Scientists at the Alaska Fisheries Science Center collect a variety of information about fish that aids in the effective management of commercially important fish and crab stocks. We study different aspects of a fish's life and development including growth, maturity and natural mortality.
Knowing the age composition of commercially exploited fish populations is critical to determine fish population size and set sustainable catch limits each year. For instance, if a fish stock has a range of old and young fish it is indicative of a more healthy fish population.
To determine how old fish are, scientists collect and analyze fish otoliths (a calcium carbonate structure found in a fish’s ear). Otoliths contain annual growth zones that are deposited each year. Counting otolith growth zones to estimate fish age is analogous to counting tree rings. More than 30,000 otoliths are read annually by Center scientists.
Otoliths are collected from NOAA Fisheries surveys, fisheries observers, foreign fisheries agencies and state agencies. Current species studied include: walleye pollock, sablefish, Pacific cod, Atka mackerel, yellowfin sole, Pacific ocean perch, salmon, and various other flatfish and rockfish species.
To confirm the accuracy of age estimates, the Alaska Fisheries Science Center’s Age and Growth Program use a number of age validation techniques including stable isotopes, the novel use of bomb radiocarbon (14 C) derived from above-ground atomic bomb testing, and other validation methods.
- Age and Growth FAQ
- Age Determination of Alaska Groundfish Species
- Age Reading Interactive Demonstration
- Alaska Age and Growth Procedures for Otolith Examination
- Fish Otolith Chronologies
- Fish Otolith Collection Database
- Fish Otolith Thin Sectioning Procedures
- Determining Age and Growth Through Stable Isotopes
- Determining Age and Growth Through Radiocarbon Age Validation
- Radiometric Fish Age Validation
- Otolith Growth Validation and Corroboration
- History of Age Determination of Walleye Pollock
- Age Determination of Pacific Cod
- Developing Ageing Criteria for Shortraker Rockfish
- History of the Ageing of Groundfish Species
- Ageing Request Tables Database
- Fish Species Maximum Age Data
- Age and Growth Manual