Recruitment in a changing environment: the 2000s North Sea herring recruitment failure

Abstract

Payne, M. R., Hatfield, E. M. C., Dickey-Collas, M., Falkenhaug, T., Gallego, A., Gröger, J., Licandro, P., Llope, M., Munk, P., Röckmann, C., Schmidt, J. O., and Nash, R. D. M. 2009. Recruitment in a changing environment: the 2000s North Sea herring recruitment failure. – ICES Journal of Marine Science, 66: 272–277. Environmentally induced change appears to be impacting the recruitment of North Sea herring (Clupea harengus). Despite simultaneously having a large adult population, historically low exploitation, and Marine Stewardship Council accreditation (implying sustainability), there have been an unprecedented 6 sequential years of poor juvenile production (recruitment). Analysis suggests that the poor recruitment arises during the larval overwintering phase, with recent survival rates greatly reduced. Contemporary warming of the North Sea has caused significant changes in the plankton community, and a recently identified regime shift around 2000 shows close temporal agreement with the reduced larval survival. It is, therefore, possible that we are observing the first consequences of this planktonic change for higher trophic levels. There is no indication of a recovery in recruitment in the short term. Fishing mortality is currently outside the agreed management plan, and forecasts show a high risk of the stock moving outside safe biological limits soon, potentially precipitating another collapse of the stock. However, bringing the realized fishing mortality back in line with the management plan would likely alleviate the problem. This illustrates again that recruitment is influenced by more than just spawning-stock biomass, and that changes in other factors can be of equal, or even greater, importance. In such dynamically changing environments, recent management success does not necessarily guarantee future sustainability.

Role of egg predation by haddock in the decline of an Atlantic herring population

“…Importantly, factors not incorporated into our population model, such as changes in the natural mortality rate of adult herring (23) and variability in recruitment caused by changes in larval survival, also can affect the critical fishing mortality rate. For example, over the past decade in the North Sea the abundance of early stage larvae has remained high, but there has been a decline in herring recruitment, linked to a decline in larval survival during winter and possibly tied to climate-related changes in the zooplankton community (24). A decline in larval survival will reduce the critical fishing mortality rate and may cause a herring population to start trending toward a lower stable equilibrium.…”

Recolonisation of spawning grounds in a recovering fish stock: recent changes in North Sea herring

“…However, these core sites are still important for larval production when the stock has recovered. The recent dip in the abundance of larvae in the north is likely to have been caused by changes in the environment (see Nash and Dickey-Collas, 2005;Payne et al, 2009), and if this continues it may result in another non-anthropogenic change in the relative distribution and spatial heterogeneity of herring larvae in the North Sea.…”

“…A stock is usually viewed as recovered when the biomass has passed a particular threshold (ICES, 1997): B lim as a biomass threshold below which recruitment is reduced and becomes density-dependent, and B pa , introduced in 1997, as a precautionary point to B lim . However this approach does not account for recovery in terms of spatial diversity, which can have implications for the productivity of the stock and its role in the ecosystem Payne et al, 2009). The environment also impacts on the spatial diversity and productivity of a stock, and there are many examples in herring of such phenomena (Bohuslän, Norwegian spring-spawning herring, the Russell cycle, see Alheit and Hagen, 1997).…”

Regularization of a Parameter Estimation Problem using Monotonicity and Convexity Constraints

“…In addition, the productivity of a system may shift either up or down resulting in a sustained change in the underlying stock and recruit relationship [32]. This is sometimes referred to as a regime shift [27]. It is therefore inconceivable that the stock parameters α and β will remain invariant even when the recruitment f changes (non-linearly or otherwise) with the spawning stock biomass x.…”