sac fry and free swimming fry) were harvested biweekly for 127 days. Viable spawns resulted from all crosses. The NN cross produced the highest total seeds tank^?1 (2890), seeds (kg female)^?1 day^?1 (48.3), seeds m^?2 day^?1 (23.3) and seeds female^?1 day^?1 (7.9), followed by the SS and SN crosses. The NS cross had the lowest fecundity. Lower spawning parameters in the NS and SN crosses may be attributed to the lower social compatibility between the males and females compared with that of the pure parents. The survival and growth of the offspring from the four crosses will be compared in seawater (37–40 g L^?1) to assess whether hybrid vigor was produced.     

Dietary arginine requirement of fingerling hybrid Clarias (Clarias gariepinus×Clarias macrocephalus)

The dietary arginine requirement of fingerling hybrid Clarias (Clarias gariepinus×Clarias macrocephalus) (4.2±0.03 cm, 0.56±0.04 g) was determined by feeding six isonitrogenous (400 g kg⁻¹ crude protein) and isocaloric (17.9 kJ g⁻¹) amino acid test diets containing casein, gelatin and l ‐crystalline amino acids with graded levels of arginine (10.0, 12.5, 15.0, 17.5, 20.0 and 22.5 g kg⁻¹) for 4 weeks to triplicate groups. Diets were fed twice a day at 09:00 and 16:00 hours at 8% body weight day⁻¹. Maximum weight gain (523%), best feed conversion ratio (FCR, 1.41), protein efficiency ratio (1.78) and specific growth rate (6.53%) were recorded in fish fed the diet containing arginine at 20.0gkg⁻¹ of the diet. Second‐degree polynomial regression analysis of live weight gain and FCR values indicated the dietary arginine requirement at 17.8 and 20.0 g kg⁻¹ of dry diet respectively. Significantly higher carcass protein and protein deposition values were recorded at the requirement level (20.0 g kg⁻¹). Higher fat and lower moisture values were obtained in carcass of fish fed the diet with 15.0g kg⁻¹ arginine. The maximum carcass ash value was noticed in the fish fed at 20.0 g kg⁻¹ dietary arginine. We recommend that the diet for hybrid Clarias (C. gariepinus×C. macrocephalus) should contain arginine in the range of 17.8–20.0 g kg⁻¹ of the dry diet, corresponding to 44.5 and 50 g kg⁻¹ of dietary protein respectively.     

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

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 < 0.001). These results indicated an overall intermediate inheritance of the studied characters.     

Growth,salinity tolerance and microsatellite analysis of the F2 reciprocal hybrids of Oreochromis niloticus×Sarotherodon galilaeus at different salinities

Oreochromis niloticus (O), the sixth generation of Genetic Improvement of Farmed Tilapia, shows rapid growth but poor salt tolerance, while Sarotherodon galilaeus (S) exhibits opposite traits. To combine the traits, F₁ progeny was obtained through artificial fertilization. Fertile F₁ produced F₂ by natural spawning. The mean survival times, the median survival time (ST₅₀) or the survival rate of hybrids was greater than O. niloticus in a gradual or an acute salinity change. Plasma osmolarity, [Na⁺] and [Cl^?] of the hybrids fluctuated in 32 g L^?1 water during a 24‐h period, but eventually reached levels similar to fish in freshwater. O. niloticus♀×S. galilaeus♂ (OS F₂) or S. galilaeus♀×O. niloticus♂ (SO F₂) showed the fastest growth at 22.5 g L^?1, equal to about 78.2% or 69.7% of O. niloticus at 0 and 3.87 or 3.45 times that of S. galilaeus at their individual optimum growth. Growth in OS F₂ was 12% faster than SO F₂. Microsatellite analysis showed that F₂ had more alleles, a higher polymorphism information content and greater observed and expected heterozygosity than O. or S. Population differentiation was not detected between F₁ and F₂. All the results indicated that F₂ could be exploited for commercial production under saline conditions.     

