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Status of Stocks & Multispecies Assessment Program

Exploring Climate Impacts of Growth on Eastern Bering Sea Yellowfin Sole

AFSC researchers Tom Wilderbuer, Jim Ianelli, Beth Matta, and Tom Helser conducted a study on the use of climate-growth relationships of Bering Sea yellowfin sole to improve stock assessments. Recent applications of dendrochronology (tree-ring techniques) have been used to develop biochronologies from the otolith growth increments of northern rock sole (Lepidopsetta polyxystra), yellowfin sole (Limanda aspera), and Alaska plaice (Pleuronectes quadrituberculatus) in the eastern Bering Sea. These techniques ensure that all growth increments are assigned the correct calendar year, allowing for estimation of somatic growth by age and year for chronologies that span approximately 50 years and indicate that somatic growth is highly correlated with water temperature.  Yellowfin sole length/weight data collected when obtaining otolith samples in AFSC surveys (n=7,000) also indicated that length and weight at age was variable and seemed to relate to summer bottom water temperature observations with a lag of 2-3 years for the temperature effect to be seen. The analysis indicates that yellowfin sole somatic growth is positively correlated with May bottom water temperature in the Bering Sea.  The results for yellowfin sole were used to explore climate impacts on growth by incorporating the temperature-dependent growth into an age-structured stock assessment model and then comparing the results with the base model that uses time-invariant growth.

Preliminary results indicate that warm and cold ocean conditions influence the time series of spawning biomass estimates and may have an impact on female spawning biomass per recruit estimates. Inclusion of variable growth in the assessment model may also increase the uncertainty on spawning biomass which may also increase the buffer between the acceptable biological catch and overfishing level estimates for yellowfin sole. The authors plan to use Intergovernmental Panel on Climate Change (IPCC) climate scenarios to forecast their impact on yellowfin sole stock conditions.

By Tom Wilderbuer
 

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