Ectoparasitic infestation of the Nile Squeaker, Synodontis schall (Bloch and Schneider, 1801) from the Cross River Estuary, Nigeria

The objective of this study was to determine the abundance, intensity and prevalence of ectoparasites of Synodontis schall from the Cross River Estuary, Nigeria. A total of 150 fresh samples were collected between May and October, 2013 from the catches of the artisanal fisheries at Nsidung beach. The skin, gill and fin scrapping were prepared from each specimen and examined following standard methods for microscopic analysis. The results showed that 21 specimens were infested with 77 ectoparasites belonging to five species, including Trichodina sp., protozoan cyst, Ergasilius lizae, Dactylogyrus sp. and Gyrodactylus sp. with an overall prevalence of 14.0%. Infestation rate was highest in 10-14.9 cm class size (53.55%), followed by 15-19.9 cm (34.00%), ≥20.0 cm (8.00%) and 5-9.9 cm (4.67%) size classes. Parasites were more prevalent in the gills (82%), followed by the skin (14%) and least (4%) in the dorsal fin. Prevalence and abundance of ectoparasites was highest (28.57% and 0.71) in 5-9.9 cm size class, followed by 10-14.9 cm (16.25% and 0.60), 15-19.9 cm (9.80% and 0.41) and ≥20.0 cm (8.33% and 0.25) classes. Prevalence and abundance of ectoparasites was higher in female (15.63% and 0.56) than male (11.11% and 0.43). Dactylogyrus sp., Trichodina sp., protozoan cyst and E. lizae exhibited organ specificity as they were specifically recovered from the gills whereas Gyrodactylus sp. was found in the skin and fin. However, it was concluded that to prevent zoonosis, S. schall should washed with clean water and cooked properly before consumption

REPRODUCTIVE PERFORMANCE OF HATCHERY-BRED, WILD-CAUGHT BROODSTOCK, AND THEIR OUTBREED OF THE AFRICAN CATFISH Clarias gariepinus (Burchell, 1822)

This study was conducted to evaluate the reproductive performance of hatchery-bred and wild-caught broodstock of Clarias gariepinus. Thirty pairs of each hatchery-bred and wild-caught broodstock (15 females and 15 males) was used for the study. Induced breeding was carried out in four groups with three replications at a ratio of 1:1 by hypophysation method. Group A: hatchery-bred male and hatchery-bred female (HBM m + HBF f); B: wild-caught male and wild-caught female (WCM m + WCF f), C: hatchery-bred female and wild-caught male (HBF f+ WCM m) and D: wild-caught female and hatchery-bred male C. gariepinus (WCF f + HBM m). Results showed that egg diameter, sperm motility, sperm density, and male GSI were not significantly different (P>0.05) whereas ovary weight, sperm volume, fecundity, female GSI, and percentage fertilization were significantly higher (P<0.05) in hatchery-bred broodstock than wild-caught broodstock. Hatchability was significantly higher (P<0.05) in Group C and D than A and B. In conclusion, a better reproductive performance in C. gariepinus with an economic advantage could be recorded through the combination of wild-caught and hatchery-bred broodstock

USPOREDNO ISTRAŽIVANJE GONADOSOMATSKOG INDEKSA (GSI) I MORFOLOGIJE GONADA AFRIČKOG SOMA (Clarias gariepinus) HRANJENOG UNICAL AQUA HRANOM I KOMERCIJALNOM HRANOM PROIZVOĐAČA COPPENS

