THE PREDATION SELECTIVITY OF FEROCIOUS FISH (SILURUS ASOTUS AND CHANNA ARGUS) TO PROCAMBARUS CLARKII LARVAE IN POYANG LAKE

Since the closure of fishing in the Yangtze River, the population of ferocious fish in Poyang Lake has been steadily increasing. In order to investigate whether the Predatory activity of ferocious fish impact the population of Procambarus clarkii, we employed Silurus asotus and Channa argus as predators, using eight different types of bait organisms in this study. Three sizes of P. clarkii larvae (small: 39.20±1.30 mm; medium: 49.82±2.13 mm; large: 58.99±1.16 mm), along with Cyprinus carpio, Carassius auratu, Squaliobarbus curriculus, Mosquitofish, Hypophthalmichthys molitrix, Pseudorasbora parva and Macrobrachium nipponense, were used as prey to examine the species selectivity of S. asotus and C. argus and the size selectivity of P. clarkii larvae. The results revealed that: (1) S. asotus and C. argus exhibited a preference for nocturnal predation, with their peak predation occurring between 20:00—8:00; (2) In the presence of various food organisms simultaneously, S. asotus and C. argus did not prey on P. clarkii larvae, displaying clear predation preference for C. carpio, mosquitofish and M. nipponense. (3) When presented with P. clarkii larvae of the same size, S. asotus exhibited a pronounced predation preference for small size P. clarkii larvae, while C. argus preyed significantly more on small-sized P. clarkii larvae than on large-sized ones (P<0.05). (4) In the equal polyculture combination of various sizes of P. clarkii larvae, both S. asotus and C. argus displayed a clear preference for small size P. clarkii larvae, and this preference intensified with increasing size gap among the P. clarkii larvae. In summary, when multiple food organisms coexist, P. clarkii is not the preferred prey for ferocious fish, however, when the variety and quantity of other food organisms are limited, smaller-sized P. clarkii larvae remain at a high risk of predation.