International Journal of Fisheries and Aquatic Studies 2023; 11(6): 102-109 E-ISSN: 2347-5129 P-ISSN: 2394-0506 (ICV-Poland) Impact Value: 76.37 (GIF) Impact Factor: 0.549 IJFAS 2023; 11(6): 102-109 © 2023 IJFAS www.fisheriesjournal.com Received: 10-07-2023 Accepted: 17-08-2023 Jibrin B Department of Agricultural Technology, Federal Polytechnic, P.M.B 05 Bali, Taraba State, Nigeria Shu’aibu N Army Barrack Road, Old Teachers’ Quarters Nyibango, House No. 11, Jimeta North Yola, Adamawa State, Nigeria Food and feeding habit of Mormyrus rume (Valenciennes, 1846) in Lake Geriyo, Adamawa, Nigeria Jibrin B and Shu’aibu N DOI: https://doi.org/10.22271/fish.2023.v11.i6b.2882 Abstract Mormyrus, a prominent fish within the Mormyridae family in Lake Geriyo and are commercially found in fresh, smoked, fried and roasted forms across the diverse markets of Adamawa, Nigeria. The feeding habit of elephant snout fish from Lake Geriyo was studied during the period of dry season between October, 2022 to March, 2023. A total of 134 samples of fish species were sampled monthly from commercial fishers’ catches at exactly 6:00am at the landing site. The major fishing methods employed by fisher folks for collecting the specimens were cast netting and set netting. The stomach contents were analysed using numerical and frequency of occurrence approaches. The results from this study indicated out of the 134 specimens collected during the study period, 69 were males, and 65 were females. Stomachs of 65 and 64 individuals were found to have recognizable food items. The higher percentage of identified food items by number were benthic insects and detritus which accounted for 69.713% and 64.155% respectively, while the higher percentage frequency of occurrence were detritus and chlorophytes accounted for 100% and 98.462% respectively. This revealed that M. rume is a bottom feeder, since benthic insects and detritus were the dominant food components. Diatoms, crustaceans, rotifers and protozoans had relatively lower contributions. The numerical analysis revealed insectivorous behaviour, the frequency of occurrence indicated detritivorous behaviour, and the relative contribution index demonstrated a preference for insects over detritus. Variation in stomach fullness revealed that 45.522% of the total stomachs examined were at a half-full capacity and females consistently showcase higher foraging intensity than males. The most influential factor affecting the foraging activity of M. rume was the cold phase of the dry season. Keywords: Food, feeding habit, stomach content, Mormyrus rume, Lake Geriyo Corresponding Author: Jibrin B Department of Agricultural Technology, Federal Polytechnic, P.M.B 05 Bali, Taraba State, Nigeria Introduction Members of the family of Mormyridae are among the important commercial fishes found in Lake Geriyo, Adamawa State, Nigeria. Elephant snout fish (Mormyrus rume) also known as ‘Bani Aron Baki’ in Hausa language, is a type of fish categorized within the family Mormyridae, in the order Osteoglossiformes (Jibrin and Shu’aibu, 2023) [27]. The members (Elephantfishes) of the family Mormyridae inhabit freshwater environments in tropical Africa (Greenwood et al. 1966), and are equipped with weak electric organs (Ladich and Tanja, 2016) [35]. These fish have distinctive appearances, with significant variations in head shape and the size of their unpaired fins. Generally, every fish needs energy for growth, reproduction, and migration, and this energy is derived from its food sources. “Food refers to any substance consumed, typically derived from plants or animals, and it contains the necessary nutrients”. These nutrients can be broken down by the fish, assimilated by the fish cells, and utilized for energy production to sustain life or promote growth. On the other hand, “feeding constitutes the primary activity throughout the entire lifespan of fish (Royce 1972) [43]”. According to Gerking (1994) [16], feeding behavior of fish involves the pursuit and consumption of food, whereas food habits and diet refer to the substances that fish consistently consume. The dietary preferences and feeding behaviors of various fish species frequently exhibit significant variations. Moreover, the same fish may display varying food preferences as it matures or with changing seasons (Maar et al., 1983) [36] . ~ 102 ~ International Journal of Fisheries and Aquatic Studies However, numerous studies have been undertaken on the stomach contents of various tropical fish species to better understand their natural feeding habits and how they interact with their environments (Ugwumba et al., 1990; Nadeem et al., 2019) [46, 39]. Information on interactions of