STUDY ON LIFE-HISTORY PATTERN OF SEVEN FRESHWATER FISHES IN THE DONGJIANG RIVER, GUANGDONG

Life history of fishes may l,e divided into two patterns, i.e. r-selection and K-selection. In this paper, seven ecological parameters, namely, asymptotic body-length (L∞), asymptotic body-weight (W∞), growth coefficient (K), instantaneous natural mortality (M), primary reproductive age (Tm), maximum age (Tmax) and genital gland indices (GI) are used for the analyses of lifehistory patterns of fishes. Seven fishes from Dongjiang River, Guangdong, viz., Cyprinus carpio L, Carassius auratus L., Squaliobarbus curriculus R., Xenocypris davidi B., Cirrhina molitorella C. et V., Siniperca kneri G., Eleotris oxycephala T. et S. seem to have their strategy inclined to r-selection and the genital gland indices (GI), instantaneous natural mortality (M) and growth coefficient (K) have been used as the main basis for this opinion.Equilibrium yield formula is applied to calculate the catch when the instantaneous catching mortality (F) and fishery recruit age (tc) of a particular fish population are changed. Analysis of catch curves demonstrates that for the fish populations of r-selection, higher catch can be obtained through a moderate increase of fishing strength, yet a reckless increase in fishing effort is harmful. Moreover, fish yield may have a certain increase by raising harvesting age when fishes are young, but fish yield will decline greatly by continuously raising harvesting age after fishes reach a certain age. If the decline is due to catching, fish populations will easily recuperate and the maximum sustained fish yield can be expected as long as harvesting strength and harvesting age are regulated reasonably.