THE PHENOTYPIC BASIS, ECOLOGICAL CONSEQUENCES AND FASTING RESPONSES TO ANGLING OF JUVENILE GIBEL CARP (CARASSIUS AURATUS GIBELIO)

According to previous studies on fish angling, a correlation has been established between vulnerability to angling and metabolic traits in fish. However, it still remains unknown that whether other phenotypes (i.e., swimming performance and personality) of fish are related to the vulnerability to angling. To examine the phenotypic basis, ecological consequences and fasting responses to angling in Cyprinids fish, juvenile gibel carp (Carassius auratus gibelio) was used as experimental model in this study. This study first measured the phenotypic traits (i.e. energy metabolism, swimming performance and personality) of the experimental fish, and then the fish were angled in the buckets (named as control group) under laboratory condition. After all measurements of phenotypes and angling having been completed, all fish were fasted for 7 days and angled again at the end of fasting period (named as fasting group), following by a 14-day period of continuous feeding (named as refeeding group). There were four parallel angling samples (n=40 individuals per sample) in each angling test, which was ceased when the 20^th individual was successfully angled. The angled 20 individuals were considered as angling group (i.e. higher vulnerability to angling), and the other 20 individuals were considered as un-angling group (i.e. lower vulnerability to angling). The factorial aerobic scope of the angling group was smaller than that of the un-angling group. The results showed that no differences in morphology (body weight, body length and condition factor), energy metabolism (standard metabolic rate, SMR; maximum metabolic rate, MMR; and aerobic scope, AS), swimming performance (maximum accelerated swimming capacity, U_cat; and gait transition speed, U_gt), and personality (exploration, activity and boldness) between the angling group and the un-angling group. The fish had a higher percent latency in the exploration test than that in the boldness test, which led to shorter time spent in moving and lower frequency in passing through door in the exploration test than those in the boldness test. SMR was not related to U_cat and U_gt (P>0.05), whereas MMR and AS were positively correlated with bothU_cat and U_gt (P<0.05). The energy metabolic parameters were related to some personality parameters. Fasting increased the total angling time, average individual angling time and coefficient variance of the individual angling time in juvenile gibel carp. The specific growth rate (SGR) of body mass was higher in the un-angling group than that in the angling group during the fasting period, but no difference in SGR was found between the un-angling group and the angling group during the refeeding period. With the exception of MMR and AS, SMR was negatively related to SGR during both the fasting period and the refeeding period (P<0.05), suggesting that higher SMR individuals decreased their body mass faster during fasting, and grew slower during refeeding. Our study suggested that the juvenile gibel carp may not have the phenotypic basis, and would decrease their vulnerability to angling due to fasting. There was difference in the ecological consequences between two phenotypes of vulnerability to angling, but this difference disappeared after the 14-day period of refeeding, indicating that the vulnerability to angling of the juvenile gibel carp is context-dependent to some extent.