Joint U.S.-Canada Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey
The Hake Survey provides data to support sustainable populations of Pacific hake on the West Coast.
Hake Survey Basics
The Fisheries Engineering and Acoustic Technologies team from the Northwest Fisheries Science Center and Fisheries and Oceans Canada Pacific Region conduct the hake survey. It provides vital data to help manage the migratory coastal stock of Pacific hake (hake, Pacific whiting, Merluccius productus). The hake survey, officially called the Joint U.S.-Canada Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey, occurs every odd-numbered year.
The U.S.-Canada International Hake/Whiting Treaty governs the management of the hake fishery. The treaty outlines how the Total Allowable Catch for hake is set for the entire coast.
West Coast Survey Locations
Hake mostly spawn during the early winter months in larger groups offshore in the southern part of their range, but in some years are believed to spawn in the northern part of their range as well. During the summer months, their migration and movements are assumed to be minimal, and they feed in large groups along the continental shelf break.
We take advantage of this situation to survey the population, working from approximately Point Conception, California to Dixon Entrance, Alaska. Survey boundaries are not firmly set, and we may go further south, north, or west than planned if there is still a sign of hake at the edges of our survey area.
We cover the survey area with parallel lines that mainly run east to west, called transects. While the north-south position of the transects changes slightly from survey to survey, they are typically 10 nautical miles apart. The transects are surveyed using a research vessel equipped with scientific echo sounders (acoustic instruments that can transmit and receive sound) and fishing nets to validate identified schools. We begin in the southern part of the survey area, and once a transect is completed, the ship moves north to the next transect.
Because this is an international survey, two research vessels cover the entire U.S. and Canadian West Coasts. The U.S. science crew uses a NOAA ship, usually the Bell M. Shimada, and Canadian scientists use a Canadian Coast Guard ship, the CCGS Sir John Franklin (starting in 2021). The Shimada starts the survey in the south near Point Conception, California, and meets the Franklin near the U.S.-Canadian border. The ships overlap briefly before the U.S. ship ends its portion of the survey, and the Canadian ship continues northward.
Collecting Acoustic Data at Sea
As the ships survey each transect, they collect acoustic data using scientific echo sounders. An echo sounder includes a device that converts the electric energy to acoustic energy (transmitter) and vice versa (receiver), called a transducer. The transmitters send sound into the water. The sound is reflected from targets such as fish and the seafloor and picked up by the receivers. Starting with the 2021 survey, we use the Simrad EK80 echo sounder.
The signals or echoes from targets are amplified and shown on computer screens in the ship's laboratory. Our acoustic scientists, called acousticians, study the screens for signs recognized as hake schools or other organisms of interest. They mark the schools using specialized fisheries acoustics software. They then determine whether to validate the acoustic data using fishing nets to trawl through the school.
Verification, or ground-truthing, is done on this survey using a trawl net. We use an Aleutian Wing Trawl to sample a small amount of the fish. A trawl sonar unit, a Simrad FS70, is attached to the outside of the net to help the fisher estimate the number of fish going into the net. We identify, weigh, and count the organisms caught in the net. Some organisms are further sampled for other biological measures, such as sex, length, maturity, weight, and age.
During the trawl, organisms get mixed up in the closed end of the net, called the codend. We use cameras inside the net to help figure out when organisms went into the net. This helps the acousticians determine the layer of acoustic sign that is related to organisms. We have two camera systems: a stereo camera with two cameras pointing across the net, and a video camera attached to the net's top looking backward along the net toward the codend.
The ships we use in the survey collect a variety of oceanographic information using many sensors and specialized equipment deployed throughout the survey. We use the information to link hake abundance and distribution to ocean conditions.
The U.S. portion of the survey also provides a platform for partners to collect vital data on ocean conditions and other ecosystem components. Collaborators include:
- Marine Microbes and Toxins Program for Harmful Algal Bloom (HAB) monitoring
- Scientists using the Imaging Flow CytoBot plankton sampler
- Environmental DNA (eDNA) researchers
- The Estuarine and Ocean Ecology Program, which collects zooplankton using vertical nets
We also take out volunteers
We have a limited number of spots to bring out volunteers to help with the biological sampling. It is a messy, smelly, and satisfying experience. You will learn to identify common organisms, determine the sex of several species, and collect various fish specimens.
Using Our Data to Produce a Biomass Estimate
After a trawl is sorted and the organisms have been identified and measured, several summary reports are generated. A useful way to summarize the trawl is to combine an image of an echogram (usually in both 38- and 120-kHz frequencies) of the sign that caught the acousticians' attention, another echogram with a trace of the trawl moving through the fish school, a brief summary of what was in the catch, and a size distribution of any hake captured. This "trawl echogram" helps the acousticians assign data from the trawl to hake regions.
Scientists from both countries work together to produce an estimate of the total mass of hake within the survey area, called the biomass. They link biological and acoustic data using "echo integration" methodology. This methodology relates the acoustic signal's intensity to the number of fish in a predetermined sample volume. The biomass is calculated based on several advanced mathematical and physical models.
The Joint Technical Committee, a body created by the Treaty, creates a stock assessment using:
- Biomass estimate and biological information from our survey (a fishery-independent source)
- Catch and biological information from the fishery (a fishery-dependent source).
The stock assessment reports Pacific hake's status off the West Coast of the U.S. and Canada each year. It tells a story about the stock, including the age, maturity, growth rates, and mortality.
Another body, the Scientific Review Group, reviews the stock assessment before it is submitted to the final body, the Joint Management Committee. The JMC sets the final total allowable catch for the fishery, with 73.88 percent going to the U.S. and the remaining 26.12 percent to Canada.
We canceled our 2020 research cruise.