Climate change causing phase transitions of walleye pollock (Theragra chalcogramma) recruitment dynamics

Abstract

In 1976 the North Pacific climate shifted, resulting in an average increase of the water temperature. In the Gulf of Alaska the climate shift was followed (i.e. early 1980s) by a gradual but dramatic increase in the abundance of groundfish species that typically prey on pre-recruitment stages of walleye pollock. In the present study we used a previously parameterized model to investigate the effect of these climate and biological changes on the recruitment dynamics of walleye pollock in the Gulf of Alaska. Simulations covered the 1970-2000 time frame and emphasized the medium-to-long temporal scale (i.e. about 5-10 years) of environmental variability. Results showed that during periods characterized by high sea surface temperature and high predation on juvenile pollock stages, recruitment variability and magnitude were below average, and recruitment control was delayed to stages older than the 0-group. Opposite dynamics (i.e. high abundance and variability, and early recruitment control) occurred during periods characterized by low temperature and predation. These results are in general agreement with empirical observations, and allowed us to formulate causal explanations for their occurrence. We interpreted the delay of recruitment control and the reduction of variability as an effect of increased constraint on the abundance of post age-0 stages, in turn imposed by high density dependence and predation mortality. On the other hand, low density-dependence and predation favoured post age-0 survival, and allowed for an unconstrained link between larval and recruitment abundance. Our findings demonstrate that the dominant mechanisms of pollock survival change over contrasting climate regimes. Such changes may in turn cause a phase transition of recruitment dynamics with profound implications for the management of the entire stock.

Non-additive and non-stationary properties in the spatial distribution of a large marine fish population

“…However, under continuous warming and increase in abundance, their effect may be more consequential on pollock survival, as observed in adjacent areas. In the Gulf of Alaska, for example, flounder is now the dominant groundfish species, and plays a key role in regulating walleye pollock recruitment through predation on the juvenile stages [39,40].…”

Characterizing mixed microbial population dynamics using time-series analysis

“…By applying statistical methods traditionally used by animal ecologists (for example, Ciannelli et al, 2005), we estimated the underlying density-dependent effects of all three bacterial species. In the case of L. salivarius, this effect is indicative of a simple metabolic feedback mechanism ( Figure 3e).…”

“…In general ecological science one often encounters terms such as within and between species competition, cooperation and density dependence (Turchin, 1995;Stenseth et al, 1998;Ciannelli et al, 2005;Moe et al, 2005). Such concepts are much less frequently explored in the context of microbes (Hagen et al, 1982;Bradshaw et al, 1994;Rainey and Rainey, 2003;You et al, 2004;Balagadde et al, 2005).…”

Food web dynamics affect Northeast Arctic cod recruitment

“…Hence, our understanding of the dynamics of these systems is typically based upon observations corresponding to quite a narrow range of climatic and ecological conditions, which subsequently introduces an uncertainty about the ability of the model to predict future dynamics. Quite conceivably, the parameters describing the species interactions might change as the ecological and climatological state changes (Ciannelli et al 2005). Here, we develop a simple statistical multi-species model, including climatic effects, based on the most recent and more detailed time-series data, to predict the recruitment of Northeast Arctic (NEA) cod (Gadus morhua).…”