Estelar. Therefore, the study of food and feeding habits of a fish is very

Transcription

1 Chapter VIII Food and Feeding Habits of Dominant Fishes Feeding is one of the most important functions of an organism. The basic functions of an organism, like growth, development, reproduction etc. all take place at the expense of the energy, which enters the organism in the form of its food. Feeding activity influences the growth and productivity of fishes. Feeding is the dominant activity of the entire life cycle of fish (Joadder and Hossain, 2008). A comparative study on the food and feeding habits of Puntius stigma; Mystus vittatus and Nandus nandus have been reported by Ahmed et al. (1993); food of the fry of Cirrhinus mrigala (Hamilton) by Bhuiyan and Islam (1990); and food and feeding habit of Gudusia chapra by Ahmed et al. (2007). Therefore, the study of food and feeding habits of a fish is very important. This is also essential for any fishery management. Food webs based on decaying material with its associated flora of bacteria, fungi and other micro-organisms also include fishes. While some fishes can feed on decaying matter and organic detritus, most fishes feed either directly or indirectly on detritivorous invertebrates. The original source of the decaying matter may be within the community; its source is autochthonous, or it may be material originated in another community but has found its way into the aquatic community. Such material is called allochthonous (Wootton, 1992). Like all organisms, fishes require energy to fuel their body machinery and processes, including growth, metabolism and reproduction. The regularity must suit the fish ability to find and ingest food and to store energy (Islam, 2004)

2 The morphology of the organs of alimentation in fishes has attracted the attention of ichthyologists since very early times. As the biology of fish and in particular their feeding habits, were not being studied in detail at that time, only the qualitative aspect of feeding was examined and that too in a general way. Detailed studies on the biology of feeding in fish facilitated the development of ecomorphological investigation of the alimentary system. This is evident by the works of Al-Hussaini (1949), Das and Moitra (1963), Pathani and Das (1979), Singh and Singh (2000), Pathak and Singh (2001), Rao and Rao (2002), Srinivasan and Singh (2006) and Gandotra et al. (2007). The results in brief on relative length of gut and content analysis of the gut of selected fishes are given below: Observations Relative length of gut of some important fishes Labeo rohita The length of intestine varied from fish to fish; it has a definite relation with length of fish which helps to determine the feeding habits of the fish species. Relative length of gut (RLG) differs in different stages of the life history of fish. The relative length of gut of L. rohita varied from 10.4 to during the study period. The maximum values were obtained in the month of October and minimum was obtained in January (Fig. 8.1). The food contents and study of the alimentary canal show that this is a herbivorous fish (Table 8.1 and 8.2)

3 30 Labeo rohita Length (cm) Length (cm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Catla catla 5 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months (2005) Fig. 8.1 : Relative length of gut of Labeo rohita and Catla catla in Baigul reservoir -228-

4 Table 8.1: Feeding habits and Relative Length of the Gut in important Fishes of Baigul reservoir SI. No. Species No. of Fish examined Feeding habits Feeder 1. Labeo rohita 18 Herbivorous Column feeder 2. Catla catla 15 Omnivorous Surface feeder 3. Cirrhinus mrigala 18 Omnivorous Bottom feeder 4. Channa striatus 15 Carnivorous Bottom feeder 5. Labeo gonius 18 Herbivorous Bottom feeder 6. Notopterus notopterus 18 Carnivorous - 7. Gudusia chapra 18 Omnivorous Surface feeder 8. Puntius sarana 18 Omnivorous Bottom feeder Catla catla The relative length of gut of C. catla varied between 2.56 and 4.5 during the present investigation (Table 8.2). The minimum values were noted during January and maximum was noted during December (Fig. 8.1). The quantitative composition of food and features of the alimentary canal show this fish to be an omnivore. Therefore, C. catla has been categorized to be of omnivorous nature (Table 8.1)

5 Table 8.2: Relative length of gut of Labeo rohita and Catla catla in Baigul reservoir Months Labeo rohita Catla catla Length of Fish (cm) RLG Length of Fish (cm) RLG January February March April May June July August September October November December Cirrhinus mrigala The relative length of gut of C. mrigala varied from to during the study period (Table 8.3). The maximum and minimum values were observed during November and June during the period of study (Fig. 8.2). The quantitative food analysis and characteristics of the alimentary canal show this fish to be an omnivore. Therefore, C. mrigala has been categorized to be of omnivorous nature (Table 8.1). Channa striatus The relative length of gut of C. striatus varied between 1.06 and 1.32 in the present investigation (Table 8.3). The lowest values were observed in December and highest value was found during October (Fig. 8.2). According to the quantitative composition of food and -230-

