Abstract
This study presents fundamental information on the reproductive biology of Puntius denisonii, an endemic and threatened aquarium fish of the Western Ghats Hotspot. Results are based on the observations from three river systems, Chandragiri, Valapattannam and Chaliyar. Maximum observed total length in P. denisonii was 162mm and 132mm for males and females, respectively. Males attained sexual maturity at a lower size than females with mean size at first maturity determined as 85.33 plus or minus 1.52 mm for males and 95.66 plus or minus 1.15 mm for females. Puntius denisonii spawned from October to March with minor differences in the peak breeding months between the three river systems, which were studied. Sex ratio deviated significantly from 1:1 and was skewed in favour of males. Absolute fecundity varied from 376 (fish of 102mm total length) to 1098 (fish of 106mm total length) eggs. Currently, the closed seasons for P. denisonii have been put in place during June, July and October based on the (mis)assumption that the species breeds during these three months. However, the results of the present study have helped us to understand more about the reproductive biology of the species so as to recommend more appropriate seasonal closures. The months from October until March need to be designated as a closed season for protecting the breeding population of P. denisonii.
Highlights
Unsustainable collection of endemic freshwater fish for the aquarium trade is an emerging conservation issue in the tropics, which has resulted in the population decline of several species such as the Asian Arowana Scleropages formosus (Rowley et al 2009), Silver Arowana Osteoglossum bicirrhosum (Moreau & Coomes 2006), Celestial Pearl Danio Danio margaritatus (Roberts 2007) and Bala Shark Balantiocheilos
Relationship of Absolute fecundity (AF) with both Total Length (TL) and TW were determined by plotting the points on a log-log scale as these are expected to be allometric relationships described by a general power function y = axb, where y is the dependent variable, x is independent variable, b is the scaling exponent and a is the normalization constant (Kharat et al 2008)
Gonado somatic index (GSI) in all three river systems peaked during October to March with minor differences between rivers (Fig. 2)
Summary
Unsustainable collection of endemic freshwater fish for the aquarium trade is an emerging conservation issue in the tropics, which has resulted in the population decline of several species such as the Asian Arowana Scleropages formosus (Rowley et al 2009), Silver Arowana Osteoglossum bicirrhosum (Moreau & Coomes 2006), Celestial Pearl Danio Danio margaritatus (Roberts 2007) and Bala Shark BalantiocheilosOPEN ACCESS | FREE DOWNLOADThis article forms part of a special series on the Western Ghats of India, disseminating the results of work supported by the Critical Ecosystem Partnership Fund (CEPF), a joint initiative of l’Agence Française de Développement, Conservation International, the Global Environment Facility, the Government of Japan, the MacArthur Foundation and the World Bank. Unsustainable collection of endemic freshwater fish for the aquarium trade is an emerging conservation issue in the tropics, which has resulted in the population decline of several species such as the Asian Arowana Scleropages formosus (Rowley et al 2009), Silver Arowana Osteoglossum bicirrhosum (Moreau & Coomes 2006), Celestial Pearl Danio Danio margaritatus (Roberts 2007) and Bala Shark Balantiocheilos. Wild caught aquarium fish industry receives little attention from ichthyologists, local governments and conservation organizations throughout the world, with very little research, and no legislative controls (Moreau & Coomes 2007; Rowley et al 2009). Similar to other parts of the world, aquarium fish collections in WG are open access and unregulated, raising concerns about their ecobiological impact (Raghavan 2010). Several endemic species are known to be facing serious population decline due to indiscriminate collections for the trade (Kurup et al 2004; Raghavan et al 2009)
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