Comparison of the fillet yield, protein content and amino acid profile of Clarias gariepinus and the Clarias gariepinus 5 Heterobranchus longifilis hybrid

The fillet yield, total protein content and amino acid profile of the African sharptooth catfish Clarias gariepinus (Burchell) was compared with that of its hybrid with the African catfish Heterobranchus longifilis Valenciennes. The flesh of the C. gariepinus × H. longifilis hybrid had a protein content of 18.3%, compared with 18.6% for C. gariepinus. The amino acid profiles were similar for the two groups. The fillet yield of the C. gariepinus females was significantly lower than that of the male and female hybrids and C. gariepinus males. The difference in fillet yield was attributed to the high gonadosomatic index (GSI) of the C. gariepinus females, compared with the other groups. The overall fillet yield was 38.9% for C. gariepinus and 43.8% for the hybrid, which has important implications for African catfish production.     

Genetic basis of pectoral fin deformities in the African catfish Clarias gariepinus (Burchell, 1822), Heterobranchus longifilis (Valenciennes 1840) and their hybrids

Morphological aberrations of the pectoral fins in nine mating combinations involving Clarias gariepinus (Burchell, 1822), Heterobranchus longifilis (Valenciennes, 1840) and their hybrids were investigated to determine the level and genetic basis of occurrence. The highest mean percentage survival in a Clarias× Clarias group was 75%, whereas the least mean percentage survival was 2% in the same group. The least mean percentage survival (40.3%) in the remaining three groups occurred in the cross of female hybrid (right pectoral fin absent) × male C. gariepinus (right pectoral fin absent). A maximum of nine types of aberrations was observed in the four mating groups – double dorsal fin, curved posterior dorsal fin, spineless right pectoral fin, right pectoral fin absent, left pectoral fin absent, rudimentary pectoral fin, both pectoral fins absent, double anal fin and curved anterior dorsal fin. These nine aberration types were recorded in the Clarias× Clarias group, with a total frequency ranging from 7.14% to 75.00%. The least number of aberrations was observed in the hybrid ×Clarias group (double dorsal fin and both pectoral fins absent) with a frequency range of 1.47–5.55%. No aberration was observed in two crosses involving female hybrid (right or left pectoral fin absent) × female C. gariepinus (normal). The level of aberrations in some of these crosses indicates the involvement of genotype rather than the influence of environment.     

Production of the Malawi chambo, Oreochromis karongae (Trewavas, 1941) association, and Oreochromis shiranus (Boulenger, 1896) in polyculture with the African catfish, Clarias gariepinus (Burchell, 1822)

Results are reported of the growth and yield of the Malawi chambo, Oreochromis karongae (Trewavas, 1941) association, and Oreochromis shiranus (Boulenger. 1896) in polyculture with Clarias gariepinus (Burchell. 1822). Six ponds of 150 m² were assigned to two replicates of three treatments: C. gariepinus and O. shiranus; C. gariepinus and chambo spawned on station; C. gariepinus and chambo collected from the lake. Total fish stocking density was 3 m^?2, and stocking ratio 1:2 (C. gariepinus: titapias). Initial mean body weights were 10.9 g for O. shiranus. 13.2 g for C. gariepinus and 13.3 g for chambo. The ponds were fertilized with chicken manure at the rate of 13.5 kg dry matter ha^?1 day^?1, representing the daily NPK loading of 0.618.0.186 and 0.191 kg ha^?1, respectively. Maize bran was applied at 3% body weight day^?1 for 168 days. Fish growth rate for C. gariepinus was significantly higher (P < 0.05) than that of the tilapias. Weight gains were 0.48-0.57 g day^?1 for C. gariepinus, 0.30-0.31 g day^?1 for chambo and 0.24 g day^?1 for O shiranus. There was no difference (P > 0.05) in the growth of chambo despite the source of fingerlings. More fish biomass came from C. gariepinus stocked at 1 m^?2 than from the tilapias stocked at 2 m^?2. Extrapolated fish yields in the range of 4.37-4.75 t ha^?1 year^?1 were obtained from the polyculture of chambo and C. gariepinus. Oreochromis shiranus and C. gariepinus gave 3.95 t ha^?1 year^?1. Low water temperatures for 112 days slowed the growth of tilapias but did not seem to inhibit the growth of C. gariepinus. Chicken manure and maize bran, applied at smallholder farmer's level, has produced higher yields than by using O. shiranus in monoculture at optimal temperatures. The yields obtained show that the polyculture system is feasible during the cold season and may justify investment in aquaculture at semi-intensive level in Malawi.     

