024092 Singh N;Bhatt K C (Zoology Department, P.O. Box 83, HNB Garhwal University, Srinagar Garhwal, Uttaranchal) : Behavioural and functioning interactions in the schizothoracid community in the river mandakini: An assessment through altering sex ratio patterns. J Bombay Nat Hist Soc 2004, 101(3), 374-80.
The interrelationships and functioning of three closely related species, Schizothorax plagiostomus Heckel, Schizothorax richardsonii Gray and Schizothoraichthys progastus McClelland (Teleostei, Family Cyprinidae, Subfamily Schizothoracinae), comprising the snow trout or schizothoracid community, as reflected by the altering sex ratio patterns, have been assessed quantitatively. Observations were made for two years, from January 1991 to December 1992, at four landing sites: Bheri (1,020 m), Chandrapuri (827 m), Agastyamuni (760 m) and Tilwara (724 m), covering the lower stretch of over 30 km of the high altitude glacier-fed River Mandakini in the Garhwal Himalaya. The water characteristics of the river (total water discharge, water velocity and water temperature) were measured at Chandrapuri. The total fish catch of these species from all the sites was first pooled and arranged according to sex, percentage, breeding and non-breeding seasons. The sex ratio was determined. These species breed twice a year, from March to May and August to October, with well-defined non-breeding intervals. These species individually followed a similar pattern of response to changes in the environment, as revealed by the altering sex ratio patterns i.e., highest values during first breeding season of 1991 and 1992(2.65:1,3.0:1,3.89:1 and 2.56:1, 3.86:1,4.75:1 respectively) when water parameters began rising from the lowest in the extreme winter. The lowest values of sex ratio were observed during the second breeding seasons of 1991 and 1992(2.03:1, 1.51:1, 1.58:1 and 1.59:1, 1.82:1, 1.74:1 respectively) when water characteristics values were at a peak, or just began plummeting from the peaks of monsoon. The corresponding values of sex ratio in the entire schizothoracid community were observed as 2.78:1, 2.83:1 and 1.91:1, 1.61:1 respectively, during the first and second breeding seasons of 1991, 1992. Sex ratio begins to alter at the commencement of just rising and/or peak, or just plummeting periods. Altering sex ratio pattern is one of the indicators of the beginning of the breeding process. That is the fish take the changes in surroundings as the cue to initiate breeding process. Both the species and the community of schizothoracine fishes alter their sex ratio pattern in response to changes in their surroundings. This pattern can serve as an indicator of the functioning and interrelationship at individual, population, species and community levels. Patterns of sex ratio change must be utilized for assessing the behavioural and evolutionary processes over a period as well as an effective tool in the regulative management of snow trout community in the high altitude glacier-fed hillstreams of Garhwal Himalaya.
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