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Preliminary studies on the food and feeding habits of membraneceus from Ogobiri River, Nigeria

Allison, M. E. / Youdubagha, S. E.

Abstract Thefood andfeeding habits of Synodontis membraneceus of Ogobiri River of Bayelsa State, Nigeria was studied using 44 male and 51 female specimens that were boughtfrom fishers in the study area measuring between 5 and 25 em total length. The Numerical and the Frequency of Occurrence method of analysis were used. For the males, thefood items by the numerical method were copepods (168), insects, (118), Cladocera (69), and unidentified items (32). In thefemale specimens, thefood items were Cladocera (286), Insect (216) Copepod (100) and unidentified organisms/materials (65). In the Frequency of Occurrence method for the males, Copepod was still the highest with a total of (48), Cladocera (44), Insects (29) and unidentified (I 6). For thefemales, Cladoera (48), Insects were (30) followed by Copepods (35) and unidentified (J9). The Percentage composition offood items by the Numerical method was Cladocera (45.5%), Insects (34.5%), Copepod (12.5%), and unidentified items (7.0%) while the Percentage Frequency of Occurrence was, Cla• docera (30.5%), Insects (30.9%), Copepod (29.6%), and unidentified items (9.0%). Keywords:Numerical method,frequency of occurrence, S. membraneceus, Ogobiri River.

Introduction ish is a very important source of food for humans (FAO, 2010). Information about the food habits of fishes is on defin• ing predator-prey relationship (Saa et al., 1997) and the creation of trophic models as a tool to understanding complete Fecosystem (Lopez-Perata and Arcila, 2002; Bachok et al., 2004). It also guides the choice of feed stuff needed for ar• tificial diet of cultured for optimal production (Ketoye, 2007). Synodontis are generally bottom dwellers but several species,including Synodontis membraneceus, spend most of their time swimming and feeding in an upside down position. They feed on worm, , detritus, seeds and decaying vegetable matter (Friel and Vigliotta, 2006), and are caught by mosttypes of fish gear.The serrated spines also cause them to become entangled in all types of nets. According to Ezenwa et al (1987),Synodontis species are commercially important fish species occurring in Nigerian waters especially the Niger Delta Region.The different Synodontis species vary in commercial value in different locations; many are important food fishes and somehave attractive skin colour and exhibit behavioral characteristics that make them potential ornamental candidates. The spineof the males is much larger than those of the females (Friel and Vitgota, 2006) and they inhabit a large proportion of the Africanfresh waters (Idodo Umeh, 2003). S. membranaceus is highly relished as either fresh or smoked-dried fish. S membranaceus is generally preferred by fishermenand consumers because of its relatively large sizes which command a higher market value than other species of the (Owalabi, 2005). Olojo and Olum (2003) observed monthly variations in feeding intensity which was determined as a measureof the percentage of food containing stomachs. S membranaceus is regarded as omnivorous, feeding on insects, nematodes,crusteaceans, mollusks, , seeds, algae, fish scales, detritus, insect larvae and worms (Fagade, 1983; Win• emiller,1996and Idodo-Umeh, 2003). Agood knowledge offood and feeding habits offish species is very vital in fish culture (Njoku,et al. 2009) with regard to evolution (Collar, et al. 2009), selection of prey, predation etc (Allison and Sikoki, 2013) Materials And Method This study was carried out using a total of 95 fresh specimens of S membranaceus that were bought from fishers of Ogobiri River,which is a fresh water ecosystem, in Southern [jaw Local Government Area of Bayelsa State. The study lasted from April- June, 2012 of which 44 specimens were males and 51 were, females. The total length (ern) and weight (kg) were P1{UCEEVINGS OF 2t\TH ANNUAL CONFERENCE,NOV. 25-30, 2013

measured for each specimen. The gut of the fish was removed by making a longitudinal incision along the mid ventral line from the mouth to the anus to expose the visceral organs. The stomachs were cut open and the content examined with stereo microscope to determine the food of the fish which was analyzed by the numerical and frequency of occurrence methods (Hyslop, 1980). In the numerical method the number of different food items were counted and recorded. In the frequency of V1 occurrence method, all stomachs containing particular food items were recorded

By the numerical method of analysis the food items of the 44 male specimens of S. membranaceus were Copepod (168) fol• lowed by Insects, (118), Cladocera (69), and unidentified items (32) as shown in Table lao

Table 1a: Numerical analysis and % of food items in male S. membranceceusin Ogobiri River

I Number Copepod Insects Cladocera Unidentified items Size Range of fish No % No % No % No % 5-10cm 8 '40 24 11 9 16 23 4 13 11-15cm 16 33 20 37 31 17 25 9 29 16-20cm 12 50 30 49 42 26 38 11 34 21-25cm 8 45 26 21 18 10 14 8 25 Total 44 168 100 118 100 69 100 32 100

A total of 5l female specimens were studied out of the 95 specimens,By the Numerical method of analysis, the food items were Cladocera (286), Insect (216), Copepod (100) and unidentified (65)(Table lb).

