Effect of microalga-based diet on oxidative stress enzymes of African catfish,Clarias gariepinus

Here an indigenously isolated microalgal strain Ascochloris spp. cultivated in synthetic medium was evaluated as an aquaculture feed supplement. The daily dietary supplement includes microalgal feed (AF) and commercial diet feed (CF) (as control), respectively. These diets were fed separately to the juvenile Clarias gariepinus fishes (n = 4) under controlled conditions for an experimental period of 100 days. The protein, glycogen and lipid contents in the muscle extracts were found to be marginally higher in fishes that were fed with CF than AF diet. Similarly, CF fishes showed significantly higher glutathione-s-transferase, catalase, superoxide dismutase, and lipid peroxidase activities, except glutathione content. Zero mortality of the fishes with no significant difference in the overall body mass with the two dietary supplements strongly suggests that algal biomass could supplement the requisite nutrients for their metabolic activities. This preliminary investigation helps in exploring algal biomass as a potential alternative feed additive in the aquaculture industry.     

Sertoli cell proliferation and FSH signalling in African catfish, Clarias gariepinus

Sertoli cell proliferation occurs mainly during the phase of rapid spermatogonial proliferation, allowing the cyst-forming Sertoli cells to form an increasingly large space for housing the growing germ cell clone. There is no information in fish on the regulation of Sertoli cell proliferation; follicle-stimulating hormone (FSH) stimulates Sertoli cell proliferation in mammals. Increasing or decreasing FSH and FSH receptor expression experimentally in male African catfish was associated with respective changes in Sertoli cell proliferation or testis growth, suggesting that also in fish, one role of FSH may be to regulate Sertoli cell numbers.     

Steroidogenesis during induced oocyte maturation and ovulation in the African catfish,Clarias gariepinus

Changes in ovarian steroidogenesis accompanying oocyte maturation and ovulation were studied in the African catfish,Clarias gariepinus. Laboratory-reared females with postvitellogenic ovaries were treated with pimozide and LHRH-analogue. The plasma gonadotropin levels were determined by means of a homologous radioimmunoassay, the condition of the ovaries was studied by histological examination of the follicles, and the steroidogenetic capacity of the ovaries was analyzed byin vitro incubation of tissue fragments for 3 h with [³H]-pregnenolone and [³H]androstenedione as precursors. Data were collected at regular intervals between 0 and 16 h after pimozide-LHRH analogue administration.Until 4 h after the beginning of the experiments the plasma gonadotropin levels did not rise above 25 ng/ml, the ovaries remained in the stage of postvitellogenesis, and testosterone was the main end product of steroidogenesis. Four hours later the gonadotropin concentration in the blood had risen to more than 150 ng/ml, and the ovaries had entered the stage of germinal vesicle migration. At the same time steroidogenesis shifted towards the production of 17,20-dihydroxy-4-pregnen-3-one, 5-pregnane-3, 17-diol-20-one, 5-pregnane-3,6,17-triol-20-one, 5-pregnane-3,17,20-triol and 5-pregnane-3,6,17,20-tetrol. During the subsequent stage of germinal vesicle breakdown the plasma gonadotropin level remained high, and the synthesis of the C₂₁-steroids showed a further increase. Simultaneously, the production of some C₁₉-steroid glucuronides was enhanced. The preovulation and especially the postovulation stages were accompanied by a gradual decrease in steroidogenic capacity of the ovaries, even though the plasma gonadotropin level remained high. It is concluded that the prematuration surge of gonadotropin influences the activity of enzymes involved in steroidogenesis, leading to a reduced C_17,20-lyase and to an augmented activity of the enzymes 20-hydroxysteroid dehydrogenase (HSD), 5-reductase, 3-HSD, 6-hydroxylase and UDP-glucuronosyltransferase. During ovulation the activity of all steroidogenic enzymes, including such key enzymes as 3-HSD and 17-hydroxylase, gradually decreases.Not only 17,20-dihydroxy-4-pregnen-3-one, but also the 5-reduced pregnanes may be involved in inducing oocyte maturation and/or ovulation. The very polar triol and tetrol products may function, together with the steroid glucuronides as sex pheromones.A preliminary account of these results was presented at the XIII Conference of European Comparative Endocrinologists, Belgrade, September 7–12, 1986     

