Saltwater sleuths: Seeking clues to help determine the ages of fish and shellfish p...(n many areas. Observer program samples c...)

Burnett says the samples from the different groups provide a range of sizes and ages, and include species that are both commercially fished and those which are not, making it a good representation of what occurs in nature. Age estimates are based on visible growth increments that are deposited annually, much like tree rings.

Otoliths are the most common hard part used for aging species and are read whole, baked and broken, or sectioned. Wherever possible, fish scales are impressed in laminated plastic for aging, which is very cost-effective because there is little processing necessary to collect and process scales. Some species, however, require special attention: baked vertebrae are used to age monkfish, and thin sections of chondrophores, a cavity at the hinge of bivalve mollusks, are used to age surfclams.

The majority of requests for age data come from stock assessment teams, and others from state fisheries agencies and other nations. Given the demand for age data, the NEFSC laboratory in Woods Hole, Mass. analyzes more samples than any other NOAA Fisheries laboratory or state fisheries program in the Northeast U.S., partly because many agencies dont have enough qualified readers or have abandoned their aging programs.

Burnett emphasizes that quality control and quality assurance measures are critical to the groups success. When counting annual rings, you have to validate that one year is really one year, and that everyone is reading the samples in the same way so there is a high degree of accuracy in the data you provide.

To maintain the quality of the data and a high level of precision or repeatability in age reading, the program has assembled a reference collection of known age samples. Annual exchanges for quality control and precision for cod and haddock age reading ar
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