Chrysichthys Auratus Research Articles

DNA barcoding, phylogeography and evolutionary dynamics of Chrysichthys auratus

This study embarked on an exploration into the genetic structure and evolutionary history of the Chrysichthys auratus species, leveraging PCR amplification, phylogenetic trees, and haplotype networks. Specific DNA segments were successfully amplified and visualized through electrophoresis. Newly obtained sequences were Bank into GenBank and given accession numbers (OR730807-OR730808-OR730809). The Neighbor-Joining method provided insights into the evolutionary relationships among taxa, further augmented by bootstrap values and the Tamura 3-parameter method. A comprehensive geographical haplotype network showcased pronounced genetic differentiation, especially between remote populations. Nonetheless, shared haplotypes between proximate regions indicated either ancestral genetic connections or ongoing gene flow. Employing the COI-DNA barcodes, an in-depth understanding of intra- and inter-populational genetic diversity was achieved. The study's findings unravel the intricate genetic landscape and evolutionary dynamics of C. auratus, offering novel perspectives into its demographic history across its vast native habitat.

Evaluation of Bacteria Composition in Smoked Fish Processed in Yeji-Pru East District, Ghana

Background: Fish safety and quality have been a major area of public health concern. This situation was heavily influenced by several factors ranging from the harvesting environment to the dining table.
 Aim: This study aimed at assessing the bacteriological quality of smoked fish in three (3) major fish processing communities in the Yeji-Pru East District, Ghana.
 Study design: The study was a comparative cross-sectional design to explore bacteria species occurrence and abundance (loads) of smoked fish in Yeji-Pru East District, Ghana. It also was directed towards determining the characteristics of the situation as it existed during the period of the study, from June to December 2017.
 Method: A closed-ended structured questionnaire was used to collect sociodemographic data from 20 owners of the fish processing site. Forty-eight smoked fish samples including; Oncorhynchus sp., Clupea harengus, Chrysichthys auratus and Oreochromis niloticus were surface sterilised, rinsed and dried at 45°C for 24 hours. Ten grams of each fish sample were diluted with 10 ml of Buffered Peptone Water. Further dilution was prepared using 5 ml of the same diluent. The prepared samples were made to settle for isolations and later inoculated on MacConkey Agar, Shigella-Salmonella Agar, and Salt Mannitol Agar. Microbial colonies were then enumerated using the pour plate method. Data collected were analysed using Microsoft Excel, SPSS and Interactive Chi-square Test at a test significance of 5%.
 Results: The results showed absence of Salmonella and Shigella in all fish samples studied. However, it revealed the presence of Escherichia coli and Staphylococcus species at a rate of 79.2 (n= 38) and 89.6% (n= 43), respectively. The microbial load for E. coli and Staphylococcus species were community specific. Statistical analysis showed a significant difference (p < 0.05) between the microbial loads in fish samples obtained at each study site. However, there was no spatial variation in the mean microbial abundances of each selected sample (p > 0.05). The bacteria load observed were lower than the permissible level for human consumption authorised by both the Ghana Standards Authority and the International Commission on Microbiological Specifications for Foods.
 Conclusion: The study showed that the pre-smoking and post-smoking activities along the fish processing chain could affect the microbial load and diversity. Therefore, the adoption of a good processing practice was highly advocated.

Ecological studies on the helminth parasites of catfishes Bagrus spp. (Bagridae) and Chrysichthys auratus (Claroteidae) inhabiting Damietta branch, River Nile, Egypt