Catecholestrogens inhibit dopamine methylation in the gonadotrops of the African catfish,Clarias gariepinus

Isolated gonadotrops of the African catfish,Clarias gariepinus, were incubated with dopamine (DA) and/or catecholestrone and the activity of the enzyme catechol-O-methyltransferase (COMT) was determined by measuring the methylated products. From the apparent Km values for DA and catecholestrone of 0.4–1.3 M and 17.9–25.2 M respectively, it was concluded that catecholestrone is a better substrate for the enzyme COMT, compared to DA. Moreover, the methylation of DA is inhibited by comparatively low concentrations of catecholestrone.     

Metabolic enzyme activities in larvae of the African catfish,Clarias gariepinus: changes in relation to age and nutrition

The influence of ontogeny and nutrition on metabolic enzyme activities in larvae of the African catfish, Clarias gariepinus, was studied. After start of exogenous feeding, the larvae were reared for 10 days under three different nutritional conditions: Artemia nauplii, a dry starter diet, and starvation. The live feed gave the best growth (96 mg within 10 days) whereas the dry diet resulted in low growth (33 mg). This growth difference was reflected in larval RNA and DNA concentrations, but not in the levels of soluble protein. Enzymes representing the following aspects of metabolism have been analysed: NADPH generation (G6PDH, ME), glycolysis (PFK, PK), gluconeogenesis (FDPase), amino acid catabolism (GOT, GPT) and oxidative catabolism (CS). All enzymes were present from the start of exogenous feeding onwards, but their maximum specific activities displayed different developmental patterns. In catfish larvae fed on Artemia, G6PDH and ME activities steadily increased with age and weight of the larvae. CS levels remained, after an immediate enhancement upon onset of exogenous feeding, on a rather stable plateau. The amino acid-degrading enzymes GOT and GPT showed maximum levels at days 3–5 of feeding or at a body weight of 10–20 mg, but decreased thereafter. Activities of PFK, PK and FDPase showed low initial levels, and increased significantly with age and size. Based on the ontogenetic patterns of metabolic enzymes, in C. gariepinus larvae an early and a late developmental phase can be distinguished. During the early phase, the glycolytic and gluconeogenetic capacities are low, whereas they are enforced during the later phase. The oxidative capacity is high both during the early and the late phase. The metabolic changes in catfish development coincide with other major ontogenetic events, e.g., alterations of muscle organization, gill morphology, respiration and stomach structure and function. Rearing catfish larvae on a dry diet instead of Artemia partly altered the developmental pattern described: The ontogenetic elevation of CS, PFK and FDPase was delayed and the early peak in GOT and GPT activities was not realized. Particularly during the early developmental phase, the enzyme behaviour of the larvae fed on dry food was similar to that of starved larvae.Abbreviations CS citrate synthase - FDPase fructose-1,6-diphosphatase - GOT glutamate oxaloacetate transaminase - GPT glutamate pyruvate transaminase - G6PDH glucose-6-phosphate dehydrogenase - ME malic enzyme - PFK phosphofructokinase - PK pyruvate kinase     

Oxidative nutritional stress associated with feeding rancid oils to African catfish, Clarias gariepinus (Burchell) and the protective role of α-tocopherol

