Studies on fecundity and spawning of blue crab (Callinectes Amnicola) in Cross River Estuary

Studies on identification of species, fecundity and development stages of blue crab, (Callinectes amnicola) were investigated at the Cross River Estuary between the months of December, 2018 and May, 2019. The parameters used for the study were gonadosomatic and hepatosomatic indices, egg diameter and counts. All measurements followed standard procedures. Gonadosomatic index was at its peak in December (88.9) and April (83.3). This coincided with the peak in egg size suggesting that spawning occurred twice within the period.The low values of hepatosomatic index around December (1.20) and April (0.45) added to confirm the spawning in these months. The species spawns at a mean egg size of 17.55mm. The dimension of crabs examined were in the following range: carapace length 40.0 to 70.0mm, carapace width, 5.0 to 60mm and body weight 40.0 to 140.0g. The relationship between fecundity and weight of crab was significant (r = 0.295: p<0.05), indicating positive correlation. Absolute fecundity of the species ranged between 1,375 and 225,132 eggs. The smallest crab with egg had a carapace width of 39.5mm and weight of 46.9g. Spawning at this size seems to be a strategy adopted by the species to cope with exploitation pressure. The result of this study revealed that C. amnicola had a high reproductive potentials. Hence, adequate regulation is required to enhance sustainability of the species in the Cross River Estuary.

Effects of seasonal variation and locations on microbial load in sediment and water of a polluted ecosystem

Seasonal effects on microbial load of sediment and water at different locations along Bonny Estuary of Niger Delta was investigated for a period of 12 months. All analyses followed standard procedure. Results revealed that total fungi counts in sediment and water at different locations were not significantly different (p > 0.05) at both wet and dry seasons while hydrocarbon utilizing fungi showed significant differences (p < 0.05) at both seasons in both sediment and water samples. During the wet season, total faecal counts ranged from 5.0 to 10.0 x 105 CFU/g for sediment and 4.0 to 7.0x 105 CFU/g in water. In dry season, the concentration of hydrocarbon utilizing bacteria in the sediment ranged between 0.1 x 105 CFU/ml/g and 8.0 x 105 CFU/ml/g in wet season while in dry season, the concentration in water ranged between 0.1 x 105 CFU/ml/g and 6.0 x 105 CFU/ml/g at Abuloma. At Okwujagu, total heterotrophic bacteria counts in sediment ranged from 0.1 to 8.0 x 105 CFU/g in dry season. This was higher than the range 0.1 to 6.8.0 x 105 CFU/ recorded in Abuloma, Okwujagu and Slaughter at dry season. The highest vibrio counts in water (11.0 x 105 CFU/ml) for wet and (10.0 x 105 CFU/ml) for dry seasons were recorded at Slaughter. In Oginiba, the feacal count recorded 3.0 x 105 CFU/ml in water during the wet season and 2.0 x 105 CFU/ml for dry season. Generally, there were significant differences (p < 0.05) in the bacterial concentrations in both sediment and water. This showed that different seasons favour the growth of certain microbial types.

Impacts of population growth in relation to changes in aquaculture and fisheries prices

The paper reviewed the impacts of population growth and the ways it affects aquaculture and fisheries prices. As the world population continues to grow arithmetically, great pressure is placed on arable lands, water, energy, and biological resources to provide an adequate supply of food while maintaining the integrity of the ecosystem. In 2010, FAO projected the world population to double from 6.2 billion in October, 1999 to 12.5 billion in the year 2050. This had created serious negative impacts on the aquaculture and fisheries prices. At present fertile crop lands had been lost at an alarming rates while some abandoned during the past 50 years because erosions made it unproductive. Other vices such as food crisis, political unrest and war (Mexico, Uzbekistan, Turkistan, Yemen, Iraq, Afghanistan, Syria, Morocco and Sudan), civil strife and multiple years of draught (Niger, Mauritania and Senegal), impacts of HIV/AIDS Ebola, Lassa fever and Coronavirus the world over, clashes between cattle rearers and farmers and boko haram issues (Nigeria) as well as kidnapping and corruptions have severely affected aquaculture and fisheries production and accompanied prices. Thus, this review was conducted to raise a cry for farmers and citizens to engage and participate in intensive culture and fisheries practices in order to fill the demand - supply gap so as to make fish food products available for the teeming masses.

