Heterobranchus Longifilis Research Articles

Effect of the combination of two types of fish feed with nutritional quality on the performance of two species of fish raised on rural and peri-urban farms in Cote D'ivoire

For 160 days, juvenile Oreochromis niloticus and Heterobranchus longifilis were in ponds on a farm in San Perdo located in the southwest of Côte d’Ivoire.The juveniles grouped in four lot per species and in triplicate were fed in pairs of industrial feed and feed produced on the farm and an agri-feed by-product from four feeding techniques (Batch 1: juveniles fed with an industrial lime in the pre-growing phase followed by an agricultural by-product in the growing phase. Batch 2: Juveniles fed with an industrial feed then a feed formulated with an agricultural product during the growing phase ; Batch 3: juveniles fed with an agricultural by-product in the pre-growing phase followed by an industrial feed in the growing phase. Batch 4: Juveniles fed with a formulated feed in the pre-growing phase then with an industrial feed in the growing phase). At the end of the experiment, the best zootechnical parameters were obtained whatever the species by the juveniles fed in the pre-grossing phase with a produced feed followed by industrial feed in the production growing phase.

Field and DNA-barcode based surveys reveal evidence of rare endemic fishes in the Rufiji River Basin

Endemic fish species have long supported the livelihoods of local communities in the Rufiji River Basin (RRB). However, destructive fishing practices have led to a concerning decline in endemic fish stocks. To assess these changes, this study employed key informant interviews, focus group discussions (FGDs), and fishery surveys to assess the historical and contemporary distribution of endemic fishes within the RRB. DNA barcoding was also used to verify species identities. Out of 37 reported fish species, 33 species (54.55% endemic and 45.45% exotic to RRB) were confirmed through DNA barcoding and morphological characteristics. About 5 species including, Heterobranchus longifilis, Citharinus congicus, Labeo congoro, Mormyrus longirostris, and Labeobarbus leleupanus were rarely found in the field, despite being classified as Least Concern by IUCN. Additionally, five species that were reported to be present in the RRB by experienced fishers were not captured during sampling. This highlights the need for validation of the existence of such species through eDNA metabarcoding. Moreover, due to the rarity of some species in the area, their IUCN assessment should be revisited.

Quadriacanthus (Monogenea, Dactylogyridae) from Catfishes in the Democratic Republic of the Congo: Description of a New Species from Heterobranchus longifilis (Teleostei, Clariidae).

Studies on monogeneans parasitizing representatives of Siluriformes in Africa remain scarce and fragmentary. In order to contribute to fill this gap, we screened Heterobranchus longifilis from the Lindi River in the Democratic Republic of the Congo. Heterobranchus longifilis was purchased from fishermen in DR Congo, province of Tshopo, in Kisangani town, the Lindi River. The monogeneans were individually isolated from the gill and transferred directly onto a slide in a drop of Hoyer's medium. Quadriacanthus lindiensis n. sp. is morphologically similar to Quadriacanthus longifilisi. However, it is distinguished from the latter by its non-sclerotized vagina, its dorsal cunei shape and the size of its bars. Only Q. lindiensis n. sp. was found on the gills of the single individual of H. longifilis screened. In the future, a representative sampling should enable us to verify if Q. lindiensis n. sp. co-occurs with other species known to parasitize H. longifilis.

Growth and survival assessment from African lungfish (Clarias gariepinus) and its hybrid with two species of heterobranchus