ABSTRACT The results of a survey on the helminth parasites of the catfishes Bagrus spp. Forsskål, 1775 and Chrysichthys auratus Geoffroy,1809 inhabiting Damietta branch of the River Nile at Mansoura city, Dakahlia Governorate, Egypt, have been demonstrated. During the period of March 2020 to February 2021, five species were detected from Bagrus spp. and represented by one monogenean Quadriacanthus bagrae from the gills, three digeneans Acanthostomum absconditum, Acanthostomum spiniceps and Haplorchoides cahirinus and a single nematode species Capillostrongyloides fritschi from the intestine. Only one monogenean species Protoancylodiscoides mansourensis was detected from the gills of Chrysichthys auratus. Except for a few months, most monogeneans, digeneans and nematodes of Bagrus spp. and C. auratus were recorded in all months of the year. The digeneans A. absconditum, A. spinicips, and H. cahirinus are eudominant and A. absconditum was the most dominant while the nematode C. fritschi is subrecedent. In Bagrus spp., the digenean parasites attained the highest prevalence over the monogeneans and nematode parasites throughout the year (77.7%). There was a definite seasonal change in the studied helminths, but no general common trend or pattern was observed. Most helminth parasites showed a higher prevalence in male fishes than females while they attained a higher abundance in females than males. There was a significant difference in the mean prevalence as well as in the mean intensity of most examined parasite species in male fishes and females but a significant difference in the mean abundance of males and females was only recorded for the digenean parasites. Most parasites showed a higher prevalence as the condition factor of the host increased.

Age and growth of Chrysichthys auratus (Geoffroy 1809) (Family: Claroteidae) from Lake Nasser, Egypt

Chrysichthys is a widely distributed catfish in all inland and coastal water bodies and is one of the important commercial catfish families in Lake Nasser, Egypt. A total of 1176 Chrysichthys auratus specimens were collected from Lake Nasser during monthly catches in 2019. Total length (TL) ranged from 13 to 31 cm (mean 22.0 ± 3.0 cm), and total weight ranged from 23.1 to 320.2 g (mean 133.5 ± 52.2 g). For males, females, and combined sexes, the length–weight relationship revealed negative allometric growth. The condition factor values were highest during May for males, females, and combined sexes, and all values were >1.0, indicating that the fish were in good condition. Three age groups were identified from the data, with mean TLs of 19.16, 23.18, and 26.21 cm, as determined using vertebral growth rings. The growth constants of von Bertalanffy were calculated as L∞ = 35.43 cm TL, K = 0.41 y−1, and to = − 1.7. The growth performance index was 2.55, and longevity was 9 y. The using of vertebrae was validated to age determination of C. auratus. These findings will contribute to assess the fishery status and fisheries management of C. auratus in Lake Nasser.

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.

Interspecific and intraspecific differences in pectoral-fins spine morphology in Nile River and Lake Nasser catfishes, Siluriformes

The structure of the pectoral fins spine of 4 catfish species Heterobranchus longifilis, Clarias gariepinus, Chrysichthys auratus, Synodontis schall and Synodontis serratus were described. The fish specimens were collected from Asyut City and Lake Nasser about 319 and 900 Km south of the capital Cairo, Egypt respectively on 10 November 2017 are described. The species examined showed variation in the shape of the spine-shaft tip varies from finely to broadly and rounded pointed; the curvature of the spine-shaft is either straight or curved partially or complete; the anterior serrae varies between is either broad or irregular; the anterior ridge groove is well developed, deep, and curved, with some pores in some species; the anterior dentations varies between short and sometimes are merged together or curved and their number decreased towards the tip; the posterior dentations can vary between absent or long and numerous and sometimes increased in their number towards the tip of the spine; the dorsal, anterior and ventral processes are well developed structures, with rounded, flange-like, and the shape of the basal fossa varies in having narrow, elongated, boat-shape, with high walls at sides; and very wide fossa and lunate in shape. It is usually deep with high walls.