fish within aquatic systems are derived from an understanding of the dietary preferences and feeding behaviors of fish (Bayhan et al., 2013;) [6]. This knowledge is pivotal for selecting suitable fish species for aquaculture (Azadi et al., 2009; Manon and Hossain, 2013) [2, 38]. Fish feeding activities are influenced by various factors, including composition of available food organisms (Manon and Hossain, 2013;) [38]. Analyzing stomach contents provides valuable information on fish food consumption and assimilation rates (Azadi et al., 2009; Bayhan et al., 2013) [2, 6]. Furthermore, information regarding diet composition, relative gut length (RGL), index of fulness (IF), index of relative importance (IRI) and foraging intensity are crucial for fish farming practices (Gumus et al., 2002; Bakhoum and Fatas, 2003; Manon and Hossain, 2013) [19, 5, 38] . These parameters help to evaluate environmental variations (Bonato et al., 2012) [8], and serves as a biological indicator for assessing fish foraging intensity (Bocholtz et al., 2009) [9]. Fawole (2002) [14] reported that the main food items in stomach of M. rume in Lekki Lagoon (Nigeria) were detritus and plants. According to Babatunde and Raji (2004) [3] , M. rume were bottom-dweller that predominantly fed on insect larvae. In contrast, Ipinjolu et al. (2005) [24] reported that M. rume in River Rima and Goronyo reservoir (Nigeria) consumed both plant and animal-derived items. Moreover, Odedeyi and Fagbenro (2010) [48] documented that M. rume in River Ose (Nigeria) relied primarily on benthic insects and crustaceans as their main source of food. Irrespective of its significance in the local economy, there has been no prior research conducted on the dietary and feeding behaviors of M. rume in Lake Geriyo. Therefore, there is a critical need for a study to investigate these aspects of this fish species. Understanding the food preferences and feeding https://www.fisheriesjournal.com patterns of M. rume will provide essential information on how nutrients move through aquatic ecosystems (Fatema et al., 2013; Rahman et al., 2020) [13, 42]. As this will aid in effective species management for optimal yield in aquaculture because a fish success in its environment is closely tied to its dietary choices, and offers valuable insights into its natural history (Kim et al., 2019; Khanom et al., 2020) [32, 31]. Therefore, the current study aimed to examine the food and feeding habit, occurrence, distribution, periods of active foraging and level of intensity in M. rume in the Lake. The data obtained will contribute to both academic knowledge and practical applications. Materials and Methods Study Area The study was conducted in Lake Geriyo, Yola North Local Government Area of Adamawa State. Lake Geriyo is positioned at coordinates 09º 18’ 11"N and 12º 25’ 36"E (Figure 1) and occupies natural depression close to the upper Benue River in the north-eastern part of Nigeria (UBRBDA, 1985). Based on the information provided by the leader of the local fisher folk, Lake Geriyo was naturally formed when the River Benue became blocked due to significant silt accumulation approximately 60 years ago. This blockage created a small gully, which eventually filled with water from rainfall and the flooding of the River Benue. The Lake is relatively shallow, with an average depth of around 2 meters. During the rainy season from May to September, the River Benue causes the lake to become flooded. The aquatic vegetation in the Lake consists of various types of floating weeds, including water hyacinth, typha grass, water lilies, and wild guinea corn. These plants tend to drift across the surface of the Lake due to prevailing winds (Ekundayo et al., 2014) [11] . The primary commercially important fish species in the Lake are Clarias and Tilapia (UBRBDA, 1985) as cited by Kefas and Abubakar (2022) [30]. Fig 1: Map indicating the geographical position of the research area within Adamawa State ~ 103 ~ International Journal of Fisheries and Aquatic Studies https://www.fisheriesjournal.com Sample collection Specimens were consistently obtained at 6:00 am from commercial fisherfolks operating at Lake Geriyo’s landings each month during dry seasons spanning from October 2022 to March 2023, covering a period of six-month. The major fishing gears employed for harvesting the entire set of 134 specimens were cast and set nets, and they were identified using keys for identification authored by Olaosebikan and Raji (2013). Fish specimens (see Plate I) collected were meticulously stored in an ice-chest container with ice-block to inhibit deterioration before being transported to the laboratory for further examinations. Where: % O𝑖 is the frequency of occurrence of given food 𝑖 N𝑖 is the number of stomachs containing prey 𝑖 N is the total number of stomachs with some food Index of fullness Mahesh et al., (2019) [37] Where: ISF = Index of Stomach Fullness % Wg = weight of the stomach contents (g), Wf = fish body weight, Index of Relative importance (George and Hadley, 1979; Hyslop, 1980) [15, 23] Plate 1: Specimen (M. rume) Laboratory procedures In the laboratory, the species were categorised as males and females by examining the shapes of their genital papillae and genital openings using a handheld magnifying lens. Total lengths (TL) and standard length (SL) were measured to the nearest 0.1 cm from the scale whereas Body weight (BW) and stomach weight (SW) were taken with Digital Electric weighing balance (Adam AFP 4100L) and recorded to the nearest 0.1g. Examination of gut contents The state of fullness of each stomach was determined visually based on the distension of the stomachs before dissection; recorded and categorised as empty (º/₄), one-quarter full (¼), Half-full (²/₄), Three-quarter full (¾), and Full stomach (⁴/₄). Gut content analysis The specimens were dissected and the stomach contents were preserved in 5% formalin solution for subsequent examination. The stomach contents were mixed with 2.0 mL distilled water in a sterile petri dish. Visible large food items were easily identified with the naked eye and also with the aid of handheld magnifying lens, while microscopic ones were carefully dispersed on a cleaned slide and observed under a microscope. All food items were identified using identification keys and taxonomic work (Jeje and Fernando, 1986; Kolb, 1986; Kadiri, 2002) [25, 33, 20]. The gut contents identified, were subjected to analysis using numerical and frequency of occurrence methods and food analysis index to assess the foraging intensity of M. rume and the prominence of each food item, thus; Numerical method (Hynes, 1980; Hyslop, 1980; Mahesh et al. 2019) [22, 23, 37]. Where: % Nⅈ is the percentage of food item 𝑖 Nⅈ is the number of particular food item 𝑖 Nₜ is the total number of food (gut content) items Frequency of Occurrence (Hyslop, 1980; Baker et al., 2014; Mahesh et al. 2019) [23, 4, 37]. Where: RI = Relative Importance AI = Absolute Importance Index (% Number + % Occurrence + % Volume) of food items, n𝑖 = Number of different food items, Statistical analysis Data regarding the Total length measured in centimetres, along with Body and Gut weight recorded in grams, were further analysed in terms of mean, standard error and deviation using SPSS v.25. Results The total length for the 134 specimens ranged from 5.50 to 65.50 cm with a mean value of 26.205±1.339; 15.50 (Mean ± SE; SD.); Body weight ranged from 7.80 to 98.60 g with a mean value of 44.216±2.299; 26.623 (Mean ± SE; SD) and Gut weight ranged from 0.10 to 0.99 g with a mean value of 0.452±0.024; 0.282 (Mean ± SE; SD). On the other hand, the total length for the 69 male specimens ranged from 5.50 to 55.50 cm with a mean value of 18.551±1.628; 13.521 (Mean ± SE; SD); Body weight ranged from 7.80 to 96.50 g with a mean value of 35.255±2.869; 23.839 (Mean ± SE; SD) and Gut weight ranged from 0.10 to 0.95 g with a mean value of 0.351±0.029; 0.242 (Mean ± SE; SD) while, the total length for the 65 female specimens ranged from 5.50 to 65.50 cm with a mean value of 28.146±1.988; 16.028 (Mean ± SE; SD); Body weight ranged from 8.50 to 98.60 g with a mean value of 53.728±3.259; 26.281 (Mean ± SE; SD) and Gut weight ranged from 0.10 to 0.99 g with a mean value of 0.558±0.035; 0.285 (Mean ± SE; SD) (Table 1). Table 2 displays stomach fullness values for specimens across various months. At the end of February, 2.239% of full guts were observed and sharply increased to 12.687% in March. Three-quarter full ~ 104 ~ International Journal of Fisheries and Aquatic Studies https://www.fisheriesjournal.com stomachs were present in October, February, and March, accounting for 5.223%, 4.478%, and 5.070%, respectively. Half-full stomachs were consistently observed throughout all the months, with the highest percentage occurring in October at 25.373%. One-quarter full stomachs were identified in November, December and January, with the highest percentage in December at 11.194%. Empty stomachs were exclusively found in January, representing 2.985%. The highest indices of stomach fullness were recorded in October and March with values of 10.246% and 10.656% respectively. Table 3 indicates active foraging behaviours in March, characterized by warm temperature, with stomach fullness ranging from three-quarter to full, with values of 4.348% to 5.797% for males and 7.692% to 20.00% for