Tropical Freshwater Biology

Helminths parasite diversity in amphibians from a residential wetland in Edo State, Nigeria

O. Edo-Taiwo — 2025-02-06

Research on amphibian helminths parasites from a residential wetland (Ikpe) in Ikpoba-Okha Local Government Area of Edo State, Nigeria was carried out. Nine amphibian species belonging to six families (Bufonidae, Dicroglossidae, Hyperollidae, Ptychadenidae, Pyxicephalidae and Ranidae) were studied. The parasites (and their prevalence) recovered from the amphibians were Acanthocephalan cystacanths (4.76%), cestodes (4.76%) (Cylindrotaenia jaegerskioeldi), monogeneans (9.52%) (Polystoma aeschlimanni and P. pricei), digeneans (19.05%) (Diplodiscus fischthalicus, Mesocoelium monodi, Metahaemotoloechus aubriae and M. exoterorchis) and nematodes (61.90%) (Amplicaecum africanum, Amplicaecum sp., Aplectana sp., Camallanus dimitrovi, Chabaudus leberrei, Cosmocerca commutata, C. ornata, Oswaldocruzia hoepplii, Paracosmocerca sp., Physaloptera sp., Rhabdias africanus, Rhabdias sp. and unidentified nematodes). There was a high diversity and prevalence of helminth parasites (80.31%) observed. However, infection intensity was low across all parasite taxa. Despite being a wetland, the Ikpe community had only a few amphibian species with high parasitic infection. The helminth infection was dominated by nematode parasites that required no intermediate hosts, while parasites that required one or more intermediate hosts were scarcely represented. Given that certain nematode parasites could not be identified; additional research is required to determine their true species status.

Impact of various fertilization techniques on the hatchability and survival of the African catfish Clarias gariepinus (Burchell, 1882)

E.T. Adebayo — 2025-02-06

Egg fertilization is a major factor in successful catfish fry-fingerling multiplication. This study was therefore conducted to evaluate the three methods of fertilization on hatchability and survival of Clarias gariepinus brooder eggs. The methods examined in this study were the Dry Method (DM) with 1800 eggs and 2.0 ml of sperm, Wet Method I (WM1) with 1800 eggs, 2.0 ml sperm, and 5.0 ml normal saline, and Wet Method II (WMII) with 1800 eggs, 2.0 ml sperm, 5 ml normal saline and 10.0 ml water. The temperature, pH, dissolved oxygen (DO), and conductivity were measured using standard instruments. Data were analyzed using one-way analysis of variance. Early hatching was observed at 17.2 hrs in DM and was significantly (P<0.05) lower than in other methods. The highest fertilization rate (82.6%), hatching rate (74.8%), and survival rate (81.8%) were observed in DM and differed significantly (P<0.05) from the values in other methods. All physicochemical parameters in the methods showed no significant difference (P>0.05), except for a significantly (P<0.05) higher temperature of 28.69± 0.43°C in DM. An increase in temperature must have contributed to the overall positive results in DM; thus, DM was the most effective method among the tested.

Exploring the nexus between human activities, ecosystem attributes, water quality, and ecological dynamics of macroinvertebrate functional community in Nigerian streams

O.T. Akinpelu — 2025-02-06

Understanding macroinvertebrate functional feeding groups (MFFGs) is essential for assessing the ecological health of freshwater ecosystems. Abirunmu, Awoosun, Mogimogi, Olumirin, and Aboto streams were investigated in Osun State Southwest ecoregion, to evaluate the ecological health of these water bodies by analyzing the interactions between human activities, ecosystem characteristics, physicochemical factors, and MFFG. Between December 2019 and October 2021, spanning early and peak wet and dry seasons, 2,077 macroinvertebrates were sampled, encompassing 16 orders, 40 families, and 80 species. Aquatic insects dominated the functional community, while other identified specimens were Mollusca, Crustacea, Arachnida, and Annelida. Predators consistently held the top position as the most common MFFG in all the streams, while collectorgatherers consistently ranked as the least abundant. The streams trophic status revealed Abirunmu and Aboto to be autotrophic, Awoosun and Olumirinheterotrophic, and Mogimogi was oligotrophic. All the streams except Aboto had functional riparian zones. Abirunmu, Awoosun, Olumirin, and Aboto had an ample supply of FPOM to support suspended feeders unlike Mogimogi. Also, all streams except Mogimogi had stable habitats with diverse substrates and none of the studied sites showed a balanced predator-to-prey ratio. Cluster analysis identified Olumirin as a unique site among the other streams. Physicochemical results showed notable spatial variations (p < 0.05) in channel width, dissolved oxygen (DO), total dissolved solids (TDS), and electrical conductivity (EC). Canonical correspondence analysis (CCA) did not show significant ecological correlations between MFFGs and physicochemical parameters, but regression analysis revealed ecological relationships between physicochemical variables, MFFGs, and ecosystem attributes. This study thus explores the use of MFFGs for assessing lotic ecosystem health and water quality, providing insights into their role as biological condition indicators.

