Each year, the Fish 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.
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.
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.