Fish behavior

Researchers at the Marine Institute and The Michelsen Centre for Industrial Measurement of Science and Technology has further developed a methodology for measurement of fish behavior using sonar.

Many believe that sonar has revolutionized modern fisheries more than any other electronic appliance, only the engine is transferred to the fishing fleet more efficiently. Whilst many see fish finding equipment as a threat to fish stocks, the equipment is also an effective tool to develop and operate a sustainable fishery.

On the screen, the crew can see if there are fish in the area, as stains on the blue screen shows how close the fish are. Not only can they see if there are fish, but they can also see how many there are, how large they are and generally what kind of fish they are.

Modern software embedded in the devices interpret the information better than the old troll, but not everyone agrees that fishermen have been given these tools as it is easier than ever to find the fish. In developing countries, visual localization of pelagic fish shoals at the surface is still used. This results in them maybe finding the fish, or maybe not and as they must consume more fuel, the profitability of these fisheries is often low.

Sonar is often thought to ruin a fish school whose fishery is not regulated, but at the same time, the technology can be a very resource-friendly technology that contributes to targeted and sustainable fishing. Modern sonar provides by far the best form to engage in fishing directed at specific sizes and species, however, there is still a long way to go before fishermen with adequate security can control the size of the herring or mackerel electronically. Additionally, governments can fine-tune quotas by introducing detailed rules for how much can be taken in each size group.

In regulated fisheries, sonar technology can increase profitability and be a tool in strategic taxation of a fish population. In unregulated fisheries technology can mean a quick change to stocks. The International Council for the Exploration of the Sea (ICES) already measures herring's condition with sonar. In the article "Estimating tail-beat frequency needs something split-beam echosounders" published in the ICES Journal of Marine Science, it states that:

"[Sonar] can among other things, tell how fat the fish are and thus how it has good access to food. With this we can observe the aspect of the behavior of the herring which we had previously attached electronic tags on to. Researchers at the Marine Institute and The Michelsen Centre for Industrial Measurement of Science and Technology has further developed a methodology for measurement of fish behavior using sonar."

Observing the behavior of individual fish and their swimming path is a highly developed method, researchers at the Institute of Marine Research have found that this method can be used to calculate how fish swim, by determining how fast the tail of the fish is moving. To do this, they send down a sonar in a cable, and send sound pulses horizontally into the schools.

When the technology becomes available, the authorities may prohibit extensive fishing of the biggest and fattest fish. It is important for the recruitment of the correct fish, as bigger fish will be subjected to much greater mortality than smaller fish over time, the genetic evolution may result in the development of fish stocks where small fish predominate. This trend is already registered in many fish stocks. But again, regulatory measures such as reduction in fishing quotas for much larger fish may provide a balance with targeted withdrawals.

Sonar technology has existed since the French physicist Paul Langevin invented the first effective one in 1917. It was known as "asdic" and was primarily a device that was used in a military context to track submarines.

In the future, sonar technology will be a very important tool in identifying strains of fish, size and condition, the fish migration both over time and in the course of one day, and not least the technology is important for the further development of an efficient and environmentally sustainable fishing.

By Terje Engo





Associated companies: