First report on the successful hybridization of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

Salinity tolerance in Clarias gariepinus (Burchell, 1822): insight on blood parameter variations and gill histological changes

This study was designed to evaluate the tolerance of Clarias gariepinus juveniles to a gradual and abrupt increase in salinity over time. To this effect, C. gariepinus juveniles were exposed to three salinity incremental protocols namely 1 g L-1 day-1, 5 g L-1 day-1, and 10 g L-1 day-1. Changes in the hematological parameters and the gill histology of fish were analyzed to determine the impact of osmotic stress on the health status of the fish and its osmoregulatory ability. The result obtained showed that juveniles of C. gariepinus can tolerate salinity stress up to 14 g L-1. At 15 g L-1 and beyond, all samples died regardless of gradual (i.e., 1 g L-1 day-1 administered for 15 days) or abrupt salinity exposure (i.e., 5 g L-1 day-1 administered for three days and 10 g L-1 day-1 administered for two days). Interestingly, more than 90% of the fish survived a direct 10 g L-1 exposure for 24 h without prior acclimation. The hematological parameters accessed in the fish exposed to 10 g L-1 (either gradually or abruptly) showed a significant increase in the white blood cells and a decrease in the red blood cells, packed cell volume, hemoglobin concentration, and all derived blood parameters. The results of the serum biochemistry show a lower total protein and albumin in the salinity-treated fish compared to the control group. However, the serum glucose and the plasma electrolytes (i.e., K+, Na+, and Cl-) were higher in the former group than in the latter. Aside from the stress response expressed in the blood parameters, severe gill degenerations were seen in the histological micrograph obtained for the salinity-treated fish, while the control had a near-normal gill architecture. It was concluded that C. gariepinus could tolerate salinity exposure of 10 g L-1 day-1 (administered gradually or abruptly) and below without killing the fish within 24 h.

Ovarian lavage method as an alternative route for hormonal administration and short-term sperm storage in Clarias gariepinus

Ovarian lavage is a term used to describe the injection of fish with a catheter through the oviduct into the ovary. In this study, the efficacy of this technique was evaluated as a route for hormone administration and sperm preservation in the African catfish Clarias gariepinus. Firstly, the effects of hormone injection routes (namely, intramuscular, intraperitoneal, and ovarian lavage) were evaluated on breeding and haematological parameters. In the second study, the fish's spermatozoa were stored in the ovaries for 1, 2, 3, and 4 days before stripping, sperm activation with freshwater, and fertilization. The breeding performance was then compared with eggs fertilized using spermatozoa refrigerated for the same duration. The study showed that the administration of synthetic hormone (ovaprim®) through the ovaries was comparable to the intramuscular route, while those injected intraperitoneally had the least values (P < 0.05) for breeding performance. The trend of the haematological parameters also suggests the intraperitoneal administration procedure elicited more stress compared to intramuscular or ovarian lavage routes (P < 0.05). In the second experiment, the use of sperm stored in the ovaries or refrigerated for 24hr didn't affect (P > 0.05) the fertilization (92-93%) and hatching (81-83%) of the eggs when compared to the control (91% and 82%). Beyond this 24hr threshold, breeding performances were significantly reduced in the ovarian lavage treatments compared to those fertilized with refrigerated sperm (P < 0.05). The loss of fertilizing capacity observed herein was justified by the reduction in sperm quality over time (P < 0.05). It was concluded that ovarian lavage is a viable route for hormonal administration and 24hr sperm storage in C. gariepinus.

Effects of GnRHa and hCG with or without dopamine receptor antagonists on the spawning efficiency of African catfish (Clarias gariepinus) reared in hatchery conditions

Optimization of artificial reproduction is essential for minimizing genetic diversity, especially when fish are captured from their natural habitats and spawned in controlled conditions. In the present study, there was evaluation of the effects of gonadotropin-releasing hormone analogue (GnRHa) and human chorionic gonadotropin (hCG) with or without dopamine receptor antagonists such as domperidone (DOM) and metoclopramide (MET) on the spawning efficiency of African catfish (Clarias gariepinus) reared in captivity. The control group was intramuscularly (IM) injected with 1 mL of sterile saline solution. The fish specimens of the other six groups were injected IM with GnRHa or hCG, or in combination with either DOM or MET. None of the specimens had ovulations in the control group. There was the longest latency period in specimens treated with only GnRHa or hCG. There were the largest egg mass weight, fecundity, and hatchability (%) in specimens of the GnRHa + MET group. These findings indicate that GnRHa or hCG combined with dopamine receptor antagonists such as DOM and MET resulted in a marked enhancement of ovulation rate and increased the egg mass, fecundity, and hatchability of the treated C. gariepinus, and the values when there was inclusion of the MET treatment exceeded those when there was treatment with DOM.

