Reference Collections

The Fishery Biology Program has implemented reference collections for selected species. These collections consist of a few hundred fish of a given species, for which the age is reliably known. This website gives access to both annotated and unannotated images from these collections. These reference collections are used as training resources and to quantify the accuracy of age data generated by the FBP. In addition, age readers may review these samples to refresh their skills for a given species.

The development of a reference collection requires the comprehensive selection of age structure samples from representative lengths, ages, sexes, seasons, stock areas, and sampling sources for each species (Campana et al., 1995).  Ideally, samples should be from known-age fish, such as those provided by tag/recapture or age validation studies, but these are difficult to obtain. As that is often not feasible, reference collections may instead consist of fish which have been aged by consensus of multiple age readers, often through age-structure exchanges and/or workshops.

Currently, the Fishery Biology Program has reference collections for American shad, Atlantic cod, haddock, and yellowtail flounder. Details of how each collection has been assembled are given below. This site will be updated as more samples are added tothe collections, and as annotated images become available.

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Haddock

These sectioned otoliths are from NEFSC survey cruises to Georges Bank. All were aged by consensus between (at least) two NEFSC readers and an age reader from the Department of Fisheries and Oceans Canada, as part of regular ageing exchanges between the two laboratories. These fish have been aged using the methods described in our Ageing Manual (Penttila and Dery, 1988).

American Shad

These fish were caught on the Delaware River while migrating upriver to spawn, by the Pennsylvania Fish and Boat Commission (PFBC). The fish were marked with oxytetracyline as fry (also by the PFBC); hence the ages are known exactly. Ageing methods are described in Duffy et al. (2012). We appreciate PFBC's generosity in allowing us to use their samples.

Cod

These otoliths are from NEFSC survey cruises to Georges Bank. They were baked to enhance contrast and then broken at the nucleus. All were aged by consensus between (at least) two NEFSC readers and an age reader from the Department of Fisheries and Oceans Canada, as part of regular ageing exchanges between the two laboratories. These fish have been aged using the methods described in our Ageing Manual (Penttila and Dery, 1988).

Yellowtail Flounder (Images not yet available)

These scale impressions are from NEFSC survey cruises and commercial samples, and represent both sexes, all stock areas, and all sampling seasons.  Samples were distributed to four age readers (from both NEFSC and the Massachusetts Division of Marine Fisheries) experienced in ageing this species via the methods described in our Ageing Manual (Penttila and Dery, 1988).  Only fish for which these readers agreed on the age were selected for the collection.  Samples from more recent years were consensus-aged by two NEFSC readers.

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Testing

These collections are regularly used to assess ageing accuracy. In these tests, a subsample of 50-100 fish from the reference collection is re-aged, and the test ages compared with the ages given here. Tests are usually given both before and after a year's worth of production ageing; test results are available online here.

References

Campana SE, Annand MC, McMillan JI. 1995. Graphical and statistical methods for determining the consistency of age determinations. Trans. Am. Fish. Soc. 124:131-138.

Duffy WJ, McBride RS, Hendricks ML, Oliveira K. 2012. Otolith age validation and growth estimation from oxytetracycline-marked and recaptured American shad. Trans. Am. Fish. Soc. 141:1664-1671.

Penttila J, Dery LM. 1988. Age determination methods for northwest Atlantic species. NOAA Tech. Rep. NMFS-72; 135 p. (Available at http://www.nefsc.noaa.gov/fbp/age-man.html)

 

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(File Modified May. 23 2017)