Development of Active and Passive Acoustic Measurements to Improve the Production and Profitability of U.S. Aquaculture
Warmwater Aquaculture Research Unit
2012 Annual Report
1a.Objectives (from AD-416):
Develop technology and methodology for both passive and active acoustic applications to improve the production and profitability of aquaculture in the United States. This includes the use of ultrasound to mechanically clean water, utilizing acoustic stimuli on catfish to improve seining operations and passive acoustic monitoring of small fry. This project supports the unit objective to develop new equipment and technologies to improve profitability of channel catfish farming.
1b.Approach (from AD-416):
Preliminary acoustic measurements of commercial algae control systems will be made in the National Center for Physical Acoustics (NCPA) calibration tank. Customized equipment will be assembled at the NCPA and delivered to National Warmwater Aquaculture Center (NWAC) for lab and field trials by USDA personnel. Measurements on fish stimuli with sound will be made at USDA-NWAC tanks and ponds with later trials performed in conjunction with seining to determine effectiveness. Equipment for passive monitoring of catfish fry will be assembled at the NCPA. Measurements will be made by NCPA personnel at USDA-NWAC facilities.
The purpose of this agreement is to investigate active and passive acoustic techniques to improve the profitability of U.S. aquaculture. Work progressed on the use of sound to move fish in advance of seine nets to improve harvesting. Previously captured sounds, both man-made and natural, were introduced into concrete raceways to observe fish reactions. Many sounds produced a slight startle response with minimal movement of the fish. Some sounds produced fish movement but the fish acclimated after only minutes of exposure. One particular series of intermittent, low frequency noise bursts near 100Hz, however, provided a dramatic effect with a strong startle response and rapid fish movement each time the sound came on. Use of this sound in larger outdoor ponds was hampered by the difficulty in observing fish reactions to stimuli. The previously developed SONAR built to inventory ponds had difficulty observing fish moving rapidly as they disturbed large volumes of bottom sediments which obscured the sound waves. Other means of evaluating the noise’s effectives on fish motion are being pursued in the summer of 2012 with one possibility being direct assessment on ponds slated for harvesting. Work continued on the use of a commercially available sonicator (a high amplitude acoustic source) to eliminate the Ram’s Horn snail, an intermediate host to trematodes that infect catfish. In order to expand upon initial tests and to obtain a meaningful efficacy rate, twenty groups of ten snails were exposed to the same duration of sonication. This test resulted in approximately 35% of the snails exposed being killed immediately after exposure. However, it was observed that a few days after experimentation a significant number of the surviving snails were dead as well (42% of the stock of sonicated snails compared to 9% of the untested colony). This presumed ‘mortal wounding’ effect shows more promise than the ‘instant kill’ as it might allow for shorter durations of exposure as well as reduced power requirements. This effect will be further investigated in an attempt to determine the maximum efficiency achievable with the current hardware and technique.