In Search of Salmon

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Researchers Revealed is an exciting new series profiling the research performed in UBC’s Biodiversity Research Centre. Produced by Philippe Roberge, the series looks at new ways in which researchers harness technology to study the natural world in ways that were not possible before.

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It’s 5am as we head out onto the outermost pier,  where our trusty vessel awaits. Fog clings to the surface of the water as harbour seals play in the marina’s kelp beds below. Our team from UBC, under the supervision of Dr. Mei Sato, is on a mission to examine the impacts of food availability on killer whales residing in the Juan de Fuca strait. Mildly exhausted from our early-morning wake up, the 6 of us cram ourselves into a boat designed for 4, squeezing ourselves in amongst scientific equipment worth more than our cumulative annual salaries. Today we’re measuring the accuracy of the most expensive instrument on our boat – a special underwater sonar that will – hopefully- provide UBC’s marine mammal unit with unprecedented levels of detail. 

Designer of the sonar and project lead Dr. Mei Sato describes how it works: “It [the sonar] uses four different frequencies. The lower frequencies pick up only on larger objects like salmon while the higher frequencies pick up on objects both large and small – a range that spans everything from salmon to plankton. By subtracting the small objects that show up only on the high frequency reading, we are then left with only the larger objects, at a higher level of detail than would be available had we only performed the lower frequency reading.”

Commercial and sport fishermen have been using consumer grade sonars to find fish for decades, but the accuracy of this sonar is considerably higher. The sonar is so accurate in fact, that Mei is using it to discern between different fish species – for example, to tell the difference between a chinook and coho salmon. In order to test the accuracy however, we have to validate the reading by catching the fish that show up on the reading, and checking to see if our prediction was right.

Some of the fish are also kept for further laboratory examination. In order to prevent them from deteriorating under the beating July sun, Alicia gets to work dissecting the  specimens. In less than 3 minutes the fish’s weight and length are measured, the gut and its contents are removed, tissue samples are extracted, and everything is stored on ice. The samples will be analyzed for nutritional content, as it is both the quantity and the quality of the food that is being measured.

The Juan de Fuca strait is the primary channel connecting the Salish Sea to the Pacific Ocean. The middle of the straight serves as the border between Canada and the United States. Connected directly to the pacific ocean, the seas in the channel are often rougher than those of the surrounding inlets, as the crew soon found out. As the wind battered our faces, the boat was rocked continuously by waves, the horizon rising and falling along with our sea legs.

We pass a flock of gulls in some sort of frenzy, and look at our sonar to see that they are atop a large bait ball. By 5pm, we start our return trip to the marina. Back in the harbour we are greeted by our aptly named aquatic friends as we tie the boat to its moorings.

Ultimately, the sonar could then be used to count fish populations in a non-destructive manner, and grant insight into wether commercial fishing has impacted the food availability of the resident killer whale population that inhabits the area.

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