Fisheries
- Department SAMBA
With its long coastline, fishing has been important to Norway for centuries, and the country is currently the largest fishing nation in Europe. Sustainable fishing requires knowledge about the population size of the targeted species. At NR, we work with population estimation of wild fish and whales, as well as strategy analysis for the fishing industry.
Population estimation of fish
Obtaining knowledge about population sizes is known as population estimation, and NR began its work in the field around 1990. At the time, our focus was on quantifying the number of minke whales so Norway could resume commercial whaling on a scientific and sustainable basis after a hiatus of several years.
Collaboration with the Institute of Marine Research
Today, we still work with population estimation, primarily focusing on fish, but also on whales and seals. We collaborate closely with the Institute of Marine Research.
In addition to general method development, we also specifically with certain species, such as cod, herring, mackerel, haddock and redfish.
Population estimation is considered to consist of three elements: catch per age, population development over time, and a final population estimate. We work on methodology within all three elements.
Estimatation of annual catch per age
We calculate capture per age. Here we look at how much fish is caught each year, distrbuted by age and/or length. Random samples of catches are collected and subsequently combined in order to estimate the annual catch per age.
Population development over time
We examine how the population has evolved over time. This is done during research expeditions using echo sounders or systematic trawling in a selected area. Typically, it is exceedingly difficult to determine the absolute number of fish. Instead, we assess relative changes from year to year and between age groups. The information is then combined into a survey index.
A population estimation for sustainable fishing quotas
These two types of data are then combined to generate a final population estimate, usually distributed by age, using a population model that describes the growth and mortality of the fish. Using this estimate, it is possible to calculate how much can be caught the following year without endangering the species and subsequently set sustainable fishing quotas.
