FOOD and FEEDING HABITS of the AFRICAN PIKE CHARACIN Hepsetus Odoe (BLOCH, 1794) in the CROSS RIVER SYSTEM, NIGERIA Eteng, Sunda

U6CAU Proceedings Volume 1, Number 1, 82 - 90, September, 2019 Maiden Edition on Harnessing African Potentials for Sustainable Development, Calabar, Nigeria ISSN 1596-1273

FOOD AND FEEDING HABITS OF THE AFRICAN PIKE CHARACIN Hepsetus odoe (BLOCH, 1794) IN THE CROSS RIVER SYSTEM, NIGERIA 1Eteng, Sunday Urom* and 2Ifon, Honor Tajoes 1Faculty of Oceanography, University of Calabar, Calabar, Nigeria 2Department of Zoology and Environmental Biology, University of Calabar, Calabar, Nigeria Corresponding author: [email protected]

ABSTRACT This study aimed at providing information on the fish food items and feeding habits of Hepsetus odoe (African pike characin) in the Cross river system, Nigeria. The study was carried out for 10 months from June 2018 to March 2019. H. odoe was sampled from the landings of artisanal fishers that use hook and line as well as cast nets for fish harvest, at Itu beach, Nigeria. The laboratory analysis of the gut contents revealed that fish parts (54%) was the most abundant food item in the stomach of large specimens, crabs (51%) were preferred by medium size group while insects predominates (65%) the stomach of the small specimens. Generally, major diet composition was made up of fish parts, crustaceans and insects. Although statistical analysis revealed no significant variations (P>0.05) in stomach contents with fish size, numerical values indicated that small-sized individuals showed higher feeding frequency. There was also significant difference (P<0.05) with sex as males showed lower feeding activities. Percentage of individuals with low gut contents decreased with size while relative importance of fish components increased with size. These results indicate size specific shift in diets of H. odoe from insectivore to piscivores as they grow older. From the different kinds of food items observed in the guts of H. odoe, it can be concluded that this species exhibits benthic predatory habit in the Cross river. Similar studies on other freshwater species of the Cross River and adjoining rivers are required to provide inputs for trophic modelling. This will help in the understanding of the trophic structure of freshwater fishery for proper multispecies management of the Cross River ecosystem. Keywords: Gut contents, feeding habits, trophic structure, Hepsetus odoe, Cross River, Nigeria

INTRODUCTION elongated body form with a pronounced snout. Matured individuals have visible red and black Hepsetus odoe is the only member of its genus spots on their dorsal and caudal fins. They bear and a characiform belonging to the family remarkable resemblance to the European pike Hepsetidae. It is an important game and food with dentition being their most striking feature. fish inhabiting fresh water bodies including Both upper and lower jaws are filled with sharp rivers, streams and lakes. It has also been pointed teeth. These traits promote their reported in marine waters, swampy predatory habit. H. odoe is piscivorous, feeding environments, lagoons etc. (Adedokun et al., on several species of smaller fishes in the 2013). They are widespread in the tropical genera Synodontis, Barbus, Schilbe, Tilapia regions throughout Africa. It is found in most and several species from the family rivers in West Africa from Senegal to Botswana Mormyridae and Clariidae and has been (Stewart, 2014). H. odoe is well known for its reported to cannibalize (Adedokun et al., 2015). The feeding habits of fish is species specific, 82

