The Indian river shad, Gudusia chapra, is a commercially important clupeid that contributes to subsistence and artisanal fisheries in inland waters in Bangladesh. Population parameters for this species were collected from a study of a population in a large perennial pond in Mymensingh, Bangladesh from May 2003 to April 2004. The gonado-somatic indices indicated a spawning season in spring, with a mean birth date estimated as 30 April. The growth equations, provided by three models, for males and females respectively, were: Lt = 140.42 (1- exp (-0.026 (t + 6.717))) and Lt = 145.39 (1- exp (-0.025 (t + 7.113))) for the von Bertalanffy model; Lt = 121.53 exp (-exp (-0.050 (t - 8.274))) and Lt = 124.95 exp (-exp (-0.048 (t - 8.421))) for the Gompertz model; and Lt = 114.27 / (1 + exp (-0.074 (t – 14.260))) and Lt = 117.19 / (1 +2 exp (-0.071 (t - 14.524))) for the Robertson model, where Lt is standard length (mm) at age t (weeks). Growth was best described by the von Bertalanffy growth equation for both male and female based on Chi-squared (χ2) values and Akaike’s information criterion. The absolute growth rates of males were slower than that of females. The von Bertalanffy growth model expressed in terms of body weight (BW) yielded functions for males and females of: BWt = 53.63 (1- exp {-0.028 (t + 6.320)))3 and BWt = 53.89 (1- exp (-0.023 (t + 9.215))3, respectively.
Colour traits can be elaborated through sexual selection and have potential to drive reproductive isolation. Male three-spined sticklebacks (Gasterosteus aculeatus) express striking visual signals to attract choosy females during courtship, typically expressed as red carotenoid-based pigmentation on their throat and jaw during the breeding season, along with blue eyes and blue/green flanks. The extent and intensity of red colouration in males have been linked to fitness benefits to females, including body condition, parasite resistance, parental ability and nest defence. In some populations in the Pacific Northwest of North America, male three-spined sticklebacks express melanic nuptial colouration. In these populations, male possess black throats instead of red, and have dark or black bodies. Melanic males are associated with waterbodies that are red-shifted due to the presence of tannins, where the ambient light environment is dominated by long wavelengths. Here we report the first discovery outside North America of melanic populations of threespined sticklebacks on the island of North Uist in the Scottish Hebrides, on the northwest Atlantic coast of Europe. These populations are associated with a hotspot of stickleback morphological diversity and occur in association with red-shifted waterbodies.