females respectively. In contrast, passive feeding was observed during November, December and January, characterized by cold temperature, with stomach fullness ranging from one-quarter to half-full, varying between 2.899% to 31.884% for males and 1.538% to 18.462% for females respectively. Analysing the stomach contents of 134 M. rume unveiled the identification of 12 food items, encompasses protozoans (23.636%), fish eggs (24.303%), crustaceans (34.068%), insects (68.713%), algae (41.789%), rotifers (38.562), nematodes (29.341), annelids (25.296%), detritus (64.155%), sand particles (28.733%), cnidarians (39.773%), plants parts (24.528%), diatoms (29.899%), and fragments of unidentified origin (26.500%) (Table 4). In terms numerical representation, insects and detritus comprised the greatest percentages, with values of 68.713% and 64.155% respectively, whereas detritus occurred in 100% of the stomachs of sampled specimens (Table 4). Notwithstanding, insects and detritus formed the predominant dietary components, with index relative contribution values, 3.235% and 3.003% respectively (Table 5). Table 1: Descriptive statistics of body morphometric of M. rume examined from Lake Geriyo Sex Variables Minimum Maximum Mean ± SE; SD ♂♀ TL 5.500 65.500 26.205±1.339; 15.500 BW 7.800 98.600 44.216±2.299; 26.623 GW 0.100 0.990 0.452±0.024; 0.282 ♂ TL 5.500 55.500 18.551±1.628; 13.521 BW 7.800 96.500 35.255±2.869; 23.839 GW 0.100 0.950 0.351±0.029; 0.242 ♀ TL 5.500 65.500 28.146±1.988; 16.028 BW 8.500 98.600 53.728±3.259; 26.281 GW 0.100 0.990 0.558±0.035; 0.285 TL = Total length (cm), BW = Body weight (g), GW = Gut weight (g), SE = Standard error, SD = Standard deviation, ♂ = Male, ♀ = Female Table 2: Gut status for combined sexes of M. rume (n=134) examined in Lake Geriyo during dry season between October, 2022 to March, 2023. Degree of stomach fullness Month (º/₄) % (¼) % (²/₄) % (¾) % (⁴/₄) % IF October 34 25.373 7 5.223 10.656 November 10 7.462 10 7.462 8.432 December 15 11.194 3 2.239 7.053 January 4 2.985 3 2.239 10 7.462 5.211 February 2 1.493 6 4.478 3 2.239 9.341 March 2 1.493 8 5.970 17 12.687 10.246 Key: (º/₄) = Empty stomach, (¼) = One quarter full stomach, (²/₄) = Half full stomach, (¾) = Three quarter full stomach, (⁴/₄) = Full stomach, and (IF) = Index of fullness Table 3: Active and passive foraging periods of M. rume (n=134) examined from Lake Geriyo during dry season between October, 2022 to March, 2023. (♂ = 69) Months October November December January February March (♀ = 65) Months October November December January February March (º/₄) 3 - % 4.348 - (¼) 7 9 2 - % 10.145 13.043 2.899 - (²/₄) 22 6 2 6 1 1 % 31.884 8.696 2.899 8.695 1.449 1.449 (¾) 1 3 % 1.449 4.348 (⁴/₄) 2 4 % 2.899 5.797 Total 23 (33.333) 13 (18.841) 11 (15.942) 11 (15.942) 3 (4.348) 8 (11.593) 1 - 1.538 - 3 6 1 - 4.615 9.231 1.538 - 12 4 1 4 1 1 18.462 6.154 1.538 6.154 1.538 1.538 6 6 5 9.231 9.231 7.692 1 13 1.538 20.000 18 (27.693) 7 (10.769) 7 (10.769) 6 (9.231) 8 (12.307) 19 (29.231) Table 4: Numerical Distribution (%) and Occurrence Frequency (%) of various food items in the diet of M. rume (n=130) examined from Lake Geriyo during dry season between October, 2022 to March, 2023. Food items Protozoa Fish eggs Crustacea Insecta Chlorophyta Rotifera Numerical Numerical 39 61 170 285 235 59 Distribution Percent 23.636 24.303 34.068 68.713 41.789 38.562 ~ 105 ~ Frequency of Frequency 27 37 93 63 128 24 Occurrence Percent 20.769 28.462 71.538 48.462 98.462 18.462 International Journal of Fisheries and Aquatic Studies Nematoda Annelida Detritus Sand particles Cnidaria Plant parts Ochrophyta Unidentified fragments https://www.fisheriesjournal.com 49 64 562 152 70 78 148 53 29.341 25.296 64.155 28.733 39.773 24.528 29.899 26.500 23 47 130 93 34 94 91 32 17.692 36.154 100 71.538 26.154 72.308 70.000 24.615 Table 5: Relative contribution and importance index (%) of different food items in the diet of Males (n=66) and Females (n=64) M. rume examined from Lake Geriyo during dry season between October, 2022 to March, 2023. Food items Protozoa Fish eggs Crustacea Insecta Chlorophyta Rotifera Nematoda Annelida Detritus Sand particles Cnidaria Plant parts Ochrophyta Unidentified fragments Numerical Distribution (%) Males Females 24.242 23.232 24.706 24.096 32.601 35.841 65.441 70.874 40.483 43.019 36.538 42.857 30.952 27.711 27.273 24.026 62.238 65.996 27.426 29.795 32.500 41.912 20.710 28.859 29.565 30.189 25.641 27.711 Frequency Of Occurrence (%) Males Female 21.212 20.313 18.182 39.063 77.273 65.625 37.879 59.375 98.485 98.438 24.242 12.500 16.667 18.750 31.818 40.625 100 100 66.667 76.563 15.625 37.500 50.000 53.125 66.667 73.438 27.273 15.625 Discussion