Cestode infections of two clariid and two claroteid catfish species in River Galma, Zaria, Nigeria

Four catfish (Siluriformes) species comprising two clariids, Heterobranchus bidorsalis (65) and Heterobranchus longifilis (15) and two claroteids, Auchenoglanis occidentalis (31) and Chrysichthys auratus (19) from River Galma Zaria, Nigeria, were examined for gastrointestinal cestodes between May 2016 and February 2017. Helminths recovered were stained, dehydrated, cleared and mounted in Canada balsam for microscopic examination. A total of seven cestode species were recovered from the clariids and claroteids. The cestodes were distributed among the fish examined as follows: in C. auratus: Wenyonia longicauda (26.32%), W. virilis (10.53%), and W. minuta (5.26%); in H. bidorsalis: W. acuminata (3.08%), W. virilis (18.46%), Monobothrioides woodlandi (6.15%), Proteocephalus sp. (1.54%) and Tetracampos ciliotheca (4.62%); in H. longifilis: M. woodlandi (6.67%), W. longicauda (6.67%) and W. acuminata (6.67%). Prevalence of cestode infection in C. auratus was higher in the wet than in the dry season; however, prevalence of infection in H. longifilis and H. bidorsalis was higher in the dry than in the wet season. The prevalence was higher in male than in female H. longifilis while higher in female than in male C. auratus and H. bidorsalis. Prevalence decreased with increase in standard length of C. auratus, H. longifilis and H. bidorsalis. A seemingly posteriorly deformed W. minuta was recovered from C. auratus. None of the 31 A. occidentalis examined in this study was infected by cestodes. All the fish used in this study were collected mostly on the basis of availability. It is therefore recommended that larger sample of assorted sizes be obtained, especially of H. longifilis (15) and C. auratus (19), of which very few specimens were examined during the period of this study to obtain a clearer picture of infection by the cestodes from RiverGalma, Zaria, Nigeria.
 Keywords: Cestodes; catfish; clariid claroteid; siluriformes; infection; prevalence; intensity.

Length-weight relationships of 19 fish species from two tropical artificial reservoirs (Manantali and Selingue) in Mali, West Africa

Length-weight relationships (LWRs) were estimated for 19 fish species sampled from two artificial reservoirs (Manantali and Selingue) in Mali: Brycinus leuciscus, B. macrolepidotus, B. nurse, Chrysichthys auratus, C. nigrodigitatus, Coptodon zillii, Distichodus brevipinnis, D. rostratus, Hemichromis fasciatus, Hydrocynus forskahlii, Labeo coubie, L. senegalensis, Lates niloticus, Mormyrus rume, Sarotherodon galilaeus, Schilbe intermedius, S. mystus, Synodontis schall, S. sorex. The fish were collected between June 2002 and October 2003 during three experimental fishing campaigns using gillnets deployed overnight. All fish were measured (total length) to the nearest mm and weighed to the nearest g (total weight). Coefficients of determination of the LWRs (r²) were mostly high (> 0.9). The values of the allometry coefficient b ranged from 2.651 (Chrysichthys auratus) to 3.270 (Brycinus leuciscus). This study provides new information about LWRs of two fish species, which have been published but are not yet available in Fishbase (Distichodus brevipinnis and Mormyrus rume)

Aspects of Reproductive Ecology of Chrysichthys Auratus in the Volta Lake, Ghana

The study was conducted in 2018, on the Chrysichthys auratus in the Volta Lake, due to its socio-economic importance to the many and varied dependent fishermen, fish processors and fish traders. The objective was to determine the reproductive strategy to facilitate sustainable management of the fish stocks. A total of 452 fish samples collected on monthly basis were measured, weighed and dissected for determination of, sexual maturity, sex ratio, gonadosomatic index GSI, hepasomatic index HSI, condition factor k, visceral fat index VFI, and monthly stomach fullness in relation to sexual maturity. According to the length at first maturity determined, 89% of the female fish caught, fell below that critical length, suggesting growth overfishing, attributed to size and sex selective tendencies of bamboo pipe fishing. During gonad development, the correlation of the GSI to the HSI and the VFI was inverse and insignificant but in the post gonad development phase it switched to a positive and insignificant relationship. The point of switch, in September, was synonymous with spawning and indicative of the spawning period. It was concluded that the reproductive strategy was to time the spawning process, in September, to coincide with the upwelling phenomenon (June – September), associated with fish food abundance, thereby enhancing the survival of the offspring. A seasonal ban on fishing and a total ban on bamboo pipe fishing were recommended.