Ecotoxicological assessment of commercial glyphosate-based di-ammonium salt formulation on haematological indices of Clarias gariepinus

The study evaluated sub-lethal toxicity of commercial glyphosate-based Di-ammonium formulation commonly known as ‘Touchdown’ on haematological profile of Clarias gariepinus juveniles. A total of two hundred catfish juveniles of mean weight 31.07±1.23g and mean length 19.50 ± 0.50cm were exposed to different concentrations of Di-ammonium formulation (1.26, 2.52, 5.03 and 0.00 mg/l) for eight (8) weeks. Each concentration was treated in triplicate using a static bioassay system. Physico-chemical parameters of the test water were monitored throughout the study period. Results showed that haematocrit (HCT), red blood cell (RBC), haemoglobin (HGB), Mean Corpuscular Volume (MCV), Mean Corpuscular Haemoglobin (MCH), Mean Corpuscular Haemoglobin Concentration (MCHC) and Platelets (PLT) counts decreased significantly (p<0.05) with increase in concentrations of Touchdown. Whereas, white blood cell (WBC) counts increased significantly (p<0.05) with increasing concentrations of the glyphosate-based formulation. Water temperature, pH, Total dissolved solid (TDS) and electrical conductivity (EC) increased linearly with increasing concentration, while dissolved oxygen content decreased significantly (p<0.05). The results from this study indicated that Di-ammonium glyphosate–based formulation had negative consequences on the blood of treated fish. In view of this, the application of Di-ammonium glyphosate-based formulation should be done in a sustainable manner with proper regulations.

Toxicity of glyphosate-based isopropylamine salt and polyethoxylated tallow amine formulations on juvenile Clarias gariepinus

The formulation of glyphosate composed of Isopropylamine salt and Polyethoxylated tallow Amine (Clearweed) is widely used as herbicide to control weeds both in the terrestrial and aquatic environments. A static bioassay was conducted to examine toxicity of this formulation on juvenile African catfish (Clarias gariepinus). Catfish juvenile (mean weight 27.97±0.03g) were exposed to glyphosate at concentrations of 0.00mg/l (control), 5.00, 7.50, 10.00, 12.50 and 15.00mg/l. Each concentration was treated in triplicate and the exposure period lasted for 96 hrs. Mortality rates and physico-chemical parameters of water were monitored. Results revealed that fish mortality increased with increasing concentration of glyphosate and time of exposure. The median lethal concentration (96-hr LC50) value was 8.88mg/l with the upper and lower limits of 9.10mg/l and 7.75mg/l respectively. Behavioural changes observed the treated fish included: erratic swimming, jerky movement, increased opercula and tail movements, gulping of air, lost of balance and consciousness, cessation of opercula and tail movement signifying eventual death. Water quality parameters increased significantly (p<0.05) with extract concentration except dissolve oxygen levels which reduced (p<0.05). However, all values reported were within the permissible limits of the Federal Ministry of Environment (FMEnv) for water samples. The results of this study indicated that glyphosate formulation has toxic effects on catfish. Thus, the herbicide should be cautiously used to avoid ecotoxicological hazards particularly on non-target organisms.

Substitution of fishmeal with solid-state fermented pigeon pea and effects on growth and gut microbiomes of Nile Tilapia

Solid state fermented pigeon pea meal (FPP) was used in substituting fish meal (FM) in diets of Oreochromis niloticus. Five diets varying in inclusion levels of FM: FPP as followed: Feed 1, 250:50; Feed 2, 200:100; Feed 3, 150:150; Feed 4, 100:200 and Feed 5, 50:250 were made. A commercial feed (Feed 6), was used as a control. Triplicate groups of tilapia fingerling were stocked in plastic aquaria at six fish per unit and fed ad libitum for 60days. Results showed that specific growth rate (SGR) of tilapia fed Feed 5 (2.60±0.12% day-1) was better (p<0.05) than those recorded in Feed 1 (2.36±.07 % day-1). Similarly, food conversion ratio (FCR) (1.13±0.01) and mean weight gain (60.00±0.04g) were higher (p<0.05) in Feed 5 when compared with those in Feed 1 where FCR was 1.19±0.02 and MWG (50.96±0.04g). The results of Aspartate amino transferase (AST) and alanine amino transferase (ALT) decreased with increasing inclusion level of FPP. Gut microbial load increased with increasing level of FPP. The fish group fed Feed 5 had the highest foregut (2.60 x 10-5 CFU/ml), midgut (3.98 x 10-5 CFU/ml) and hindgut (4.52 x 10-5 CFU/ml) micrbiota. In general, gut microbiomes were dominated by cellulose and carbohydrate utilizing bacteria: Citrobacter fruendi, Bacillus subtilis and Staphylococcus aureus. Inference from the study revealed that O. niloticus was able to utilize the diets due to the presence of probiotics in them.