FOOD/ FEEDING HABITS OF AFRICAN PIKE Part A: Science, Engineering and Technology Eteng and Ifon, 2019 while some are known to be suspension feeders Cross river originate within the Manyu River in which feed on plankton and organic matter, Cameroon, and are a part of the Cross River others are described as deposit feeders which Basin (Zapfack et al., 2001). feed on detritus, carnivores feeding on other The climate around Cross river system is animals, herbivores feeding on plants, and considered tropical with an average temperature omnivores feeding on a variety of food items of 16 ‒ 33 °C during wet and dry seasons. The (Blay, 2006). Zengeya (2011) reported fairly high temperature observed during the dry detritivorous feeding habit for Oreochromis season is due to the influence of the hot north- mossambicus in Limpopo River, South Africa eastern continental air mass from the Sahara although there were evidence of phytoplankton Desert (Ekpo, 2013).The wet season (April – and aquatic macrophytes in their guts. Other freshwater species like the Nile Tilapia October) is characterised by high precipitation (Oreochromis niloticus) and Nile Perch (Lates (3050 mm), while the dry season (November – niloticus) from Lake Victoria, Tanzania have March with peak in December – February, is been reported as omnivores having their main marked by low precipitation (300 mm) with food items to include plant materials, diatoms, mean annual rainfall of 2000 mm. The highest algae, detritus and insects (Jihulya, 2014). In precipitation is obtained from July to October, a the Cross River estuary, Enin and Enidiok period that accounts for more than 80% of the (2002) described the tongue sole (Cynoglossus total annual discharge. There is usually a cold, senegalensis) as benthic feeder as they prey dry and dusty period between December and mainly on bivalve larvae, crabs shrimps, January known as the harmattan period. polychaetes and detritus. Adeyemi (2010) Relative humidity is usually high throughout described African lungfish (Protopterus the year ranging from 60% in the dry season to annectens) from Idah area of River Niger as an 90% in the wet season. Salinity is generally omnivore, feeding on other smaller fish, insects, plants, crustaceans, cyst, worms and below 1‰ especially during the rains having as detritus. This study aimed at providing low as 0 ppm (Ama-Abasi and Akpan, 2011) information on the natural food items and but maximum salinity of 5‰ may be expected feeding habits of Hepsetus odoe in the Cross during the dry season (Asuquo, 1989). river system, Nigeria. The information obtained Collection of Samples in this study will encourage its culture for Samples of H. odoe were collected from the continued food availability and conservation of landings of artisanal fishers using hook and line this economic important fish species. as well as cast nets at Itu beach. Collection of MATERIALS AND METHODS samples took place monthly for 10 months from The Study Area June 2018 to March 2019. Twelve freshly Cross river is a floodplain river in Cross River caught samples from each month with a total of State situated within the southeast portion of one hundred and twenty samples were obtained. the Nigerian coast. Geographically it lies This comprised of different size classes of between latitudes 4°45ꞌ and 6°15ꞌ N and small, medium and large groups between longitudes 8°00ꞌ and 8°55ꞌ E. It is bounded in standard lengths of 13.50 and 40.20 cm. The the North by Benue state, in the West by samples were stored fresh in ice crest and taken Ebonyi and Abia states, in the South West by immediately to the Department of Zoology and Akwa Ibom state, in the south by the Atlantic Environmental Biology laboratory, University Ocean and in the East by the Republic of of Calabar, Nigeria for analysis. Cameroun (Fig. 1). The headwaters of the

FOOD/ FEEDING HABITS OF AFRICAN PIKE Part A: Science, Engineering and Technology Eteng and Ifon, 2019

Fig. 1: Map of Cross river system showing the study area (Itu beach). Laboratory Analysis stomach containing each food item was The standard length (from the tip of the snout expressed as percentage of full stomach for to the end of caudal peduncle) of each percentage frequency of occurrence (Olojo et specimen of H. odoe was measured to 0.1 cm al., 2003). below by the use of a measuring board (Polat Determination of Food Volume et al., 2015) The fresh weight of individual was measured using an electronic weighing The food volume of each gut was determined balance (model: Mettler P-1210N) to 0.1 g by displacement method as reported by Hyslop below. The weight of each fish specimen was (1980). In this method, 10 ml of distilled water recorded against its corresponding length (cm) was placed in a glass cylinder of 50 ml and further grouped into male and female. capacity where individual gut was dropped one With the aid of a surgical scissors, the after the other. As the gut displaced some abdominal portion of each fish specimen was quantity of water, the volume displaced was cut open and the individual fish gut was noted and taken to represent the food volume extracted with care. The gut taken from the tip in the gut (Hyslop, 1980). This was recorded of oesophagus to the end of the rectum was on spread sheet against the corresponding fish carefully removed by the use of forceps length and weight. (Adedokun and Fawole, 2015). The number of 84

