Sarotherodon Galilaeus Research Articles

Size structure, size-weight relationship and condition factor of Coptodon dageti and Sarotherodon galilaeus, two Cichlids from Lake Selingue, Mali

Size structure, size-weight relationship and condition factor of Coptodon dageti and Sarotherodon galilaeus, two Cichlids from Lake Selingue, Mali

Species Composition and Abundance of the Cichlid Fishes in Owalla Reservoir, Osun State, Nigeria

Fish production plays crucial roles in enhancing food security and alleviating poverty of many people in Nigeria. As demand for fish increases steadily over the years, production becomes inadequate. One of the ways in which adequate fish production could be met is adequate conservation efforts. This study was conducted with a view of providing a more recent catalogue and update of species composition and abundance of cichlid fishes in Owalla reservoir. Sampling for cichlids fishes in the reservoir was done monthly for 24 weeks with the use of dugout canoe. Four experimental gillnets, each measuring 2 by 30 m, with various stretched mesh sizes (25.4, 38.1, 50.8 and 63.5 mm) were designed to sample various sizes of the fishes. Other sampling techniques adopted include the use of cast net, fish traps and hook and line. The six species of cichlid fishes identified during study are Hemichromis fasciatus (SL=7.35±0.12 cm; mean weight=15.58±9.01g), Sarotherodon galilaeus (SL=11.77±3.12 cm; mean weight=89.48±14.17 g), Oreochromis niloticus (SL=8.35±1.90 cm; mean weight=36.11±10.02 g ), Tilapia zilli (SL=9.95±1.09 cm; mean weight=88.03±16.04 g ), Tilapia mariae (SL=9.83±1.07 cm; mean weight=57.81±14.01 g ) and Tilapia dageti (SL=11.12.±2.01 cm; mean weight=85.30±20.01 g). The fish species were adequately represented, well distributed and occurred frequently in both wet and dry seasons, though the occurrence was higher in the wet season. The mean values of length and weight recorded for the fishes were small when compared with the values of cichlids from similar Nigerian inland waters and was attributed to the indiscriminate use of gillnets with unregulated mesh sizes. Overfishing by the artisanal fishermen could not be ruled out due to lack of regulations on the reservoir. Therefore, regular qualitative and quantitative information on cichlid fishes in the reservoir is necessary for enhancement of management and appraisal of the fisheries potential of the reservoir becomes essential.

Ultrastructural observation on the parasitic copepod, Lamproglena monodi Capart, 1944, infesting the gills of Sarotherodon galilaeus caught from the River Nile and Lake Manzala, Egypt, using the parasite as a bioindicator for pollution

Ultrastructural observation on the parasitic copepod, Lamproglena monodi Capart, 1944, infesting the gills of Sarotherodon galilaeus caught from the River Nile and Lake Manzala, Egypt, using the parasite as a bioindicator for pollution

SPECIES COMPOSITION, SIZE DISTRIBUTION, CONDITION FACTOR AND GROWTH PATTERN OF CICHLIDS FROM ZOBE RESERVOIR, DUTSIN-MA, KATSINA STATE, NIGERIA.

The species composition, size distribution, condition factor and growth pattern of cichlids from Zobe reservoir Dutsin-Ma, Katsina State was investigated between August and November 2022, with a view to understanding the distribution and well-being of cichlids in the water body. One hundred (100) cichlids were sampled from two (2) major landing sites (Makera and Garhi) of the reservoir, the fish were identified and separated before being transported in an ice box to the laboratory Biology Laboratory of the Federal University Dutsin-ma. At the laboratory, the length was measured to the nearest centimeter using a ruler while a sensitive weighing scale was used to measure the weight in grams. The results showed that four species were identified; Oreochromis niloticus (40), Oreochromis aureus (21), Sarotherodon galilaeus (21) and Coptodon zilli (18). The mean total length and weight were significantly higher (P<0.05) in O. niloticus compared to other species. The least was observed in O. aureus although it was not different significantly compared with C. zilli and S. galilaeus. The condition factor (K) of >1 was obtained in all the species with O. niloticus having the highest value of 2.26 which was significantly higher than 1.48 observed in O. aureus. All the species showed negative allometric growth, however, C. Zilli and O. aureus were very close to isometric growth with b values of 2.96 and 2.85 respectively. Although negative allometric growth was observed in all the species, the K values of >1 showed that all the cichlids in the Zobe reservoir are healthy and in good biological condition