Table lb: Numerical analysis and % of food items in female S. membranaceus in Ogobiri River.

Number of Cladocera Insects Copedpod I Unidentifieditems Size Range fish No. % No. % No % No. % 5-10cm 15 94 33 62 29 30 30 13 20 11-15cm 12 88 31 68 31 35 35 15 23 16-20cm 19 93 32 75 35 25 25 21 32 21·25cm 5 11 4 11 5 10 10 16 25 Total 51 286 100 216 100 100 100 65 100

In the frequency of occurrence method for the males (Table 2a), Copepod W3S still the highest with a total of (48), fol• lowed by Cladocera (44), Insects (29) and unidentified (16).

Table 2a: Frequency of Occurrence (F) and % of food items in male S. membranaceus in Ogobiri River.

Unidentified Number Copedpod Cladocera Insects Size Range items of fish F % F % F % F % 5-10cm 8 11 23 10 23 4 14 1 6 11·15cm 16 15 31 15 34 11 38 6 38 16-20cm 12 11 23 13 29 9 31 5 31 21·25cm 8 11 23 6 14 5 17 4 25 Total 44 48 100 44 100 29 100 16 100

In the frequency of occurrence method for the females (Table 2b), Cladocera was the highest (48), followed by Insect (35),Copepods (30) and unidentified organisms/materials (19). Table 2b: Frequency (F) of occurrence and % of food items in female S. membranceceus in Ogobiri River. Cladocera Copepod Unidentified Number Insects Size Range items of fish F % F % F % F % 5·10 cm 15 11 23 8 23 7 23.3 3 16 11·15 cm 12 13 27 11 31 8 26.7 6 32 16·20 cm 19 20 42 12 34 13 43.3 9 47 21-25 cm 5 4 8 4 11 2 6.7 1 Total 51 48 100 35 100 30 100 19 100

234 PROCEEDINGS OF 28TH FISON ANNUAL CONFERENCE, NOV. 25-30, 2013

The percentage numerical and percentage frequency of occurrence of food items in the stomachs of Smembraneceus examined are shown in Table 3. By the numerical composition,Cladocera consisting of Moina, Bosmina, Daphnia and Di• aphanosomaspecies were predominant (45.5%) followed by Insects (Chironomus larva, pupa and Water Beetles) of 34.5% and Copepoda consisting Cyclop sp. and Diopomus (12.5%) while unidentifiable organisms / materials, constituted 7.5% of the number of food items in the stomachs examined.For the Percentage Frequency of Occurrence of food items, Cladocera Vl (30.5%) and Insect (30.9%) were the dominant food items in the stomachs of S membraneceus while Copepods and unidenti• 'Tj fied organisms constituted 29.6% and 9.0% respectively. Table3: Percentage composition ofthe various food items of S. membranaceus bythe numerical and frequency ofoccurrence offood items.

Foodspecies Number(%) Frequencyofoccurrence(%) CLADOCERA Moinasp 98 12.3 13 5.8 Bosminasp 92 11.6 11 4.9 Daphniasp 88 11.0 22 9.9 Diaphanosoma 84 10.6 22 9.9 45.5 30.5 INSECT ChirinomusLarva 90 11.3 24 10.8 ChirinomusPupa 87 11.0 25 11.2 WaterBeetles 97 12.2 20 9.0 34.5 30.9 COPEPOD CyclopsSp 58 7.3 37 16.6 Diopomus 41 5.2 29 13.0 12.5 29.6 Unidentified Organisms 60 7.5 20 9.0 TOTAL 795 100 223 100

Discussion The study revealed that does not have a strict feeding habit being an and a predator. The stomach contents of S membranaceus of this study are to some extent in' agreement with King (1995) for Simembranaceus in River Nile and Owolabi (2005) in Jebba Lake, Nigeria. Other observations with slight variations include Petr (1967) on S membranaceusof Lake Volta, Willoughby (J 974), in Lake Kainji and in lower River Benue. These variation in the stomach content of S membranaceus from different fresh water bodies, confirm the fact that the fish does not have a strict feeding habit. According to Olatunde (1987), the food item selected at any time of the year, depends on abundance and availability to the predator. It thus feeds on any material either of the plant origin or of the origin that is available in the habitat in which it lives. The high insect and Cladocera occurrence in the stomach of Smembranaceus (30.9%) and (30.5%) respectively in this study show that the fish prefer these food organisms in its habitat. The juveniles showed more inclination towards insect particularly insect larvae than the adults which indicates that the food preference of S membranaceus changes with age like Clariasgariepinus (Ayinla and Faturoti, 1990) and Brienomyrus longianalis (Ikomi, 1996). The results of this study also indicated that S. membranaceus feeds more on animal materials than plant materials similar to the feeding habit of S Schall (Olatunde, 1987). Conclusion The results of the present study indicated S membranaceus as an omnivorous species feeding on any available food item in its environment such as cladoceras, copepods and insects and this makes it suitable for culture in fresh water ponds.

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