Fifty eight days separated trial 2 and 3 and, although studies
have suggested that fish are capable of long term memory, it is un-
likely that the fish would remember the noise without some sort of
association, for example with pain or food reward (
Gleitman and
Rozin, 1971
). If pain was associated with the air gun noise then a
more pronounced behavioural response would be expected as
would a physiological stress response (
Schreck, 1990
). The accli-
mation time for the fish in trial 2 was 24 days. This time period
is generally accepted as sufficient for fish to become acclimated
to a new environment, especially as the pink snapper had been
reared in a captive environment (
Pottinger and Pickering, 1992
).
Therefore, it is most likely that the ear damage observed at the
conclusion of trial 2 resulted in altered hearing capabilities and is
responsible for the lack of behavioural response to air gun noise
in trial 3. The effect, if any, that the observed damage had on hear-
ing capabilities was not investigated. However, some of the alarm
responses that were observed in trial 3 appeared to be in response
to the noise. Therefore, it can be assumed that, if the damage to the
ears did compromise hearing, it did not prevent all fish from sens-
ing the air gun noise at high levels.