6 250 Cirrhinus mrigala Length (cm) Length (cm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 25 Channa striatus Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months (2005) Fig. 8.2 : Relative length of gut of Cirrhinus mrigala and Channa striatus in Baigul reservoir -231-

7 length of alimentary canal show, this fish appears to be a carnivore. Therefore, C. striatus has been categorized to be of carnivorous nature (Table 8.1). Table 8.3: Relative length of gut of Cirrhinus mrigala and Channa striatus in Baigul reservoir Months Cirrhinus mrigala Channa striatus Length of Fish (cm) RLG Length of Fish (cm) RLG January February March April May June July August September October November December Labeo gonius L. gonius was a dominant species in the present investigation. The relative length of gut of L. gonius from reservoir ranged from 9.3 and 12.2 (Table 8.4). The highest values were obtained during November and lowest values occurred during March (Fig. 8.3). The quantitative composition of food and length of the alimentary canal show this fish to be a herbivore. Therefore, L. gonius has been categorized to be of herbivorous nature (Table 8.1). Notopterus notopterus The relative length of gut values of N. notopterus ranged -232-

8 40 Labeo gonius Length (cm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 25 Notopterus notopterus Length (cm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months (2005) Fig. 8.3 : Relative length of gut of Labeo gonius and Notopterus notopterus in Baigul reservoir -233-

9 from 0.25 to 1.05 during the study period (Table 8.4). The maximum values were obtained in January and minimum values were noted in the month of December (Fig. 8.3). The food analysis and study of the alimentary canal show this fish to be a carnivore. Therefore, N. notopterus has been categorized to be of carnivorous nature (Table 8.1). Table 8.4: Relative length of gut of Labeo gonius and Notopterus notopterus in Baigul reservoir Months Labeo gonius Notopterus notopterus Length of Fish (cm) RLG Length of Fish (cm) RLG January February March April May June July August September October November December Gudusia chapra The relative length of gut of G. chapra varied between 1.14 and 1.6 in the present investigation (Table 8.5). The highest values were obtained in December and minimum was obtained in the month of June (Fig. 8.4). The food quantity and study of the alimentary canal show this fish to be an omnivore. Therefore, G. chapra has been -234-

10 Length (cm) Length (cm) Gudusia chapra Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Puntius sarana Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Months (2005) Fig. 8.4 : Relative length of gut of Gudusia chapra and Puntius sarana of Baigul reservoir -235-

11 categorized to be of omnivorous nature (Table 8.1). Puntius sarana The relative length of gut of P. sarana varied from 1.04 to 1.13 during the study period (Table 8.5). The maximum values were obtained during February and minimum was obtained during March and November in the Baigul reservoir (Fig. 8.4). The food analysis and study of the alimentary canal show this fish to be an omnivore. Therefore, P. sarana has been categorized to be of omnivorous nature (Table 8.1). Table 8.5: Relative length of gut of Gudusia chapra and Puntius sarana in Baigul reservoir Months Gudusia chapra Puntius sarana Length of Fish (cm) RLG Length of Fish (cm) RLG January February March April May June July August September October November December

12 Food feeding habits of some important fishes The knowledge of food of fishes, their feeding behaviour and physiology of digestion is of great importance for planning modern fishery programmes. In view of this fact in mind, food and feeding habits of some important fishes of the Baigul reservoir have been studied. The gut analysis of some quantitatively important species namely, Labeo rohita, Catla catla, Cirrhinus mrigala, Channa striatus, Labeo gonius, Notopterus notopterus, Gudusia chapra and Puntius sarana were carried out during the present investigation. Since the availability of experimental fishes was confined to fishing season, the food analysis could be carried out only during that period. Only adult individuals were used in the study of the gut contents. 15 to 18 specimens of each fish were examined and the results were presented as the mean per cent of different food items present in the gut (Figs. 8.5 to 8.8). Labeo rohita The gut content of L. rohita comprised of detritus, (42.2 %), algae (30 %), submerged macrophytes (12.4 %), zooplankton (4.8 %), insects (4.6 %) and unidentified matter (6 %). The algal component included the members of Chlorophyceae such as Chlorella vulgaris, Zygnema sp., Pediastrum simplex and Scenedesmus sp.; Bacillariophyceae such as Melosira granulata, M. varians, Tabellaria fenestrata, Diatoma vulgare and Pinnularia sp. (Fig. 8.5). Detritus formed the main component of the gut content. Submerged macrophytes, which accounted for 12.4 % of the gut contents, were represented by portions of plants such as, -237-

