Abstract: Fishes are constantly subjected to strong angling pressure in nature. There are substantial inter and intra specific differences in the vulnerability to angling in fishes. To investigate the differences of vulnerability to angling between two species of Cyprinidae and whether such difference might be related to their external morphology, we used juveniles of two widely cultured species in China, Carassius auratus gibelio and Cyprinus carpio, as the experimental model. We conducted a series of angling experiments including three treatments \[gibel carp Carassius auratus gibelio, common carp Cyprinus carpio and mixed group (Carassius auratus gibelio plus Cyprinus carpio)\] in the laboratory at (25±0.5) ℃. There were three replicates for each treatment with each replicate including 40 individuals. After 20 fish individuals had been angled for each replicate, the angling activity was ceased for this replicate. During the angling process, we recorded the total angling time for each replicate and angling rank number of the individual which was successfully angled, and then calculated average time spending on angling for each individual. The body length of C. carpio in the mixed treatment was larger than those in other two treatments. The condition factor of the common carp group was higher than those of other two treatments. The condition factor of both the angled common carp and gibel carp in the mixed group was larger than that of the un-angling common carp. We found no difference in total angling time among the three treatments. However, there was a significant difference in the average time spending on-angling among the three treatments, with the time spending on angling of the common carp being longer than that of the gibel carp in the mixed treatment. The proportion of angled gibel carp was higher than that of the angled common carp in the mixed group, and the average angling rank number of the gibel carp was smaller than that of the common carp. Our results suggested that the juvenile gibel carp had a higher vulnerability to angling than the juvenile common carp, which may be related to the differences in ecological habits and morphological traits.

Key words: photosynthesis, simultaneous gas exchange and chlorophyll fluorescence method, the curve-fitting method, instantaneous carbon isotope (¹³CO₂) discrimination method., mesophyll conductance