Over a 56-day feeding period, during which juvenile African catfish, Clarias gariepinus (Burchell) increased in body weight at least threefold, diets containing fresh or rancid oils (0.352 and 9.133 mmol MDA equivalents per g oil, respectively) at two levels of supplemental vitamin E (20 or 100 mg all-rac-α-tocopheryl acetate kg^-1 dry diet) were fed at 3% body weight per day. On termination of the feeding trial, growth performance and food utilization were assessed. Additionally, health criteria such as hepatosomatic index (HSI), haematocrit, plasma haemoglobin and plasma α-tocopherol concentration were determined. Plasma α-tocopherol was seen to increase significantly (P < 0.05) concomitant with dietary dose of the vitamin. Oxidation of dietary lipid source was observed to cause significant depletion (P < 0.05) of α-tocopherol from the plasma pool on consumption of the rancid test-diets. Final body weights of the catfish revealed that vitamin E supplementation in rancid diets significantly improved growth (P < 0.05), although supplementation into fresh-oil diets did not result in appreciable benefits in terms of final attained weight (P > 0.05). Values of other growth parameters and nutrient utilization indices were seen to respond positively to increased vitamin E levels and fresher dietary oils. With respect to other health indices, HSI was strongly correlated (P < 0.05) to dietary vitamin E dose and not oil oxidation state, with catfish fed lower α-tocopherol doses exhibiting larger livers proportional to somatic mass. Haematocrit values were significantly (P < 0.05) lower in fish fed low-tocopherol/fresh-oil diets. Although no measurably significant differences were found between treatments with respect to plasma-haemoglobin concentration, higher mean values for the fish fed rancid oils at the lower α-tocopherol inclusion level may indicate heightened Spontaneous haemolysis in this group. Mechanisms to account for dietary modulation of health indices in catfish under the present dietary regime are postulated. It was concluded that supplemental α-tocopheryl acetate in diets likely to undergo oxidation, would protect catfish from the nutritional stress imposed by rancid oils and increase growth above levels associated with unsupplemented dietary treatments.     

Mismatch between patterns of circulating and testicular androgens in African catfish, Clarias gariepinus

11-Ketotestosterone (11-KT) is an important plasma androgen in male African catfish. The quantitatively predominating androgen produced by the testis, however, is 11-hydroxyandrostenedione (OHA). Our working hypothesis to explain this mismatch assumed that OHA is converted to 11-KT at extratesticular sites. First, we examined the in vivo metabolism of [³H]-OHA in mature males after sham-operation or removal of either the testes (TC), the seminal vesicles (SVC), or both (TSVC) by analysing the pattern of circulating [³H]-androgens two hours after intravenous injection of [³H]-OHA. [³H]-OHA was converted to [³H]-11-KT to the same extent in all groups, indicating that neither ablation of testes nor of seminal vesicles, or both attenuates this conversion. We then examined the in vitro metabolism of [³H]-OHA by several types of tissues. Liver and seminal vesicle tissue were found to produce significant amounts of [³H]-11-KT. The conversion capacity in vivo was assessed by injecting TSVC-castrated males with increasing doses of radioinert OHA, followed by the quantification of OHA and 11-KT plasma levels. Saturation of the conversion capacity was not reached but the 11-KT production capacity is at least 80 ng per ml of plasma per hour. Moreover, liver fragments were tested for their OHA to 11-KT conversion capacity in vitro using increasing concentrations of radioinert OHA. The 11-KT producing increased with time and OHA concentration. The production rate was 90 pg 11-KT mg^-1 liver h^-1. Considering the results of the surgical experiments and the fact that the total hepatic mass by far exceeds that of the seminal vesicles, we conclude that the hepatic conversion is of primary relevance in vivo.     

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     

Nicotinic acid supplementation of diets for the African catfish, Clarias gariepinus (Burchell)