FOOD/ FEEDING HABITS OF AFRICAN PIKE Part A: Science, Engineering and Technology Eteng and Ifon, 2019

Determination of Diet Components Food variations based on size classes (small, Before the determination of the diet medium and large) components of the guts, each gut was first Out of a total number of 120 specimens preserved in glass bottles containing 4% assessed, the ratio of number of empty formalin for three days. This helps in the stomach against the total number of specimens coagulation of the diet components for easy was 5/120 (4.17%). Among the sampled identification (Adedokun and Fawole, 2015). specimens, variations in diet composition of The contents of each gut was extracted with a food items were also observed (Table 2). For spatula into a glass Petri dish and examined small size group (<30.0 cm), the diet with both hand lens and stereo microscope numerical and relative abundance were fish depending on the size of food items. parts 3 (13.04%), crabs 4 (17.39%), insects 15 (65.22%), unidentified materials 1 (4.35%), Determination of Numerical and Relative detritus (which could not be quantified). For Abundance of Diet Components medium size group (30.0 ‒ 47.0 cm), the diet The identified components in the gut of each numerical and relative abundance were fish fish specimen were counted and the quantity parts13 (22.81%), crabs 29 (50.88%), insects of a particular food item in each gut was noted 10 (17.54%), unidentified materials 5 (8.77%), and recorded. These were added up to detritus (which could not be quantified). For determine the overall quantity of diet large size group (>47.0 cm), the diet numerical components in all the guts for the purpose of and relative abundance were fish parts 19 knowing which food items were mostly (54.29%), crabs 9 (25.71%), insects 4 consumed (Olojo et al., 2003). To determine (11.43%) and unidentified materials 3 (8.5). the relative abundance of the individual diet Laboratory analysis of the gut contents components, the number of each diet revealed that fish parts (54%) were the most component (n) was divided by the sum of all important food item in the stomach of large the diet components „N‟ and multiplied by specimens, crabs (51%) were preferred by 100. This is represented mathematically as: medium size group while insects predominates

(65%) the stomach of the small specimens. where: %RA= relative percentage occurrence, Generally, major diet composition was made n= number of individual diet components; up of fish parts, crustaceans (predominantly N=total number of all diet organisms identified crabs) and insects (Fig. 2). from the guts. Food variations based on sex (male and RESULTS female) Quantitative Assessment Results of the analysis showed variation in Throughout the sampling period, (June 2018 to food items in the stomach of male and female March 2019), the guts of samples of H. odoe Hepsetus odoe in the Cross River Nigeria. For showed a total of 5 different diet groups. The males, the numerical and relative abundance of results showed different numerical and relative food items were fish parts 10 (8.70%), crabs abundance which were computed as follows: 12 (10.43%), insects 11 (9.57%), unidentified fish parts 35 (30.43%), crabs 42 (36.52%), materials 2 (1.74%), detritus (could not be insects 29 (25.22%), unidentified materials 9 quantified). For females the following were (7.83%), detritus (unquantified). A total of 115 obtained, fish parts 25 (21.74%), crabs 30 food items were identified in the gut of H. (26.09%), insect 18 (15.65%), unidentified odoe as at the time of sampling (Table 1). materials 7 (6.09%), detritus (unquantified) (Table 3). 85

FOOD/ FEEDING HABITS OF AFRICAN PIKE Part A: Science, Engineering and Technology Eteng and Ifon, 2019

