Reproduction and Feeding Habits of the River Catfish Eutropiichthys Vacha

Anila Naz Soomro, Wazir Ali Baloch,Our Nature Sayed (2012) Iftikhar 10: Hussain269-280 Jafri, Ghulam Hussain Burdi and Bernerd Fulanda / Our Nature (2012) 10: 269-280 Reproduction and feeding habits of the River Catfish Eutropiichthys vacha (Hamilton, 1822) (Siluriformes, Schilbidae) in an impacted habitat: Kotri hydrodam, River Indus, Pakistan Anila Naz Soomro1 *, Wazir Ali Baloch1, Sayed Iftikhar Hussain Jafri1, Ghulam Hussain Burdi1 and Bernerd Fulanda2** 1 Department of Fresh Water Biology and Fisheries, University of Sindh, Jamshoro-76080, Sindh, Pakistan 2 Kenya Marine and Fisheries Research Institute, Marine and Coastal, P.O. Box 81651, Mombasa-80100, Kenya. Email: *[email protected],**[email protected] Abstract Reproduction and feeding habits of Eutropiichthys vacha were studied in Kotri hydrodam, a man-made and human impacted stretch of the Indus River, Pakistan during 2005-2006. A total 303 specimens were sampled and analyzed for maturity stages and gonadal development and food and feeding habits assessed from gut contents. Results showed male dominance over females: sex ratio 1.16:1.0. Minimum size at sexual maturity was 13.9 cm total length (TL). Mean fecundity ranged 1.38x104 to 2.17 x 105. Gonado-somatic index (GSI) was 0.1-2.5 and 0.3-6.5 for males and females, respectively. Highest GSIs were recorded in April. We observe an ontogenic dietary shift in E. vacha: young are omnivorous with insects dominating diet while adults are omni-piscivores with Puntius ticto accounting for 35.4% of species. Other species were Colisa spp., juveniles of Channa spp. and some cyprinids. Feeding intensities were lowest in April at peak of spawning. The intensities increase rapidly after spawning indicating voracious feeding in E. vacha. Feeding intensities in adults are low during the cold season. These results provide for assessment of spatial-temporal variations in feeding intensity in E. vacha while GaSI and diet composition reveal information on environmental shifts and ecosystem fluctuations in the impacted habitats of the River Indus for sound fisheries management. Key words: Schilbeid catfish; Eutropiichthys vacha; Reproduction; Feeding habit; River Indus Introduction The river catfish Eutropiichthys vacha (Hasan et al. 2002) and is commercially (Siluriformes, Schilbidae) is an economi- important as a food- and game fish species cally important freshwater fish and is in Pakistan (Soomro et al. 2007). Moreover, widely distributed in Indus River basin of there is a strong export market in the Middle across northern India, southern Nepal and East and European markets and also the Bhutan, through Bangladesh and Myanmar entire demand for this fish species in the to the far western areas of Thailand. (Talwar domestic market is met through capture and Jhingran 1991; Menon 1999; Riede from rivers. Consequently, the sound 2004). The fish is popular among consumers management of the wild stocks is critical. 269 Anila Naz Soomro, Wazir Ali Baloch, Sayed Iftikhar Hussain Jafri, Ghulam Hussain Burdi and Bernerd Fulanda / Our Nature (2012) 10: 269-280 The commercial catches of E. vacha in species in the wild and exploitation of its the Indus River are on the decline and the full potential for aquaculture. Therefore, the species has been reported as "vulnerable" in present study investigated the reproduction some regions (Mirza and Bhatti 1999; and food and feeding habits of wild river Mijkherjee et al. 2002). Knowledge on the catfish E. vacha in the Kotri hydrodam on reproduction, food and feeding habits as the River Indus, south Pakistan in order to well as various aspects of its biology are provide the much needed information for important for sound management of its exploitation of its full potential for both fishery. However, despite the numerous capture and culture fisheries. studies on this species, information on its reproduction, food and feeding habits have Materials and methods clearly been lacking for the lower Indus Study area and sampling River and the situation is further augmented The Indus River, originating in the Tibetan by the construction of the numerous plateau, enters Pakistan via the Gilgit- hydrodams for power generation, flood Baltistan area (Bhatti, 1999; Albinia, 2008) control and irrigation. Furthermore, this and flows in a southerly direction for type of information is useful for the ~3,180 km before discharging into the Sapta development of management strategies Sindhu delta of Pakistan (Bhatti, 1999). The that aimed at conserving the riverine Kotri hydrodam straddles 25º 26' N and 68º biodiversity associated the E. vacha fishery 19' E measuring 920 m across the River (Turan et al. 2005). Therefore, knowledge Indus, Hyderabad, southern Pakistan and is on the reproduction, food and feeding habits the last hydrodam on the River Indus. E. vacha in the habitats where it is Below, the river runs about 100 km before distributed is needed for the sound discharging into the Arabian Sea near the management of its fishery as well as for port city of