Zoologist (The)

The zooplankton and environmental characteristics of Yardantsi Reservoir, Gusau, Nigeria

2023-01-10T15:52:42+00:00

Zooplankton play an important role in the faunal biodiversity of aquatic ecosystems as they assist in transferring algal energy to higher trophic levels through grazing and also eliminate harmful algae from water. The zooplankton and environmental characteristics of Yardantsi Reservoir were studied in order to provide essential information on this important ecosystem that serves as domestic and irrigation water supply, and fishing ground. Samples for water quality and zooplankton analyses were collected from the reservoir from May, 2015 to April, 2017 using standard methods. Three groups of zooplankton (Copepoda, Cladocera and Rotifera) comprising of thirteen genera were encountered. Rotifera (36.69%) and Cladocera (34.44%) were numerically dominant during the rainy and dry seasons, respectively. The highest zooplankton abundance (5646), species richness (11), Shannon-Weiner index (2.25) and Margalef's index (1.16) were observed during the rainy season. Axes 1 and 2 of the principal component analysis (PCA) explained 74.82% and 11.89% of the zooplankton-environmental variable relationship. Diaphanosoma sp, Eubranchipus sp, Kellicottia sp and Macrothrix sp were mostly influenced by NO₃, BOD, depth, pH and dissolved oxygen while Cyclops sp and Daphnia were mostly influenced by changes in alkalinity, hardness and chloride. Brachionus patulus, the dominant species in the reservoir was mostly influenced by PO₄-P. The study shows that the reservoir is slightly polluted and it is essential to adopt effective management strategies such as reduced agricultural run-offs and riparian animal grazing to prevent further deterioration of water quality.

Nutritional and socio-economic analyses of processed catfish (Clarias gariepinus) using three kilns in Lagos State, Nigeria

2023-01-10T15:58:23+00:00

Smoke-drying is a major way of processing catfish and this prompted the study of nutritional and socio-economic assessment of smoke-dried catfish in Makoko fish market in Lagos State, Nigeria. Standard methods were utilised for the analyses of proximate content and the administration of 25 structured questionnaires to the catfish processors in the Fish Market. The fish smoked-dried in Traditional Drum Kiln (TDK) had the highest protein content (61.42±1.86g/100g), highest ash content (10.73±1.80g/100g) but lowest fat (3.19±0.91g/100g) and fibre content (1.84±0.36g/100g). However, the highest contents of fat (12.81±1.72g/100g), fibre (4.50±1.13g/100g) and moisture (37.58±7.10g/100g) were obtained in fish smoked-dried with Oil Drum Kiln (ODK). Fifty percent (50%) of processors who smoke-dried catfish in Makoko fish market used TDK, 30% used ODK while 20% of the processors used Lagos State Kiln (LSK). Weekly fixed cost of smoke-drying was found to be lowest using TDK at ₦500 while the highest weekly costs was found with LSK at ₦1,250. The variable costs were the same regardless of the type of kiln to be used in the smoke-drying process. The weekly profit was estimated at ₦49,750, ₦50,450 and ₦50,500 for LSK, ODK and TDK, respectively. The study showed that smoke-drying business is profitable and TDK yields more profit with good quality smoke-dried catfish.

Bacterial assessment of smoke-dried fishes sold at three landing market sites in Anambra State, Nigeria

2023-01-10T16:07:31+00:00

The study focused on the bacteriological profile of four different smoke-dried fishes Clarias gariepinus (CG), Oreochromis niloticus (ON), Malapterurus electricus (ME), and Citharinus citharus (CC) sold at three landing market sites (Otuocha, Ose, and Ogbakuba) in Anambra State, Nigeria. Bacteria isolates from fish samples were examined and identified using microscopic, morphological, and biochemical characteristics. The results revealed the presence of Escherichia coli, Enterococcus faecalis, Staphylococcus aureus, Salmonella enterica and Shigella flexneri in all the fish samples from the three markets. The highest number of bacteria (1471 cfu/g), was found at the Ose fish landing market followed by Ogbakuba (1353 cfu/g), while the lowest number was found in Otuocha (957 cfu/g). Some of the isolated bacteria, Staphylococcus aureus and Salmonella sp are known to cause food borne diseases and are of public health concern. Therefore, regular disinfection and cleaning as well as regular inspection by health officers are advocated to improve the hygiene of the markets. However, it is recommended that consumers should cautiously subject the fish to additional processing such as adequate cooking in order to eliminate these bacteria and to avoid food poisoning.

