Semester

Summer

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

Patricia M Mazik

Abstract

Intensive aquaculture systems, particularly recirculating systems, often require noise producing equipment such as pumps, blowers, and filters that inadvertently increase sound levels within the culture environment. These systems are often very effective at culturing healthy, fast growing fish; however, the potential impacts of underwater noise on fish within intensive aquaculture systems have not been evaluated. Limited research suggests that subjecting fish to noise could result in impairment of the auditory system, reduced growth rates, and increased stress. The studies presented within this manuscript were conducted to gain a better understanding of aquaculture production noise and its potential impacts on rainbow trout growth, survival, and physiology.;Chapter 1. The objective of this study was to evaluate practical structural changes (retrofits) to reduce underwater noise within fiberglass fish culture tanks. Retrofits eliminated contact between PVC piping and tank surfaces and buffered sound transmission into tanks using insulated materials. Each retrofit contributed to a reduction of underwater sound. As retrofits were combined, a cumulative four-fold reduction in sound level was observed. Sound frequency spectra also indicated that nearby pumps and blowers created tonal frequencies that were transmitted into the tanks. The tank modifications used during this study were simple and inexpensive and could be applied to existing systems and designs. Optimal retrofits were applied to tanks used in subsequent studies to create "quiet" control tanks.;Chapter 2. This study was conducted to evaluate the long term effects of aquaculture production noise on the hearing sensitivity, growth, survival, and disease susceptibility of rainbow trout. Two cohorts of rainbow trout were cultured for eight months in replicated tanks (n = 2) consisting of three sound treatments: 115, 130, and 150 dB re 1 muPa RMS, representing sound levels that were lower than, similar to, and higher than mean sound levels recorded within commercial scale recirculating systems. There were no significant differences between sound treatments for hearing threshold, growth rate, mortality, and disease susceptibility. This study indicated that rainbow trout were not negatively impacted by noise levels common to recirculating aquaculture systems.;Chapter 3. Anecdotal evidence of slight (but non-significant) differences in growth between treatments during the Chapter 2 study, particularly over the first month, prompted additional research. The objective was to provide an in-depth evaluation of the long term effects of aquaculture production noise on the growth, condition factor, feed conversion efficiency, and survival of rainbow trout with increased replication (n = 4). Two sound treatments were used: 117 and 149 dB re 1 muPa RMS. No significant differences were identified between the treatments for mean weight, length, specific growth rates, condition factor, feed conversion, or survival (n = 4). Analysis of growth rates of individually tagged rainbow trout indicated that fish from the 149 dB tanks grew slower during the first month of noise exposure; however, fish acclimated to the noise thereafter. This study further suggests that rainbow trout growth and survival are unlikely to be affected over the long term by sound levels common to intensive aquaculture systems.

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