Iran. J. Ichthyol. (June 2018), 5(2): 86-95 Received: January 18, 2017 © 2018 Iranian Society of Ichthyology Accepted: May 29, 2018 P-ISSN: 2383-1561; E-ISSN: 2383-0964 doi: 10.22034/iji.v5i2.260 http://www.ijichthyol.org Research Article Food and feeding habits of critically endangered bagrid catfish Hemibagrus punctatus (Jerdon, 1862) (Teleostei: Bagridae) in the Cauvery River, South India Manickam RAJA*, Pachiappan PERUMAL Department of Biotechnology, School of Biosciences, Periyar University, Periyar Palkalai Nagar, Salem - 636 011, Tamil Nadu, India. * Email: [email protected] Abstract: The aim of the study was to investigate the variation in diversity and abundance of food items in Hemibagrus punctatus in relation to season and also to assess its food preference and feeding behaviour which may reflect the availability of prey items in upstream and downstream areas of Hogenakkal area under the Cauvery river systems. Through its stomach content analysis, the fish has been found to be omnivorous and euryphagous, with only a few qualitative differences in the diet. Feeding rate was found to vary in relation to monsoon caused environmental changes during the course of a year. Among the wide variety of prey consumed, juvenile fishes (39.88%) formed an important dietary component. The next major food group was insects (19.50%) followed by diatoms (11.54%), green algae (8.40%), crustaceans (7.29%), blue green algae (3.98%), plant matter (2.79%), worms (2.71%), copepods (1.33%), cladocerans (1.33%), and mollusks (1.33%). All the food items of this fish (% of food- composition) was found vary in monthly. The present findings would facilitate the examination of complex food and feeding regimes of fishes and would help identify the groups of species that use similar resources within a specific community and could also serve as a reference database for feeding ecology of fishes in highly impacted tropical habitats. Keywords: Siluriformes, Feeding ecology, Abundance, Preference, Tropical habitats. Citation: Raja, M. & Perumal, P. 2018. Food and feeding habits of critically endangered bagrid catfish Hemibagrus punctatus (Jerdon, 1862) (Teleostei: Bagridae) in the Cauvery River, South India. Iranian Journal of Ichthyology 5(2): 86-95. Introduction resource partitioning at spatial, temporal and trophic Food habits and feeding ecology research are a level may increase the tolerance of niche overlap by fundamental tool to understand the role of fishes in reducing competition pressure between co-occurring aquatic ecosystems since they indicate relationships species. Generally, the head water streams of the based on feeding resources and indirectly indicate Western Ghats have been found to be poor in primary community energy flux (Yanez-Arancibia & Nugent production, and the organisms living in this 1977; Hajisamaea et al. 2003), which allows inferring environment depend mainly on allochthonous competition and predation effects on community resources as their major food (Johnson 1999). The structure (Krebs 1989). Other features like space and fact that species share resources such as food, space time have also been important for community and time with co-existing species results in problems ecology and the ecological theory predicts that in resource partition (Pianka 1969; Schoener 1985). 86 Raja and Perumal- Food and feeding habits of Hemibagrus punctatus Ross (1986) identified that in aquatic environments, (Ali et al. 2013). The information about the food and food is the main factor and that its partition defines feeding habits of this species is still lacking. The functional groups within the community, which get present study focusses on the feeding biology of together in guilds according to trophic similarity. The H. punctatus from Cauvery River. food availability and feeding behaviour of fishes vary from season to season. Seasonal change in Materials and Methods temperature not only influence the food consumption The Cauvery is one of the perennial rivers of Tamil and rate of digestion but also quality and quantity of Nadu, flowing from west to east with a number of available food organisms. Studies on the food and distributaries and tributaries before it confluence into feeding habits of different fishes have been made by the Bay of Bengal. The study was conducted in different workers (Hynes 1950; Bhuiyan et al. 1992, upstream and downstream areas of Hogenakkal water 1994, 1999). falls, (12°07’09.1”N, 77°46’26.4”E), Cauvery river The Nilgiri Mystus, Hemibagrus punctatus, a system of Tamil Nadu, India. The Hogenakkal rare bagrid catfish, endemic to the Western Ghats, waterfalls is located on the borders of Krishnagiri and has been currently listed in the IUCN Red List, as Dharmapuri district of Tamil Nadu state. The falls ‘Critically Endangered’ with a possibility