Long-Range Sonar Fish School Detection and Identification System

White Paper

Patrick K. Simpson and Gerald F. Denny
Scientific Fishery Systems, Inc., P.O. Box 242065, Anchorage AK 99524

Background: The ability to rapidly assess the fish stocks in a broad area remains a daunting task. Current techniques use a combination of trawls and down-looking sonar to see what is directly along the path of a survey vessel. From these sparse measurements, estimates of biomass are created and used for making management decisions. Each year, there is more intense scrutiny on the data, there are less resources to collect the data, and the data is becoming more expensive to collect.

Scientific Fishery Systems, Inc. (SciFish) has recently completed the design of a long-range fish school detection and classification system that can locate and identify fish up to 15 miles from a vessell. A system would radically change the way that fish stocks are assessed. Large aggregations of pelagic fish could be located and measured much more rapidly, reducing the cost of stock assessment and, at the same time, increasing assessment efficiency.

In addition to improved stock assessment within our own waters, the long-range fish school detection and identification system can be used to monitor those fish stocks along our transnational boundaries. A survey track along the border between Russia and the United States in the Bering Sea would allow stock assessments 15 miles into Russian waters. Also, sockeye salmon could be located and tracked in the North Pacific, learning more about their migratory patterns as they make there way back to U.S. and Canadian waters. Finally, a long-range fish school detection and identification system such as this could become a pivotal tool in the reduction of dolphin bycatch in the tuna purse seine industry. Using this system, it will be possible to locate tuna schools that are not associated with dolphins. Using this tool, a dolphin would never be in harmís way from a tuna seiner again.

Current Status: The design of such a long range fish school detection and identification system emphasizes a low-risk, low-cost approach has recently been completed. This design uses technologies and equipment developed for naval work over the past 30 years. Because of this, commercial off-the-shelf (COTS) equipment is available for this tuna detection system. Input from several sources was used to build a workable design, including members of the tuna commission, NMFS Tuna Safe Program, NMFS Bering Sea Survey program, tuna boat skippers. This design stresses intuitive use and ease of understanding, in order to achieve the required performance goals.

To accomplish these objectives, this system utilizes active broadband sonar techniques. Current commercial sonars operate in a narrowband mode, similar to looking into an unfamiliar room with a colored lamp. By broadening the bandwidth, much more is not only detectable, but identification is enhanced as well. In the lamp analogy, a white light enables one to see a much wider variety of colors and textures than with a colored lamp. Navy funded research work by Love, Nero, Fueillade and others, in broadband sonar techniques has produced important results. They have identified frequency-dependent fish bladder resonances for several species of fish in both the Atlantic and Pacific oceans. In the sonar sense, different size or species fish reflect a broadband illumination at specific frequencies, just as a wall full of books reflect different colors in daylight. The design challenge is to find components that do not require a destroyer full of equipment to accomplish the task.

The prototype system is portable, to minimize impact to the vessels. It consists of an independent projector and receiver array on separate cables that provide both electrical and tow strength capability. The towed receive array is similar to, but smaller and less complex than those used on Navy surface ships and submarines. The transmitter is also less powerful, and less costly, than Navy projectors, and operates in non-military frequency regions. Processing of the transmit and received signal occurs in an augmented standard commercial PC. The display incorporates ship heading information, water temperatures (an important fishing clue) and array status as well as the target information. A key element of the design is the use of patented proprietary broadband fish identification techniques that allow species identification.

Description of Benefits: A detection system as described above would:

Program Breakdown: This proposed 3-year program is put forth to implement the long-range sonar fish school detection and identification system design recently completed under Saltonsdall-Kennedy Grant NA77FD0044. The intent is an aggressive development schedule to build the designed system in the first year. Testing of the system at sea and refinements would occur in the second year. Full field testing aboard research and fishing vessels would happen in the third year, with some allowance in material and engineering effort for further minor refinements.

For More Information. A complete system design specification with detailed cost breakdown is immediately available. For this information, or other questions relating to the proposed effort, contact: Patrick K. Simpson, President, Scientific Fishery Systems, Inc., P.O. Box 242065, Anchorage, AK 99524, Phone (907) 563-3474, (fax) (907) 563-3442, and Email scifish@alaska.net.