The Escape-ability Of Two Cyprinid Fish Species And Its Underlying Behavioral Mechanism

To investigate the escape ability of two cyprinid fish species and its underlying behavioral mechanism, the present study selected the juvenile snakehead(Channa argus) as predator, the juvenile common carp(Cyprinus carpio) and crucian carp(Carassius auratus) as preys, respectively. The parameters involved fast-start escape responses i.e. response latency(R), the maximum line velocity(Vmax) and the maximum acceleration(Amax), the parameters of spontaneous activities such as the average velocity and percent time spent moving, the boldness as suggested by the time when prey emerged from the sheltered site as well as the constant acceleration speed(Ucat) of preys were firstly measured. Then, length of time when either common carp or crucian carp were caught by predator was measured to evaluate the escape ability for each species. An additional experiment was performed to see which species was firstly caught by the predator when one crucian carp and one common carp were paired in a prey-predator interaction test. The main results as follows1. The Vmax, Amax, Ucat, and S120 of the juvenile crucian carp were significantly higher than those of the juvenile common carp, while the R of the juvenile crucian carp was significantly lower than the juvenile common carp.2. The spontaneous activity indicated by both the average swimming velocity and time percentage spent on movement of the juvenile common carp were higher than those of the juvenile crucian carp, whereas the time when prey emerged from the shelter of the juvenile crucian carp was longer than that of the juvenile common carp.3. The time(average 244.44 min) taken by predator(i.e. snakehead) to hunt the juvenile crucian carp successfully were longer than that(average 160.11 min) of the juvenile common carp when either species were individually exposed to the predator. Furthermore, the proportion of the juvenile common carp which was firstly hunted by juvenile snakehead were higher than those of the juvenile crucian carp when two fish species exposed to predator in pair.4. The behavioral and locomotion parameters such as the average swimming velocity(Vmean) and time percentage spent on moving(Pmoving) of the crucian carp were positively correlated with the parameters related with survival ability, whereas it is not in the juvenile common carp. The results show that1. The escape capability of the juvenile crucian carp is higher than the juvenile common carp.2. All of the swimming performance parameters of the juvenile crucian carp were higher than those of the juvenile common carp, which may be the primary reasons for the higher avoidance ability of the juvenile crucian carp when exposed to the predator.3. The boldness and routine activity level of the juvenile crucian carp were lower than the juvenile common carp, which may be the behavioral mechanism for the higher survivorship of the juvenile crucian carp when exposed to predator.4. The inter-individual differences in either swimming performance or behavior showed no connection with predator escape ability in the juvenile common carp. It may be due to the overwhelming advantage of snakehead when prey on common carp in the present study which made the physiological and behavioral differences meaningless.