Nutritional evaluation of toasted Mucuna utilis seed meal and its utilization in the diet of Clarias gariepinus (Burchell, 1822)

The value of toasted Mucuna utilis seed meals was investigated in this study by evaluating the nutritional profile and the utilization of the processed seeds in isonitrogenous (35% CP) and isocaloric diets (17 kJ g?1) for African catfish Clarias gariepinus (Burchell 1822). Toasting the M. utilis seed significantly reduced the levels of tannins, phytate, trypsin, and hemagglutinin in the seeds. However, protein, gross energy, arginine, histidine, and valine were increased (P ≤ 0.05). The processed seed was then used to formulate five experimental diets by progressively increasing its inclusion (by 50 g kg?1) from zero up to 200 g kg?1. A sixth diet was also formulated with raw M. utilis included at 200 g kg?1 to determine the efficacy of the processing method applied in this study. Fifty fingerlings of C. gariepinus (2.02 g ± 0.08) stocked in 18 hapas measuring 1 × 1 × 1 m³ were then fed the diets for 56 days. The growth of C. gariepinus fingerlings was significantly improved by the addition of the toasted M. utilis seed meal. However, fish fed the diet containing 200 g kg?1 of raw M. utilis had poor growth with higher mortality (35%). Estimation of the feeding cost using the diets revealed reduction in production cost of fish with the inclusion of toasted M. utilis seed meal. It was concluded that toasting significantly improved the nutritional quality of this unconventional feedstuff, allowing better utilization at up to 200 g kg?1 inclusion level in the diet of African catfish C. gariepinus.     

Effect of stocking density on growth performance,survival, production,and financial benefits of African sharptooth catfish (Clarias gariepinus) monoculture in earthen ponds

ABSTRACT

The present on-farm study assessed the effect of different stocking densities on growth, production, and financial benefits of African sharptooth catfish (Clarias gariepinus) in earthen ponds for 180 days. Low stocking density (LSD), medium stocking density (MSD), and high stocking density (HSD) of 3, 6, and 9 fish m^?2, respectively, were tested. C. gariepinus stocked at LSD and MSD showed significantly higher weight gain, specific growth rate, and final mean weight than those cultured at HSD (P < .05). There was a significant linear relationship between the stocking density and the yields and financial variables (P < .05). Net fish yields were significantly higher for C. gariepinus reared at HSD and MSD than those stocked at LSD (P < .05). Similarly, C. gariepinus raised at MSD and HSD generated significantly more profit than those cultured at LSD (P < .05). Results demonstrated that farmers can achieve high net yield and financial benefits by stocking C. gariepinus at HSD of 9 fish m^?2.     

