Spatial covariation in productivity of Pacific herring (Clupea pallasii) in the northeast Pacific Ocean

I examined spatial patterns of covariation in productivity indices estimated for 24 Pacific herring (Clupea pallasii) stocks and 5 stock aggregates in the northeast Pacific Ocean. Spatial covariation was weak among stock productivity indices. Correlations existed among stocks at close distances (less than 400 km), but the direction of the correlations were both negative (as low as -0.82) and positive (as high as 0.94), resulting in weak overall correlation (r = 0.16) among nearby stocks, suggesting small-scale oceanic processes are likely driving stock productivity. A small increase in correlation among stocks in distant regions (between 2,000-3,000 km) was seen, which was more evident among the stock aggregates than in the individual stocks analyzed. Developing a better understanding of the underlying productivity among herring stocks in the northeast Pacific offers an approach that can help differentiate competing hypotheses about the drivers of productivity shifts by helping identify the most likely spatial scale of potential drivers of productivity.