Aspects of the growth and reproductive characteristics of Labeo coubie (Ruppell 1832) in Upper Benue River, Nigeria

2023-01-10T16:22:07+00:00

Labio coubie is an ecologically and economically important fish of River Benue, thus the length-weight relationship, condition factor and fecundity of the fish were investigated in order to provide information essential for its sustainable management. Fish specimens were collected monthly from sampling stations at Jimeta, Yola, Adamawa State between September, 2017 and February, 2019. A total of 849 specimens were collected and their standard length, body weight and fecundity measured. Regression analysis of the length-weight relationship produced positive allometric growth coefficient, the values of regression coefficient (b) in males, females and combined sexes were 4.02, 3.52 and 3.34, respectively. Condition factor obtained ranged from 2.35-3.38 (mean=2.54±0.22), 2.36-2.78 (mean=2.52±0.11) and 2.36-3.00 (mean=2.53±0.14) for males, females and combined sexes, respectively. Fish condition factor was generally not significantly different (p˃0.05) between seasons. The fecundity of L. coubie ranged between 33,331eggs and 596,250 eggs (mean 78,017±165,667eggs). The mean values of condition factor showed that L. coubie was in a good state of wellbeing in the habitat during the period of study. These results confirm the suitability of upper River Benue for survival of Labeo coubie. There is however need for a systematic closed fishing regime to be employed in order to make way for sustainable growth of L. coubie fisheries in the river.

Quality assessment of smoke-dried Clarias gariepinus and Chrysichthys nigrodigitatus stored in two storage facilities

2023-01-10T16:40:28+00:00

The quality of smoke-dried fish can be enhanced by storing the products in good storage facilities. This research was carried out to determine the proximate composition, microbiological quality and sensory properties of smoke-dried Clarias gariepinus and Chrysichthysis nigrodigitatus stored in refrigerator and kitchen cabinet during a 6-week storage period. Sensory properties were assessed using panel of assessors. Bacterial load was done using plate count agar spread plate technique. Fish were purchased alive, washed, sacrificed and smoked for 72 hours. Percentage weight loss after smoking C. gariepinus and C. nigrodigitatus were 57.42% and 65.91%, respectively. Results for crude protein, moisture and lipid content of smoke-dried C. gariepinus stored in refrigerator ranged between 67.80-68.31%, 8.32-9.00% and 12.15-12.34% while the values for those stored in kitchen cabinet ranged from 67.04-68.30%, 8.30-8.49% and 12.15-12.34, respectively; for smoke-dried C. nigrodigitatus the ranges of the nutrients were 61.75-62.20%, 7.40%-8.00, 16.15-16.28% and 60.89-62.19%, 7.40-7.49%, 16.15-16.28% for those stored in refrigerator and kitchen cabinet, respectively. The results showed no significant difference (p>0.05) in proximate composition of the samples in the two storage facilities. Microbes isolated from the smoke-dried fish samples were Staphyloccus aureus, Bacillus subtilis and Escherichia coli. Total bacterial counts (TBC) at week 6 for C. gariepinus were 0.17×10^-6 and 0.25×10^-6; C. nigrodigitatus, 0.24×10^-6 and 0.31×10^-6 in refrigerator and kitchen cabinet, respectively, and the values were not significantly different (p>0.05) in the two storage facilities. No fungal growth was present throughout the six-week storage period. The sensory quality ratings ranged between 8.00±0.00 for flavour and 4.67±0.58 for overall acceptability. Sensory quality was significantly different (p<0.05) in flavour, texture, appearance and aroma at week 2 and 6. The findings of this study show that the storage facilities retained good nutritional and sensory qualities as well as overall acceptability of the smoke-dried fish throughout storage.

Ethnobotanical study of plants used for treating intestinal worms in Ibadan, Nigeria

