Positive temperature effects on the initiation and intensity of cannibalistic behaviour of larval pike,Esox luciusL. Is cannibalism reflected in otolith fluctuating asymmetry?

摘要

Cannibalism can be a significant factor limiting the survival of pike,Esox lucius, early life stages in both natural and aquaculture conditions. In the present research, type I cannibalism was studied in pike larvae (size range: 9-32.5 mm standard length, SL) in controlled conditions for 45 days post-hatching (dph). For this purpose, the occurrence of cannibalistic pairs, i.e. prey caught by a cannibal inside the cannibal's mouth, was monitored for 15 min periods by two observers six times daily. Cannibalism was not observed in fish that still had yolk-sacs, but it did occur as soon as the yolk-sac was absorbed on 5 dph at a body size of 13 mm at 22 degrees C and 10 dph at a body size of 13.4 mm at 15 degrees C. The ratio of prey to predator size was on average 87%, but the smallest observed size difference was only 1.3%. The intensity of cannibalistic attacks depended on water temperature with more intense cannibalism at 22 degrees C than at 15 degrees C, and no cannibalism at 10 degrees C. Fluctuating asymmetry (FA) in all three sagittal otolith size parameters (area, width, and length) was higher in prey than in cannibals, the differences were not statistically significant.