Effect of Different Doses of 17 Α -Methyltestosterone on Masculinization, Pre-Post Treatment Growth Parameters and Condition Factor of Sarotherodon Melanotheron in Pond System

Over-population and stunted growth had been major challenges in the culture of tilapia. The use of synthetic androgen 17- α Methyl Testosterone (MT) was a breakthrough. However, its optimum level towards effective masculinization and growth is a concern. The aim of this research was to ascertain the optimum level of MT towards effective all-male population production and growth of Black-Chinned tilapia. In the present study, the effect of different dose rates of synthetic androgen 17-α Methyl Testosterone (MT) i.e., 0, 30, 60, and 120 mg of the hormone per kg of feed on sex, growth, and condition of Black-Chinned tilapia was evaluated. MT was administered orally by using powdered dry starter feed (Crude Protein 40 %) and Ethanol. The fry was fed for 30 days in the experimental tanks. At the end of the experiment, the sex ratios were determined by examining the operculum coloration as a means of sex identification. Growth performance was monitored by measuring and recording the morphometric characteristics. Bodyweight and total length of the fish on the start of feeding, end of feeding (one month sex reversal period), and two months after feeding were measured. The results of the present study showed that all MT receiving treatment showed a significantly higher male proportion than the control (0 mg MT/kg feed individuals). In all MT treatments groups, the control expects the 30 mg MT/kg in feed individuals’ deviate significantly from the normal 1:1 sex ratio (Chi-square analysis). The dose rate of 120 mg MT /kg feed resulted in the maximum male population (92.7%). Hence, for an effective high percentage of all-male population production in Black-Chinned tilapia, 120 mg MT /kg in feed is recommended. In terms of growth and condition factor, all the individual treatments, as well as the control, showed no significant difference. All the treated individuals showed similar condition factors during the pre and post-treatment, however, the individuals treated with 30 mg MT /kg feed exhibited better condition during the pre-treatment than the post-treatment period. Temperature, pH and dissolved oxygen recorded in this study were within the desirable limit for tilapia.

Hazard Analysis of Trace Metals in Muscle of Sarotherodon Melanotheron and Chrysichthys Nigrodigitatus from Okulu River, Rivers State, Nigeria

Introduction: An instance of fish deaths in marine waters surrounding some communities in Bonny and Andoni Local Government Areas in Rivers State was reported in March-April 2020. This study investigated trace metals hazard in muscle of Tilapia (Sarotherodon melanotheron) and Silver Catfish (Chrysichthys nigrodigitatus) from Okulu River, Rivers State, Nigeria. Materials and Methods: Tissues of 24 samples of Sarotherodon melanotheron and Chrysichthys nigrodigitatus obtained from the river were analyzed using atomic adsorption spectrophotometer, and the health risk was estimated based on estimated daily intake (EDI), target hazard quotient (THQ), and total target hazard quotient (TTHQ). Results: The concentration (mg/kg) of iron, zinc, manganese, copper, cadmium, lead, and chromium in both species ranged 4.00 – 197.30, 9.20 – 35.30, 0.20 – 5.00, 0.00 – 73.10, 0.00 – 1.30, 0.00 – 54.70, and 0.00 – 0.50, respectively. The EDI of trace metals resulting from the consumption of both fish species was higher than the permissible tolerance intake (PTI) mg/day/60kg body weight. The THQ and TTHQ were < 1, indicating that the consumption of this food fish portends no known health concern. However, the carcinogenic risks exceeded the threshold level of 10-6 - 10-4, thus, reflecting carcinogenic tendency. Based on the results obtained, it must be ensured that the effluents discharged into open water bodies meet the recommended limits. Conclusion: There is a need to create awareness among consumers of food fish in the study area. There should be periodic monitoring of trace metals in surface waters and its food fish population to forestall potential health impact on humans.