Breeding performance and embryogenic development of three strains of Heterobranchus longifilis in Nigeria

The study sought to investigate the chronology of events and timing of embryogenesis, as well as breeding performances of three strains of Heterobranchus longifilis from Nigeria. Fish samples were collected from Benue River in Makurdi, Niger River in Onitsha, and Rima River in Sokoto for this study. Induced spawning of the strains was carried out so that egg development could be tracked from fertilization to hatching using a simple microscope. The microphotographs obtained showed that the embryogenesis of the strains followed a similar pattern to those of other members of the family Clariidae, however with changes occurring in the specific timing of the sequences of events (i.e. interstrain and interspecies differences). When the different strains were compared, the study noted similarities (P > 0.05) in the overall breeding performance (except for fertilization rate), survival at different stages of development, timing of embryogenesis, and larvae characteristics. The outcomes of this study, therefore, provide baseline information on what genetic improvement of the species through strain crossing can be attempted in future studies.

Dataset for the morphological and erythrocytes parameters of Clarias gariepinus, Pangasianodon hypophthalmus, and their reciprocal hybrids

Discrimination of different fishes can be done through different means which includes morphological appearance. When two fishes are successfully hybridized, they produce progenies that have shared morphology between their pure parent, hence, making morphometric characterization an important aspect of hybrid discrimination. However, erythrocyte characterization is also a simpler method for characterization. The dataset presented in this article represents the traditional morphological data, truss network data and erythrocyte data of pure and novel hybrids from reciprocal crosses of African catfish Clarias gariepinus and Asian catfish Pangasianodon hypophthalmus. Breeding of the broodstocks was done to produce pure and hybrid progenies which were maintained for a period of four to six months. Based on the cross combinations and morphotypes, traditional measurement of twenty-five morphological characters and five meristic counts were recorded. Thereafter pictures of the different fish groups were used to determine values of thirty-six distances between ten landmark points. The morphological abnormality of the hybrids at market size is also presented in this data article for the very first time. Blood was then collected from the caudal peduncle of ten fish per group and smeared on a slide for observation under a compound microscope (at 100 × magnification). Data gotten included erythrocytes parameters such as cell major axis, cell minor axis, nucleus major axis, nucleus minor axis cell area, nucleus area, cell volume, and nucleus volume. Data recording was through the Microsoft excel spreadsheet; which was also used to process the data to get the exclusive ranges of values for paired progenies. The data as presented is associated with the research article “Morphological characterization of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)” [1]. The dataset presented in this article can be used for easy identification of the novel hybrid progenies of the African Catfish and Asian Catfish.

Aquaponics production of catfish and pumpkin: Comparison with conventional production systems

Aquaponics is known to be a smart way of producing fish and crops simultaneously; however, there is a paucity of information about the extents of this system's efficiency over other conventional methods of food production. Thus, this study was designed to evaluate the performance of a catfish-pumpkin aquaponics system in comparison with recirculatory and static aquaculture systems (for fish performance), as well as irrigated and nonirrigated systems (for pumpkin performance). Results obtained showed that the production of fish in the aquaponics system was 29% and 75% more efficient than recirculatory and static aquaculture systems, respectively. The survival of the fish was also significantly improved probably due to better water quality in the aquaponics system. With respect to pumpkin production, yield in the aquaponics system was about five times the performance in irrigated land and eleven times those in nonirrigated land. This study gives definitive evidence to support the efficiency of the aquaponics system over other conventional food production methods.

Optimization of artificial insemination outcomes of African catfish (Clarias gariepinus) with differing hatchery conditions

The African catfish is one of the most promising warm-freshwater species for aquaculture development in the upcoming years, although there are two primary limitations in its production: less-than-desirable survival rates and low larvae quality. In this study, a novel method of egg fertilization for this species was evaluated which has already been successfully utilized in the production of other finfish. The results indicate that dividing the semen designated for fertilization of eggs into smaller aliquots and adding it to the eggs at 30 s intervals (i.e., 0, 30 and 60 s), after activation of the eggs with water, increased the hatching rate percentage (97.1%) compared to control groups (87.9%) in which the entire portion of semen was added to eggs at the time of water addition for egg activation. Results with repeated evaluations in the field confirmed that eggs with greater biological quality were fertilized at a similar rate using the modified and control methods for fertilization, although when the eggs were of a lesser biological quality, the fertilization rate was greater using the modified methods than the control methods.

Morphological characterization of the progenies of pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822)

Twenty-five traditional and thirty-four geometric morphometric comparisons were carried out on pure and reciprocal crosses of Pangasianodon hypophthalmus (Sauvage, 1878) and Clarias gariepinus (Burchell, 1822). Thirty fish samples each of the C. gariepinus (CH), P. hypophthalmus (PH), Pangapinus (♀PH × ♂CG) and the two distinct morphotypes of the Clariothalmus (♀CG × ♂PH) (Clarias-like and Panga-like) between the ages of four and six months were used for this study. Phenotypically, the Clarias-like Clariothalmus and the Pangapinus progenies were indistinguishable from their maternal parents while the Panga-like Clariothalmus was a phenotypic intermediary of the putative parents but looks more closely to the paternal parent. Hence, both univariate proportion and multivariate analysis of the collected data successfully separated the different fishes into three multivariate spaces. The analysis of the dendrogram with complete linkage and Euclidean distance further showed the close relationship of the isolated Panga-like Clariothalmus progenies to the paternal parent, however, Clarias-like Clariothalmus and the Pangapinus were completely intermingled with their maternal parents. The most important index of discrimination of these fishes into different multivariate spaces was the fin characteristic which showed 100% exclusive ranges for the individual groups in many cases.