Karachi. Together with Sukkur successful commercialization and and Thatta, the Kotri hydrodam is one of the conservation of the species to recompense major fishing centres along the Sindh course declining wild catches. Moreover, of the lower reaches of the River Indus information on reproduction, and food and (Bhatti 1999). feeding aspects forms an important guide Monthly samples were collected from for assessment of nutritional requirements the small-scale commercial fish landing site and trophic status for aquaculture selection at Jamshoro, on the Kotri hydrodam over a and for formulation of commercial feeds. period of one year. The samples were Further, this information is also important in chilled in ice and transferred to the development of trophic models in order to laboratory for analysis. Total length (TL, understand the ecosystem of the species cm) and body weight (BW, g) were taken both in the natural environment as well as using a using a digital slide calipers within culture facilities (Lopez-Peralta et al. (accuracy 0.1 cm) and weighing balance 2002; Bachock et al. 2004). Consequently, (accuracy 0.1 g), respectively. the lack of such crucial information on the river catfish E. vacha has been a hindrance Reproduction in Eutropiichthys vacha to the sustainable management of the The reproductive aspects E. vacha were 270 Anila Naz Soomro, Wazir Ali Baloch, Sayed Iftikhar Hussain Jafri, Ghulam Hussain Burdi and Bernerd Fulanda / Our Nature (2012) 10: 269-280 studied from a total of 281 adult specimens. estimated according to the method by The fish were sexed and TL and BW Bagenal and Braun (1978), as follows. measurements of each individual fish Three sub-samples were obtained from the recorded. The specimens were then anterior, middle, and posterior sections of dissected to remove the gonads and the the ovaries and the number of eggs counted gonad weight (GW, g) recorded against each in each sub-sample. The total fecundity (F) specimen. The maturity stages of the was then estimated using the equation: F = river catfish E. vacha were classified based (GW × NS) / WS; where GW is the weight on both macroscopic study of the gonads (g) of the gonad while NS and WS are the and microscopic examination of ova. In the number of eggs and weight (g) of the sub- females, the ovaries form a U shaped loop sample, respectively. The gonad cycle was of two lobes that open to the outside by a determined monthly from the gonado- common duct and differentiate as maturity somatic indices (GSI) using the formula: progresses along with the enlargement in GSI = (GW × 100) / BW; where GW and size and change in colour. In the males, the BW are the gonad weight and body weight, testes first as slender thread structures in the respectively. Physico chemical parameters vent area of abdomen, changing to including water temperature were measured prominent strips as maturity progresses, and using a portable digital meter (Ecoscan- at full maturity, the testes extend to the Temp6, Eutech, Netherlands). anterior region of the body cavity. Ova samples were sampled from the Food and feeding habits of Eutropiichthys ovary at the mid-section (Bowden et. al. vacha 1990) to obtain the most advanced oocytes A total of 303 specimens were used for the stages (Teshima et al. 1989). The ovary analysis of food and feeding habits. The tissues were stored in a 1:9 formalin-water specimens were dissected and the entire gut solution buffered with 20 g/l sodium acetate contents including the examined visually before analyses. The gonad maturity stages both by naked eye and under a binocular were assigned to five-stage maturity phases microscope (Nikon Eclipse E200, Nikon, based on macroscopic and microscopic Japan). Stomach fullness was determined by examination of the ovaries (Hinckley, 1986; the Hynes (1950) gravimetric method and Morrison, 1990). Sample ovaries were then categorized into five levels as; 100 %, 75 %, embedded in paraffin, thin sectioned to a 4- 50 % and 25 % full, and 0 % or empty. The μm thickness, and stained and stomach contents were then placed in a Petri counterstained with Haematoxylin and dish suspended in water and the food items Eosin according Moe (1969) as adopted by identified to the lowest possible taxon using Tessy (1994). All microscopic examinations identification keys for microscopic were conducted under a binocular freshwater life (Ward and Whipple 1959) microscope (Nikon Eclipse E200, Nikon, and the fish prey identified according to Japan). The ovaries were then fixed in species keys Talwar and Jhingran (1991). Gilson’s fluid for gravimetric analysis. Further, digested materials were categorized Preserved ovaries were washed and cut into into digested and semi-digested. The three sections, and the total number of eggs percent volume of major gut items was 271 Anila Naz Soomro, Wazir Ali Baloch, Sayed Iftikhar Hussain Jafri, Ghulam Hussain Burdi and Bernerd Fulanda / Our Nature (2012) 10: 269-280 estimated by the points method adopted Further, sex ratios were 1.0:1.16 male: from Pillay (1952).

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