Obtaining good quality and quantity of fish seeds for increasing fish production is a major quest by fish farmers. This study examined the growth responses and survival of Clarias gariepinus and two species of heterobranchus. One thousand five hundred (1500) fry (28-day after hatched) were randomly selected from each of the three crosses of Clarias gariepinus (T1), C. gariepinus x Heterobranchus longifilis (T2) and C. gariepinus x Heterobranchus bidorsalis (T3) broodstocks. They were stocked separately in triplicate at a stocking rate of 500 fish per replicate and reared for 90 days. The data were analysed for significant differences (P<0.05) by Analysis of Variance (ANOVA). There was no significant difference in the growth parameters but fish in T3 had the highest value of mean weight gain while T1 had the least. No significant difference (p>0.05) was observed in the body weight gains from day 40 to day 90 except at day 70 where T3 had the highest weight gain (18.97 g) which was significantly different (p<0.05) to the value recorded in T1 (18.20 g) but not significantly different (p>0.05) to the value recorded in T3 (18.97 g). The results of length increment showed that the growth pattern from day 0 to day 80 were similar. A little difference was observed at day 90 with T3 >T2>T1. The fish in T1 (Clarias gariepinus) had the highest significant percentage survival (89.60%). The results of water quality parameters showed that the mean temperature was 28oC, pH 6.8, dissolved oxygen 5.6 mg/l and turbidity 5.45 NYU. The culture of C. gariepinus by farmers will improve their output and consequentially increase in profit.Keywords: aquaculture; fish breeding; hybrids; weight gain

Risk Assessment and Heavy Metals Accumulation in Organs of Clarias Gariepinus and Heterobranchus Longifilis from Omambala River, Anambra State Nigeria

Heavy metals are toxic to organisms even at low concentrations. In recent times, there has been the high occurrence of cancer cases locally, traceable to heavy metal contaminations of foods consumed by man and animals. The experimental site for this study was Omambala River which serves as a source point of many fresh fishes as well as its distribution throughout the state both in dry and rainy seasons. One hundred (100) samples each of Clarias gariepinus and Heterobranchus longifilis, with the size of 17–21 cm were selected from Omambala River. Heavy metal determination was done using the digestion method. All the digested samples were analyzed three times for heavy metals using SP-V21A Vis Spectrophotometer and the instrument was calibrated with standard solutions. For Risk assessment analyses, the target hazard quotients (THQ) index was applied to assess the potential non-cancer risk associated to consumption of the different species of marine organisms sampled. While the total target hazard quotient (TTHQ) was calculated as the arithmetic sum of each THQ value. The lifetime cancer risk (TR) was calculated by multiplying the daily dose by the cancer slope factor (CSF) derived by response-dose curve for toxicant ingestion. The bioaccumulation factor (BAF) was determined by dividing the metal concentration in the tissue of the organism by the metal concentration in the environment or medium. From the correlation analysis, there was a positive correlation between the four different organs of the fish species and the selected heavy metals. The toxicity of magnesium and zinc are higher in C. gariepinus while the toxicity of iron is higher in H. longifilis. The degree of toxicity is zinc > iron > magnesium > lead > cadmium > copper > mercury > chromium. The water quality index (WQI) for all the heavy metals in four different organs of the two fish species was found to be less than 1 (WQI < 1) meaning low pollution; which further means that the consumption of C. gariepinusand H. longifilis may not pose any health risk to the people of the area. However, there are reports of lifetime cancer risk on daily consumption of Chromium, Cadmium, Lead and Mercury in fish. Chemicals when found in large quantities.

Impact of water quality and morphometric indices on the spatio-temporal prevalence of fish endo-parasites and diversity in the Ase River, Niger-Delta, Nigeria.

Three stations along the Ase River, Delta State Nigeria provided water and 85 fish samples which were analyzed. The fish were measured and examined for endoparasites according to established protocol. All water quality parameters investigated were within the WHO-acceptable values for surface waters. Station variation of physicochemical parameters was not statistically significant (p > 0.05). Fish body conformation indices positively correlated with the prevalence of parasites in Clarias gariepinus, Heterobranchus longifilis, Parachana africana, Chromidotilapia guntheri guntherii, and Denticeps clupeodes. The overall parasite prevalence of 63.53% was established with the most abundant parasite being Trichodina mutabillis. The parasites had a predilection for the gastrointestinal tract with a high occurrence of 307 individuals. Stations 1, 2, and 3 had 326, 213, and 259 parasites, respectively, out of a total of 798 parasites detected. P. laevis was absent in station 1. All parasites were found in stations 2 and 3. Statistically, there was a significant difference (p < 0.05) in the prevalence in all stations. The correlation index of T. mutabillis and R. congolensis in stations 1 and 3 was positively strong (p < 0.05) with the concentrations of water quality. However, water conditions in stations 1 and 3 had a deleterious impact on P. laevis. T. mutabillis maintained a high positive correlation with physicochemical water quality in all three stations. Shannon-Weiner's index in station 3 (H = 1.337) shows that the parasites were more diverse. PCA and biodiversity indices have enabled us to comprehend how parasite-host-environment systems interact.

Quality assessment of smoked catfishes (Clarias gariepinus, Heterobranchus longifilis and Synodontis clarias) from selected fish markets in Benue State, Nigeria

The quality assessment of smoked catfish from selected fish markets in Benue state was carried out. Clarias gariepinus, Heterobranchus spp. and Synodontis spp. each weighing 500g were collected from Abinsi and Wadata markets. The proximate composition, mineral composition and organoleptic assessment were carried out. Association of Official Analytical Chemists (AOAC) methods were adopted for the determination of proximate and mineral composition while a 9-point Hedonic scale ranging from 1(dislike extremely) to 9(like extremely) was a procedure for organoleptic quality determination. Results for proximate and mineral compositions showed good standard but varied from market to market. Abinsi fish markets showed that Heterobranchus spp. had 10.16%, 12.74%, 58.98%, 16.42%, 1.71%. Clarias gariepinus had 9.09%, 10.10%, 66.11%, 13.94%, 0.76%. Synodontis spp. had 8.19%, 11.07%, 55.80%, 22.68%, and 2.27% as values for moisture content, ash content, protein content, lipid content and carbohydrates content while Wadata fish market Heterobranchus spp. had 10.34%, 11.89%, 59.48%, 15.71%, and 2.59%. Clarias gariepinus had 8.88%, 11.37%, 68.97%, 10.37%, 0.38%. Synodontis spp. had 8.36%, 12.19%, 56.35%, 21.30%, and 1.81% for moisture content, ash content, protein content, lipid content and carbohydrates content respectively. The mineral composition for Abinsi fish showed that Heterobranchus spp. had 240.33 mg/100g, 395.48 mg/100g, 32.44 mg/100g, 0.03 mg/100g, 0.80 mg/100g, 5.37 mg/100g; Clarias gariepinus had 270.30 mg/100g, 278.05 mg/100g, 32.14 mg/100g, 0.21 mg/100g, 0.30 mg/100g, 5.06 mg/100g; Synodontis spp. had 330.05 mg/100g, 257.78 mg/100g, 34.24 mg/100g, 0.24 mg/100g, 0.40 mg/100g, 6.98 mg/100g; for Potassium, Calcium, Sodium, Copper, Zinc and Iron while in Wadata fish market Heterobranchus spp. had 250.30 mg/100g, 127.88 mg/100g, 39.84 mg/100g, 0.39 mg/100g, 0.68 mg/100g, 4.95 mg/100g; Clarias gariepinus had 410.15 mg/100g, 159.33 mg/100g, 33.03 mg/100g, 0.22 mg/100g, 0.60 mg/100g, 5.96 mg/100g; Synodontis spp. had 300.45 mg/100g, 295.48 mg/100g, 33.93 mg/100g, 0.30 mg/100g, 0.71 mg/100g, 12.0 mg/100g; for Potassium, Calcium, Sodium, Copper, Zinc and Iron. The sensory evaluation revealed that taste, appearance, texture and odour were accepted by the panellist and significant difference occurred (P&lt;0.05) among samples from both markets. The three catfish species from this study were found to be rich in protein content, Potassium, Calcium, and Sodium with low presence of Copper, Zinc, Iron, lipid and carbohydrate contents.Keywords: Catfishes; markets; quality assessment; smoked

Effects of Multiple Batches of Stripped Eggs on the Reproductive Performances of Heterobranchus longifilis