Re-validation of biochemophysical variables as metrics for assessing the ecological integrity of an aquatic ecosystem (Badagry Lagoon, Lagos, Nigeria)

Assessment of ecological integrity of aquatic ecosystem is a major priority for scientists, government and private concerns all-over the world. In this study, multi-metric indices (physico-chemistry, biodiversity, length–weight relationship and condition factor) was used to evaluate the ecological integrity of Badagry Lagoon, Lagos, Nigeria. Three sampling sites (Akarakumo, Topo and Ajido) were selected based on extent of fishing activities. Water and fish samples were collected monthly from the three sampling stations for ten consecutive months (February to November, 2018). Standard methods were used for the analysis of physico-chemical parameters, fish diversity, length–weight relationship and condition factor of some fish species from the study sites. Simpson’s dominance index (0.056–0.057) and Shannon diversity index (3.11–3.13) were similar for the three sampling stations. The initial growth coefficient (a) in this study varied within a very narrow range (0.01–0.04) while the growth coefficient (b) had wider range (2.14–3.16). Growth pattern was predominantly negative allometry. Most of the fish species encountered were not under threat of extinction except Sarotherodon melanotheron and Sarotherodon galilaeus that were critically endangered and vulnerable, respectively. The physico-chemical variables of the sampling stations indicated that the ecological integrity of the water body is high, and this was corroborated by the results of biodiversity study, length–weight relationship and condition factors. Therefore, these metrics can be used in the assessment of the ecological integrity of aquatics.

Status of conventional and molecular breeding of salinity‐tolerant tilapia

AbstractAquaculture is an important sector for ensuring global food security. Due to the scarcity of freshwater available for expanding aquaculture, the development of omnivorous fish species and varieties that can tolerate high salinity will enhance fish production. Some tilapia species are good candidates for aquaculture in brackish and seawater because they can grow in high salinity. Among tilapia species, Oreochromis mossambicus, Oreochromis aureus, Oreochromis spilurus, Oreochromis urolepis hornorum, Sarotherodon galilaeus and Coptodon zillii are the most salinity‐tolerant. Hybrids derived from salinity‐tolerant tilapia species are tolerant to a certain level of salinity. They have been used in aquaculture production in brackish water and full seawater. Conventional selective breeding has been applied to increase the growth rate of salinity‐tolerant tilapias. However, their growth rate is lower than that of the freshwater Oreochromis niloticus. Recently, many genomic resources and tools have been developed for salinity‐tolerant tilapia. Quantitative trait locus (QTL) mapping and genome‐wide association studies (GWAS) for important economic traits, including salinity tolerance and other desired traits, have been carried out and applied in molecular breeding for superior salinity‐tolerant tilapia lines. In this review, we systematically analysed tilapia species that can be cultured in brackish and saltwater. We summarized previous works in conventional breeding and molecular breeding for salinity‐tolerant tilapia. We pointed out a few known and potential challenges in the selective breeding and culture of salinity‐tolerant tilapia. Due to the rapid advances in molecular and other disruptive technologies, we are optimistic that novel breeding approaches will significantly increase the production salinity‐tolerant tilapia.

Length-Weight Relationship and Condition Factors of Sarotherodon galilaeus (Linnaeus, 1758) from Nguru-Gashua Wetlands, Northeast Nigeria.

This study examined the length-weight relation and condition factor of Sarotherodon galilaeus (Linnaeus, 1758) from Nguru-Gashua wetlands, Northeast, Nigeria. A total of 375 specimens were purchased from local fishermen at the designated landing sites for six months. Results of morphometric characteristics showed that the body weight of male S. galilaeus ranged from 127-770 g (601.7±28.01) and females ranged from 272 – 704 g (711.3±38.12). Meristic features show that spinous anal fin rays were constant in both sexes while soft dorsal fin rays, pectoral fin rays, soft anal fin rays and spinous dorsal fin rays had the same range for both sexes. The sex ratio (1:2.18) observed in this study tends to favour male species but contrasts with the general assumption of a sex ratio of 1:1. Mean coefficient of determination was 0.89±0.07 and 0.87±0.07 for male and female S. galilaeus respectively indicating that length-weight relationship model is very reliable. This implies that the change in weight of the sampled fish was caused by 88.52% and 86.68% change in length of male and female S. galilaeus respectively. It was further revealed that both sexes (b = 2.86±0.18 and 2.88±0.35) had negative allometric growth patterns. The wetland's environmental conditions were within a tolerable range for cichlids.