Effects of dietary nano and macro iron oxide (Fe2O3) on the growth,biochemical, and hematological profiles of African catfish (Clarias gariepinus) fingerlings

Effects of nano and macro iron oxide as dietary iron sources on the growth, hematological, and biochemical characteristics of African catfish, Clarias gariepinus, fingerlings have been studied. Conventional basal feed was supplemented with nFe₂O₃ and Fe₂O₃ as treatments T₁ and T₂ (each at 0.0, 0.2, 0.4, 0.8, 1.2, and 1.6 g/kg supplementation levels) and given to C. gariepinus fingerlings (initial average weight and length 5.01 ± 0.80 g and 7.0 ± 0.53 cm respectively) for 7 weeks. After 7 weeks, the highest percent weight gains of 395.6% for T₁ and 767.4% for T₂ occurred simultaneously at the supplementation level of 0.4 g Fe kg^?1 dry feed of both treatments, while the highest value for the control was 332.5%. Iron accumulations in liver were 2.727, 1.443, and 1.225 ppm, and red blood cell counts were 2.3, 6.0, and 7.0 x 10¹²/l for the same treatments. Supplementation of iron oxide in both nano and macro forms significantly improved the growth and health indices of C. gariepinus up to a concentration of 0.4 g Fe kg^?1 dry feed. Also macro iron oxide was more effective than the nano form in enhancing fish growth within the supplementation levels (0.2?1.6 g kg^?1) considered.     

The growth and gonadal maturation of the African catfish, Clarias gariepinus (Burchell) broodstock fed differently heated soybean-based diets

An investigation was carried out to assess the growth and gonadal maturation of Clarias gariepinus (Burchell) fed differently heated soybean diets in concrete tanks. Four hundred and eighty male and female C. gariepinus (182 ± 10 g for females and 208 ± 5 g for males) were randomly distributed in groups into hapa nets. Iso‐nitrogenous (310 g kg^?1 crude protein) and iso‐caloric diets (355 Kcal kg^?1) prepared from raw soybean (D0) and soybean autoclaved for 5, 10, 15, 20, 25 and 30 min labelled D0, D5, D10, D15, D20, D25 and D30, were fed to the fish for 84 days. The fish meal based diet tagged DFM served as control. The male and female broodfish fed the fish‐meal‐based diet and diet D25 had significantly higher (P < 0.05) growth performance, gonad maturation, gonadosomatic index, relative fecundity and percentage egg fertilization and hatchability than the fish fed the other diets. The females had significantly higher (P < 0.05) weight increases and healthier condition over their male counterparts fed the same diets. This study showed that diet D25 was found to be the best substitute for fish meal that provided adequate nutrients required for the formation of genital products that produced strong offspring in C. gariepinus broodstock culture.     

Approaches to optimizing dietary protein to energy ratio for African catfish Clarias gariepinus (Burchell, 1822)

An 8‐week feeding trial was conducted in a recycling water system at 28 ± 1 °C to investigate protein to energy ratio (P/E ratio) in African catfish Clarias gariepinus (10.9 ± 0.04 g). Six fishmeal‐based diets of two protein levels (330 and 430 g kg^?1), each with three lipid levels (40, 80 and 120 g kg^?1) resulted in P/E ratios ranging from 15.5 to 21.3 mg protein kJ^?1 gross energy (GE) were fed to 20 fish (per 30‐L tank) in triplicate. Fish were fed 50 g kg^?1 of their body weight per day adjusted fortnightly. Significantly higher (P < 0.05) growth rates and feed conversion efficiency were evident in fish fed with higher protein diet. The highest growth rate was found by fish fed 430 g kg^?1 protein, 21.2 kJ^?1 GE with a P/E ratio of 20.5 mg protein kJ^?1 GE. Significantly indifferent (P > 0.05) values of protein utilization were found in‐between the both (higher and lower) protein diets. Higher lipid deposition (P < 0.05) in whole body and liver was observed with increasing dietary lipid level at each protein diet and as higher (P < 0.05) for the lower protein diets. Liver glycogen tended to decrease with increasing gross energy at each protein diet and higher protein diet showed comparatively lower values (P > 0.05). Digestive enzyme activities (protease and lipase) and histological examination of intestine and liver of fish fed varying P/E diets found no significant differences in response to experimental diets. The study reveals that African catfish C. gariepinus performed best the diet containing 430 g kg^?1, 21.2 kJ g^?1 and 20.5 mg protein kJ g^?1 GE protein, gross energy and P/E ratio, respectively.     