Nematode infections of Clariid and Claroteid catfish species in River Galma, Zaria, Nigeria

Two clariids, Heterobranchus bidorsalis (65) and Heterobranchus longifilis (15), and two claroteids, Auchenoglanis occidentalis (31), and Chrysichthys auratus (19) from River Galma were examined for gastrointestinal nematodes from May 2016 to February 2017. Overall, five species of nematodes were recovered from the clariids and claroteids. The nematodes were distributed as follows: in Heterobranchus bidorsalis, Procamallanus laevionchus (12.31%), Paracamallanus cyathopharynx (9.23%) and Rhabdochona sp. (1.54%); in Heterobranchus longifilis; Paracamallanus cyathopharynx (6.67%); in Auchenoglanis occidentalis: Procamallanus laevionchus (25.81%); in Chrysichthys auratus: Procamallanus laevionchus (5.26%), Contracaecum sp. (5.26%) and Spirocamallanus spiralis (15.79%). Nematode prevalence in C. auratus was higher in the wet than in the dry season; however, prevalence of infection in A. occidentalis, H. longifilis and H. bidorsalis was higher in the dry than in the wet season. Prevalence of nematode infection was also higher in male than in female H. longifilis while it was higher in female A. occidentalis, C. auratus and H. bidorsalis than males of the same species. Nematode prevalence was higher in larger (24.0-31.9cm) Heterobranchus bidorsalis and Auchenoglanis occidentalis. Prevalence of infection was higher in smaller (8.0- 15.9cm) Chrysichthys auratus. It is recommended that a larger sample size of especially Heterobranchus longifilis and Chrysichthys auratus, of which only 15 and 19 specimens respectively, were examined during the period of this study, be examined, to have a clearer picture of their infection by nematodes in River Galma.
 Keywords: Nematode; catfish; clariid; claroteid; infection; prevalence.

Detection of Organochlorine Pesticides Residues in Nile Fish and Its Risks in Qena City

Fifteen organochlorine pesticides (OCP) residues were determined in Nile tilapia (Oreochromis niloticus), African catfish (Clarias gariepinus) and Long fin catfish (Chrysichthys auratus) in Qena city, Egypt by gas mass chromatography. Nile tilapia fish significantly (P < 0.05) had the highest concentrations of Dichlorodiphenyldichloroethylene (DDE), endrin, methoxychlor, Dichlorodiphenyldichloroethane (DDD) and endosulfan sulfate with mean±SD concentration of 6.27±0.68, 25.02±0.01, 6.98±1.88, 33.35±1.76 and 47.82±12.51 ppb respectively. Long fin catfish significantly had the highest concentrations of D-chlordane, alpha hexachlorobenzene (a-BHC) and aldrin with mean±SD concentration of 82.27±0.45, 11.89±0.56, 11.73±0.48 ppb respectively. Finally African catfish significantly had the highest concentration of dieldrin with mean concentration 3.53±0.03 ppb and had significant lowest concentration of endrin 1.99±1.39 ppb. OCP residues in all examined raw fish samples were below the maximum permissible limits (MPL) set by Food and Drug Administration. The effect of pan frying on OCP residues showed that the highest reduction rate in OCP in Nile tilapia was 100% for dieldrin and endosulfan sulfate while reduction rate in African catfish was 100% for dieldrin, methoxychlor and endosulfan sulfate. On the other hand the reduction rate in Long fin catfish was 100% for dieldrin, endrin, methoxychlor, heptachlor epoxide and endosulfan sulfate. The lowest reduction rate was detected in DDD, DDE, b-BHC, heptachlor and DDT respectively. Consumption of studied fish had no potential hazard to human health as hazard ratio was below one. Carcinogenic risk (CR) value considered acceptable risk for b-BHC and considered level of concern for heptachlor epoxide, total DDTs, lindane and total heptachlor.