Mitogenomic Features and Evolution of the Nile River Dominant Tilapiine Species (Perciformes: Cichlidae).

To better understand the diversity and evolution of cichlids, we sequenced, assembled, and annotated the complete mitochondrial genomes of three Nile tilapiine species (Coptodon zillii, Oreochromis niloticus, and Sarotherodon galilaeus) dominating the Nile River waters. Our results showed that the general mitogenomic features were conserved among the Nile tilapiine species. The genome length ranged from 16,436 to 16,631 bp and a total of 37 genes were identified (two ribosomal RNA genes (rRNAs), 22 transfer RNA genes (tRNAs), 13 protein-coding genes (PCGs), and 1 control region). The ND6 was the only CDS that presented a negative AT skew and a positive GC skew. The most extended repeat sequences were in the D-loop followed by the pseudogenes (trnSGCU). The ND5 showed relatively high substitution rates whereas ATP8 had the lowest substitution rate. The codon usage bias displayed a greater quantity of NNA and NNC at the third position and anti-bias against NNG. The phylogenetic relationship based on the complete mitogenomes and CDS was able to differentiate the three species as previously reported. This study provides new insight into the evolutionary connections between various subfamilies within cichlids while providing new molecular data that can be applied to discriminate between Nile tilapiine species and their populations.

Size selectivity of trammel nets applied in small-scale fisheries of Lake Nasser, Egypt

In spite of the significance of trammel nets for small-scale fisheries (SSFs) in Egypt in what concerns landings, economic value, vessels and fishermen numbers, few studies on their size selectivity have been conducted. This study investigates the trammel nets’ size selectivity as a key métier of SSFs in three areas of Lake Nasser. A full survey of the commercially used trammel nets and experimental fishing trials using different models of trammel nets were carried out. The results of the survey indicated that the catch had a limited species variation, which included mango tilapia (Sarotherodon galilaeus), Nile tilapia (Oreochromis niloticus), and redbelly tilapia (Coptodon zillii). Regarding experimental fishing, four different mesh sizes (83, 95,108, and 120 mm) were applied and the nets selectivity curves indicated that the size-frequency distributions of all species showed shifting of the mean length to the right with increased mesh size in all nets. The best model was determined from the outcomes of model comparisons and it was the log-normal model for O. niloticus and bimodal for both S. galilaeus and C. zillii. This information can be useful in applying the technical measures for fisheries that depend on the trammel nets.

Absence of Figla-like Gene Is Concordant with Femaleness in Cichlids Harboring the LG1 Sex-Determination System.

Oreochromis niloticus has been used as a reference genome for studies of tilapia sex determination (SD) revealing segregating genetic loci on linkage groups (LGs) 1, 3, and 23. The master key regulator genes (MKR) underlying the SD regions on LGs 3 and 23 have been already found. To identify the MKR in fish that segregate for the LG1 XX/XY SD-system, we applied short variant discovery within the sequence reads of the genomic libraries of the Amherst hybrid stock, Coptodon zillii and Sarotherodon galilaeus, which were aligned to a 3-Mbp-region of the O. aureus genome. We obtained 66,372 variants of which six were concordant with the XX/XY model of SD and were conserved across these species, disclosing the male specific figla-like gene. We further validated this observation in O. mossambicus and in the Chitralada hybrid stock. Genome alignment of the 1252-bp transcript showed that the figla-like gene’s size was 2664 bp, and that its three exons were capable of encoding 99 amino acids including a 45-amino-acid basic helix–loop–helix domain that is typical of the ovary development regulator—factor-in-the-germline-alpha (FIGLA). In Amherst gonads, the figla-like gene was exclusively expressed in testes. Thus, the figla-like genomic presence determines male fate by interrupting the female developmental program. This indicates that the figla-like gene is the long-sought SD MKR on LG1.

Estimation of Cadmium in Muscles of Five Freshwater Fish Species from Manzalah Lake, and Possible Human Risk Assessment of Fish Consumption (Egypt)