Evaluation of mixed feeding schedules with respect to compensatory growth and body composition in African catfish Clarias gariepinus

An 8‐week feeding trial was conducted in a recycling water system at 28 ± 1 °C to investigate compensatory growth and body composition in African catfish Clarias gariepinus (13.05 ± 0.05 g). A fishmeal‐based diet containing 350 g kg^?1 protein and 17.5 kJ g^?1 gross energy was fed to triplicate groups of 20 fish (per 30‐L tank). Fish were fed the diet either to satiation or feed restricted in six feeding schedules as satiation 56 days; restricted 28 days + satiation 28 days; restricted 14 days + satiation 14 days; restricted 7 days +satiation 7 days; restricted 3 days + satiation 4 days; and restricted 2 days + satiation 2 days. The restricted regime was achieved by offering fish 1% (maintenance ration) of their body weight per day adjusted after fortnightly weighing. African catfish showed partial compensatory growth under alternating periods of feed restriction and satiation feeding with significantly different values (P < 0.05) from fish fed in satiation throughout. However, significantly indifferent (P > 0.05) values of feed, protein, lipid and energy utilization were found under alternating periods of feed restriction and satiation feeding. Significantly higher (P < 0.05) feed intake was observed in treatment with satiation throughout than those in other treatments. All the feeding schedules showed no significant differences (P > 0.05) on body composition, organ indices, eviscerated carcass composition, viscera lipid and liver lipid. These studies reveals that C. gariepinus showed partial compensatory growth responses at alternating periods of restricted and satiation feeding.     

Heterosis analysis at early generations for complete diallel crosses in three different geographical culture populations of Sinonovacula constricta (Lamarck 1818) in Zhejiang,China

The paper reports a study focused on breeding new rapidly growing and heat‐tolerant strains in a commercially important Asian bivalve, Sinonovacula constricta. To breed a new strain of S. constricta with fast growth and high temperature tolerance, complete diallel crosses were carried out using three different geographical culture populations from Zhejiang (Z), Fujian (F) and Guangdong (G) provinces, China. Larval and spat growth and the survival and heat tolerance of spats were compared in detail. The experimental serial growth traits extracted from larval and spat measurements (shell length and shell height) indicated that there was no difference between six hybrid crosses and parental crosses at the larval stage; while at the spat stage, some differences were observed. The hybrid crosses ZF (Z♀ × F♂), ZG (Z♀ × G♂) and FG (F♀ × G♂) outperformed the parental groups in shell length at the end of intermediate culture, with lengths of 21.77 ± 0.28 mm, 21.55 ± 0.29 mm and 21.44 ± 0.20 mm respectively. For spat survival rate, the hybrid cross ZF (Z♀ × F♂) had a significantly larger value (88.89 ± 4.16%) than all the other groups, and the hybrid cross ZG (Z♀ × G♂) had a significantly larger rate than the cross GZ (G♀ × Z♂) and parental crosses ZZ (Z♀ × Z♂) and GG (G♀ × G♂). The hybrid crosses ZF (Z♀ × F♂), ZG (Z♀ × G♂) and FG (F♀ × G♂) exceeded the parental groups in heat tolerance, but there was no significant difference. The growth, survival and heat tolerance results showed that the crosses ZF, ZG and FG in this study were the best hybridization combinations for genetic improvement, which could have significant implications for the development of razor clam aquaculture. This work provides a theoretical basis for breeding new varieties (strains) that grow rapidly and are heat tolerant.     