that it could situated on the banks of the river Cauvery, the falls is be extinct (see Raghavan & Ali 2011). The last often referred to as Kaveri. The Hogenakkal water validated record of H. punctatus was known to be in falls cascades form an average altitude of around 750 1998, and several surveys since then have not been feet above sea level from the Melagiri Hills. The falls able to collect the species from its native range (Ali are located at a place where river Cauvery enters into et al. 2013). Jerdon (1849) described Bagrus Tamil Nadu as a big stream. Because of the ‘critically punctatus, now included in the genus Hemibagrus endangered’ status of H. punctatus, fish collection Bleeker, 1862 from the River Cauvery in southern was restricted to specimens caught by local India, and suggested its occurrence in the river and fishermen and available at landing centers and its various tributaries. The exact type of location, markets located along the banks of the river. Samples however, was not mentioned. Subsequently, Day were collected from January 2017 to December 2017. (1867, 1878) recorded the species from the Bhavani A total of 238 fish individuals were collected live and (a tributary of the Cauvery), at the foothills of the were fixed in buffered formalin (10%) for further Nilgiri Hills. Since then, only a very few validated analyses. Before gut analyses, the standard lengths records and voucher specimens of this rare catfish are (SL) of fishes were measured to the nearest 0.5mm available. The Nilgiri Mystus, H. punctatus is with a Vernier caliber. Fish guts were dissected under endemic to the Western Ghats (Dahanukar et al. a dissection microscope (5X magnification). And 2004) where it is restricted to the tributaries and dissected the anterior third of the intestine (up to the reservoirs in the Cauvery drainage (Ng & Ferraris first bend) (Herder & Freyhof 2006) and stored the 2000; Raghavan & Ali 2011; Ng & Kottelat 2013; Ali contents in 70% ethanol. Later, gut content samples et al. 2013). This fish inhabits rapid rivers and were examined under a dissection microscope (5X) streams (Menon 1999). The species is also known to for identification of different food categories. occur in midland areas with slow to moderate flow, poor vegetation cover, and with mud, sand and gravel Results as the major substrates. It prefers pristine, clear water The monthly variations of gut content of Hemibagrus streams and is affected by siltation (Biju 2005). The punctatus: There were 11 categories were made up of distribution of H. punctatus is currently restricted to stomach contents of this fish. It comprises of fishes type localities and stocks are declining in the wild (39.88%), insects (19.50%), diatoms (11.54%), green 87 Iran. J. Ichthyol. (June 2018), 5(2): 86-95 Fig.1. Proportion of food items in the gastro-intestine of Hemibagrus punctatus. Table 1. Monthly percentage frequency of different prey types in the gastro-intestine of Hemibagrus punctatus during the study periods of 2016 Jan-Dec. Food Item Jan Feb Mar April May June July Aug Sep Oct Nov Dec Diatoms 11 6 8 18 5 12.5 12 14 17 15 12 8 Blue green algae 3 2 1 3 12 5.5 2.25 3 4 2 4 6 Green algae 10 15 9 10 10 3.5 6.75 7.5 10 7 5 7 Plant matter 6 3 1 1 1 4.5 1.5 1.5 1 2 3 8 Insects 31 34 3 7 27 28 22 15 10 13 11 33 Crustaceans 8 10 18 27 2 6.5 5 7 1 2 1 0 Mollusks 0 0 0 0 4 2.5 3 2 2 0 1 1 Fishes 22 22 51 33 38 32.5 45 42 53 57 55 28 Worms 2 3 4 1 1 3.5 1 6 1 1 3 6 Cladocerans 1 3 3 0 0 0.5 1 1 1 1 2 2 Copepods 6 2 2 0 0 0.5 0.5 1 0 0 3 1 algae (8.40%), crustaceans (7.29%), blue green algae gracilis, and Cymbella ruttneri), crustaceans (prawn (3.98%), plant matter (2.79%), worms (2.71%), body parts, Nauplius and Cypris) (Amphibalanus copepods (1.33%), cladoceans (1.33%), and amphitrite), blue green algae (Anabaena circinalis, mollusks (1.33%). The experiment on gut content A. fertilissima, A. variabilis, A. oryzae, Nostoc analysis of fishes presented that the fish feed on carneum, N. commune, Microcystis protocystics), variety of food items. Food organisms are found in plant matter, worms, Copepods (Cyclops vicinus), the stomachs such as fishes (small size of fish and cladoceans and Molluscs (Table 1, Fig. 1). body parts), insects (body parts), diatoms, green Percentage composition of food items in relation to algae (Crucigenia apiculata, Closterium linula, months: The highest percentage composition of Palmella sp., Tetraspora sp., Euglena granulata, fishes was reported in the month of October (57%) Chlorella vulgaris, Scendesmus sp., Paediastrum sp., and the lowest during January and February (22%). Cladophora glomerata), diatoms (Cyclotella Insect percentage compositions were highest in the meneghiniana, Fragillaria crotonensis, Diatoma month of February (34%) and lowest during March vulgare, D.