3. Results
3.1. Experimental conditions
Mean sound levels for the control tanks and the experimental tanks
were 117±1 dB re 1 μPa RMS and 149±0 dB re 1 μPa RMS, respectively.
Sound pressure levels generally varied depending on location within
the tanks, with the loudest areas closest to the side walls and the
bottomof the tank, and quietest locations near the top and center of the
tanks (Tables 1 and 2). Mean spectral plots for each treatment are
presented in Fig. 1. There were significant differences between
treatments for the following water quality parameters: total ammonia
nitrogen, total suspended solids, and dissolved oxygen (Table 3). All
water quality parameters were well within safe recommended limits
(Colt and Tomasso, 2001) and the differences between treatments are
small and therefore would not have impacted growth.
3.2. Observations
When the 149 dB treatment was initiated the fish responded with
an initial alarm reaction, scattering throughout the tank and swimming
erratically. Fish began swimming in normally distributed patterns
within a few hours following the onset of the sound.
3.3. Growth (Weight)
Following random stocking rainbow trout weights were 39±0 and
40±0 g, for the 117 dB and 149 dB tanks, respectively (Fig. 2). Fish from
the 117 dB tanks were slightly larger (1.5%), but not significantly larger
(p=0.672), than fish from the 149 dB tanks to begin the study (Fig. 3).