Molecular Identification of an Invasive Sarotherodon Species from the Atchakpa Freshwater Reservoir (Ouémé River Basin, Benin) and Comparison within S. melanotheron Using COI Markers

The Atchakpa freshwater reservoir (Ouémé Basin, Benin) was found to harbour an unexpected population of a cichlid species that was presumed to be Sarotherodon melanotheron. This species became dominant in the reservoir and became the main fisheries target species. We applied DNA barcoding to identify this population. Besides specimens from the reservoir, we also sequenced S. melanotheron from its native range in Benin at the lower Ouémé and Sô Rivers, and from Lake Nokoué, and Porto-Novo Lagoon. High sequence similarity indicated that all specimens were conspecific. Hence, we cannot exclude that a natural range extension led to the presence of the species in the reservoir. A comparison with sequences from NCBI GenBank confirmed that all samples belonged to the subspecies S. m. melanotheron, which is native to Benin. This comparison also showed that this subspecies was previously introduced in the Philippines. We call for further studies to investigate the socioeconomic, ecological and environmental impacts of the species in the Atchakpa reservoir.

Length-weight Relationship and Condition Factor of Cichlids in Eniong and Lower Cross Rivers, Niger Delta, Nigeria

Length-weight relationship and condition factor are essential parameters used in determination of growth and well-being of fish. The length-weight relationship and condition factor of eight species of cichlids were examined from a total of 358 cichlids belonging to fourteen species and seven genera. Sampling was between January and June, 2020 in Eniong River and lower Cross River in the Niger Delta from three stations: station one in Eniong river, station two at the confluence of Eniong and lower Cross River, and station three at the lower Cross River. The length and weight of each fish was measured to the nearest millimeter and gram, respectively. The length-weight relationship (LWR) and condition factor (K) of the species Coptodon dageti, Coptodon guineensis, Coptodon zilli, Chromidotilapia guntheri, Hemichromis elongatus, Oreochromis niloticus, Pelmatolapia mariae and Sarotherodon melanotheron were determined using standard methods. Total length of fish ranged from 12.9 ± 5.01 in H. elongatus to 20.7 ± 3.37cm in C. zilli. Total weight ranged from 24.8 ± 13.80 in H. elongatus to 146.4 ± 68.0 g in C. zilli. The exponent b ranged from 1.54 for H. elongatus to 3.34 in Pelmatolapia mariae. The coefficients of determination (r2) varied between H. elongatus (0.74) and O. niloticus (0.96). Fulton’s condition factor (K) ranged from 1.2 6 ± 0.50 (H. elongatus) to 1.89 ± 0.43 (O. niloticus). Length-weight relationship revealed negative allometry for six species and positive allometry for two species (O. niloticus and P. mariae). Cichlids in this study were observed to be in good condition, as the K values were greater than one.

Evaluation of Mustard Seed (Brassica Nigra) Powder as Anaesthetic Agents in Different Life Stages of Black Jaw Tilapia (Sarotherodon Melanotheron)

This study assessed the anesthetic effects of mustard seed (Brassica nigra) powder in different life stages of Black Jaw Tilapia (Sarotherodon melanotheron). A total of 540 fish comprising of 180 each of: fingerlings (mean length 5.54cm ± 1.08SD and mean weight 12.04g ± 2.09SD); juveniles (mean length 10.02cm ± 3.91SD and mean weight 30.91g ± 4.02SD) and adult (mean length 13.01cm ± 2.66SD and mean weight 70.82g ± 7.01SD) of S. melanotheron were used for the study. They were exposed to aqueous extracts of mustard seed (Brassica nigra) powder at different concentrations: 0.00-control; 10.00; 20.00; 30.00; 40.00 and 50.00 mg/L at the rate of 10 fish per tank in triplicates. The results obtained indicated a size related response of the fish to mustard seed extracts. The induction time decreased significantly (P < 0.05) as the concentrations of the mustard seed extracts increased. The recovery time in the three sizes of exposed fish, generally increased as the concentrations of the anaesthetics increased. The survival rate was 100.00% in adult sizes of the exposed fish in all concentrations. While in fingerlings and juveniles, 90-95% survival rates were recorded at higher concentrations of the anaesthetics. This study therefore revealed that mustard seed can effectively be used as anaesthetics agent in S. melanotheron at optimum dose of 30mg/L.