Nonlinear dynamics and noise in fisheries recruitment: A global meta‐analysis

Abstract

The relative importance of environmental and intrinsic controls on recruitment in fishes has been studied for over a century. Despite this, we are not much closer to predicting recruitment. Rather, recent analyses suggest that recruitment is virtually independent of stock size and, instead, seems to occur in distinct environmental regimes. This issue of whether or not recruitment and subsequent production are coupled to stock size is highly relevant to management. Here, we apply empirical dynamical modelling (EDM) to a global database of 185 fish populations to address the questions of whether or not variation in recruitment is (a) predictable and (b) coupled to stock size. We find that a substantial fraction of recruitment variation is predictable using only the observed history of fluctuations (~40% on average). In addition, although recruitment is often coupled to stock size (107 of 185 stocks), stock size alone explains very little of the variation in recruitment; In ~90% of the stocks analysed, EDM forecasts have substantially lower prediction error than models based solely on stock size. We find that predictability varies across taxa and improves with the number of generations that have been sampled. In the light of these results, we suggest that EDM will be of greatest use in managing relatively short‐lived species.

Density dependence in total egg production per spawner for marine fish

“…This means that the processes from hatching to recruitment are more stochastic by environmental variability than currently recognized. Accordingly, we support the conclusion of recent meta‐analyses to emphasize the emerging need for understanding the environmental effects on survival and recruitment processes of fish (Cury et al., ; Munch et al., ; Szuwalski et al., ). Furthermore, the approaches in studies on recruitment mechanisms should also be reconsidered.…”

“…Another controversial issue is the relative roles of density-dependent (self-regulating) and density-independent (environmentally regulating) processes throughout the life stages (Andersen et al, 2017;Minto et al, 2008;Myers & Barrowman, 1996;Pierre, Rouyer, Bonhommeau, & Fromentin, 2018). Recent meta-analyses showed that the spawner-recruitment relationships were weaker than previously recognized (Cury et al, 2014;Munch, Giron-Nava, & Sugihara, 2018;Szuwalski et al, 2015). For sardine, the strong density dependence was found at the time of spawning.…”

Disentangling density‐dependent effects on egg production and survival from egg to recruitment in fish

“…As in asymptotic spawner–recruitment models, it has been considered that density‐dependent effects dominate the regulation of populations, even though the SSB–R relationships are highly variable (Andersen et al, ; Minto et al, ; Myers & Barrowman, ). On the contrary, recent meta‐analyses showed that the SSB–R relationships were weaker than previously recognized, highlighting the need to evaluate the effects of density‐independent climate impacts on recruitment more intensively (Cury et al, ; Munch et al, ; Szuwalski et al, ).…”

“…The relative roles of density‐dependent and density‐independent processes throughout the life history are of considerable significance in the population dynamics of fish (Andersen, Jacobsen, Jansen, & Beyer, ; Archambault, Pape, Bousquet, & Rivot, ; Cowan et al, ; Houde, , ; Myers, ; Nash, 1998; Nash, & Dickey‐Collas, ). Indeed, a controversial issue has been the relative dominance of density‐dependent (Andersen et al, ; Minto et al, ; Myers & Barrowman, ) versus density‐independent effects (Cury et al, ; Munch, Giron‐Nava, & Sugihara, ; Szuwalski et al, ) in SSB–R relationships. Furthermore, the relative roles may change over the life history.…”

“…Indeed, a controversial issue has been the relative dominance of density-dependent (Andersen et al, 2017;Minto et al, 2008;Myers & Barrowman, 1996) versus density-independent effects (Cury et al, 2014;Munch, Giron-Nava, & Sugihara, 2018;Szuwalski et al, 2015) in SSB-R relationships. Furthermore, the relative roles may change over the life history.…”