Studying the effects of multiple batches of stripped eggs contributes to the sustainability and viability of aquaculture practices by improving our understanding of reproductive performance and informing best practices in breeding programs, hence, the need to investigate on the effects of multiple batches of stripped egg on reproductive performances of Heterobranchus logifilis became necessary. The aim was to provide valuable information for decision-making processes in aquaculture operations. Nine brood stocks of H. longifilis (6 male &amp; 3 female) with average body weight of 2.3 kg and average length of 64.2 cm where carefully selected for the study. Six matured males were sacrificed for the removal of testis without hormonal inducements. The milt collected from the six males were pulled together and divided into twelve portions each diluted with 2ml of normal saline solution. Three female brood stocks where separately induced at single dosage of 0.5ml/kg body weight and allowed for a period of 10 hours before stripping. Stripping of eggs from each brood stock where in four batches, each batch measured 50g and labeled A, B, C &amp; D. 3g of eggs containing approximately 2000 oocytes (eggs) where measured out from each batch and mixed with the diluted milt and incubated in a 2 x 1 x 10cm3 of water in a concrete pond at temperature of 26oC in three replicates. The result revealed that the reproductive performances considered in this study decreased as the batches of stripped eggs increased from 1- 4 batches. The first batch of stripped eggs produced 90.17 ± 0.44%, 97.78±0.86%, 89.48 ±1.08% fertilization, hatchability and survival respectively, while the least batch of stripped eggs (batch 4) produced the least value of fertilization (5.83 ± 1.69%); 45.00±4.90% hatchability and survival value of 5.59 ± 0.61%. Sequel to the findings of the present study, the least batch of stripped eggs should be avoided for use in fertilization since the unhatched or dead eggs has some detrimental effects on the fertilized eggs including fry at the hatchery level.

Morphological Characterisation of Three Populations of Heterobranchus longifilis from Nigeria.

This study attempted to discriminate the population of Heterobranchus longifilis in Nigeria using their morphological characteristics. Therefore, 60 sexually mature wild samples of H. longifilis (1:1 for the male and female ratio) of relatively similar size (40 cm) were collected from three eco-regions namely, Guinea Savanna (Benue River, Makurdi), Rainforest Savanna (Niger River, Onitsha) and Sahel Savanna (Rima River, Sokoto). They were transported to the hatchery unit of the Fisheries and Aquaculture Department, Joseph Sarwan Tarka University Makurdi where the morphometric data was collected. The data for 39 traditional morphometric measurements and 5 meristic counts obtained from each fish were subjected to univariate and multivariate analysis. While significant differences were observed in some parameters following univariate analysis; it was revealed that the morphometric parameters and meristic counts could not separate the fish from the different ecoregions into distinct multivariate spaces or clusters following Principal Component Analysis. Hence, this suggests that morphological parameters cannot be used to discriminate H. longifilis from the different ecoregions. Studies using molecular markers are needed to further characterise the distinctiveness of the different populations.

Overcrowding-Induced Stress in Catfish (Heterobranchus longifilis) Is Associated with Serum Chemistry Derangement

Overcrowding-Induced Stress in Catfish (Heterobranchus longifilis) Is Associated with Serum Chemistry Derangement

Dietary Tryptophan Supplementation Made No Difference on the Cannibalism, Survival and Growth of Heterobranchus longifilis fingerlings

Heterobranchus longifilis is a popular cultured and food fish but its cannibalism greatly reduces harvest thus necessitating proactive control measures. Tryptophan is believed to raise the serotogenic activity in the brain at certain levels leading to reduced aggression and cannibalism in certain species of fish which possibilities this research tried to explore in Heterobranchus longifilis. Fingerlings (0.58 ± 0.123g mean weight and 3. 8 ± 0.52cm mean length) were stocked in 18 round plastic tanks, each 45 litres containing 40 litres of water, at 45 fish per tank. Tryptophan was incorporated at 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 % in commercial Catfish feed by spraying each tryptophan - 70% alcohol solution to separate feed samples to form six different experimental feeds. The dried feeds were fed to the fish daily at 4 % body weight for 8 weeks. The experiment used a complete randomized design with 6 feed treatments and 3 replications. Water quality, growth, mortality and feed utilization data noted and at the end, their associated indices were determined and subjected to the analysis of variance for significant differences (P= 0.05). The results revealed that tryptophan supplementation at the levels used in the diets of Heterobranchus longifilis did not have any significant effects on all the parameters examined excepting mean weight gain. This was discussed in the context of growth and cannibalism.