Evaluating the potential health risks of heavy metal pollution in sediment and selected benthic fauna of Benin River, Southern Nigeria

The potential ecological and human health risk of heavy metal pollution in sediment and Benthic Fauna (Chrysichthys auratus and Tympanotonus fuscatus) of Benin River, Southern Nigeria, was evaluated. Three sampling sites associated with heavy anthropogenic activities along the course of the river were sampled. Heavy metals concentrations were determined in the samples using atomic absorption spectrophotometer (Model 210 VGP, Buck Scientific). In all sediment samples, only Pb exceeded the threshold/probable effect level (TEL). Very high contamination degrees (CD > 24) 181.74, 50.11, and 101.96) for stations 1, 2, and 3, respectively, were observed indicating serious anthropogenic pollution. Geoaccumulation index (igeo) showed slight pollution with Pb and Cd and severely to extremely polluted with Fe across the stations. Cd exhibited moderate individual potential risk (E_{text{r}}^{i}), and the other heavy metals showed low E_{text{r}}^{i}. Potential ecological risk index (RI) showed low risk of contamination for heavy metals in sediment. Human health risk assessment for Co, Cd, Cu, Zn, Mn, Fe, and Ni in C. auratus and Co, Zn, Mn, Fe, and Ni in T. fuscatus indicated no obvious health risk from these heavy metals over a lifetime of exposure. However, hazard quotient (HQ) values for Pb in C. auratus and Cd, Cu, and Pb in T. fuscatus indicated significant health risk. The hazard index (HI) values for both C. auratus and T. fuscatus were > 1 indicating significant adverse health risk of non-carcinogenic effect. Therefore, the consumption of these contaminated fish and shellfish by the people of Koko portends risks of the health of the public. The industries operating in this community should adopt more sustainable and eco-innovative management options in order to attenuate potential ecological and human health risk of metal pollution.

Helminth parasites of Synodontis clarias, Chrysichthys auratus and Chrysichthys nigrodigitatus from Omambala River, Otuocha, Anambra State, Nigeria

Roundworms are the most common parasites found in both freshwater and marine fishes. A study was conducted to examine helminth parasites in some catfishes from Omambala River, Anambra State, Nigeria. Two hundred and fifty randomly selected fish samples comprising of 100 Chrysichthys auratus, 62 Chrysichthys nigrodigitatus and 88 Synodontis clarias were collected between the months of January and June, 2017. They were examined for intestinal helminth parasites using standard conventional parasitological methods. The rate of infection was determined using low power (x10) binocular microscope to enumerate number of worms. Results revealed that Caryophyllaeus and Cosmoxyema were present in C. nigrodigitalus, Wenyonia, Polyonchobothriom, Paraglaridacris and Cosmoxyema were recovered from Synodontis clarias and parasite was observed in C. auratus. Small intestine was the site preference for the parasites. Parasite prevalence was lower in C. nigrodigitatus (8.1%) (p 0.05) in infection rate of parasites between C. nigrodigitatus and C. gariepinus. The males of C. nigrodigitatus had a lower prevalence (6.25%) than the females (10%). Similar trend was observed in S. clarias with the males having a prevalence of 84.9% while the females recorded a prevalence of 86.7%. This may mean that female fish had higher loads of parasite infections than their male counterpart. The study showed that helminthes are important parasites of S. clarias in Omambala River. Key Words: Fresh water fish, Omambala River, Helminth parasites, Rondonia sp, Chrysichthys auratus.