Effects of dietary Lactobicillus plantarum on the growth,carcass quality,and immune response of African catfish (Clarias gariepinus) challenged with Salmonella typhi

An experiment was conducted to investigate the effects of Lactobacillus plantarum on the production of African catfish (Clarias gariepinus). Five experimental diets containing 0, 10³, 10⁵, 10⁷, and 10⁹ CFU of Lactobacillus plantarum g^?1 diet (T₁–T₅ treatments respectively) were fed to African catfish (Clarias gariepinus) (9.20 ± 0.1 g initial body mass), for 70 days. Results indicated significantly lower growth performance in the fish fed diet without probiotics and in those fed diet with the least probiotic level. Treatments with probiotics significantly improved the blood profile and carcass protein but significantly reduced the carcass fat (P < 0.05); these treatments also marginally improved the carcass minerals in comparison with the treatment without probiotic (P < 0.05). Challenging the fish fed the experimental diets with Salmonella typhi showed higher immunity of fish fed the probiotic diets than those fed the nonprobiotic diet. Duncan’s multiple range test showed that the best fish performance was observed with 10³ CFU g^?1 L. plantarum for very parameter measured. However, regression analyses showed the optimum level of the bacteria to be 10^4.13–10⁵ CFU g^?1     

Combined effects of photoperiod and temperature on growth and survival of African catfish (Clarias gariepinus,Burchell 1822) larvae under laboratory conditions

ABSTRACT

The effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance of Clarias gariepinus larvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L^?1 and fed twice a day on catfish starter diet (40% CP) at 10 % BW day^?1. Highest mean weight gain (31.00 mg), SGR (7.56% day^?1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D.     

Bioavailability of ascorbyl phosphate calcium in hybrid catfish,Clarias macrocephalus (Gunther) × Clarias gariepinus (Burchell) feed

A 10-week feeding experiment was performed in hybrid catfish (Clarias macrocephalus (Gunther) × C. gariepinus (Burchell, 1822) with initial average weight of 1.17 g, in glass aquaria of 200-L capacity. The experiment comprised seven treatments with three replicates each. Ascorbyl phosphate calcium (APCa) was included at 30, 75, 150, 300 and 1000 mg kg⁻¹ feed and compared with one with ascorbyl polyphosphate (APP) at 36 mg kg⁻¹ feed and one without vitamin C supplementation. Fish fed APCa-supplemented feed showed better growth, feed conversion ratio, survival rate and protein utilization compared with those without such supplementation. Ascorbate concentrations in liver and head kidneys were correlated closely with dietary APCa levels. Vertebral collagen and hydroxyproline contents were significantly lower in the fish group without ascorbate supplementation. Red blood cell and white blood cell counts showed no correlation with vitamin C supplementation. Serum protein level was lowest in the group fed feed without vitamin C supplementation and this was lower than those fed feed with APCa and APP supplementation. The fish fed APCa- and APP-supplemented feed showed no difference in serum protein levels. External scorbutic symptoms and histopathological changes of gill tissue were noted in fish fed feed without APCa supplementation. The study indicates that 12.6 mg kg⁻¹ of ascorbic acid molar equivalent supplied as APCa (30 mg kg⁻¹) provided maximum growth and no gross signs as well as histological changes resulting from vitamin C deficiency.     

Swim-up fry production in the African Catfish Clarias gariepinus (Burchell) broodstocks fed with differently heated soybean-based diets