13 Detritus Algae Submerged marophyte Zooplankton Insects Unidentified matter Green Algae Diatoms Blue green algae Rotifers Crustaceans Insects Labeo rohita 42.2 Catla catla Fig. 8.5 : Pie diagram showing the per cent composition of food (gut content) of Labeo rohita and Catla catla -238-

14 8% Detritus Blue green algae Insects % Fish 21.8 Green matter Detritus 8% Diatoms Submerged macrophytes Zooplankton 7.0 6% Insects Molluscs Unidentified matter 20.0 Cirrhinus mrigala 32.2 Channa striatus 10% 63% Fig. 8.6 : Pie diagram showing the percent composition of food (gut content) of Cirrhinus mrigala and Channa striatus -239-

15 Detritus Algae Submerged macrophytes Zooplankton Insects Unidentified matter Fish Green matter Unidentified matter Insects Detritus Labeo gonius 44.8 Notopterus notopterus Fig. 8.7 : Pie diagram showing the percent composition of food (gut content) of Labeo gonius and Notopterus notopterus -240-

16 Fish Molluscs Carp fry Insects Detritus Shrimps Green matter Detritus Blue green algae Submerged macrophytes Zooplankton Zooplankton Diatoms Green algae Insects Gudusia chapra 45.0 Puntius sarana Fig. 8.8 : Pie diagram showing the percent composition of food (gut content) of Gudusia chapra and Puntius sarana -241-

17 Potamogeton spp., Chara sp. Hydrilla verticillata and Vallisnaria spiralis. In addition, some parts of leaves and roots of unidentified species were also noted. Zooplankton, comprising of rotifers and cladocerans, constituted 4.8 % of the volume of the gut. Insects (dipteran larvae), crustacean appendages and molluscan eggs formed 4.6 % of the food mass. Only 6 % unidentified matter was recorded in L. rohita Catla catla The gut content of C. catla comprised of green algae (25.6 %), diatoms (18 %), blue-green algae (8 %), rotifers (20 %), crustaceans (22 %), and insects (6.4 %) (Fig. 8.5). The algal component included the members of Chlorophyceae such as Chlorella vulgaris, Pediastrum spp., and Scenedesmus sp. Bacillariophyceae comprised such forms as Melosira granulata, M. varians, Diatoma vulgaris, Tabellaria fenestrata, Synedra spp., Amphora ovalis and Nitzschia sp. Cyanophycean which accounted for 8 % of the gut contents, were represented by portions of plants such as, Microcystis aeruginosa and Anabaena spiroides. Zooplankton comprising of rotifers and crustaceans constituted 20 to 22 % of the volume of the gut. Insects (dipteran larvae) and molluscan eggs formed 6.4 % of the food mass. Cirrhinus mrigala In case of Cirrhinus mrigala, the gut contents included detritus (32.2 %), diatoms (20 %), blue-green algae (21.8%), zooplankton (7 %), insects (4 %) and submerged macrophytes (15 %) (Fig. 8.6). The identified species of diatoms comprised Melosira spp., Nitzschia sp., Synedra spp., Amphora ovalis, Pinnularia sp. and Fragillaria sp