Semi-purified diets containing 39% crude protein and 5% lipid were used to identify the qualitative requirement of African cattish, Clarias gariepinus (Burchell), for niacin and to characterize the pathologies associated with a deficiency of this vitamin. After 48 days of feeding, C. gariepinus supplied with the unsupplemented diet had developed severe deficiency symptoms and were subsequently withdrawn from the growth study. Niacin deficiency was characterized by feed refusal, listlessness, weight loss, poor feed utilization and high mortality. The skin overlaying the lateral line of the deficient fish became haemorrhagic and this clinical sign was accompanied by severe anaemia. After 126 days of feeding, fish fed diets containing 17.0 mg niacin kg^?1 had also developed a dermopathy. but without anaemia or high mortality. The feeding of diets containing less than 33.1 mg niacin kg^?1 resulted in suboptimal feed efficiency and poor protein utilisation. Allometric analysis of proximate composition indicated that carcass moisture, protein and ash were influenced by fish size, and not by dietary niacin content. However, significantly more lipid per unit of weight gain was deposited in the carcasses of fish fed the unsupplemented diet than in fish fed diets containing 17.0mgkg^?1. The indicators used in the present study could not be applied to accurately determine a value for niacin requirement. However, until a more accurate assessment is performed, it is recommended that diets for C. gariepinus contain not less than 33.1 mg nicotinic acid kg^?1 feed.     

Characterization of the receptor for gonadotropin-releasing hormone in the pituitary of the African catfish,Clarias gariepinus

Receptors for gonadotropin-releasing hormone (GnRH) were characterized using a radioligand prepared from a superactive analog of salmon GnRH (sGnRH), D-Arg⁶-Pro⁹-sGnRH-NEt (sGnRHa). Binding of¹²⁵I-sGnRHa to catfish pituitary membrane fractions reached equilibrium after 2 h incubation at 4°C. Displacement experiments with several GnRH analogs as well as other peptides, demonstrated the specificity of¹²⁵I-sGnRHa binding. Specific binding was enhanced in the presence of the cation chelator ethylene bis (oxyethylenenitrilo) tetra-acetic acid (EGTA), indicating an inhibitory effect of cations on GnRH-receptor binding. The binding of¹²⁵I-sGnRHa to pituitary membranes was found to be saturable at radioligand concentrations of 5 nM and above. A Scatchard analysis of the saturation data suggested the presence of a single class of high-affinity binding sites (Ka=0.901±0.06×10⁹M^–1, Bmax=1678±150 fmol/mg protein). A comparative study on¹²⁵I-sGnRHa binding to pituitary membrane fractions of male and female catfish, indicated that there were no differences in binding affinity and binding capacity between both sexes. The results demonstrate the presence of specific, saturable GnRH receptors in the African catfish pituitary.     

Effect of plant density in coupled aquaponics on the welfare status of African catfish,Clarias gariepinus

We investigated the effects of plant density on the welfare of African catfish, Clarias gariepinus, in coupled aquaponics over 85 days. The moderate density (mpd) of basil, Ocimum basilicum, was compared with the high density (hpd) and control (n = 0). The behavior was analyzed by visual and video observations, and after the application of induced stressors, skin injuries, blood glucose, lactate, and plasma cortisol responses were considered. The hpd fish showed the least activity (control: visual 77.8%, video 81.6%; mpd: 74.6%, 82.6%; hpd: 63.2% [p < 0.05], 78.8%). High agonistic behavior (control: 5, 131; mpd: 4, 57; hpd: 1, 45) and the highest number of injuries (control: 3.9; mpd: 2.9; hpd: 3.4) were observed in the control. Glucose and lactate levels did not differ significantly (control: 5.5, 2.6 mmol/L; mpd: 5.6, 2.7 mmol/L; hpd: 5.3, 2.6 mmol/L); however, cortisol levels did (control: 18.8 ng/mL, mpd: 19.9 ng/mL, hpd: 25.8 ng/mL). pH adjustment led to additional stress, resulting in temporal cortisol alterations. While in the control and mpd, low cortisol levels were followed by acute responses and downregulation, the hpd fish showed prior elevation and lagged an acute response. However, comparing injuries and behavioral patterns with control, aquaponics with high basil density influenced African catfish positively.     