Table 1: Numerical and relative abundance of food items in the gut of Hepsetus odoe in the Cross river system, Nigeria (June 2018 to March 2019). S/N Food items Numerical Relative abundance abundance (%) 1 Fish parts 35 30.43 2 Crabs 42 36.52 3 Insects 29 25.22 4 Unidentified materials 9 7.83 5 Detritus ** ** Total 115 100 Note: ** Unquantified

Table 2: Numerical and Relative abundance of food items in different size groups of Hepsetus odoe (June 2018 to March 2019). S/N Diets (Food items) Numerical/Relative abundance Small size Medium size Large size (<30.0 cm) (30.0 – 47.0 cm) (>47.0 cm) N % N % N % 1. Fish parts 3 13.04 13 22.81 19 54.29 2. Crabs 4 17.39 29 50.88 9 25.71 3. Insects 15 65.22 10 17.54 4 11.43 4. Unidentified materials 1 4.35 5 8.77 3 8.57 5. Detritus ** ** ** ** ** ** Total 23 100 57 100 35 100 Note: ** Unquantified; N=Numerical abundance, %=Relative abundance 70 65%

60 54% 51% 50 Fish 40 Crabs 30 26% 23% Insects 20 17% 18% 13% 11%

Relative Relative abundance(%) 9% 9% 10 4%

0 Small Medium Large Size groups

Fig. 2: Relative abundance (%) of food items in the guts of different size groups of Hepsetus odoe in the Cross River, Nigeria (June 2018 to March 2019).

FOOD/ FEEDING HABITS OF AFRICAN PIKE Part A: Science, Engineering and Technology Eteng and Ifon, 2019

Table 3: Diet composition of the gut of male and female Hepsetus odoe in the Cross River, Nigeria (June 2018 to March 2019) Male Female S/N Food items N % N % 1 Fish parts 10 8.70 25 21.74 2 Crabs 12 10.43 30 26.09 3 Insects 11 9.57 18 15.65 4 Unidentified materials 2 1.74 7 6.09 5 Detritus ** ** ** ** Total 35 30.43 80 69.57 Note: ** Unquantified; N=Numerical abundance, %=Relative abundance

Statistical Results have been reported to account for remarkable Small-sized individuals (small and medium percentage of the total mortality of fish size groups) showed higher feeding frequency community. On the Cross River floodplains or when compared with large sized counterpart. mudflats, there is tendency for bottom feeders Also males showed lower feeding activities to dominate the artisanal catch by weight even (Table 3). Also, percentage of individuals with though only few species have been noted to low gut contents decreased with size while belong to this trophic level. The Cross River relative importance of fish components community structures usually contain very increased with size. Statistical analysis high proportion of predatory species and revealed no significant variations (ANOVA, piscivorous-predators are generally common. P>0.05) in stomach contents and composition According to Offem et al. (2009), the relative of food items with fish size but with sex (T- abundance of these predators tends to increase Test, P<0.05). during the dry season. Variation in numerical as well as relative abundance of food items in DISCUSSION the stomach of Hepsetus odoe in the Cross The finding of this study revealed that major River, Nigeria could be attributed to food diet composition of H. odoe in the Cross River selection or different feeding intensity was made up of fish parts, crustaceans and exhibited by the different size classes. insects indicating that the species exhibits Previous studies have indicated the quality and benthic predatory habit. This finding agrees quantity of food consumed by different size with that of Adedokun et al. (2015) who groups of fish and attributed such variation to reported that H. odoe is piscivorous, feeding age differential. For example Adedokun et al. on several species of smaller fishes of diverse (2015) reported that food items in the stomach genera. Although Adeyemi (2010) described of H. odoe constituted on the average 0.17% of P. annectens as an omnivore, preying on their body weights. The abundance of detritus smaller fishes was an outstanding feeding in the stomach of small sized individuals habit. However, the studies of Jihulya (2014) indicates their breeding near vegetated banks on feeding habits of O. niloticus and L. where they forage for aquatic insects while niloticus did not record any fish parts in their hiding from predators. The spawns have small guts. A number of fish species are known to mouth and feeds voraciously on insect larvae predate on fish and macro invertebrates which around the vegetated areas where breeding 87

