FOOD COMPOSITION OF RICE FIELD EELS AND PREDATION INTENSITY ON CRAYFISH

Rice-crayfih-eel co-culture is a high benefit comprehensive culture model that integrating rice planting, crayfish and eel cultivation. However, study on the predatory relationship between eel and crayfish is lacking, which is one of the key issues related to the establishment of this model. This study explored the potential food organisms and food composition of eel in rice-crayfish fields and its predation selection for crayfish by investigating the resources of macroorganisms and benthos and analyzing the gastrointestinal contents of eel in rice crayfish fields. The results showed that the natural bait for rice field eels was abundant in the paddy field environment, a total of 16 genera of basic bait organisms were found. Crayfish was the most preferred prey for eel, followed by caridina, earthworms and aquatic oligochaetes. The percentage of crayfish in the food mass of rice field eels was the highest from April to August, with a maximum of 93.90% in August, and a minimum of (76.85±20.66)% in April. When crayfish was the only food, the average daily predation of each large-size eel (≥200 g) was (1.63±0.065) g; when crayfish, caridina and earthworms were used as food, the rice field eels mainly fed on crayfish and did not feed on earthworms with the selection indices were 0.066, –0.266 and –1.000, respectively, When the live crayfish and feed (fresh surimi and crayfish artificial compound) were used as food, the rice field eels were mainly fed on feed but not on crayfish with the selection indices were –0.846 and 0.591, respectively. The results of this study provide a theoretical basis for the establishment of rice-crayfish-eel co-culture model and reasonable stocking of eel under this model.