Estimated production figures for 1 January
through 30 September 2007.
Species
Specimens Aged
Giant grenadier
359
Greenland turbot
502
Flathead sole
516
Alaska plaice
449
Dover sole
447
Northern rock sole
1,241
Yellowfin sole
496
Bering flounder
258
Walleye pollock
11,131
Pacific cod
4,999
Sablefish
2,366
Atka mackerel
1,629
Pacific ocean perch
2,316
Northern rockfish
506
Rougheye rockfish
1,502
Shortraker rockfish
772
Blackspotted rockfish
390
Warty sculpin
185
Yellow Irish lord
513
Total production figures were 30,577 with
8,785 test ages and 329 examined and
determined to be unageable.
A Bit of AFSC Ageing History
Determining fish ages from reading otoliths underwent a revolution during the early 1980s when it was determined that older specimens of many species aged from otolith surfaces were being underaged. At the AFSC, the Age and Growth Program began applying a new technique of ageing otoliths, the break and burn method, in 1981. The break and burn method entails taking a transverse cross section by breaking (usually sawing) an otolith in half and then exposing the transverse surface to an alcohol flame. This process makes finer marks associated with later annual marks more visible than viewing from the otolith surface.
Both the surface and break and burn methods are often used to best estimate a specimen’s age, but the percentage varies by species and to a large extent the year the otoliths were aged. For example, the percentages of otoliths aged with the break and burn method were typically low in the early 1980s, then increased and plateaued in the 1990s. However, the percentage broken and burned for rockfish is typically high for all years.
The statistics for this aspect of ageing history at the Center are now available on the AFSC website at http://access.afsc.noaa.gov/al/collection_details/collection_search.php. The site provides summaries of ageing methods (surface, break and burn, or section) used to age fish otoliths. Result tables can be viewed showing the numbers read using each method, by year collected, by year read, or by individual collections. Results include specimens collected as far back as 1980 and are updated daily around midnight.