In this current study, the minimum size of available specimens in the catches was 5.50 cm while the maximum was 65.50 cm, smaller and bigger than the size (15.0 to 50.0 cm) utilized by Odedeyi and Fagbenro (2010) [48]. The study revealed a greater prevalence of males in the catches compared to females, suggesting a potential decrease in reproductive efficiency. However, the prevalent presence of half-full stomachs (²/₄) with values of (45.522%) and the infrequent occurrence of full stomachs (⁴/₄) with values of (14.926%) imply a low level of feeding intensity in M. rume. This observed outcome may be due to prey encounter rate in the Lake. On the other hand, a great proportion of full stomachs were observed in March, the warmer phase of dry season in the study area. This suggests an increased abundance of food items in the habitat. Comparable findings were reported by Jewel et al. (2019) [26], who noted increased richness of food items during the summer season in Padma River (Bangladesh). This result is incomparable with the findings of Ipinjolu et al., (2005) [24], who reported that (48.1%) of M. rume specimens captured in River Rima and Goronyo Dam (Nigeria) had empty stomachs and no sample with full stomach. According to Vinson and Angrandi (2011) [47] , the empty stomachs in fish may be attributed to autecological factors such as variations in gastric evacuation rates, diet, feeding habits, gut clearance rate, presence of nonfeeding life stages, as well as individual fish health. Environmental conditions, such as prey encounter rate and temperature, and sampling arti-facts like regurgitated or digested contents upon capture, also play a role. Additionally, species-specific fish behaviour may impact the occurrence of empty stomachs, with certain species being more vulnerable to specific gears when exhibiting increased activity or a higher likelihood of taking baited hooks. The findings also showed a decreased in foraging activities of species during the colder periods of dry season, spanning from November to February, followed by an increased in the warmer periods RI M 0.115 1.176 0.366 0.735 1.010 0.224 1.190 1.010 0.962 0.422 0.485 0.592 0.435 0.855 F 0.302 0.602 0.442 2.500 1.515 0.233 1.205 0.649 2.041 0.342 0.735 0.671 0.377 1.205 Total RI 0.417 1.778 0.808 3.235 2.525 0.457 2.395 1.659 3.003 0.764 1.220 1.263 0.812 2.060 from February through March. This agrees with the findings of Beamish (1978) [7], who noted that lower temperature result in a reduction of metabolic rate in fish, consequently leading to a decreased in the feeding activity of fish species. On the other hand, Jobling (1994) [28] observed that elevated temperature causes an increase in metabolism, subsequently enhancing the feeding activity of a fish species. Additionally, Shafland and Pestrak (1982) [44], reported that fish tend to lose appetite, come to a halt, and ultimately cease ingesting food at temperatures well before reaching the ultimate maximal critical temperature for the species. Helene and Ivar, (2020) [20] , also documented that the effects of temperature on feeding differ among species, but generally, voluntary food intake tends to rise with moderate temperature increases, and decline when temperatures fall outside the optimal temperature range for the fish. Moreover, the research demonstrated that females M. rume exhibited higher foraging activities compared to their male counterparts. This could be attributed to the territorial defence activities of males, which could lead to a reduced frequency of food consumption of males. This agrees with the findings of Green et al. (1984) [17]. They reported that males consume food less frequently compared to females. Notwithstanding, investigation also revealed that M. rume ingested a diverse range of food categories. The predominant items in their diet were benthic insects and detritus. These were consistently present in all stomachs observed with food. These results were partly in line with the discoveries of Ugwumba et al. (1990) [46], who observed that Mormyrids in Lekki lagoon (Nigeria) primarily consumed insects and crustaceans; Omotosho (1993) [40], who documented that M. rume fed on detritus, algae and macrophytes; Paugy (2002) [41] , who reported insectivorous behaviour in M. rume from Baoule River (Mali); Fawole (2002) [14], who identified detritus and plant parts as the primary dietary components for M. rume in Lekki lagoon; Odedeyi and Fagberon (2010) [48], who observed insects and crustaceans as the major food items ~ 106 ~ International Journal of Fisheries and Aquatic Studies https://www.fisheriesjournal.com for M. rume in River Ose (Nigeria); except Abdulaziz et