Environmental factors affecting recruitment of northern shrimp Pandalus borealis in West Greenland waters

Survey estimates of northern shrimp Pandalus borealis biomass in West Greenland waters increased from about 178 000 t in 1998 to about 598 000 t in 2003. The increase in stock size was preceded by several consecutive years in which recruitment was substantially above average. Recruitment has been poor since then despite record high levels of female stock biomass. Ricker-type stock-recruitment functions did not indicate that the variability in recruitment was related to female biomass. Multiple regression analysis revealed that mean female length, ambient bottom temperature and biomass of Greenland halibut Reinhardtius hippoglossoides had the most important effect on the variations of the 'recruit per female biomass' time series for the years 1993 to 2011. Variables which did not contribute significantly to the model included biomass of Atlantic cod Gadus morhua. This can be explained by the low stock size of Atlantic cod throughout the major part of the study period. The final model explained 83% of the variation in the recruit per female biomass index. However, the observations for 5 out of the 19 years considered in the present study were outside the 95% confidence interval of the fitted model, possibly due to a mismatch between the timing of larval hatch and the timing of the phytoplankton bloom, which could not adequately be addressed due to data limitations.