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Age and Growth Studies in the Northeast

The Fishery Biology Program in the Northeast conducts age and growth studies. Knowing the age structure of a fish population helps to monitor, assess, and manage stocks for long-term benefits.

Otolith aging, using microscop and large monitors.

Each year, the Fishery Biology Program at the Northeast Fisheries Science Center determines the ages of about 60,000 fish and shellfish from more than 20 species. Structures used to age the fish, which includes otoliths also known as ear stones, are sampled from between the Gulf of Maine and Cape Hatteras, NC in the northwest Atlantic Ocean. The age data is used with other data to build mathematical models of the entire population. These models estimate the total number of fish in the wild and predict the effects of fishing.

Species Collected

Bar graph of numbers of fish aged by species for 2016-2018.

In 2016–2018, the Fishery Biology Program aged over 26,000 haddock, 17,000 cod, 15,000 silver hake, 52,000 flounder of 6 species, and 64,000 samples from 13 other species.

The samples mainly come from three sources: NOAA’s surveys, commercially-landed fish, and fisheries observers aboard fishing boats. Survey samples give us a glimpse into the entirety of fish populations, including the youngest fish. Commercial fishermen, who target mature fish, bring their fish to ports along the coast. Some of these fish are sampled after they are unloaded from the boats. Aboard commercial boats, observers sample “discards,” which are fish captured by fishing gear but not brought to market.

When the samples arrive at the lab, some need to be sliced across the core or baked to reveal internal details. Prepared samples are then examined by experienced scientists, who view the samples on a microscope and determine each fish's age. This information is entered into a database so it can be incorporated into models of fish populations.

Both parts of image show a white structure with 1-2 concentric dark rings.  Dots are on the edge, the inner ring, and nearer to the center.

Whole earstone (lower) and earstone section (upper) from a 13-inch Silver Hake (age = 3 years). Dots show the positions of winter zones.

In addition to providing age data in support of fish population assessments, we are continually striving to improve and streamline our methods. Recent research has focused on finding ways to get accurate ages for monkfish, butterfish, and black sea bass.


The program was established in 1965 to determine ages for haddock and yellowtail flounder. Up through the 1970s, methods were developed for processing and reading samples from an ever-increasing number of species. The program has gradually expanded to cover not only fish growth but also other aspects of the biology of fish and shellfish.



Age Determination Methods for Northwest Atlantic Species

This is the full text of the 1988 manual describing methods for 18 species, including quality images. There is also an online version of the manual,…


Reference Collections For Age Determination Of Select Northwest Atlantic Species

These collections of otoliths images may be used as a training resource or to measure the accuracy of age estimates. These images are of fish for…



Precision Templates for Ageing

A series of templates were designed to automate the calculation of measures of ageing precision, including percent agreement and the total…


Brodeur's Guide to Otoliths of Some Northwest Atlantic Fish

A guide to otoliths of many Northwest Atlantic species with hand-drawn images. This version was released on the 30th anniversary of the original…


How To Request Samples From The Age-Structure Archive

Samples in the Northeast Fisheries Science Center's archived collection may be borrowed by outside personnel. If interested, please submit a request…