18 Among the blue-green algae Microcystis aeruginosa was recorded as the dominant component. The green algae were represented by Volvox sp., Oocystis irregularis and Cosmarium sp. The detritus on the other hand, was mainly represented by dead algal cells and leaf fragments of submerged aquatics. The zooplankton were represented by the individuals of cladocera, copepoda and rotifera. Main forms of zooplankton were Brachionus calyciflorus, B. falcatus, Keratella sp., Mesocyclops leuckartii and nauplius larvae. The insects and their larvae belonging to hemiptera and diptera (Chironomus larvae), were also recorded in the gut contents. The submerged aquatics such as Chara sp., Hydrilla sp. and Vallisnaria sp. were also observed and they accounted for 15 % of the gut contents (Fig. 8.6). Channa striatus The gut contents of majority of Channa striatus (62.4 % of the total individuals examined) contained small fishes, such as Puntius spp., Gudusia chapra, Oxygaster bacaila, Chanda spp., Nandus nadus and Colisa fasciatus as well as carp fry. The second dominant group of organisms observed in the gut content of C. striatus comprised of insects (10 %) which obviously included members of hemiptera, odonata, diptera and ephemerida. The gut contents of this fish also included mollusks (5.4 %), such as Bellamya bengalensis and Lymnaea acuminata. The detritus accounted for 8 % of the gut content along with sand and mud. Blue green algae and other plants materials constituted 7.8 % of the total contents of the gut. Unidentified matter comprised only 6.4 % of the gut content (Fig 8.6)

19 Labeo gonius The gut content of L. gonius comprised of detritus, (44.8 %), algae (27.2 %), submerged macrophyte (15 %), zooplankton (5 %), insects (2 %) and unidentified matter (6 %). The algal component included the members of chlorophyceae such as Chlorella vulgaris, Zygnema sp., Pediastrum simplex, Melosira spp. and Scenedesmus sp. (Fig. 8.7). Submerged macrophytes, which accounted for 15% of the gut contents, were represented by portions of plants such as, Potamogeton spp., Hydrilla verticillata and Vallisnaria spiralis. In addition, some parts of leaves and roots of unidentified species were also noted. Zooplankton comprising of rotifers and cladocerans constituted 5% of the volume of the gut. Insects (dipteran larvae), crustacean appendages and molluscan eggs formed 2 % of the food mass. Detritus formed the main component of the gut content. Notopterus notopterus The gut contents of majority of Notopterus notopterus (54 % of the total individuals examined) contained small fishes, such as Oxygaster bacaila, Puntius spp., Chanda ranga, Gudusia chapra, Nandus nadus and Colisa fasciatus as well as carp fry. The second dominant group of organisms observed in the gut content of N. notopterus comprised of insects (15.6 %) which obviously included members of hemiptera, odonata, diptera and ephemerida. The detritus accounted for 10.8 % of the gut content along with sand and mud. Blue-green algae and other plant materials constituted 12.8 % of the total contents of the gut. Unidentified matter comprised only 6.8 % of the gut content (Fig. 8.7)

20 Gudusia chapra The gut contents of adult G. chapra comprised mainly of carp minnows and weed fishes like Puntius spp. and Oxygaster bacaila (45 %), carp fry (10.2 %) and shrimps (5 %). The remaining fraction of gut contents included molluscs (18.4 %), insects (8.4 %), detritus (8 %), green matter (4 %) and zooplankton (2 %) (Fig. 8.8). Class Insecta was represented by the individuals of coleopteran, diptera and ephemerida (mayfly nymphs). The mollusks included L. acuminate and a few eggs of mollusks. Besides, diatoms (Synedra spp.), filamentous green algae, diaptomids and rotifers were also occasionally noted in the gut contents. The detritus was composed of mud and sand particles. Puntius sarana In case of P. sarana, the gut contents included detritus (30.4 %), diatoms (28.6 %), blue-green algae (14 %), green algae (10 %), zooplankton (1.8 %), insects (3.8 %) and submerged macrophytes (11.4 %) (Fig. 8.8). The identified species of diatoms comprised Melosira granulata, M. varians, nitzschia sp., Synedra ulna, Amphora ovalis, Nitzschia palea and Fragillaria sp. Among the blue-green algae Microcystis aeruginosa was recorded as the dominant component. The green algae were represented by Volvox sp. and Cosmarium sp. The detritus on the other hand, was mainly represented by dead algal cells and leaf fragments of submerged aquatics. Zooplankton were represented by the individuals of cladocera, copepoda and rotifera. The insects and their larvae belonging to hemiptera, coleoptera and diptera (Chironomus larvae), were also recorded in the gut contents. The submerged aquatics such as Chara -245-

