A spatial approach to understanding herring population dynamics

Abstract

Johan Hjort's so-called second recruitment hypothesis addressed the fate of offspring that drift out of areas suitable for their survival. This hypothesis has forged the concept of a population as a closed life cycle, making countercurrent adult spawning migration a necessary mechanism in balancing larval drift. The Norwegian spring-spawning (NSS) herring stock (Clupea harengus), the object of much of Hjort's work, is spread over large areas in the Northeast Atlantic, with spawning along the Norwegian coast, nursery areas in the Barents Sea, feeding areas in the Norwegian Sea, and overwintering areas outside northern Norway. Understanding the spatial dynamics of highly migratory fish stocks such as the NSS herring, therefore, is critical to understanding their population dynamics. Here I review hypotheses on the spatial dynamics of fish focusing on NSS herring and discuss consequences for population dynamics and interactions with other ecosystem components. The results illustrate the key role that strong herring cohorts play both as predators in the Barents and Norwegian seas and as prey on the overwintering and spawning grounds along the Norwegian coast. It is advocated that spatial full life cycle models should be developed for key fish stocks as a meeting place for model assumptions and observations and as a test bed for a multiple hypothesis testing approach.Résumé : La thèse communément appelée « deuxième hypothèse de recrutement » de Johan Hjort abordait le destin de la progéniture qui dérive vers l'extérieur de zones convenables pour sa survie. Cette hypothèse est à la base du concept de la population comme cycle vital fermé, qui rend nécessaire la migration à contre-courant d'adultes en frai pour compenser la dérive des larves. Le stock de harengs (Clupea harengus) norvégiens frayant au printemps (NSS), l'objet d'une bonne partie des travaux de Hjort, couvre de vastes superficies dans le nord-est de l'Atlantique, dont des aires de frai le long des côtes norvégiennes, des aires d'alevinage dans la mer de Barents, des aires d'alimentation dans la mer de Norvège et des aires d'hivernage au large de la Norvège septentrionale. La compréhension de la dynamique spatiale de stocks de poissons hautement migrateurs comme les harengs NSS est donc d'importance clé pour la compréhension de la dynamique de leurs populations. J'examine les hypothèses touchant à la dynamique spatiale des poissons en mettant l'accent sur le hareng NSS et je discute des conséquences pour la dynamique des populations et les interactions avec d'autres composantes de l'écosystème. Les résultats illustrent le rôle clé que de fortes cohortes de harengs jouent aussi bien comme prédateurs, dans les mers de Barents et de Norvège, que comme proies, dans les aires d'hivernage et de frai le long des côtes norvégiennes. Il est recommandé que des modèles spatiaux de l'ensemble du cycle biologique soient élaborés pour des stocks de poissons clés, comme lieu de rencontre pour les hypothèses de modélisation et les observations et comme banc d'e...

Spatial scaling of population synchrony in marine fish depends on their life history

“…In other words, as local abundances fluctuate, local mortality and dispersal dynamics will be affected by density regulation processes thereby affecting abundance distribution patterns, while high reproductive rates at a specific region will not necessarily cause that region, or nearby ones, to receive a greater recruitment in the future. Nevertheless, social learning from older cohorts to younger ones has been suggested for species like herring ( Clupea harengus ; Huse ) and capelin ( Mallotus villosus ; Fauchald et al ), where older cohorts lead younger ones to particular regions based on experience. This behaviour is reportedly strengthened with the abundance of the older cohort, thereby drawing an indirect link between local abundances of consecutive years.…”

Long‐term variability in overwintering copepod populations in the Lofoten Basin: The role of the North Atlantic oscillation and trophic effects

“…In turn, the Norwegian spring spawning herring ( Clupea harengus ), one of the main copepod predators in the region, follows the spatiotemporal dynamics of C. finmarchicus . Although herring migration patterns are variable and have changed after the collapse of the fishery in the 1960s, in the last years, nursery areas have been located in the Barents Sea from where young adults around 5 yr old migrate to southern Norway to spawn off Møre at the beginning of spring and then move to the northeast toward the Lofoten Basin as the bloom progresses (Huse et al ; Huse ).…”

Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well

“…Altogether, the current recruitment problem of NSSH should be investigated between later larval stages and the 0-group stage, possibly related to mackerel predation (44) (SI Appendix, Fig. S2) or to shifts in spawning grounds (45) in warmer waters (46).…”