Gonadosomatic index-based size at first sexual maturity and fecundity indices of the Indian River shad Gudusia chapra (Clupeidae) in the Ganges River (NW Bangladesh) By M. Y. Hossain 1,2, *, Z. F. Ahmed 3 , A. B. M. S. Islam 2 , S. Jasmine 2 and J. Ohtomi 4 1 The United Graduate School of Agricultural Sciences, Faculty of Fisheries, Kagoshima University, Kagoshima, Japan; 2 Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi, Bangladesh; 3 Department of Fisheries Management, Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh; 4 Faculty of Fisheries, Kagoshima University, Kagoshima, Japan Summary The present study aims to estimate the size at first sexual maturity and fecundity for female Gudusia chapra from the lower Ganges River, northwestern Bangladesh. A total of 250 female specimens, 3.60–13.70 cm in standard length (SL) and 1.00–43.60 g in body weight (BW), were collected during March–August 2006. The gonadosomatic index (GSI) for females was calculated by the equation, GSI (%) = (GW ⁄ BW) · 100. The size at first sexual maturity of females was estimated by the relationship between their gonadosomatic index and standard length. The specimen larger (‡8.00 cm in SL) than first size at sexual maturity was used for the estimation of fecundity. The size at first sexual maturity for female G. chapra was considered to be 8.00 cm SL in the Ganges River. The mean total fecundity was 20200 ± 6500 and ranged from 10800 to 36200. This study should be useful for fisheries biologists ⁄ managers to impose adequate regulations for sustainable-fishery management in the Ganges River and elsewhere in Bangladesh. Introduction The Indian River shad Gudusia chapra (Hamilton-Buchanan, 1822) is a small, indigenous fish species of Bangladesh. As G. chapra is one of the dominant fish species in the Ganges River (northwestern Bangladesh), it is an important target species for small-scale fishermen, who use a variety of traditional fishing gear (Craig et al., 2004; Kibria and Ahmed, 2005). This species is widely distributed in the natural waters of Asia, throughout the Indian sub-continent including Bangla- desh, India, Pakistan, Nepal, Bhutan, Sri-Lanka, Myanmar, and Afghanistan (Talwar and Jhingran, 1991; Froese and Pauly, 2009). This small, indigenous species (SIS) used to be abundantly available in lotics, lentics, ditch and floodplain habits in the South Asian region, but is now disappearing from natural systems due to severe reductions in biodiversity (Mijkherjee et al., 2002). Determining the size at first sexual maturity in fish is important for distinguishing (i) different populations within species and (ii) temporal changes in length at first maturity from fisheries pressure or for other reasons (Templeman, 1987). In addition, maturation size is of special interest in fisheries management and is widely used as an indicator of minimum-permissible capture size (Lucifora et al., 1999). Knowledge about fish fecundity is essential for evaluating the potential of stocks, life histories, practical culture, and actual management of the fishery (Lagler, 1956). Such assess- ments are of paramount importance in fisheries management for estimating the number of offspring produced in a season and the reproductive capacity of species (Qasim and Qayyum, 1963). To the best of our knowledge, there is no previous information on size at sexual maturity of this shad from the lower Ganges River in Bangladesh. Nevertheless, several studies on G. chapra, such as maturity and fecundity (Jhingran and Verma, 1967), morphology, meristic and non-meristic characters (Chondar, 1975, 1976), fecundity (Chondar, 1977; Mustafa and Ansari, 1983; Quddus et al., 1990), gonadoso- matic index and fecundity (Kabir et al., 1998), age and growth (Narejo et al., 2000), and biology (Vinci et al., 2005) have been conducted. Therefore, we aim to expand knowledge on the size at first sexual maturity and fecundity for female G. chapra from the lower Ganges River, northwestern Bangladesh. Materials and methods The lower Ganges River (known as the ÔPadma RiverÕ in Bangladesh) enters Bangladesh from India through the Raj- shahi district (24°22¢N; 88°35¢E). A large number of fishes, including some commercially important species, are fished by both small- and large-scale fishermen throughout the year (Hossain et al., 2009). The G. chapra samples were collected during daytime from catches landed at Rajshahi, Bangladesh during March to August 2006. The fishes were caught using traditional fishing gear jhaki jal (cast net), tar jal (square-lift net), and dughair (conical trap) (Kibria and Ahmed, 2005). The samples were immediately preserved in ice and fixed with 5% formalin solution upon arrival at the laboratory. All specimens were sexed by gonadal observation under a binocular microscope, and only female specimens were used for this study. For each individual, standard length (SL) was measured to the nearest 0.01 cm using electric slide calipers, and whole body weight (BW) was taken on a digital balance with 0.01 g accuracy. Whole gonads were removed from each female fish and weighed (GW) with a balance to an accuracy of 0.001 g before being preserved in 10% formalin. The gonadosomatic *AuthorÕs current address: Department of Fisheries, Faculty of Agriculture, University of Rajshahi, Rajshahi 6205, Bangladesh. E-mail: yeamin2222@yahoo.com. J. Appl. Ichthyol. 26 (2010), 550–553 Ó 2010 Blackwell Verlag, Berlin ISSN 0175–8659 Received: July 22, 2009 Accepted: November 23, 2009 doi: 10.1111/j.1439-0426.2010.01454.x U.S. Copyright Clearance Centre Code Statement: 0175–8659/2010/2604–0550$15.00/0 Applied Ichthyology Journal of