Where do all the salmon go?

A researcher at the University of Rhode Island has developed a microelectronic chip designed to collect data about salmon and their habitat during oceanic migration.

University of Rhode Island researcher Godi Fischer has developed a microelectronic chip that could play a key role in collecting data about the habitat salmon prefer during their two- to three-year ocean migration.

The implantable, temperature monitoring device was developed because of concerns expressed by URI Fisheries Professor Conrad Recksiek that salmon mortality rates appear to be linked to increasing ocean temperatures caused by global warming.

But, according to Recksiek, there was no reliable way to obtain the data to confirm his hypothesis.

‘The engineering challenge was in providing the chip with enough power to last for the two or three years that the fish are at sea,’ said Fischer, a professor of electrical and computer engineering. ‘We also had to include all the necessary functions – the thermal sensor, data converter, memory, control circuitry and oscillator – all together on one tiny chip. No one had done that before.’

The device is said to consist of a silicon chip measuring not more than 2.1 by 3.3 millimetres and a tiny battery that produces one micro-amp of electrical current. The chip is programmable, so temperature data can be collected as often as desired.

A prototype of the device will be tested on salmon this year. The chips will be sealed in epoxy for durability and attached to the dorsal fin of each fish. Fischer and Recksiek are also experimenting with an internal version that might be safer for the fish.

The researchers are also working on making the device inexpensive to manufacture, since thousands of fish must be tagged in order to retrieve enough of the tagged fish for the data to be statistically reliable. Retrieval rates are expected to be about 5 percent.

Salmon spawn in the same river where they were born but spend most of their lifetime in the ocean. Biologists aren’t certain exactly where in the ocean the fish travel and what habitat factors affect their survival rates. Fischer’s temperature sensor will help to shed some light on this subject.

While the electronic tag was developed for use in tracking fish, Fischer said it could also be used to record the temperature of goods that must be maintained at certain temperatures while they are transported around the world. ‘I’m sure there are many more applications that we haven’t even thought of yet,’ added Fischer.

Fischer’s next goal is another fish monitoring device that collects data on salinity, water pressure, and precise location so additional information about salmon habitat preferences can be tracked.