Levels of heavy metals in pelagic and benthic fish species in river Nun at Amassoma, Bayelsa State, Nigeri

The heavy metals content in three fish species from River nun Amassoma axis was investigated. This was done in order to gauge the concentration of heavy metals in fish tissues and to estimate the safety of consuming these fish species on human health. Three species (pelagic and benthic fishes) were collected from local fishermen at the landing jetty and analyzed for heavy metals in the soft tissues using standard procedures. The heavy metals investigated are Cadmium (Cd), Nickel (Ni), Lead (Pb) and Chromium (Cr). Result indicates that Cd>Ni>Pb>Cr in the fish samples analyzed while Chrysichthys auratus showed the greatest abundant characteristics of Cr, Pb, Ni, Cd. There was no significant difference (P>0.05) in concentrations of Cr and Ni for all fish species. However, the results showed that there is a significant difference (P<0.05) in Pb concentration between Chrysichthys auratus, Chrysichthys aluuensis and Petrocephalus bane bane. Cd concentration in the fish species reveal that there is a significant difference (P<0.05) between Chrysichthys auratus and Petrocephalus bane bane but no significant difference (P>0.05) between Chrysichthys auratus and Chrysichthys aluuensis and between Chrysichthys aluuensis and Petrocephalus bane bane Heavy metal in the fish species showed that Chrysichthys auratus>Chrysichthys aluuensis>Petrocephalus bane bane. All metal characteristics were lower than the suggested WHO permissible limit. Benthic fish species have a greater heavy metal concentration than the pelagic fishes. Based on the observation from this study, the continuous and sustained consumption of Chrysichthys auratus and indeed benthic fish species possess a higher risk to health, while Cd poisoning in fish is most culpable of pollution in River Nun at Amassoma. axis.

Effects of Artificial Reefs on Phytoplankton Community Structure in Baiyangdian Lake, China

The habitat and feeding environment of freshwater fish in freshwater lakes have been destroyed, with the problem of miniaturization and simplification of catches being serious. An artificial reef is an effective technical measure to protect and proliferate offshore fishery resources, but little research has been conducted on its application in freshwater lakes. A small artificial reef for freshwater lakes was designed according to the water depth of the lake and the habits of benthic fish. The artificial reef is composed of biomass modules, each of which is 900 × 120 mm. The community structure of phytoplankton around the artificial reef and its adjacent waters was studied. The results showed that 77 species from seven phyla were identified, with a high number of species from the Chlorophyceae. In terms of density composition, the density of cyanobacteria decreased month by month, while the phylum Chlorophyta and Cryptophyta increased first and then decreased. As for biomass composition, Chlorophyta and Cryptophyta increased first and then decreased. RDA analysis showed that water temperature, dissolved oxygen, and total phosphorus were the main influencing factors. To sum up, the artificial reef can improve the algae phase in the surrounding water column, inhibit the growth and reproduction of cyanobacteria to a certain extent, and have a significant enrichment and promotion effect on diatoms. Artificial fish reef affects the phytoplankton community structure of the surrounding water bodies mainly through the absorption of phosphorus nutrients. Artificial reefs can be popularized and applied in freshwater lakes to provide foraging and shelter for benthic fish in the lake.

Riparian-Buffer Loss and Pesticide Incidence in Freshwater Matrices of Ikpoba River (Nigeria): Policy Recommendations for the Protection of Tropical River Basins

The unregulated use of watersheds for agriculture negatively impacts the quality of river basins. In particular, the reduced quality of surface-waters, have been attributed to absence or poorly-decided riparian-buffer specifications in environmental laws. To demonstrate suitable buffer-width for protection of surface water, sediment and benthic fish populations, five riparian areas with different vegetation richness and buffer-width were selected within an organochlorine pesticide (OCP)-impacted watershed using the Normalized Differential Vegetation Index (NDVI) and multiple buffer analysis respectively. Mean OCP levels in surface water, sediment and fish sampled at each riparian stations showed site-specific differences with markedly higher levels of α-BHC, β-BHC, δ-BHC, p,p′-DDD and total pesticide residues at stations with least riparian cover. The principal component analysis further revealed more OCPs associating with sediment and fish from stations having smaller buffer-width and sparse riparian vegetation. Stations with wider buffer-width of at least 120 m provided greater protection to adjacent surface water and benthic fish populations. While this study recommends riparian buffer-widths for a typical tropical environment, further research which assesses other contaminant types in aquatic matrices adjacent to different riparian environments would be valuable and informative for regulatory guidance and strategic protection of ecosystem services.

On the definition, status of research, diversity and prospect of exploration of the Genus Garra (Cypriniformes: Cyprinidae) from Mizoram, Northeast India

The cyprinid genus Garra includes small to medium-sized, benthic fish species that are usually found in fast-flowing rivers and streams. Fish of this genus have a modified lower lip forming a mental adhesive disc and horizontally placed pectoral and pelvic fins with a flat ventral profile. The genus Garra is vast and wide with each species exhibiting various differences at the morphological and molecular level. Reports on the exploration and investigation of the genus in Mizoram are few and those that are reported need certain validation and clarifications. Re-collection and elaborated review of this genus are obligatory. Therefore, meticulous analysis of these freshwater fish using morphological as well as molecular methods is required to validate previous findings. Furthermore, the review paper will shed a light on the diagnosis of the fish, status of research, and research prospects in Mizoram.

Cadmium Accumulation and Kinetics in Solea senegalensis Tissues under Dietary and Water Exposure and the Link to Human Health

Bioaccumulation of cadmium was assessed in different tissues of the benthic fish Solea senegalensis. Juvenile Senegalese soles were simultaneously exposed to cadmium-contaminated diet (Hediste diversicolor) and water during 14 days and allowed to depurate for another 14 days. Cadmium content was measured in muscle, gills, liver and intestine, with recorded values increasing in these tissues in this same order. Muscle showed a considerably lower cadmium accumulation after 14 days of uptake. Cadmium kinetics in juvenile Senegalese soles revealed that the highest uptake flux of this metal occurred in the intestine. Cadmium depuration from the liver was not detected, which suggests the existence of a storage compartment for this metal in Solea senegalensis during uptake and depuration. Comparisons between maximum acceptable values for cadmium in the muscle, the Target Hazard Quotient and the Estimated Weekly Intake, indicated that acceptable limits were not exceeded, and the muscle of juvenile Senegalese soles could be considered safe for human consumption.