Monorchidism observed in a two-year-old male broodstock of Heterobranchus longifilis, Red mud catfish: a case report

Ten mature male broodstocks of Heterobranchus longifilis, Red mud catfish were purchased from a reputable farm, Arewa in Zaria for the research. A two-year-old mature male broodstock weighing 0.5kg among the ten mature male broodstocks was discovered to be a monorchid. This was observed when the broodstock was euthanized and a mid-ventral line incision of about 2-3 cm long was made using scalpel blade in order to explore its abdominal cavity for testicular exteriorization. Upon abdominal exploration, only the right testis was present but the right testis was completely absent without remnant. The left testis present was observed to be twisted in the middle along its vertical axis. The morphometric and milt parameters of the right testis present were determined as: testicular length (4.2 cm), testicular weight (1.05 g), milt volume (0.12ml), sperm motility (75%) and sperm concentration (377 x 106/ ml). Keywords: Broodstocks, Exteriorization, Monorchidism, Morphometric and Testis

Predisposing Factors that Promote Prevalence of Heavy Metals Assimilation and Bioaccumulation in Aquatic Medium and amongst Fishes

The degree of heavy metals assimilation and bioaccumulation in fish tissues (muscles, gills, liver, and kidneys), amongst scale-less fishes- Chrysichthys macrotis, Chrysichthys nigrodigitatus, Clarias gariepinus and Heterobranchus longifilis, -scaly fishes- Cynoglossus senegalensis, Oreochromis aureus, O. niloticus, Lutjanus fulgens, Pomadasys rogeri, and Tilapia galilea, water columns and sediments, were investigated. Heavy metals assimilation and bioaccumulation varied among organisms with or without scales, tissue types, and fish location (water column &amp; sediments) and pollution level. Fishes with scales had lower concentrations of heavy metals than scale- less fishes. The scalier the fish, the lower the metal assimilation and bioaccumulation. As expected, trace metals were generally lower in muscles than liver, and kidney. Liver had highest followed by kidney, gills and then muscles. Fish trophic level (water column or sediments) and water pollution levels affected heavy metal concentrations. Concentrations were always more in sediments than water column or tissues. The more polluted the water, the more the assimilation and accumulation of trace metals.

Effects of reproductive hormones on reproductive biology of commonly consumed fish in Akwa Ibom State, Nigeria

Nutritionally proteinous food and feed are required for a balance healthy living. This study was designed to assess the efficacy of some reproductive hormones: human chorionic gonadotropin (HCG), Ovaprim (OVA), extract of carp pituitary (CPE) and deoxy- corticosterone acetate (DOCA) on some aspects of reproductive biology of gravid Heterobranchus longifilis and Clarias gariepinus. A 25 number each of gravid males and females H. longifilis and C. gariepinus were employed in this study. Five experimental set up were designed for the study. Each treatment group was dosed with the required amount of the four reproductive hormones while in the fifth treatment breeders were treated with normal saline. This served as the control experimental. All protocol followed standard procedure. Results showed the highest mean value of relative fecundity (148.177) recorded in H. longifilis treated with ovaprim. This was followed by HCG treated C. gariepinus (145.668). Egg fertility rate had the highest mean value of 61.4803 in C. gariepinus treated with ovaprim, followed by 55.583 mean value in H. longifilis with HCG treatment. Egg hatchability mean value of 70.9280 was the highest observed in H. longifilis with ovaprim treatment. The mean values of survival rate were high in both species with OVA and HCG treatment showing values of 61.86% and 61.00% respectively. Treatment of the species with these reproductive hormones yielded good outcomes, except in the case of DOCA. Thus, CPE, OVA and HCG are recommended for breeding of C. gariepinus and H. longifilis.

