Abstract
Life-history traits of Pacific (Clupea pallasii) and Atlantic (Clupea harengus) herring, comprising both local and oceanic stocks subdivided into summer-autumn and spring spawners, were extensively reviewed. The main parameters investigated were body growth, condition, and reproductive investment. Body size of Pacific herring increased with increasing latitude. This pattern was inconsistent for Atlantic herring. Pacific and local Norwegian herring showed comparable body conditions, whereas oceanic Atlantic herring generally appeared stouter. Among Atlantic herring, summer and autumn spawners produced many small eggs compared to spring spawners, which had fewer but larger eggs—findings agreeing with statements given several decades ago. The 26 herring stocks we analysed, when combined across distant waters, showed clear evidence of a trade-off between fecundity and egg size. The size-specific individual variation, often ignored, was substantial. Additional information on biometrics clarified that oceanic stocks were generally larger and had longer life spans than local herring stocks, probably related to their longer feeding migrations. Body condition was only weakly, positively related to assumingly in situ annual temperatures (0–30 m depth). Contrarily, body growth (cm × y−1), taken as an integrator of ambient environmental conditions, closely reflected the extent of investment in reproduction. Overall, Pacific and local Norwegian herring tended to cluster based on morphometric and reproductive features, whereas oceanic Atlantic herring clustered separately. Our work underlines that herring stocks are uniquely adapted to their habitats in terms of trade-offs between fecundity and egg size whereas reproductive investment mimics the productivity of the water in question.
Highlights
Life-history traits of Pacific (Clupea pallasii) and Atlantic (Clupea harengus) herring, comprising both local and oceanic stocks subdivided into summer-autumn and spring spawners, were extensively reviewed
The Northeast Pacific and North Atlantic herring are largely confined to boreal ecosystems with California herring (CAH) at the upper thermal habitat range of about 13 °C associated with Californian upwelling ecosystem, and WSH of the lower thermal habitat range of less than 4 °C associated with ecosystems close the Arctic (Fig. 1; Table S1)
The spatial extent of the stocks reflects the spatial structure of the ocean climate in the various regions: (1) the Northeast Pacific herring stocks were distributed along a 3000 km coastline from around Cape Mendocino at the Californian coast to Shelikof Strait in Alaska over which distance the annual mean ambient temperature changes from 13 to 6 °C (Table S1); (2) the Northwest Atlantic herring stocks differ in spatial distribution from the other groups of herring stocks, because of the extraordinary strong latitudinal thermal gradient along the Canadian east coast where the cold southwardflowing Labrador Current encounters the warm northward-flowing Gulf Stream (Sundby 2000; Sundby and Drinkwater 2007)
Summary
Based on the above outlines, the main objective of this article is to compare variation in observed adult life-history traits of different herring stocks distributed both in the North Atlantic and Northeast Pacific Oceans. We aimed to consider both fecundity and egg size jointly
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