al. (2019) [1], who documented Petrocephalus bane in Debiram Dam prey mainly on zooplanktons. Reported that these variations could be attributed to differences in food availability across the various habitats. The stomach contents also included chlorophytes, cnidarians, rotifers, crustaceans, and nematodes in moderate percent whereas diatoms, annelids, plant parts, fish eggs, and protozoans were less in abundance as revealed in the study. However, sand particles and fragments of unknow origin were found in almost all the stomachs containing food. These were likely consumed while foraging at the sediment bed of the lake. This observation indicates that M. rume is a benthic dweller. This agrees with the findings of several researchers (Omotosho, 1993; Paugy, 2002; Fawole, 2002; Odedeyi and Fagbenro, 2010) [40, 14, 48]. All food items were found in the stomachs of M. rume regardless of their size, sex or the season of examination. This corresponds with the findings of Kouamelan et al. (1999) [34], who noted no significant variations in the food composition of M. rume from River Bia (Cameroon). Similarly, Fawole (2002) [14] observed the presence of food items in the stomachs regardless of size, sex or season in Lekki lagoon (Nigeria). Odedeyi and Fagbenro (2010) [48] also documented no variations in the food composition of M. rume from River Ose (Nigeria). However, it was observed that rainy season ended in October, accompanied by an influx of allochthonous materials, particularly insects, seeds, leaves, and numerous kinds of materials from inundated forests into Lake Geriyo through River Benue basin caused by the water released from Lagdo Dam. These materials settle at the bottom of the lake and underwent decomposition by bacterial and fungal activities. Therefore, the higher percentage occurrence of detritus recorded, coupled with its high index of relative contribution in diet, implies that M. rume is a detritivore. The distinctive trunk-like snout and small terminal mouth of M. rume further support its detritivorous behaviour. Holden and Reed (1972) [21] reported that this elongated tubular snout is employed for burrowing in pursuit of their food items. However, plankton in the lake is predominantly composed of Chlorophyta, Ochrophyta, and crustacea. Despite the relatively lower occurrence of insects compared to detritus in the benthos of the lake, insects surpassed detritus in prominence in the stomachs of M. rume. This indicates a heightened preference for insects over detritus, suggesting that M. rume is also an insectivorous. In the diet of M. rume in Lake Geriyo, the result further showed that insects and detritus make up the majority and were considered the most crucial food components. Following closely were chlorophytes and nematodes as the second most significant dietary items. The third tier includes fish eggs, annelids, plant parts, and cnidarians. Diatoms, crustaceans, rotifers, and protozoans constitute the remaining food items, each contributed less than 1% to the diet despite rotifers and crustaceans were ingested in reasonable percentage. Collectively, these items make up (19.572% IRI) and out of this %IRI, the contribution of food items to the diet of females were higher with values of (11.272%) compared to males (8.300%). Conclusion The current research presents the food and feeding references of M. rume during dry season in Lake Geriyo, Adamawa State, Nigeria. The M. rume exhibited a varied diet, incorporating insects, detritus, phytoplankton, zooplankton, macrophytes, and fish eggs. Benthic insects and detritus were the predominant and the most important food items consumed by the specimens. Food of minor importance was crustaceans, rotifers, and protozoans. The study observed an augmentation in both the availability of food and foraging activity during the warm phase of the dry season, accompanied by a corresponding declined during colder periods of dry season. This investigation distinctly characterizes M. rume as a benthic dweller, concurrently functioning as an insectivorous and detritivorous. The study also indicated preference for insects over detritus, suggesting that M. rume is an insectivore. Additionally, the research identified a higher male population compared to female and was further confirmed that females consistently displayed greater foraging intensity than males throughout the period of dry season. The current discoveries concerning the feeding biology and dietary preferences of M. rume have the potential to enhance our understanding for the sustainable management of this species, which is susceptible to exploitation. Furthermore, the findings from this research may aid in formulating suitable