Effect of zinc oxide nano-particles on activities of biochemical enzymes in the tissues of Heterobranchus longifilis

The unregulated release of nano-particles into the environment induces toxicity in living organisms by interfering with normal cell processes. This study investigated the toxicity effects of both lethal and sub-lethal concentrations of ZnO-NPs on biochemical enzymes in the tissues of African catfish, Heterobranchus longifilis, by exposing to lethal concentrations (0.00, 60.00, 80.00, 100.00 and 120 mg/l) and sub-lethal concentrations (0.00, 6.00, 8.00, 10.00 and 12.00 mg/l) of ZnO-NPs for 96 h and 45 d in static renewal bioassays with continuous aeration respectively. After the exposure periods, blood was collected through the caudal fin of the fish from control and exposure groups and sacrificed to remove the gills and liver for biochemical assay. The results revealed a significant (P&lt;0.05) increase in the activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), acetyl cholinesterase (AChE), and the levels of total protein and glucose also increased significantly (P&lt;0.05) in the blood, gills and liver with increase in the concentrations and exposure periods compared to the control. The alterations in the biochemical enzymes of the fish indicated that the release of ZnO-NPs into aquatic environment could be dangerous and may cause health risk in man through food chain.

Comparative effect of inducing broodstock with natural and artificial hormones on reproductive performances of Heterobranchus longifilis

This study was conducted to assess the effects of ovaprim and pituitary extract on the reproductive performances of Heterobranchus longifilis (African catfish). A total of twenty broodstock, 12 males and 8 females with mean weight of 2 kg each were selected for breeding following the external morphological characteristics and standard breeding procedure. The water parameters for indoor culture tanks during the study were optimal for breeding: dissolved oxygen – 5.18 mg L-1 ; pH 7.31; temperature, 27.6 ˚C. The result revealed no significant (P &gt; 0.05) differences in water quality parameters between the culture tanks for artificial and natural hormonal applications in this study. The percentage fertilization, hatchability, survival and fry production success were: 84.25 %, 92. 31 %, 88.14 % and 68.42 %; and 75.17 %, 69.57 %, 64.33 % and 33.66 %, respectively, for pituitary extract and Ovaprim®. Pituitary extract recorded higher values and significantly performed better (P &lt; 0.05) between the two treatments. This indicates that the use of natural pituitary extract is equally as effective as the use of the artificial hormone Ovaprim® for the artificial propagation of Heterobranchus longifilis. It is therefore recommended.

Hybridization and Growth Performance of Progeny from Crosses between Clarias gariepinus and Heterobranchus sp.

Mixed hybridisation trials involving Clarias gariepinus (CG), Heterobranchus longifilis (HL), and Heterobranchus bidorsalis (HB) were carried out with success using Ovulin as inducing agent. The crossing was followed by an early growth trial using post-yolk sac larvae that lasted ten days. Latency periods in the two catfishes differ, with 11 hours in crosses involving female CG and 12 hours in crosses involving female HL. The fertilisation rates of eggs from the females of the two species indicate that there is no significant discernment in fertilisation (p&gt;0.05), with values ranging from 68.38% (CG×HB) to 80.94% (HL×CG). However, rates &lt;80% indicate egg quality problems. The hatching rate was significantly higher (p&lt;0.05) in both C. gariepinus (62.12%) and Heterobranchus sp. (47.75%) line crosses than the hybrids. There is an additive genetic effect due to the combination of pure-line male and female gametes that elicit better growth as against survival in crosses involving C. gariepinus. The genotype for better survival is in the maternal line of H. longifilis. These culminate into heterosis for growth in hybrid CG×HB and survival in hybrid HL×CG.

Study of the Substitution of Marine Animal Oils in Maggot Flour by Vegetable Oils for the Growth and Larval Survival of African Catfish, Heterobranchus longifilis Valencienne, 1840 in Aquarium