Steroids and steroid glucuronides in the ovarian fluid of the African catfish,Clarias gariepinus,between ovulation and oviposition

As part of a series of experiments concerning a possible pheromonal function of steroids and steroid glucuronides excreted by the sex organs of the African catfish,Clarias gariepinus, qualitative and quantitative studies, using GCMS, were carried out to examine the presence of the steroids, that can be synthesized by the ovary during oocyte maturation and ovulation, and of the corresponding steroid glucuronides, in the fluid surrounding the eggs in the ovarian cavity shortly after ovulation.Full mass spectra were obtained of 5-pregnane-3,17-diol-20-one, 5-pregnane-3,17,20-triol, 5-pregnane-3,6,17-triol-20-one, 5-pregnane-3,6,17,20-tetrol, 5-androstane-3,17-diol and 5-androstane-3,17-diol-11-one. After selected ion monitoring the following steroids could be detected by the presence of at least two characteristic ions at the expected retention time: 5-pregnane-3, 17,20-triol, etiocholanolone, 5-dihydrotestosterone, 5-androstane-3,11-diol-17-one, testosterone and estradiol. After treatment with -glucuronidase the following steroids could be determined in a similar way: 5-pregnane-3,17-diol-20-one, 5-pregnane-3,17,20-triol, 5-pregnane-3,17,20-triol, 5-pregnane-3,6,17-triol-20-one, 5-pregnane,3,6,17,20-tetrol, 5-androstane-3,17-diol, etiocholanolone, 5-dihydrotestosterone, testosterone and estradiol.The free steroids 5-pregnane-3,6,17,20-tetrol and 5-pregnane-3,6,17-triol-20-one and the steroid glucuronides of testosterone, 5-dihydrotestosterone and estradiol appeared to be the most abundant of these compounds. The results indicate that very polar steroids and steroid glucuronides, synthesized in the ovary, can be excreted via the ovarian fluid shortly before and during oviposition, and possibly function as sex attractants, inducing reproductive behaviour in male conspecifics.     

Inherent variation in growth efficiency of African catfish Clarias gariepinus (Burchell, 1822) juveniles

Understanding the major causes of growth variation is crucial for the success of fish farming since its reduction contributes to maximize production efficiency, reduce food waste and improve water quality. The growth variation observed in aquaculture has been associated with the establishment of social hierarchies. However, some studies suggest that this variation may not be mainly a consequence of social hierarchies but mainly a result of inherent (genetic) differences. This study investigates the magnitude of individual responses, independently of group effects (fish housed individually), in growth efficiency and feeding behaviour of African catfish Clarias gariepinus (Burchell 1822). Despite the low variation in initial body weight (6.5%) and cumulative feed consumption (7.5%) over the experimental period, catfish exhibited high variation in final body weight (18.1%), specific growth rate (17.2%) and feed conversion ratio (27.9%), suggesting that individual variation in growth efficiency is important in determining growth rate. This individual variation may be related with individual differences in protein/fat deposition since faster growing fish deposited more protein and less fat than slower growing fish. Pronounced individual differences in feeding behaviour (reaction towards feed and time spent eating) were also observed and correlated with individual differences in growth efficiency. Fast eaters were the fast growers. We suggest that the growth variation observed in African catfish may be inherent and that the use of grading to increase uniformity should be further investigated.     

Effects of density,PVC‐tubes and feeding time on growth,stress and aggression in African catfish (Clarias gariepinus)

Successive exposure to aquaculture‐related stressors may compromise the allostatic capacity of African catfish and lead to allostatic overload and poor welfare. Therefore, we tested the effect of (i) feeding during the light or dark phase, (ii) density (51 fish per 140 L versus 51 fish per 43 L) and (iii) altered available resting space/shelter on stress handling were studied in African catfish (Clarias gariepinus). Available resting space/shelter was manipulated by providing PVC‐tubes in the tanks. Growth, baseline stress load (cortisol and osmolality), metabolism (glucose, lactate and non‐esterified fatty acids) and aggression (measured by skin scar incidence) were assessed. Upon completion of the experimental period, we determined the adaptive capacity of the fish by the response to air exposure. We show that night‐feeding enhances growth and lowers feed conversion ratio compared to day‐feeding. No effects of density were found for baseline stress hormones, basal metabolism or aggression. Low density seems to stimulate aggressive behaviour after air exposure. Unexpectedly, providing PVC‐tubes under high‐density conditions increased aggression, raised baseline cortisol levels and decreased basal metabolism as well as growth; also the endocrine response to air exposure was stronger. We argue that these effects relate to a reduction in available space, i.e. a further increase in density, or to an increased competition for shelter. Overall, our data suggest that night‐feeding optimizes growth and that care should be taken in using objects as shelter/enrichment for African catfish.     