Buffering potency of calcium carbonate and oyster shells on the water quality for Clarias gariepinus larvae

F.A.R. Ehigiator — 2025-02-06

This study examines the buffering potency of calcium carbonate and mangrove oyster (Crassostrea gasar) shells on water acidity for Clarias gariepinus larvae. A concentration of 7.2 g for five treatments; calcium carbonate (CaCO₃) [T1], unburnt uncrushed oyster shells (UUOS) [T2], burnt uncrushed oyster shells (UCOS) [T3] burnt crushed oyster shells (BCOS) [T4] burnt uncrushed oyster shells (BUOS) [T5] and the control (C), replicated thrice, was dissolved in 10 litres of water. C. gariepinus was spawned artificially and a measured quantity of the eggs and milt were stripped into each experimental bowl. pH, temperature, dissolved oxygen (DO), calcium and total alkalinity were measured weekly for four weeks. Results obtained showed that the treatments containing shells increased the pH of the water as did the conventional calcium carbonate. T₃ and T₄ effected similar changes just as T₁ (the conventional calcium carbonate) 7.87±0.06 in increasing the water pH to 7.43±0.08 at week 1 for T₃ and 7.32±0.17 at week 1 for T₄. The mean temperature ranged from 28.33±0.5 to 30.00±1.00. The mean Calcium ranged from 16.33±0.86 to 78.77±0.18 in week 4 control and T₁ week 1.

Heavy metals in water, sediment and soft tissues of clams in the middle reaches of Forcados River, Delta State, Nigeria

O.B. Najomoh — 2025-02-06

Freshwater ecosystems are among the most threatened on the planet, confronting unprecedented pressures that result in habitat loss and overexploitation of natural resources due to increasing human population and anthropogenic pressure. The purpose of the study is to determine and compare the level of some heavy metals (Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), and Zinc (Zn)) in water, sediment and soft tissue of clams with WHO limit along selected Forcados River banks. Heavy metals in the river water, sediment, and clams were determined using an atomic absorption spectrophotometer (AAS). The other physicochemical parameters such as temperature, pH, electrical conductivity, dissolved oxygen, biochemical oxygen demand and total dissolved solids were determined using standard procedures. Most heavy metals were found in more significant concentrations in sediment samples from all three sampling areas, which is the clam's natural habitat. For the physicochemical analysis, the average temperature of the water samples ranged from 27.63 to 28.25^oC, the average pH ranged from 6.85 to 7.18, the average DO ranged from 4.71 to 5.2 mg/l, the average EC ranged from 26.76 to 33.64 µS/cm, the average BOD ranged from 1.37 to 1.88 mg/l, and the average TDS ranged from 14.63 to 18.14 mg/l. This highlights the importance of monitoring potential contaminants in our aquatic environment. The concentrations of heavy metals in the tissues of clams were within regulatory limits. However, there was evidence of bioaccumulation of metals, especially chromium. The Distribution Coefficient (Kd) was computed. Cd and Zn were the most and least stable metals, respectively (Mean Log (K_d) = 3.87 and 1.43). Based on Log (K_d), metals were ranked as Pb>Cd>Cr>Cu>Zn.

The imperative of conservation of aquatic genetic resources in Nigeria

S.O. Ajagbe — 2025-02-06

The conservation and sustainable use of aquatic genetic resources are critical to maintaining biodiversity, ensuring food security, and supporting the resilience of fish populations in the face of environmental changes. This review explores the significance of genetic diversity in fish populations, highlighting the consequences of its loss due to human activities, habitat degradation, and climate change. The use of molecular genetics and genetic markers is discussed as a vital tool for monitoring genetic variation and informing conservation strategies. Furthermore, advancements in genetic improvement technologies such as selective breeding, hybridization, and genetic engineering are examined for their role in enhancing aquaculture productivity and ensuring the sustainability of cultured fish species. Despite the successes, several limitations hinder the widespread adoption of genetic improvement programs, particularly in developing regions like Nigeria. These challenges include inadequate technical skills, research infrastructure, and financial resources. The review emphasizes the need for increased investment in research, capacity development, and collaborative efforts to safeguard aquatic genetic diversity and promote sustainable aquaculture practices globally.

Evaluation of fish exploitation in the Benin River stretch using the Catch Per Unit Effort (CPUE) analysis

A.E. Ogbeibu — 2025-02-06

An assessment was carried out to investigate the species abundance by Catch Per Unit Effort (CPUE) in Benin River. Fish samples were collected for 21 months starting from April 2019 to March 2021 from four different stations of the Benin River. Abundance and biomass of fishes were used to estimate the CPUE. The gears used in fishing were baited hooks and lines in a set of seven. A total of 620 fish specimens were caught; 114(18.39%) in stations 1, 142 (22.29%) in station 2, 234 (37.74%) in station 3 and 130 (20.97%) in station 4. During the rainy season, 253 (40.81%) individuals were caught with a biomass of 4470257g and 367 (59.19%) individuals, with a biomass of 5322718 g during the dry season. Chi-square test showed significant difference (P<0.001) due to seasons. Shannon diversity index (H’) was highest in station 3 (2.394) and lowest in station 4 (1.994) while evenness index was highest in station 1 (0.5765) but lowest in station 2 (0.1586). Hutcheson’s t-test showed that the diversity of station 4 was significantly lower (P<0.05) than those of other stations, which are similar to each other. The CPUE comparison revealed that the highest was recorded in September in station 3 (2571 kg/boat/day) while the lowest (27 kg/boat/day) was in June in station 2. The study recommends further investigation on CPUE based on gear types in Benin River over a longer period (for the two seasons).