2023-01-10T16:53:49+00:00

Poverty and poor sanitation in sub-Saharan Africa are the main reasons for parasitic infection prevalence. Medicinal herbs have been sources of natural and cheaper remedies for the treatment of many parasitic infections, including intestinal parasites. The study aimed to document medicinal herbs used in treating intestinal worm infections in the Ibadan metropolis through an ethnobotanical survey. The three main traditional herb markets, Oje, Oja Oba and Iwo Road, in Ibadan city, were purposively selected for the survey. The respondents, who were mainly herb sellers, were interviewed using structured questionnaires. The information obtained included demographic information, names of plants used in the treatment of worms, plant parts, dosage and method of preparation. The data collected was analysed using descriptive statistics and the Relative Frequency Citation (RFC), Use Value (UV) and Informant Consensus Factor (ICF) of the mentioned plants were calculated. The survey revealed 45 plants that are used in the treatment of intestinal worms in Ibadan. These plants belong to 31 families. The most frequently mentioned plants with their RFCs were Cryptolepis sanguinoleta (Lindl.) Schltr (0.39) and Aristolochia albida Duch (0.39) while most of the plants belong to the Families Apocynaceae and Euphorbiaceae. The roots (25%) and the leaves (18.75%) were the most commonly used plant parts. Most of the plants were indicated to be used singly while some were used in combinations of two or more. The study has revealed the medicinal plants that are used against intestinal parasites. Thus, bioassay studies to confirm the claims should be carried out to establish the activities of these plants.

The physico-chemical variables and phytoplankton of Ufiobodo and Ebonyi Reservoirs, Ebonyi State, Nigeria

2023-01-10T16:59:01+00:00

The water quality and phytoplankton of Ufiobodo and Ebonyi River reservoirs were studied for nine months from March to November, 2019 to evaluate the suitability of the reservoirs for domestic water supply and habitat for aquatic organisms. Temperature, pH, conductivity, total dissolved solid (TDS), transparency, dissolved oxygen (DO) and depth were measured in situ, while water samples were collected for determination of nitrate, iron, silicate and phosphate in the laboratory. Phytoplankton samples were also collected concurrently using plankton net of mesh size 45μm and mouth diameter (0.26m) and identified in the laboratory using standard keys. The results showed that mean conductivity (32.33μS/cm), TDS (16.00mg/l), nitrate (33.99mg/l), depth (10.36m) and phosphate (4.81mg/l) were higher at Ebonyi than Ufiobodo Reservoir but DO was lower at Ebonyi Reservoir (2.77mg/l) than at Ufiobodo Reservoir (6.67mg/l). Mean DO level was below the permissible limit for drinking water at Ebonyi Reservoir while nitrate, phosphate and iron concentrations exceeded permissible limits in both Reservoirs. Five phytoplankton Phyla were encountered, predominated by Chlorophyta (107 individuals/l, H=2.80 and d=3.85) and Bacillariophyta (81 individuals/l, H=2.39 and d=2.50) at Ufiobodo and Ebonyi Reservoirs, respectively. Principal Component Analysis (PCA) showed that temperature, conductivity, TDS, depth, DO, nitrate and phosphate were the major factors influencing phytoplankton abundance and diversity of the reservoirs. Thus, the reservoirs should be protected to maintain/improve the water quality for domestic use and to support the socio-economic and ecological services they provide.

Diversity, distribution and abundance of fish species in Lake Asejire, Oyo State, Nigeria

2023-01-10T17:06:23+00:00

Aquatic systems in Nigeria have suffered stress induced by human activities which alter the natural composition of the water resources. This study investigated the diversity, distribution and abundance of fish species in Lake Asejire. The lake was partitioned based on accessibility into upper, middle and lower sections for the study. Fish species were sampled using monofilament gill nets with stretched mesh sizes ranging from 44.45-169.33mm. Water and fish species were sampled fortnightly for a period of twelve months. Water quality parameters: temperature (28.96±0.28^oC), dissolved oxygen (5.6±0.13mg/l), pH (6.73±0.19) and conductivity (159.8±0.32μS/cm) measured were within suitable standard ranges for fish production in natural waters. A total of 16 species from 10 families were identified from the lake. Cichlids had the highest number of fish species (4) and relative abundance (66.82%) and Coptodon zillii was the most abundant fish species across the months and sampling stations (27.53%). The lower section of the lake had the highest relative abundance (52.90%) while the upper section of the lake had the least (16.14%) and the highest fish catch (13.35%) was in November. The species richness of the lake decreased from lower (S=16) to upper section (S=14), the middle section was highly diversified (H=0.73) with a combined value of H=0.67 for the lake. The fish species were evenly distributed across the lake with the highest evenness in the upper section (E=0.22). Simpson’s index was highest in the lower region (D=0.30) and there was a high probability of picking different fish species at random. Trophic grouping showed forage to carnivore (F/C) ratio of 2.06 indicating an unbalanced fish population based on food habit, which should be addressed. There is need for proper regulation such as enforcement of fishing seasons and fishing across the trophic levels to ensure sustainability of the fish resources in the lake.