POPULATION DYNAMICS AND PRODUCTION OF POLYARTHRA TRIGLA IN DONGHU LAKE, WUHAN

Polyarthra trigla is a predominant rotifer in Donghu lake, Wuhan. Its population density and eggs were estimated during the period from May 1983 to April 1984 at two sampling station, station Ⅰ and station Ⅱ, which are representatives of the bay region and the pelagic zone, respectively.By average, egg density of Polyarthra trigla was 27 egg/l(0-245 egg/l)at station Ⅰ,and 22 egg/l(0-321 egg/l)at station Ⅱ, and population density was 362 ind./l(0-6600 ind./l)and 159 ind./l(0-2770 ind/l)respectively.Egg development time decreases with increasing temperature(5 to 30℃), The relationship between temperature(T)and development time(D)was found to be curvilinear and may be described as the following equation:lnD=0.4627+1.29291nT-04995(1nT)2Average dry weight of individual rotifer is 0.07μg.The instantaneous birth rate(b), increase rate(r)and the death rate(d)were calculated according to the formula given by Paloheim(1974)and Edmondson(1965).Production rate of the present species was estimated with two different methods. Average daily production rate for P. trigla during the investigating period was 10.19μg/l using Galkovskaya's generation time method and 5.98μg/l using Edmondson's egg ratio method at station Ⅰ, and 3.96μg/l and 3.01μg/l at station Ⅱ, respectively.