Planes, boats and underwater pencils: How we calculate herring biomass

Each year our scientists collect and analyze data on herring spawn and fish biomass to help ensure sustainable fisheries.

The first step is to find out where the fish are. DFO scientists and resource managers use aerial surveys to locate herring spawn. The spawn turns waters to shades of milky white, jade and turquoise and is easy to see from the air.

Next, a test fishery is conducted using sounding equipment. We often partner with First Nations on this activity. After capturing some fish, test fishers check them for size and roe quality and keep a small number for sampling purposes. Later, scientists collect further biological data in a lab.

Once herring have finished laying their eggs, divers return to the area to collect data. After marking out squares called quadrats, they record information used to calculate the amount of herring eggs laid in a particular area.

Our scientists combine the data collected on dive surveys with commercial and test fishery sampling. Using mathematical models, they calculate the number of tonnes of fish that spawned in a particular area and make biomass forecasts for the next year.

Our fisheries management division uses the findings of these scientific surveys to develop a sustainable fishing plan, called an Integrated Fisheries Management Plan (IFMP), for the following season.