The Science of Counting Fish
During an annual at-sea stock assessment survey, Fisheries and Oceans Canada scientists use advanced acoustic technology, in conjunction with traditional fishing methods, to locate and study fish populations. Watch to learn how data collected from these surveys are used to determine a supportable level of fishing.
Transcript
The ocean is a vast and mysterious place... it's hard to know what is happening beneath the surface.
Fishers depend on being able to find and catch the fish that live there, and fisheries managers need to know how many fish there are in order to set catch limits...
But how do you measure something you can't see?
Fisheries and Oceans Canada fisheries scientists have some innovative ways to do just that.
W. E. Ricker is used for our surveys here on the West Coast of Canada. It's a trawler with mid-water and bottom trawl.
We use acoustics, which is, it's a fancy fish finder, scientific fish finder, with three frequencies that we look at.
For our survey, it's mainly an acoustic survey which means we use scientific echosounders.
We use this in conjunction with traditional fishing methods in order to groundtruth the signal that we are seeing on the sounder and then what comes up in the trawl allows us to know exactly what it is the sounder is showing us.
During their annual at-sea stock assessment trawl surveys, Chief Scientist Chris Grandin and his team use advanced acoustic technology to find the fish...
Once they find what they are looking for, a small sample is taken onboard.
In the wet lab, fish are sorted, weighed, measured, and dissected to determine: sex, sexual maturity, and digestion.
Tissue samples are taken for DNA analysis, and the ear bones are taken for aging...
The team must also take into account ocean processes - such as water chemistry and biology - that can impact ecosystem health.
DFO at-sea science trawl surveys take place in the same spots, at the same time of year - every year - allowing scientists to collect data to better understand fish movements and monitor trends and ecosystem changes over time.
We take those data and we input them into our stock assessment model along with the biomass estimate that we generated from our acoustics and we come out with an estimate of what the stock is actually looking like at this point in time... and that information is passed on to management who then set quotas based on that...
The data are entered into scientifically validated mathematical and statistical models that convert it into fish population estimates.
The estimates and models are carefully reviewed by other scientific experts to ensure the best possible advice.
The result of this process is to determine a sustainable level of fishing.
As Canada is surrounded by three oceans, effective relations and collaboration with international partners is essential to managing shared fisheries.
Canada is working with other countries and entities to lead regional fisheries management organizations towards a sustainable, science-based management approach that will ensure the sustainability of fisheries for future generations.
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