A comparative study of the gonado-somatic index (GSI) and gonad gross morphology of African catfish, Clarias gariepinus fed Unical Aqua feed and Coppens commercial feed was carried out for six months in concrete tanks. Two triplicate groups of 50 postfingerlings with a mean bulk weight of 0.50 ± 0.02 kg were stocked in circular concrete tanks, area 16.63 m2 labeled A1, A2, A3, B1, B2 and B3. Fish in units A1, A2 and A3 were fed Coppens feed while fish in units B1, B2 and B3 were fed Unical Aqua feed twice daily at 3% of their body weights. Results obtained showed that mean gonad weight (99.03 ± 16.57 g) and the GSI (15.89 ± 2.10%) of female C. gariepinus fed Unical Aqua feed was not significantly different (P>0.05) from fish fed Coppens feed with mean gonad weight (91.80 ± 12.83 g) and the GSI (13.81 ± 2.49%). In male fish fed Unical Aqua feed, mean gonad weight (7.08 ± 1.17 g) and the GSI (1.16 ± 0.30%) were not significantly different (P>0.05) from male fish fed Coppens feed with mean gonad weight (6.77 ± 1.09 g) and the GSI (1.12 ± 0.32%). In female fish fed both feeds, there was a positive significant relationship between the GSI and total length, total weight and gonad weight. In male fish fed both feeds, there was also a positive non-significant (P>0.05) relationship between the GSI and total length, total weight and gonad. Food conversion efficiency (FCE) was insignificantly higher (P>0.05) in fish fed Coppens feed (50.94 ± 0.91%) than fish fed Unical Aqua feed (50.37 ± 1.29 %). Histology of ovaries and testes of fish fed the two experimental diets showed normal development and distribution of oocytes and interstitial cells. Proximate analysis of the dry matter showed that moisture content, fat content, crude fibre content, ash content, carbohydrate and caloric value (C/V) differed significantly among experimental groups (P0.05). Physicochemical parameters were within acceptable range for fresh water fish culture. Based on these findings, Unical Aqua feed competed favorably with Coppens feed in terms of the GSI and gross gonad morphology of C. gariepinus and, on the basis of affordability, Unical Aqua feed is more economical and therefore recommended for fish farmers.Usporedno istraživanje gonadosomatskog indeksa (GSI) i morfologije gonada afričkog soma, Clarias gariepinus, hranjenog Unical Aqua hranom i komercijalnom hranom proizvođača Coppens (za životinje) provedeno je tijekom šest mjeseci u betonskim spremnicima. Dvije trostruke skupine od 50 jedinki mlađi prosječne težine 0,50 ± 0,02 kg pohranjene su u kružnim betonskim spremnicima površine 16,63 m2, s oznakama A1 , A2 , A3 , B1 , B2 i B3. Riba u jedinicama A1, A2 i A3 hranjena je hranom proizvođača Coppens, a riba u jedinicama B1, B2 i B3 hranjena je Unical Aqua hranom dvaput dnevno na 3% svoje tjelesne težine. Dobiveni rezultati su pokazali da srednja težina gonada (99,03 ± 16,57 g) i GSI indeks (15,89 ± 2,10 %) ženke C. gariepinus hranjene Unical Aqua hranom nisu bili značajno različiti (P>0,05) od težine ribe hranjene hranom proizvođača Coppens, čija je srednja težina gonada bila 91,80 ± 12,83 g, a GSI indeks 13,81 ± 2,49%. Kod mužjaka ribe hranjene Unical Aqua hranom, prosječna težina gonada bila je 7,08 ± 1,17 g, a GSI indeks 1,16 ± 0,30%, što se neznatno razlikuje od vrijednosti kod mužjaka ribe hranjene hranom proizvođača Coppens, čija je prosječna težina bila 6,77 ± 1,09 g, a GSI indeks 1,12 ± 0,32%. Kod ženki ribe hranjene i jednom i drugom hranom uočena je pozitivna značajna povezanost između GSI indeksa i ukupne dužine, ukupne težine i težine gonada. Kod mužjaka ribe hranjene i jednom i drugom hranom također je uočena pozitivna, ali neznačajna (P>0,05) povezanost između GSI indeksa i ukupne dužine, ukupne težine i težine gonada. Hranidbena iskoristivost (FCE) neznatno je veća (P>0,05) kod ribe hranjene hranom proizvođača Coppens (50,94 ± 0,91%) u odnosu na ribu hranjenu Unical Aqua hranom (50,37 ± 1,29%). Histologija jajnika i testisa kod ribe podvrgnute dvjema eksperimentalnim dijetama pokazala je normalan razvoj i distribuciju jajnih i intersticijskih stanica. Približna analiza suhe tvari pokazala je značajnu razliku između sadržaja vlage, masti, sadržaja sirovih vlakana, sadržaja pepela, ugljikohidrata i kalorijske vrijednosti (C/V) u eksperimentalnim grupama (P0,05). Fizikalno-kemijski parametri bili su unutar prihvatljivih granica za kulturu slatkovodnih riba. Na temelju ovih nalaza, Unical Aqua hrana i hrana proizvođača Coppens su prilično slične po svom učinku na GSI indeks i morfologiju gonada C. gariepinus, jedino je u smislu dostupnosti Unical Aqua hrana ekonomičnija i stoga se preporučuje uzgajivačima ribe

ODNOS PLODNOSTI I BIOMETRIJSKIH INDEKSA KOD SREBRNOG SOMA Chrysichthys nigrodigitatus (Lacepede) U ESTUARIJU RIJEKE CROSS U NIGERIJI