The Egyptian government devised a plan in 2016 to improve the unique ecological significance of northern lakes, which mentioned Manzalah Lake in the Egypt Vision 2030. In this regard, this study investigated cadmium (Cd) content in five freshwater fish species collected from Manzalah Lake in Egypt at 2018 by local fishermen. According to the findings, Clarias gariepinus recorded the highest concentration of Cd (1.40 ± 0.2 μg/g) and the lowest concentration was recorded in O. aureus (1.19 ± 0.2 μg/g). Cadmium contents of all species were largely above the permissible level of the Food Agricultural Organization (FAO)/World Health Organization (WHO) and Commission Regulation (EC). The estimated daily intake (EDI), the estimated weekly intake (EWI), and the percentages of provisional tolerable weekly intake (PTWI %) values for Cd in the C. gariepinus > Sarotherodon galilaeus > Tilapia zillii > Oreochromis niloticus > Oreochromis aureus which consumed by children, teenagers, and adults were much higher than the PTWI values established by FAO/WHO. In addition, C. gariepinus consumed by children showed the highest value of the target hazard quotient (THQ) (5.83 a day or 40.81 a week) while O. aureus that ingested by adults showed the lowest level (1.06 a day or 7.42a week). The target carcinogenic risk (TCR) of C. gariepinus in children had the greatest level (2.21 × 10−3 a day or 1.55 × 10−2 a week), whereas O. aureus in adults had the lowest level of TCR (4 × 10−4 a day or 2.81 × 10−3 a week). THQs values of Cd in the five studied species were found higher than one. Moreover, TCRs values of Cd in the five species were exceeded the US Environmental Protection Agency guideline USEPA permissible limits suggesting that a daily or weekly consumption of these species could lead to a high risk non-carcinogenic and carcinogenic for humans.

Molecular characterization of zoonotic anisakid Contracaecum spp. larvae in some fish species from Lake Nasser, Egypt

Infections with zoonotic anisakid nematode larvae Contracaecum spp. were detected in five fish species from Lake Nasser, Egypt: three tilapia species (Oreochromis niloticus, Sarotherodon galilaeus and Tilapia zillii) and two catfish species (Malapterurus electricus and Heterobranchus bidorsalis). Severely infected fish displayed general body emaciation and distended abdomen. The overall prevalence of infection was 30% (tilapia species 24.17% and catfish 41.67%). The larvae were morphologically identified as third stage larvae of Contracaecum. The internal transcribed spacer sequences of nuclear ribosomal DNA (ITS-1 and ITS-2) were used for molecular characterization, resulting in the submission of six new sequences to the GenBank database and confirming that the present larvae were members of the C. multipapillatum complex (C. multipapillatum and C. quadripapillatum). The phylogenetic analysis corroborated the molecular results and demonstrated Contracacum's polyphyletic nature. The larvae aggressively bore into the heart ventricle of tilapia species (Heartworm Disease), causing severe pathological changes such as myocardial fibre atrophy, interstitial haemorrhage, pericarditis with eosinophilic granular cells infiltration and intravascular thrombosis, and impairing heart function, whereas in catfish, the larvae encapsulated in the abdominal cavity and caused little harm. As a result, they are the causative agent of Heartworm Disease.

Reproductive biology of the main fish species in lakes Taabo, Kossou and Faé (Côte d’Ivoire) with a view to rational fishing

This study was carried out in order to find out the sizes of first sexual maturity and the reproduction period of the main fish species (Chrysichthys nigrodigitatus, Hemichromis fasciatus, Pelloluna leonensis, Oreochromis niloticus, Sarotherodon galilaeus, Sarotherodon melanotheron, Coptodon zillii, Coptodon zillii x Coptodon guineensis, Distichodus rostratus, Aucheglanis occidentalis, Hepsetus odoe, Parachanna obscura and Schilbe mandibularis) targeted by the fishery in three lakes (Taabo, Kossou, Fae). The sizes at first maturity recorded in Lake Kossou are larger than those obtained in the other two lakes. However, the sizes at first capture (Lc50) for all species in the three lakes are smaller than the sizes at first sexual maturity (L50). Monthly monitoring of the gonadosomatic index (GSI) showed that breeding activities took place during two seasons (wet and dry). The breeding activity during the rainy season is longer than during the dry season. For a sustainable supply of fish, the fishery could be closed during the period when most fish spawn (rainy season).