FOOD AND FEEDING HABITS OF SOME FISH SPECIES IN OGUN STATE COASTAL ESTUARY, OGUN STATE, NIGERIA

The food and feeding habits of eight (8) fish species Elops lacerta, Chrysichthys auratus, Schilbe mys-tus, Sardinella maderensis, Synodontis schall, Hepsetus odoe, Tilapia zillii and Mugil cephalus in Ogun estuary, Ogun State, Nigeria were studied and estimated for six months, between February and July, 2014. A total of 470 fishes were randomly collected from the commercial fishermen during the study. Results from the stomach contents analysed using frequency of occurrence and numerical methods showed that S. mystus, E. lacerta, S. maderensis, H. odoe, S. schall, T. zillii, M. cephalus and C. auratus were predators, piscivores, herbivores, piscivores, omnivores, herbivores, herbivores and omnivores respectively while H. odoe and S.mystus partly fed on E. lacerta and T. zillii respec-tively. The Diet Breadth (D) ranged from 0.76 to 0.88 and the percentage Gut Repletion Index (GRI), a reflection of frequency of feeding, ranged between 60-100%.

Comparative Studies on the Histology of Eye Retina in Some Nile Fishes with Different Dial Activities

Aim of the work: the present work aimed to study the comparative histology of some fresh water fishes inhabiting the Nile River in Egypt. These fishes have different dial activities; Oreochromis niloticus is diurnal,while Clarias gariepinus, Bagrus bajad and Chrysichthys auratus are nocturnal. Results: the retinae of all studied fishes (O. niloticus,C. gariepinus, B. bajad and Ch. auratus) are composed of ten layers. These layers are the inner limiting membrane (ILM), nerve fiber layer (NFL), ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer (INL), outer plexiform layer (OPL), outer nuclear layer (ONL), outer limiting membrane (OLM), photoreceptor layer (PL) and pigmented epithelial layer (PE). The histological structure showed three types of the photoreceptors (single and double cones as well as single rods) in Oreochromis niloticus. The pigment epithelium layer in C. gariepinus, B.bajad and Ch. auratus completely hides the photoreceptors. A considerable variation was recorded between the different studied fishes in the whole retinal thickness as well as their retinal layers. Conclusion: Whole retinal thickness in O. niloticus (diurnal activity) is large in comparison with that of the other three siluriform fishes (nocturnal activity).

Two new species of gill parasites assigned to Protoancylodiscoides (Monogenea, Ancyrocephalidae) from Chrysichthys spp. (Siluriformes, Claroteidae) in River Sanaga (Cameroon).

Host specimens were sampled in the middle course of the River Sanaga (Cameroon) from January to October 2014. Two new species, Protoancylodiscoides auratum n. sp. from Chrysichthys auratus and Protoancylodiscoides combesi n. sp. from C. auratus, Chrysichthys nigrodigitatus and Chrysichthys longidorsalis, are herein described. These new helminths differ from the congeneric species by the size of the haptoral sclerites, the male copulatory organ length, the diameter and morphology of the vagina. At this stage, the present study suggests that Protoancylodiscoides auratum is oioxenous, while P. combesi is stenoxenous. The two new Protoancylodiscoides species bring to three the number of those parasitizing C. auratus, and to four the number of those described from Chrysichthys spp.

Reproductive biology of Catfish Chrysichthys auratus, Geoffroy Saint-Hilaire, 1809, (Family: Bagridae) from Damietta branch of the River Nile, Egypt

Reproductive biology of 803 specimens of Chrysichthys auratus from Damietta branch of the River Nile, Egypt was studied between January and December 2010. The overall sex ratio (M:F=1:1.18) was significant at P<0.05 and the ratio showed insignificant variation in summer and autumn. The length of the onset sexual maturity was 12.3cmSL at age 1.34years for males and 9.7cmSL at age 0.56years for females. C. auratus showed prolonged spawning season extending from October to June with a peak in March for both sexes and the fish restart their reproductive cycle in July. The maximum value for GSI and GI were shown in March for both sexes (GSI=0.49%±0.30 and 11.17%±9.65 for males and females respectively and GI=1.02%±0.64 for males and 22.85%±20.00 for females). The reproductive load was 0.464 and 0.366 for males and females respectively. The study of ova diameters showed protracted and indefinite spawning period with diameters ranging from 0.3 to 3.0mm (mean value=1.53±0.45). The absolute fecundity ranged from 696 to 4687 eggs but the relative fecundity was from 70 to 247 eggs/unit fish length. The results showed that C. auratus has different life history strategies in Egyptian River Nile water than any other African Rivers.

