There was a general trend for the squid in trial 5 to increase their
swimming speed above noise levels of 147 dB re 1
l
Pa
2
.s and then
slow their swimming speed or become relatively stationary at the
surface during the most intense air gun signals (
Fig. 6
b).
The same animals were used in trials 5 and 6. Therefore, the
squid in trial 6 had been previously exposed to air gun noise five
days prior to trial 6. In trial 6 the squid were observed fast swim-
ming more often during air gun operation than they were when the
air gun was off. It is also interesting to note that at each of the high-
est six levels of exposure either the jetting or flash expansion of the
group was observed. As noise levels exceeded 147 dB re 1
l
Pa
2
.s
the frequency of alarm responses increased with a linear relation-
ship giving a coefficient of determination of 0.9981 (
Fig. 6
c).
The trend of the squid increasing swimming speed as the air
gun approached and then becoming stationary in the top section