techniques for feeding in the aquaculture of M. rume. Additionally, exploring the feeding biology and dietary preferences of this species in the rainy season for comparison with dry season is crucial, along with studying their spawning patterns in Lake Geriyo. Acknowledgement The authors express gratitude to the numerous biologists who gathered and published the data utilized in the analyses, the TETFUND Research and Publication Committee at the Federal polytechnic Bali, and to all my research assistants, wishing them continued prosperity. Conflict of interest In the context of this research, it is affirmed that there is no conflict of interest to disclose. References 1. Abdulaziz M, Babatunde TA, Abdulkarim B, Lawali AA. Food and feeding habit of Petrocephalus bane (Lacepede 1803) in Daberam Reservoir, Katsina. Dutse Journal of Pure and Applied Sciences (DUJOPAS). 2019;5(2b):2635-3490. 2. Azadi MA, Nasiruddin M, Rahman ASMS. Food and feeding habits of the clupeid, Gonialosa manmina (Ham.) from the Kaptai Lake, Bangladesh. Chittagong Univ J B Sci. 2009;4(1):53-61. 3. Babatunde DO, Raji A. Field guide to Nigerian freshwater fishes. 2nd ed. 2004. 4. Baker R, Buckland A, Sheaves M. Fish gut content analysis: robust measures of diet composition. Fish. 2014;15(1):170-177. 5. Bakhoum S, Fatas S. Food and feeding habits of Bagrus bajad (Forsskal, 1775) in El-Nozha hydrodrome, Egypt. Aquat Biol Fish. 2003;7(3):197-211. 6. Bayhan B, Sever TM, Kara A. Diet composition of the Mediterranean horse mackerel, Trachurus mediterraneus (Steindachner, 1868) (Osteichthyes: Carangidae), from the Aegean Sea. Belg J Zool. 2013;143(1):15-22. 7. Beamish FWH. Bioenergetics and growth of fish. New York: Academic Press; c1978. 8. Bonato KO, Delariva RL, Silva JCD. Diet and trophic guilds of fish assemblages in two streams with different ~ 107 ~ International Journal of Fisheries and Aquatic Studies 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. https://www.fisheriesjournal.com anthropic impacts in the northwest of Paraná, Brazil. Zoologia (Curitiba). 2012;29(1):27-38. Bucholtz RH, Meilvang AS, Cedhagen T, Christensen JT, Macintosh DJ. Biological Observations on the Mudskipper (Pseudapocryptes elongatus) in the Mekong Delta, Vietnam. J World Aquac Soc. 2009;40(6):711723. Dawan S, Sbaha SN. Food and feeding habits of Tilapia nilotica (Perciforms: Cichlidae). II. Diet and seasonal patterns of feeding. Bangladesh J Zool. 1979;7(2):75-80. Ekundayo TM, Sogbesan OA, Haruna AB. Study of fish exploitation pattern of Lake Gerio, Yola, Adamawa State, Nigeria. J Survey Fish Sci. 2014;1(3):9-20. El-Naggar HA, Khalaf Allah HMM, Mostafa FM, Walaa MS, Mansour AEB. Food and feeding habits of some Nile River fish and their relationship to the availability of natural food resources. Egyptian J Aquat Res. 2019;45:273–280. https://doi.org/10.1016/j.ejar.2019.08.004. Fatema K, Omar WMW, Isa MM. Identification of food and feeding habits of Mullet Fish, Liza Subviridis (Valenciennes, 1836), Valamugil Buchanani (Bleeker, 1853) from Merbok Estuar. J Life Sci Technol. 2013;1(1):47-50. http://dx.doi.org/10.12720/jolst.1.1.4750. Fawole OO. Morphometry and Diet of Mormyrus rume in Lekki lagoon, Nigeria. Rev Biol Trop. 2002;50(2):689694. George EL, Hadley WF. Food and habit partitioning between Rock bass (Ambloplites rupesttris) and smallmouth bass (Micropterus dolomieni) young of the year. Trans Am Fish Soc. 1979;108:253-261. Gerking S. Feeding Ecology of Fish. Academic Press; 1994. p. 416. Green JM, Martel G, Martin DW. Comparisons of feeding activity and diets of male and female cunners (Tautogolabrus adspersus) (Pisces: Labridae). Mar Biol. 1984;84:7-11. https://doi.org/10.1007/BF00394521. Greenwood PH, Myers GS, Rosen DE, Weitzman SH. Phyletic studies of teleostan fishes with a provisional classification for living forms. Bull Am Mus Nat Hist. 1966;131:339-456. Gumus A, Yilmaz M, Polat N. Relative importance of food items in feeding of Chondrostoma regium (Heckel, 1843), and its relation with the time of annulus formation. Turkish J Zool. 2002;26(3):271-278. Helene V, Ivar R. Effects of temperature on feeding and digestive processes in fish. Temperature. 2020;7(4):307320. DOI: 10.1080/23328940.2020.1765950. Holden M, Reed W. West African Freshwater Fish. Longman Singapore; c1972. p. 68. http://dx.doi.org/10.1080/10641262.2010.536856. Hynes HBN. The food of the freshwater sticklebacks (Gasterosteus aculeatus and Pygosteus pungitius) with a review of methods used in studies of the food of fishes. J Anim Ecol. 1980;19:36-58. Hyslop EP. Stomach content analysis: A review of methods and their application. J Fish Biol. 1980;17:41429. Ipinjolu JK, Malami ZG, Hassan WA, Abubakar U. Food habits of Elephant snout (Mormyrus rume) in River Rima and Goronyo Dam in northwestern Nigeria. Bull Sci Assoc Niger. 