Pacific-Atlantic halibut ageing workshop and otolith exchange

In 2011, representatives from the age determination units of the International Pacific Halibut Commission, the Maine Department of Marine Resources, and the National Marine Fisheries Service Northeast Fisheries Science Center attended a Pacific-Atlantic halibut otolith exchange workshop in Boothbay Harbor, Maine. The main objective of this workshop was to discuss the methodologies for otolith sample preparation prior to an interagency otolith exchange to calibrate age estimates for both Pacific halibut ( Hippoglossus stenolepis) and Atlantic halibut (Hippoglossus hippoglossus). Background Commercially and ecologically important fish species are often managed by multiple agencies over the geographic range of the species, with each agency collecting otolith samples and producing age estimates for management of their particular stock. Such multi-agency management can lead to independent development of a variety of ageing techniques, even using different age structures, to produce age estimates among agencies. In an attempt to address interagency age assignment variability among northeast Pacific fish species, the Committee of Age Reading Experts (CARE) was formed. CARE is a cooperative effort between state and federal agencies from California, Oregon, Washington, British Columbia, and Alaska dedicated to standardizing and improving age determination techniques for species managed by multiple agencies. Activities of CARE include age structure exchanges and hands-on workshops. Hands-on workshops provide an ideal format for experienced age readers from different agencies to compare and demonstrate techniques for sample preparation and age determination. Age estimates can be compared among readers with immediate feedback; a microscope with two sets of eyepieces allows two readers to view an otolith at the same time. Alternatively, an otolith image can be displayed on a screen and increments pointed out to multiple viewers at once. Workshops are also a useful tool for experienced age readers to teach new readers how to prepare and interpret age structures. Several agencies on the east coast of Canada and the U.S. are involved in ageing Atlantic halibut (Hippoglossus hippoglossus), but many of the readers have limited experience reading halibut otoliths. Staff from the age determination unit of the Maine Department of Marine Resources (DMR) contacted staff from the International Pacific Halibut Commission (IPHC) for advice on techniques and equipment for ageing halibut. Staff at both facilities discussed the possibility of a workshop for IPHC staff to demonstrate ageing techniques. Atlantic halibut otoliths are similar to those of Pacific halibut ( Hippoglossus stenolepis) and age readers at the IPHC collectively read over 30,000 Pacific halibut otoliths each year. Following the philosophy of CARE, age determination staff from the IPHC, the Maine DMR, and the National Marine Fisheries Service Northeast Fisheries Science Center (NEFSC) met for an interagency otolith exchange workshop

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