21 sp., Hydrilla sp. and Vallisnaria sp. were also observed and they accounted for 11.4% of the gut contents (Fig. 8.8). Discussion The study of food and feeding habits of fishes is considered very important in fishery biology. Food is the main source of energy and plays an important role in the life history of fishes. The basic functions of life such as growth, development and reproduction take place at the expense of energy, which enters the organism in the form of food (Nikolsky, 1963). The food habits of some fishes living in different parts of a regime may vary due to differences in physicochemical and biological characteristics of their feeding niches. The feeding habits of the adult fish have been studied by a number of workers viz., Bucke (1971), Das et al., (1974), Biswas and Nassar (1981), Biswas (1986) and Bose and Islam (1986) have found that different species with the same type of diet may differ in the structure of the alimentary canal, but the functional adaptations related to the nature of food and feeding habits remain similar, although the degree of relation between digestive tract and food varies. Phytoplankton biomass is a reasonable indicator of the level of fish production in Baigul reservoir. The highest concentration of biomass (33.48 mg/m 3 ) in the Baigul corresponds to the highest fish yield (74.04 kg/ha). Zooplankton distribution in a reservoir is usually patchy, but there may be a gradient, with low zooplankton biomass in the river-like upstream end, and higher concentrations close to the dam. Zooplankton biomass often declines in late winter. The degree to which plankton develops depends a great deal on reservoir configuration and on the water replacement rate. Dense -246-

22 fish stocks of zooplankton feeding fish may substantially reduce the concentrations of zooplankton, as well as selectively remove the larger zooplankton. Al-Hussaini (1949) gave a view that purely herbivorous fishes have a long gut. Yadav (1999) also observed that in carnivorous fishes, the gut length ratio is less or equal to the body length whereas in herbivorous fishes gut length is more than the body length. Pathani and Das (1979) studied the relative length of gut and food and feeding habits of Puntius conchonius and concluded that this species feeds upon aquatic vegetation as well as submerged grasses, having a gut length 1.17 to 1.71 times more than the body length. The relative length of gut of Puntius sarana varied from 1.04 to 1.13 during the study period. Das and Srivastava (1979) reported that Notopterus notopterus has a short gut due to its carnivorous feeding habit. Alkunhi and Rao (1951) have also reported that Labeo kontius have a long intestine and have a ratio 12.0 only due to its harbivorous feeding habit. Saxena and Chitray (1964) reported that Ompok bimaculatus and Bagarius bagarius the length of intestine is 1.1 and 0.60 times longer to its body length. In the present study, the range of relative length of gut were found as; Labeo rohita (10.4 to 13.72), Catla catla (2.56 to 4.5), Cirrhinus mrigala (10.21 to 18.52), Channa striatus (1.06 to 1.32), Labeo gonius (9.3 to 12.2), Notopterus notopterus (0.25 to 1.05), Gudusia chapra (1.14 to 1.6) and Puntius sarana (1.04 to 1.3). Kamal (1967) who obtained a progressive RLG value for L. rohita as (9.13 to 15.2) and in Cirrhinus mrigala he found the RLG value (1.2 to 15.2). Desai (1970) studied the food and feeding habits of Tor tor and -247-

23 concluded that the adult fishes mainly subsist on macrovegetation (47 %) consisting of Vallisnaria, Najas, Ceratophyllum, Hydrilla and other aquatic grasses. Rest of the food items consist of mollusca, algae, insects and their larvae, debris along with sand and mud and some pieces of teleostean fishes. In juveniles, the main food items were insects and their larvae (53 %), molluscan (22 %), macrovegetation (5 %) and filamentous algae (3 %). Food analysis of L. gonius from the Baigul reservoir revealed that it consists of detritus (44.8 %), algae (27.2 %), submerged marophytes (15 %), zooplankton (5 %), insects (2 %) and unidentified matter (6.0 %). There is little evidence of seasonal selection of food in the present investigation. Changes in diet quality are governed by the availability of type of food. Variability of feeding activity is connected with climate and breeding season (Islam, 2004). According to Khanna (1998), Catla catla has been categorized as planktivorous. Similar observation was found during the study period. Several studies have already been conducted on G. chapra. Rahman (1989) reported details of its ecology, and its distribution in the Indian sub-continent is well described (Menon, 1999; Talwar and Jhingran, 1991 and Rao, 1995). Its diet and feeding habitats have also been studied (Jhingran, 1972; Bhuiyan and Hossain, 1988; Gosh et al., 1988 and Rahmatullah et al., 1995). In addition, a handful of studies on its reproductive biology have been completed, providing basic data on size at sexual maturity, spawning season and fecundity (Jhingran and Verma, 1973; Chondar, 1977; Afroz, 2000 and Nayak et al. 2003). In the present study G. chapra was found to subsist mainly on Fishes, phytoplankton and zooplankton. The findings are similar to other studies

