We collect information about these species on research surveys, both from our own research vessels and aboard modern fishing vessels which we hire. On research surveys, the main goal is to estimate the size and spread of a given fish stock. We also receive valuable help from fishermen and fish landings that send us fish samples which we work up in the laboratory. These important commercial fish samples are also used in stock biomass estimates for the different fish stocks. The fish we research give us a collection of important and useful information; some examples of fish age, what they have eaten (stomach samples) and if they are sexually mature or not. An especially important product that we can provide is quota advice, which will advise how much of a certain fish stock should be taken provided it can be harvested sustainably with a long-term perspective.
We determine the age of most fish species by counting the age rings on the fish's otoliths. With the same method as counting year rings on trees, fish also develop such rings each year which tell us how old they are. For Norwegian spring-spawning herring, salmon and trout we determine the age on their scales; whereas for tuna, the first fin rays on the dorsal fin are used.