Length-Weight Relationship of Some Fish Species in a Tropical Rainforest River in South-East Nigeria

Abstract The Length-Weight relationship of some fish species from Oramiri-Ukwa River, was studied from January to December, 2014. The slope (b) values obtained in the nine species ranged from 1.830 to 5.670 with most of the fishes indicating a negative allometric growth pattern except for Papyrocranus afer, with b value of 3.04, thus showing a positive isometric growth pattern. The following fish species showed a high degree of positive correlation at (P &gt; 0.05); Ctenopoma kingselyae, Alestes imberi, Channa obscura, Oreochromis niloticus, Tilapia mariae, Tilapia zillii, Synodontis omais, and Papyrocranus afer. Chrysichthys auratus did not show this positive correlation. The condition factor (K) of the fish species ranged from 0.99 to 4.54, indicating that most of the fish were in good condition except for Chrysichthys auratus with 0.99.

Fishery biology of Catfish (Chrysichthys auratus, Family: Bagridae) from Damietta branch of the River Nile, Egypt

The study of fishery biology of Chrysichthys auratus from Damietta branch, Egypt showed that the population has SL range of 7–20cm, L′=11.85cm. Males represent 45.90% and females 53.98% of the population. Length–length and length–weight relationships were analyzed for males, females and combined sexes. It was: SL=−0.6231+0.8402 TL and LogW=−1.6253+2.9832 LogSL for combined sexes, respectively. The highest values of condition factor were obtained in July, August and September for both sexes. The mean value of (K) for males was higher than those of females in all different lengths. Age was assessed by Bhattacharya’s (1967) method from length frequency data to estimate the von Bertalanffy growth parameters (L∞=26.53cm, K=0.214 and to=−1.569). The individuals of this species live for about 4years and the first age dominates the population. The growth performance index in length (ФL) and weight (Фwt) was estimated as 2.18 and 1.11, respectively. The mortalities were computed as: Z=1.44, M=0.60 and F=0.84. The exploitation rate was estimated as Ecur=0.58. Length at first capture (Lc) was 9.66cm at age 0.54years. Length at recruitment (Lr) was 8.49cm and age 0.35years. It was found that the stock of Chrysichthys auratus in Damietta branch was rationally exploited.

Scanning electron microscopic studies of gill arches and rakers in relation to feeding habits of some fresh water fishes

The surface ultrastructure of the gill arches and the gill rakers of the three concerned species Oreochromis niloticus, Chrysichthys auratus and Clarias gariepinus was investigated by scanning electron microscopy. These structures show significant adaptive modifications associated with the food and feeding habits of these fishes. Short and tuberous type gill-rakers in O. niloticus, are a well interesting filter of food. In C. auratus gill rakers were short with broad base, they serve to strain water which was to bathe the gills and prevent any solid particles from passing over it. Gill rakers in C. gariepinus were long, cylindrical in shape and arising at acute angles to the arch, they help to strain food and other materials, thus protect gill filaments from damage.Prominent epithelial protuberances on the gill rakers and gill arches enable the taste buds, located at their summit, to project well above the surface of the epithelium. This could increase the efficiency of the taste buds in selective sorting of palatable food. Co-occurrence of teeth and taste buds on the epi-and hypopharyngeal bones (Types I–III) denotes that food processing and gestation occur simultaneously in the pharynx. Caniform, villiform and papilliform teeth on the epi- and hypopharyngeal bones of the three studied species respectively in O. niloticus, C. auratus and C. gariepinus were associated with a complex food-processing cycle. Mucous secretions, oozing through mucous cell openings, provide lubrication facilitating smooth passage of food through the pharynx.