24 It is known that the structure of the digestive apparatus is related to the form of the body. Besides the food and feeding habits, the phylogeny of a species is another important factor in the final construction of the digestive apparatus. Das and Moitra (1963) reported that relative length of the gut shows a well-marked gradation from the herbivorous to the carnivorous condition. In the carnivorous fishes the length of the gut is almost equal to or, in some cases, less than the body length, while in the herbivorous the length of the gut is much longer than the body length. In omnivores, the gut length varies between that of herbivores and carnivores. The results in the present study substantiate the findings reported by the foregoing authoress (Table 8.1). The study of food and feeding habits of fishes has a special significance in ecological studies. Das and Moitra (1963) have classified fishes on the basis of feeding habits into three primary groups: (1) herbivorous (2) omnivorous and (3) carnivorous. Nikolsky (1963) classified the food of fish into four categories: basic, secondary, accidental and obligatory foods. The present studies on the food of Labeo gonius indicated that this fish is a bottom feeder mainly subsisting on decayed food (44.8 %). The inferior mouth of this fish was indicative of an adaptation for bottom feeding. Jhingran (1991) has, however, classified L. gonius as bottom-column feeder herbivore. Algae constituted the next preferred food (27.2 %) due to which L. gonius of Baigul reservoir appears to be also well adopted for surface feeding (Fig 8.7). Das and Moitra (1963) have divided fresh water fishes into three groups according to the niche they occupy in the water. These are surface feeders, mid or column feeders and bottom feeders. The -249-

25 surface feeders are Catla catla, Hypopthalmichthys molitrix, Puntius ticto, Barilius sp., Oxygaster bacaila, Chanda spp., Glossogobius giuris, Gudusia chapra, Hilsa ilisha. Some species are neither true surface feeders, nor true bottom feeders and mostly depend on the organisms of the mid water. Such species are also called column feeders and include Labeo rohita, Puntius sophore, Tor tor, Wallago attu, Mystus cavasius and M. vittatus. The bottom feeders depend mainly on the bottom organisms. Fishes included in this group are Labeo calbasu, L. bata, L. gonius, Cirrhinus mrigala, C. reba, Puntius sarana, Amblypharyngodon mola, Clarias batrachus, Heteropneustes fossilis, Channa marulius, C. striatus etc. Of these the surface feeders are either omnivorous or carnivorous, while the mid and bottom feeders may be herbivorous, omnivorous or carnivorous (Khanna, 1998). The results of the present study also confirmed the predatory habit of Channa striatus. According to Jhingran (1991), this fish is a bottom feeder and highly predaceous in nature. The diet composition indicated that the fish consumes weed fishes and carp-fry in Baigul. The presence of detritus and considerable quantities of crushed molluscan shells indicated that the fish is bottom feeder as well. The results on the food and feeding habits of Gudusia chapra revealed that the fish is predominantly piscivorous in nature (Fig. 8.8). The food of this fish obviously consisted of small minnows, carp fry, insects, molluscs and shrimps. A number of diverse opinions have been expressed regarding the dietary habits of Puntius sarana in different habitats. Chitray (1965) have classified it as an herbivore, while Das and Moitra (1955), Sinha (1972) and Badola and Singh (1980) have classified it -250-

26 as an omnivore. In the present study P. sarana has been observed to feed upon a wide range of dietary materials (Fig. 8.8) such as detritus, blue-green algae, green algae, zooplankton, diatoms, macrophytes (Hydrilla, Vallisnaria and Chara) and even insects. As such, it could well be classified as an omnivorous fish of the Baigul reservoir