This study showed clearly the effect of adding palm oil to the diet of farmed fish to replace marine animal oils. For this purpose, four foods based on maggot flour at 35% protein with the incorporation of palm oil, at different levels at 0, 2, 5 and 10% were tested in the to assess their impact on the improved growth performance, food utilization, survival rate and biochemical composition of Heterobranchus longifilis larvae&#x0D; Four experimental diets were formulated based on the maggot meal as the main protein source. These diets were formulated at 35 % protein levels with maggot meal and maize flour as the major ingredients containing different concentrations of palm oil levels at 0, 2, 5, and 10 %. This study was carried out in the reproduction laboratory, at Oceanological Research Center, Abidjan, Côte d’Ivoire, between the periods of September to November 2022.&#x0D; The diets were offered to the larvae (average initial weight 0.004 ± 0.001 g) three times a day ad libitum for 49 days. At the end of rearing, the results showed that the different experimental foods distributed did not influence the quality of the rearing environment.&#x0D; The best growth was obtained with the larvae subjected to diet containing 2% palm oil with a final average weight of 3.21 g and a conversion index of 1.63. Beyond this rate, larval growth decreases. Survival rates vary from 70 to 73 %. The conversion ratios are not significantly different and ranged between 1.63 and 2.3. On the biochemical larvae submitted to diet containing 10 % of palm oil had body lipid content (2 %) and high ash rich. As against a gain of protein is observed with larvae submitted to diets containing 2 % palm oil reflects an effect of protein. &#x0D; From the present results, diet containing 2 % crude palm oil is considered optimal for Heterobranchus longifilis larvae.

Determination of Asymptotic Growth in Progenies of Crosses Between Clarias gariepinus and Heterobranchus longifilis and Attenuation of Intra-cohort Cannibalism

Using weight as a measure of size in cannibalistic species can be misleading. This research determined the growth pattern, cannibalism and heterosis of crosses between two African catfishes Clarias gariepinus (Cl) and Heterobranchus longifilis (Ht). Fry were reared communally for Cl×Cl, Cl×Ht, Ht×Cl and Ht×Ht for 14 days before triplicates of 100 fry were randomly stocked in concrete ponds. The length of the samples was taken weekly, and growth shooters were sorted out using the criteria of cut-off length earlier proposed by the authors. The Gompertz model successfully converged for the growth modelling of three crosses: Cl×Cl, Cl×Ht and Ht×Cl with asymptotic values of 40.44 mm, 59.42 mm, 57.27 mm. In contrast, the cross HtxHt converged using the monomolecular growth model with an asymptotic length of 72.09 mm. Type I and type II cannibalism were observed with a greater influence of H. longifilis. Absolute growth rate (AGR) was highest in Ht×Cl (1.52 mm.day-1) progeny and lowest in Ht×Ht (1.02 mm.day-1). There was positive heterosis for length and AGR with negative heterosis for survival (–8.93%) and sorting (–1.86%). There was positive heterosis for cannibalism. The study revealed the maximum length attainable for offspring of these crosses and sorting effectiveness/criteria.

Model experiment for practical application of inseminated sperm method for production of interspecific hybrids (Clarias gariepinus × Heterobranchus longifilis)

In this study, the inseminated sperm method (sperm injection into the ovarian lobe in externally fertilised fish species) combined with hormonal induction was conducted as a novel method to produce hybrid catfish by induced/tank spawning. In the treated group, four Clarias gariepinus ♀ were inseminated equally with Heterobranchus longifilis sperm in the ovaries at a dosage of 1 mL/fish and then introduced into four spawning cages together with four C. gariepinus ♂. Ovulation was induced by extracted carp pituitary (CPE) hormonal administration (♀; 5 mg CPE/BW kg). The hybridization rate was determined on the basis of morphological markers to distinguish between pure African catfish and hybrid in juvenile stage. A control experiment was also designed to determine this and to explore possible interactions between the two genotypes. In the control group, in vitro fertilisation (IVF) was used to produce pure progeny of C. gariepinus and the hybrid progeny between C. gariepinus ♀ × H. longifilis ♂. Exogenously fed larvae from each treatment were raised and compared after 28 days in four replications; the mixed group contained 50 C. gariepinus and 50 hybrids from IVF grown together, while every 100 larvae from each cage spawning pair were grown separately. The hybridisation rate determined based on morphological traits was 98.11 ± 1.59 (mean ± S.D.) for 28-day-old reared offspring. There were no significant differences (P > 0.05) in survival rate (%) between C. gariepinus (45.79 ± 6.82 %) and the hybrid (54.21 ± 6.82 %) in the control treatment; therefore, neither genotype had a negative effect on the other during the rearing period. From this result, we supposed that the hybridisation rate was also over 95 % at the moment of fertilisation. This approach could be an alternative method for producing hybrid catfish or other fish species without in vitro fertilisation.