The relationship between fecundity and biometric parameters of silver catfish, Chrysichthys nigrodigitatus from the Cross River estuary was studied between July and October 2012. A total of 120 gravid female fish were examined. The results show that fecundity of C. nigrodigitatus ranged between 975 eggs for fish of total length 23.2 cm, total weight 99 g, ovary weight 15 g and mean egg diameter 2.43 mm to 11,280 eggs for fish of total length 50.0 cm, total weight 1420.0 g, ovary weight 80.0 g and mean egg diameter 3.44 mm. There was a positive significant relationship between fecundity (F) and total length (TL), total weight (TW), ovary weight (OW) and mean egg diameter (MED) as follows: F = 2.457TL1.9225 (r = 0.8457 and r2 = 0.7152, P<0.05), F = 61.51TW0.6098 (r = 0.890, r2 = 0.7921, P<0.05), F = 28.162OW1.2468 (r = 0.9457, r2 = 0.8943, P<0.05),F = 704.44MED1.0624 (r = 0.2128, r2 = 0.0453, P<0.05). Fecundity and mean egg diameter increases with total weight (TW). This finding is essential for evaluating the aquaculture strategies required to intensify commercial production and management of C. nigrodigitatus stock since it is a valuable source of protein in Nigeria.Odnos plodnosti i biometrijskih parametara srebrnog soma, Chrysichthys nigrodigitatus iz estuarija rijeke Cross, proučavan je od srpnja do listopada 2012. godine. Pregledano je ukupno 120 gravidnih ribljih ženki. Rezultati pokazuju sljedeće kretanje plodnosti C. nigrodigitatus: od 975 jajašca kod ribe dužine 23,2 cm, ukupne težine 99 g, težine jajnika 15 g i promjera jajašca 2,43 mm do 11280 jajašca kod ribe ukupne dužine 50,0 cm, ukupne težine 1420,0 g, težine jajnika 80,0 g i promjera jajašca 3,44 mm. Pozitivna je i značajna veza između plodnosti (F) i ukupne dužine (TL), ukupne težine (TW), težine jajnika (OW) i promjera jajašca (MED): F = 2,457TL1.9225 (r = 0,8457 i r2 = 0,7152, P<0,05), F = 61,51TW0.6098 (r = 0,890, r2 = 0,7921, P<0,05), F = 28,162OW1.2468 (r = 0,9457, r2 = 0,8943, P<0,05), F = 704,44MED1.0624 (r = 0,2128, r2 = 0,0453, P<0,05). Plodnost i promjer jajašca povećavaju se zajedno s ukupnom težinom (TW). Ovakvi rezultati važni su za ocjenjivanje strategija u akvakulturi radi povećanja komercijalne proizvodnje i stoka srebrnog soma (C. nigrodigitatus), budući da je riječ o vrlo vrijednom izvoru bjelančevina u Nigeriji

RELATIONSHIP BETWEEN FECUNDITY AND BIOMETRIC INDICES OF THE SILVER CATFISH Chrysichthys nigrodigitatus (Lacepede) IN THE CROSS RIVER ESTUARY, NIGERIA

The relationship between fecundity and biometric parameters of silver catfish, Chrysichthys nigrodigitatus from the Cross River estuary was studied between July and October 2012. A total of 120 gravid female fish were examined. The results show that fecundity of C. nigrodigitatus ranged between 975 eggs for fish of total length 23.2 cm, total weight 99 g, ovary weight 15 g and mean egg diameter 2.43 mm to 11,280 eggs for fish of total length 50.0 cm, total weight 1420.0 g, ovary weight 80.0 g and mean egg diameter 3.44 mm. There was a positive significant relationship between fecundity (F) and total length (TL), total weight (TW), ovary weight (OW) and mean egg diameter (MED) as follows: F = 2.457TL1.9225 (r = 0.8457 and r2 = 0.7152, P<0.05), F = 61.51TW0.6098 (r = 0.890, r2 = 0.7921, P<0.05), F = 28.162OW1.2468 (r = 0.9457, r2 = 0.8943, P<0.05),F = 704.44MED1.0624 (r = 0.2128, r2 = 0.0453, P<0.05). Fecundity and mean egg diameter increases with total weight (TW). This finding is essential for evaluating the aquaculture strategies required to intensify commercial production and management of C. nigrodigitatus stock since it is a valuable source of protein in Nigeria