FOOD/ FEEDING HABITS OF AFRICAN PIKE Part A: Science, Engineering and Technology Eteng and Ifon, 2019 took place. As they grow to fingerling and natural habitat. Generally, gut contents of H. juvenile stages, they begin to forage on larger odoe were found to comprise of fish parts, insects having well developed oral organelles crabs, insects, detritus and unidentified for feeding. This could be the reason for the materials in order of importance with a abundance of insects in the guts of the small significant shift in diets from insectivore to sized group. The observed detritus might have piscivores as they grow older. The older been incidental components obtained individuals are known for their ambushing alongside the main food items during feeding. foraging tactic during the day in the thick The habitation of H. odoe in the quiet and vegetation to catch its preys notably cichlids thickly vegetated areas near the river banks to and mormyrids (Annett et al., 1999). Sex avoid the threats of predation was previously difference in feeding intensity could be reported by Adedokun in Ogbomoso reservoir, attributed to the difference in foraging mode Oyo State, Nigeria. Ontogenetic shift in diets between the male and female fish species as of freshwater and brackish water fish species previously observed by Adedokun et al. from Cross River Estuary, Nigeria had been (2015) in the Ikose/Iluju Reservoir, Oyo State, reported by Ajah et al. (2006). Nigeria. The findings revealed that juveniles were CONCLUSION predominantly benthic feeders, feeding on nematodes, diatoms and crustaceans while the This study indicates size specific shift in diets adults were observed to be predominantly of H. odoe from insectivore to piscivores as planktotrophic, with 1:1 diatoms/crustaceans they grow older. From the different kinds of ratio. Among the freshwater species, food items observed in the guts of H. odoe, it Synodontis membranaceus from Jebba Lake, can be concluded that this species exhibits Nigeria progressed from detritovorous feeding benthic predatory habit in the Cross river for small sized group through a transitional system, Nigeria. Based on the findings of this planktivoruos phase for medium sized group to study, it is recommended that similar studies a predominantly insectivorous phase for large on other freshwater species, N/C ratio and P/N sized group. Young African pike characins ratios of the Cross River and adjoining rivers continue to feed in vegetated areas, where they are required to provide inputs for trophic can avoid predation until they are mature modelling. This will help in the understanding enough to escape predators. At large sized of the trophic structure of freshwater fishery phase, they venture into the open waters, for proper multispecies management of the where they have access to other types of food Cross River ecosystem. resources, reducing feeding completion among the characins. The preference to a particular REFERENCES diet group shown by the different size classes Adeyemi, S.O. (2010). Food and feeding habits of Protopterus annectens (Owen) could be a biological strategy to minimize (Lungfish) at Idah area of River Niger, competition and increase availability of food Nigeria. Journal of Production, resources at different stages of fish Agriculture and Technology, 6(2): 69- development from fry/juvenile to adult. This 74. has been previously indicated by Yongo et al. Adedokun, M. A. & Fawole, O. O. (2015). (2019) as a biological phenomenon in food Diet Compositions of African Pike and feeding ecology of fin fishes in their Hepsetus Odoe (Bloch) In Ikose/Iluju 88

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Cite as: Sunday Urom Eteng and Honor Tajoes Ifon (2019). Food and feeding habits of the African pike characin Hepsetus odoe (bloch, 1794) in the Cross river system, Nigeria. In: Asuquo, Francis E. (Editor) on Harnessing African Potentials for Sustainable Development, Calabar, Nigeria, September 2019; UNICAL Press & GIS Publishers. U6CAU Proceedings (Maiden Edition ) Volume 1, Number 1, 82 – 90.