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The annual Atlantic herring survey

Aboard the Perley in the Gulf of St. Lawrence

By François Turcotte, Aquatic Science Biologist

Atlantic herring is one of the most abundant species of marine fish in the world. It is a food source for many animals — birds, seals, whales, tuna and other fish — and is also fished for human consumption.

To determine the quantities fishermen can catch, we need to know how many fish can be found in the waters of the southern Gulf of St. Lawrence. To answer that question, I participated in a sea sampling mission in September 2017. We set out with two Coast Guard vessels: the CCGS Frederick G. Creed and the CCGS M. Perley.

CCGS Frederick G. Creed

CCGS Frederick G. Creed

CCGS M. Perley

CCGS M. Perley

Sampling is done at night, when herring leave the sea floor to feed on plankton closer to the surface. The Creed locates schools of fish using an acoustic probe on the underside of the ship; the Perley then sends a net into the water to take a sample. The recording taken by the acoustic probe is used to determine the quantity of fish (biomass) under the ship, and the samples make it possible to characterize the individuals that make up the fish population. All of this information is compiled in a mathematical model used to assess the herring biomass in the southern Gulf and to determine the quantity that fishers may catch.

When the Creed found a school of herring, my job was to contact the captain on the bridge of the Perley and determine a strategy for fishing the school. The net used to catch fish is very long and can catch hundreds of pounds of fish. The operation, which can take over an hour, must therefore be carefully planned!

After discussing the position of the school, the strength of the current, winds and the water depth where we will be fishing, we decide on a trajectory. The five-person crew then begins its task. The deck crew puts the net in the water, and the officer controls the net's position from the workstation on the bridge.  After the officer lifts the net, I collect the samples to bring the fish to the laboratory at the Gulf Fisheries Centre in Moncton. The fish are sampled to determine their age, weight, length and maturity.

Life on board the Coast Guard vessel is very comfortable. Each crew member has a room, and the cook makes sure that everyone is well fed! Crew members are all experienced, most of them being former fishers, and have many interesting stories to tell (all true, no doubt!).

Navigating the waters of the Gulf is always a pleasant experience. We get the opportunity to see magnificent landscapes and different sea animals if we are lucky, and to meet people from different cities where we dock each morning. Working on the vessels is very stimulating, and it is very exciting when we find out there is a new school to fish. We don't always succeed, and some problems may arise, but it's never a bother. I spent three weeks on these two ships and can't wait to return!

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