Fishermen\u2019s perceptions and experiences toward the impact of climate change and anthropogenic activities on freshwater fish biodiversity in C\xf4te d\u2019Ivoire

Africa’s freshwater ecosystems are impacted by many threats due to climate change and several anthropogenic activities. In Côte d’Ivoire, the economy relies mostly on agriculture, which covers around 64% of the land surface. The study aimed to investigate Côte d’Ivoire fishermen’s perception of climate change, its drivers and other anthropogenic activities impacting freshwater fish biodiversity. The fish species locally threatened in the Ivorian freshwater ecosystems were also investigated. Face to face interviews and a structured questionnaire were used. The data obtained were analysed using descriptive statistics such as frequency, percentage, means, and standard deviation, minimum and maximum. The multinomial logit regression was also applied to test factors that influence fishermen’s awareness and perception of climate change and their perception of change in fish abundance. The results show that around 72.7% of fishermen were aware of climate change. Decreases of precipitation (87.9%) and increases of temperature (76.1%) were observed by fishermen. Also, a significant decrease in fish quantity was observed by respondents. Climate change and anthropogenic activities such as gold mining, water withdrawal, use of small-mesh fishing nets, overfishing, industrial waste pollution, pesticides use for agricultural purposes along watersheds, obnoxious fishing practices and population growth, were highlighted as the main reasons for this decline. Species such as Lates niloticus, Heterotis niloticus, Parachanna obscura, Malapterurus electricus, Sarotherodon galilaeus, Tilapia zillii, Polpyterus endlicheri and Labeo coubie were listed by fishermen as locally threatened within Ivorian freshwater ecosystems. Actions and policies are needed to be taken by local authorities to ensure the sustainability of fisheries resources. The information obtained from this study constitutes a prerequisite for developing and implementing studies or policies aimed at mitigating and combating the negative effect of climate change and anthropogenic activities on the Ivorian freshwater ecosystem.

Heavy Metal Concentrations in Fish from River Tano in Ghana and the Health Risks Posed to Consumers.

Appreciable levels of trace metals have been reported in the Tano basin, but data on the corresponding levels in fish and the risk they pose to consumers are limited. The levels of 7 trace metals in 18 fish muscles were assessed between November 2016 and October 2017 using acid digestion and PerkinElmer (PinAACle 900T) Atomic Absorption Spectrophotometry. Apart from Cu, all the metals studied were detected in all fish samples. The levels of Cr, As, and Hg were higher than the acceptable levels of fish muscles. Cr concentration ranged from 16.10 ± 0.2 mg/kg in Clarias gariepinus to 57.9 ± 4.2 mg/kg in Sarotherodon galilaeus. The levels of As ranged from 1.01 ± 0.08 in Clarias gariepinus to 3.00 ± 0.01 mg/kg in Mormyrus rume. Hg level was 0.58 ± 0.69 mg/kg in Oreochromis niloticus and 2.52 ± 0.70 mg/kg in Ctenopoma kingsleyae. However, Pb, Zn, and Cd concentrations were below the Food and Agriculture Organization limits with low target hazard quotients in all fish samples, suggesting no possible noncarcinogenic risks to adult consumers. Possible noncarcinogenic and carcinogenic health risks were recorded for As, Hg, and Cr in all fish species. Strong associations were observed between Hg, As, Zn, and Cr and between Pb and Cd suggesting a possible common source. Mormyrus rume fish species was under stress in the river, but the remaining species were in good condition. Periodic monitoring of trace metal concentrations in fish and enforcement of the buffer zone policy are recommended.

Characterization of Clinostomum cutaneum and Clinostomum phalacrocoracis in tilapia species of Aswan Governorate, Egypt: A morphological, molecular and histopathological study

Clinostomum species are digeneans, and their metacercariae infect both cultured and wild fish worldwide, causing significant economic losses and possibly possessing zoonotic potential; identification of these parasites has proven challenging due to the high degree of similarity and minor differences between different species. To identify them, we used a combination of morphological and molecular methods. Only tilapia species were positive for clinostomatids among 1200 examined fish samples from Aswan Governorate, Egypt (Oreochromis niloticus, Sarotherodon galilaeus, Tilapia zillii, Lates niloticus, Synodontis schall, Synodontis serratus and Hydrocynus forskalii). Clinostomum cutaneum and Clinostomum phalacrocoracis were isolated from cultured O. niloticus with a prevalence of 25% and 11.5%, respectively, and from wild O. niloticus, S. galilaeus and T. zillii with a prevalence of 12.5% and 27.5%, 23% and 33%, and 7.5% and 16.5% respectively. The nuclear ribosomal gene marker (28S rRNA) was amplified using PCR and sequenced, followed by phylogenetic analysis, which revealed that the two species under investigation were very closely related to C. cutaneum and C. phalacrocoracis. The histopathological changes associated with clinostomatid infections are necrosis, tissue damage and immune cell infiltration at the site of infection. C. cutaneum metacercaria was characterized for the first time in Egyptian fish. It was pathogenic to tilapia and caused significant mortality in cultured conditions.

