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Resource Ecology & Ecosystem Modeling (REEM) Program

Resource Ecology: Sculpin Age and Growth

zoeal stage 2 larval blue king crab
Figure 1.  Thin section of a yellow Irish lord otolith (age: 7 years; 37 cm, female).

juvenile stage 1 blue king crab
Figure 2.  Warty sculpin otolith aged through surface reading (5 years old).

The ages of 733 sculpins have been determined as part of a North Pacific Research Board (NPRB) project to examine the life history of sculpins. Ages were determined for 344 and 166 yellow Irish lords (Hemilepidotus jordani) in the Aleutian Islands and eastern Bering Sea, respectively, that were collected in 2006. Thin sectioning (Fig. 1) was determined to be a more appropriate method for ageing yellow Irish lords than the break and burn method.

The 2006 eastern Bering Sea shelf survey collection of warty sculpin (Myoxocephalus verrucosus) has also been aged (n = 186). A number of warty sculpin specimens were aged through surface reading (Fig. 2); otherwise the break and burn method was used. The break and burn method is also being used for the other sculpins in the study.

A total of 37 bigmouth sculpin (Hemitripterus bolini) samples have been aged from the 2004 eastern Bering Sea slope survey and the 2006 Aleutian Islands survey. The 2005 eastern Bering Sea shelf survey collection of the great sculpin (Myoxocephalus polyacanthocephalus) was aged in early 2006 prior to NPRB funding for this project.

Currently in the queue for ageing is the 2005 eastern Bering Sea survey collection of the yellow Irish lord (n = 222) and the warty sculpin (n = 176) and the 2006 eastern Bering Sea survey collections for the plain sculpin (M. jaok) (n = 445) and great sculpin (n = 398).

Quality control has been maintained throughout the ageing process. Although time intensive for new species, the development of ageing criteria and recognition of different patterns has been established for each species with the exception of the plain sculpin. A 100% test by the AFSC’s Age and Growth Program has been used for each species due to the novelty of the species being aged. The standard 20% testing of samples is initiated only after it has been determined that the quality of the ages by the first reader is satisfactory. So far, 20% testing has been initiated with the yellow Irish lord and the great sculpin. Testing and the resolution of discrepancies have not been entirely completed, so the official release of the ages has not been made. Based on work so far, however, the maximum age for the yellow Irish lord in both the eastern Bering Sea and the Aleutian Islands appears to be in the mid-20s, while the warty sculpin and bigmouth sculpin appear to be in the mid- to high teens. The great sculpin, as exhibited from the 2005 eastern Bering Sea collection, has a maximum age of 16 years.

By Todd TenBrink

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