GTH-cells in the pituitary of the African catfish,Clarias gariepinus,during gonadal maturation: an immuno-electron microscopical study

In an ultrastructural immunocytochemical study we investigated the development of the gonadotropic cells in the pituitary of two to six months old male African catfish in relation to testicular development. In this period, pituitary and testicular tissue samples were collected on five occasions (groups I–V). Blood samples could only be taken from the fish in groups III–V. The testicular development was divided in three stages i.e., immature (only spermatogonia, group I), early (spermatogonia and spermatocytes, groups II and III) and advanced (all germ cell stages including spermatozoa, groups IV and V) spermatogenesis. 11-Ketotestosterone blood levels were low, except for the last group. Antisera were raised against the complete catfish α,βGTH-II, as well as to the separate α- and β-subunits of catfish GTH-II. In the proximal pars distalis of immature fish, undifferentiated cells, somatotrops, putative thyrotrops (pTSH) and putative gonadotrops (pGTH) were found. In the two latter, secretory granules were labeled with anti-αGTH, but not with anti-βGTH-II. pTSH- and pGTH-cells were distinguished on the basis of the size of their secretory granules. During early spermatogenesis, two classes of putative gonadotrops could be distinguished. One type had the same immunocytochemical and ultrastructural characteristics as in immature fish; the secretory granules in the second cell type, which was more abundant, were also immunopositive for anti-βGTH-II. The mean volume of the secretory granules in these GTH-II cells was three times larger than that in the early appearing pGTH-cells. In addition, the later appearing GTH-II cells contained large inclusions, known as globules. These structures labeled with anti-αβGTH-II and with anti-βGTH-II, but not with anti-αGTH. It is assumed that the globules are involved in a differential storage and/or breakdown of the GTH-II subunits. During advanced spermatogenesis the two gonadotropic cell types could still be distinguished, but the early appearing pGTH-cell type was scarce. The present observations permit the conclusion that the early appearing cells may be GTH-I cells. However, definitive proof about their identity depends on the availability of antibodies or cDNA probes specific for GTH-I.     

Temperature and dietary factors affecting the nitrogen efflux rates of the African catfish, Clarias gariepinus (Burchell)

Total ammonia and total nitrogen efflux rates of the African catfish, Clarias gariepinus (Burchell), were measured under different temperature conditions (20, 25 and 30^°C) and feeding regimes (50% protein, 40% protein and non-fed for 10 days). Both ammonia and nitrogen efflux rates were directly related to temperature. At all experimental temperatures, the 50%-protein-fed groups excreted higher levels of ammonia nitrogen than both the 40% protein and non-fed groups. No correlation of relative ammonia efflux (% ammonia/nitrogen) with either temperature or diet was observed under these experimental conditions. Such alterations caused by temperature and diet may have significant implications for an aquaculture system as low levels of dissolved ammonia are synonymous with optimum water quality.     

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.     

Yields of the African catfish,Clarias gariepinus (Burchell), from a low input,homestead, concrete pond

Fingerlings of the African catfish, Clarias gariepinus (Burchell), with a mean initial average weight of 96.2 g per fish were cultured in a dug-in homestead concrete pond, 30.24 m² in four cycles (1981–1984) for a mean average of 302 days. A mean average weight of 418.4 g per fish was obtained at harvest, resulting in an overall net fish yield of 40.3 kg. Homemade ration was used in the investigation and the feed conversion ratio was 2.6 to 1. There was a mean daily increase in individual fish weight of 1.06 g with overall fish survival of 86.4%.