2005;26:173-185. Jeje CY, Fernando CH. A practical guide to the 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. ~ 108 ~ identification of Nigerian Zooplankton (Cladocera, Copepoda, and Rotifera). Kainji Lake Res Inst. 1986;142. Jewel MAS, Haque MA, Ferdous MS, Khatun MS, Hasan J, Bhuyain MAB. Food and feeding habit of Reba Carp Cirrhinus reba in the Padma River, North-western Bangladesh. Su Urunleri Dergisi. 2019;14(1):1-6. Jibrin B, Shu’aibu N. Assessment of some Morphometric parameters of Mormyrus rume (Valenciennes, 1846) from Lake Geriyo, Adamawa, Nigeria. International Journal of Fisheries and Aquatic Studies. 2023;11(5):99-105. DOI: https://doi.org/10.22271/fish.2023.v11.i5b.2854. Jobling M. Fish Bioenergetics. London: Chapman and Hall; 1994. Kadiri MO. Algae and primary productivity studies of Ikpoba Reservoir. PhD thesis, University of Benin, Benin City; 2002. 298 p. Kefas M, Abubakar KA. Assessment of Microinverbrates of Lake Geriyo, Adamawa State, Nigeria. International Journal of Agriculture and Environmental Research. 2022;8(2):2455-6939. DOI: https://doi.org/10.51193/IJAER.2022.8203. Khanom DA, Nesa A, Jewel MAS, Haque MA, Paul AK, Iqbal S, et al. Muscular tissue bioaccumulation and health risk assessment of heavy metals in two edible fish species (Gudusia chapra and Eutropiichthys vacha) in Padma River, Bangladesh. Punjab University Journal of Zoology. 2020;35(1):81-89. http://dx.doi.org/10.17582/journal.pujz/2020.35.1.81.89. Kim JJ, Atique U, AN KG. Long-term ecological health assessment of a restored urban stream based on chemical water quality, physical habitat conditions and biological integrity. Water. 2019;11(1):114. http://dx.doi.org/10.3390/w11010114. Kolb JA. Plankton identification guide. Marine Biology and Oceanography grades 9-12. Marine Science Center, Poulsbo, WA; c1986. Kouamelan PE, Teugels GG, Gourene G, Ollevier F, Thys V, Audenaerde DFE. The effect of a man-made lakeon the diet the African electric fish (Mormyrus rume Valenciennes, 1846) (Ostteoglossiformes; Mormyridae). Hydrobiologia. 1999;3(30):141-151. Ladich F, Tanja S. Diversity in fish auditory systems: one of the riddles of sensory biology. Frontiers in Ecology and Evolution. 2016;4:28-32. Maar A, Mortimer MAE, Van Der Lingen I. Fish culture in Central East Africa. Rome: FAO; c1983. p. 158. Mahesh VS, Ambarish PG, Rekha JN. Stomach Content Analusis Techniques in Fishes. Demersal Fisheries Division. ICAR-Central Marine Fisheries Research Institute. Available from: https://www.researchgate.net/publication/330621031; 2019. Manon MR, Hossain MD. Food and feeding habit of Cyprinus carpio var. specularis. J Sci Found. 2013;9(12):163-169. Nadeem S, Waheed KN, Zafarullah M, Ashraf M, Sherzada S, Nadeem H. Determination of Physicochemical water quality parameters along with food preferences in selected Fish Species collected from River Ravi, Punjab. International Journal of Fisheries and Aquatic Studies. 2019;7(4):93-100. Omotosho JS. Analysis of fish species composition of Oyun Mini-Dam, University of Illorin, Nigeria. Journal of West African Science Association. 1993;3(6):37-48. International Journal of Fisheries and Aquatic Studies https://www.fisheriesjournal.com 41. Paugy D. Reproductive strategies of fishes in a tropical temporary stream of the Upper Senegal Basin: Baoule River in Mali. Aquatic Living Resources. 2002;1(5):2535. 42. Rahman MM, Haque SM, Islam MA, Paul AK, Iqbal S, Atique U, et al. Assessment of mud crab fattening and culture practices in coastal Bangladesh: understanding the current technologies and development. Aquaculture, Aquarium, Conservation and Legislation. 2020;13:582596. 43. Royce WF. Introduction to the fishery science. Academic Press. New York; c1972. p. 323. 44. Shafland PL, Pestrak JM. Lower lethal temperatures for fourteen non-native fishes in Florida. Environ Biol Fish. 1982;7(2):149-156. 45. Specziár A, Erős T. Dietary variability in fishes: the roles of taxonomic, spatial, temporal and ontogenetic factors. Hydrobiologia. 2014;724(1):109-125. 46. Ugwumba A, Ugwumba AAA, Mbu-Oben P. Food, feeding ecology of the Mormyrids of Lekki lagoon, Nigeria. Nigerian Journal of Natural Sciences. 1990;5(12):38-46. 47. Vinson MR, Angrandi TR. ‘Stomach Emptiness in Fishes: Sources of Variation and Study Design Implications’. Reviews in Fisheries Science. 2011;19(2):63-73. DOI: 10.1080/10641262.2010.536856. 48. Odedeyi DO, Fagbenro OA. Feeding habits and digestive enzymes in the gut of Mormyrus rume (Valenciennes 1846) (Osteichthyes Mormyridae). Tropical zoology. 2010;23(1):75. ~ 109 ~