Four hundred and eighty matured yearlings of Clarias gariepinus (Burchell) (female=182±10 g; males=208±5 g) distributed into groups of 30 specimens (sex ratio 1:1) were fed differently heated soybean‐based diets. Seven approximately iso‐nitrogenous (31% crude protein) and iso‐caloric (13.97 kJ g^?1) diets were prepared from either raw soybean (SAMSOY 2, TGX 636–02D) or soybean seeds autoclaved for 5, 10, 15, 20, 25 and 30 min. The untreated and the variously heat‐treated soybean meals were mixed with other ingredients to prepare diets designated as DSoy0, DSoy5, DSoy10, DSoy15, and DSoy20, DSoy25 and DSoy30 according to the treatment time of the soybean portion of the diets, and were fed to the fish broodstocks for 84 days. The fishmeal‐based diet (DFM) served as the reference diet. The duration of heating soybean component of the experimental diet significantly (P<0.05) affected the growth performance and the number of eggs produced by the broodstocks, the percentage number of eggs fertilized and hatched as well as the survival of the progenies. The progenies of the brood fish fed diets DFM and DSoy25 with a yolk sac size of 2.78±0.6 and 2.42±0.5 mm, respectively, had significantly (P<0.05) larger yolk sacs, which were also absorbed at a significantly faster rate of 0.61±0.02 and 0.51±0.03 mm day^?1, respectively, than progenies of broodstocks fed other experimental diets. Swim‐up fry survival rates were also better in hatchlings from broodstocks fed DFM (89.5%), DSoy25 (83.8%) and Dsoy 20 (80.5%) diets than progenies from other experimental diets. This study showed that soybean meal portion processed at 116°C and 1.2 kg cm^?2 pressure for 25 min in the diet, which ensures normal reproductive function and production of healthy progenies in C. gariepinus, could serve as a substitute for fishmeal in the broodstock diets.     

Fish meal replacement by Cirina butyrospermi caterpillar's meal in practical diets for Clarias gariepinus fingerlings

Fifty‐six days feeding trial was conducted to evaluate the effect of Cirina butyrospermi caterpillar meal (CBM) as protein source in replacement of fish meal (FM) for Clarias gariepinus fingerlings. Six hundred African catfish (initial mean weight = 2.42 ± 0.01 g) were fed with four approximate isonitrogenous (48.97% crude protein), isolipidic (15.85% crude lipid) and isocaloric (21.10 kJg^?1) formulated diets, in which CBM progressively replaced FM at 0 (D1), 50 (D2), 75 (D3), 100% (D4) levels. At the end of the trial period, the best growth performance and nutritional utilization were observed in the group of fish fed with D2 and was not significantly different from those fed with D1 (the control diet). The survival rates, which ranged from 85.33% to 90.33%, were not significantly different among fish from the four diet treatments. The proximate whole‐body composition of C. gariepinus fingerlings fed the different diets showed similar moisture and protein contents. However, in contrary to ash which decreased, whole‐body lipid increased significantly when fish fed with diet containing CBM inclusion superior or equal to 75% (D3 and D4). The higher gross profit was obtained with D2 (16.73$), while the lowest was observed with D4 (10.16$). This study demonstrates that 50% of fish meal can successfully be replaced with CBM in C. gariepinus fingerlings diet without a negative impact on growth or feed utilization. This will yield a cheaper feeding for profitable production of African catfish fingerlings.     

Comparison of the physiological energetics between Mytilus chilensis,Mytilus galloprovincialis and their hybrids,under laboratory conditions

Laboratory‐produced juvenile individuals of the species Mytilus chilensis, M. galloprovincialis and their hybrids were subjected to physiological measurements under an experimental diet of Isochrysis galbana (30 × 10⁶ cells L^?1), 13°C temperature and a salinity of 30 psu. Pure species individuals showed a higher clearance rate (CR). Mytilus chilensis had a CR of 1.13 L h^?1, while M. galloprovincialis registered only 0.78 L h^?1. Also, pure taxa registered higher values (above 70%) of absorption efficiency when compared with hybrid individuals. Ammonia excretion in M. chilensis and M. galloprovincialis was 1.5% and 0.4%, respectively, while hybrids registered significantly lower values. Under these experimental conditions, M. chilensis registered the highest scope for growth (P < 0.05), compared with M. galloprovincialis and their hybrids. However, the net growth efficiency index (K ₂) in hybridization type I (♀Mg × ♂Mc) was higher (P < 0.05) than other experimental groups. The invasive mytilid M. galloprovincialis showed values that are very similar to those obtained with the hybridization I group (♀Mg × ♂Mc). Finally, we discuss that water temperature is an important factor in the biogeographic separation of both species and the potential effects that the settlement of the invasive species may have for Chilean mussel production.