Onset and
development of aggressive behavior in the early life stage of Japanese
flounder
Y. Sakakura, K. Tsukamoto-2002
Fisheries Science, 68(4):
854-861
Abstract:
Onset and development, and diel rhythm of
aggressive behavior were observed in the early life stages of Japanese
flounder Paralichthys olivaceus. The frequency of nip was counted as
an index of aggressive behavior. No aggressive behavior was observed during
the larval stage until day 39 after hatching (when fish were 13.2 mm in
standard length (SL)) in the experimental tanks. The onset of aggressive
behavior was observed on day 39, coinciding with completion of metamorphosis
from the larval to the juvenile stage, and it developed until day 46. During
the metamorphosing stage, typical shivering behavior (Ohm (W)-posture) was observed, and it showed a peak on day 19 (SL 7.6 mm)
and decreased thereafter. W-Posture disappeared in the juvenile stage. Aggressive behavior and
W-posture
were only observed in the daytime. Settlement was first observed from day 19
in less than 30% of larvae and all individuals settled from day 39. As W-posture was observed regardless of
the presence or absence of food and the peak of frequency in W-posture was observed in a specific
stage of metamorphosis, this behavior is not related to feeding behavior,
and it is possibly a precursor to aggressive behavior in this species.
(Faculty of Fisheries, Nagasaki University, Nagasaki
852-8521, Japan, Tel: 81-95-847-1111. Fax:
81-95-844-3516. Email: sakakura@net.nagasaki-u.ac.jp)