Economic realities and management systems in aquaculture production

This study reviewed and unveiled the economic sizes and managing systems in aquaculture production. The focus had been on developing new technologies and management systems in aquaculture production that can produce fish food on an economically competitive basis while still maintaining environmental health. The technique of recirculating aquaculture system (RAS) had been discussed. Economic issues such as: adequately available quality water, economic sizes, management issues, financial capabilities, various investment options, species selection, cost of production, capitalization cost of unit process, cost of pumping and bio-filtration, gas stripping and pH control, solid wastes removal, economically competitive scale, labor requirements as wellas predicted cost of production. The economic comparison of broilers and catfish production were evaluated. Also, challenges against the effective aquaculture technological application and the prospects to economic realities and management systems in aquaculture production were also highlighted. It could be concluded that economic realities and management of RAS is the soft and live wire in aquacultural development especially in developing countries like Nigeria. It is therefore, recommended that fish farmers need to engage and be trained on the use of this new fish production technology for increase production and economy benefits.

Assessment of water chemistry in a segment of Qua Iboe River Estuary by Principal component analysis

Assessment of water chemistry in a segment of Qua Iboe River Estuary, Niger Delta Region of Nigeria was carried out from January to December 2018 at three sampling stations. Seventeen physico-chemical parameters were analyzed using standards procedure. A total of 12 samples were collected from each station. Principal Component Analysis (PCA) was employed in the assessment of the study area. Three principal components, accounting for 99.59%, 100.01% and 100% of the total variance of information contained in the original data set for dry season were obtained. In the wet season, the components accounted for 66.0%, 69.97% and 67.50% of the total variance respectively. Results revealed that the most loading factor in the PCA when considering all the sampling stations in different seasons together in PC1, PC2 and PC3 axes were mainly sulphate, phosphate-phosphorus, calcium, potassium, temperature, total dissolved solids, total alkalinity, total hardness, dissolved oxygen, sodium, electrical conductivity, biological oxygen demand, pH, total suspended solids, A and magnesium. These loadings could be grouped into mineral/nutrient, physico-chemical, organic and domestic factors. General assessment of the study area did not indicate much deviation from prescribed standards, but sufficient to maintain a varied aquatic biodiversity.

SARS-COV-2 invasion in lakes: A rare transferability of the dreaded virus by nature or manmade

SARS-CoV-2 is a highly transmissible and pathogenic viral infection. Its global spread has a profound effect on the lives of millions of people resulting to worldwide economic disruptions and increased death tolls. This has created fears and concerns within the health sector globally. Thus, understanding the mode of transmissions, aetiology, pathogenesis, environmental conditions and epidemiology of SARS-CoV-2 will help in curbing and militating against further spread of the virus. It has also become imperative to look out for petty openings through which this virus may invade man's territories by nature or man-made via negligence. There is need for regular water treatment to prevent further spread that may undoubtedly predispose humans to COVID-19 in the long run as lakes often serve as the only source of drinkable water in rural communities particularly in developing countries. It is against this backdrop that we intended to investigate possible means of SARS-CoV-2 invasion in water bodies in support of the global fight against COVID-19 with a particular focus on lakes. Therefore, this article emphasizes on possible transmissions of SARS-CoV-2 from lakes and provided remedies in support of the views of some researchers that appeared to be inconclusive.

Influence of processing methods on quality and stability of silver catfish (Chrysichthys nigrodigitatus)

The study assessed different processing methods (freezing, smoking, oven drying and boiling) on fillet nutritional quality and stability of silver catfish. All analyses followed standard procedure. Results of proximate composition showed significant increase (p< 0.05) in protein (51.98%), lipid (11.65%), ash (3.82%) and calorie (432.57 Kcal/g) contents in the dried fillets. Thus, these variable increased with increasing processing temperature. On the other hand, moisture and carbohydrate contents decreased with temperature. The stability indices showed significant differences (p < 0.05) in free fatty acid of frozen (0.21%), boiled (0.8%), smoked (2.96%) and dried (9.87%). The lowest calcium (39.7%) was recorded in the frozen sample while the highest level (53.12%) in oven dried. Thiobarbituric acid decreased with increase in processing temperature with the highest level (27.14 mg MDA/100g) observed in the frozen fillet while the least value (2.08 mg MDA/100g) was obtained in the boiled samples. Calcium and phosphorus contents did not show any particular trend. The smoked fish fillet had the highest fibre content of 2.6%. Total volatile base nitrogen was generally low in all treatments. Inference from this study revealed that differently processed Chrysichthys nigrodigitatus was a rich source of fatty acids and essential minerals being very vital to the diet of humans.