Comparative assessment of food web structure and fisheries productivity of three reservoirs in Ghana

AbstractThree Ghanaian reservoirs (Tono, Bontanga and Golinga) were compared through a food web modelling approach (Ecopath with Ecosim) to assess production characteristics and food web structures. The lakes differ in size and morphology, generating specific conditions for fish growth and production. While the two top fishery target species were Sarotherodon galilaeus (L.) and Oreochromis niloticus (L.) in all reservoirs, the mean trophic level of the catch was lowest in the largest and deepest reservoir (Tono) due to higher trophic level species occupying less accessible deep “refuge” habitats. The smallest lake had the highest fish production under optimal conditions of water supply (17.1 compared with 15.5 and 10.1 t/km2/year for lakes Bontanga and Tono), but it appears to be most vulnerable under conditions of drought. For the planning and construction of adequately sized reservoirs used for fishery and irrigation purposes, the water budget (ratio of inflow and evaporation) needs to be estimated.

Replacing fish meal with rapeseed meal: potential impact on the growth performance, profitability measures, serum biomarkers, antioxidant status, intestinal morphometric analysis, and water quality of Oreochromis niloticus and Sarotherodon galilaeus fingerlings

The aim of this study was to assess the impact of using rapeseed meal as a partial replacement for fish meal in the diet of farmed tilapia. We evaluated the effect of this replacement on growth performance, profitability, serum biomarkers, antioxidant status, gut morphology, and water quality. A total of 960 apparently healthy Oreochromis niloticus (O. niloticus) and Sarotherodon galilaeus (S. galilaeus) fingerlings were randomly distributed into four dietary treatment groups for each tilapia species (triplicate design, 120 fish/group, and 40 fish/replicate). The diets consumed by these groups were formulated to replace fish meal (FM) with rapeseed meal (RM) at 0%, 10%, 20%, and 30%, respectively, for 12 consecutive weeks. Results indicated that replacing RM in the diet of S. galilaeus (up to 20%) and O. niloticus (up to 10%) resulted in increased growth performance parameters, including final weight, weight gain, length, length gain, weight gain rate, and specific growth rate (SGR), and return parameters such as a total return and relative return compared to the control group. Moreover, an increase in RM up to 30% improved net profit and increased the mucosal length, intestinal villi length, and the number of goblet cells compared with results in its relative control groups. Additionally, we observed a significant increase in serum and liver AST and ALT with increased RM replacement. With respect to water parameters, we observed a significant difference in the ammonia levels, turbidity, and conductivity with the changes to the percentage of RM in the diets. As for the effect on each species, O. niloticus showed a more significant increase in all examined parameters compared to results in S. galilaeus. In summary, up to 10% RM can be used to replace FM without any adverse effects on the growth performance, profitability measures, intestinal morphometric analysis, or water quality.

Species composition, abundance and diversity of Ichthyofauna of Ikere-Gorge, Oyo State, Nigeria

Anthropogenic activities in inland water can cause species loss and displacement. Therefore, there is a need to regularly examine species composition, abundance and diversity of freshwater ecosystem as a means to monitor its health. Ichthyofauna of Ikere-gorge, Iseyin, Oyo State was studied for a period of 24 month, from January 2017 to December 2018. Ikere-gorge was divided into four strata, each comprises three fishing villages. One village in each stratum was randomly selected as sampling site. The catches were sorted into taxonomic groups (species and families) using standard fish identification keys. Forty-one fish species from 13 families were identified in which species richness varied among the sampling villages. Asamu had 34, Agatu had 30, Spillway had 39 and Irawote had 29 species. The freshwater fish species of Nigeria is the richest in West Africa and more than 15% of these fish species are found in Ikere-gorge. Mormyridae family was the most represented with 10 species. Cichlidae was the most abundant by catch and by weight. Sarotherodon galilaeus has the highest abundance by catch and by weight. Gnathonemus brucii was identified as a vulnerable species. The result obtained from this study show that conservation program should be urgently put in place to prevent some fish from extinction. There should be introduction of closed season to allow for proper recruitment of fish population. Likewise, minimum mesh size should be set to allow juvenile and immature fish to escape and allow them to spawn at least once before being vulnerable to gear. There should regulation to set maximum number of fishermen to be allowed to fish at a particular day, this is to reduce fishing pressure.

Influence of olive leaves additive on growth and physiological parameters of Sarotherodon galilaeus

Influence of olive leaves additive on growth and physiological parameters of Sarotherodon galilaeus