Modeling sardine and anchovy low-frequency variability

The group of small pelagics (sardines, anchovies, herrings, etc.) is the largest source of wild marine protein worldwide, providing annually between 21% and 43% of the total marine capture production during at least the last 60 y (1). Even when large-scale fisheries have been operating for decades to centuries, their assessment and management remains difficult and highly uncertain (2). Such challenges are mainly because these species do not conform to the traditional assumptions of population dynamic models, such as a steady level of unexploited stock (carrying capacity), or that the influence of climate on the population is negligible when compared to fishing mortality. In other words, it has been clear for decades that the traditional toolbox of fisheries management is clearly unsuitable to these massive resources. The paper by Lindegren et al. (3) in PNAS provides an alternative framework to study and ultimately to develop management-supporting knowledge for these types of resources. The modern era of small pelagic fishes research began exactly three decades ago, when the major sardine and anchovy fisheries catch series from remote systems in the western (Humboldt and California) and eastern (Japan) Pacific were presented together, and synchrony between them was first suggested (4). The sardine-anchovy puzzle was further complicated when alternation between sardine and anchovy stocks within each system and empirical linkages with climate were proposed, conforming to what was called The Regime Problem (5, 6). During these last 30 y, very valuable research has been conducted to document abundance fluctuations, synchrony between regions, and alternation between species observed during the 20th century, and many hypotheses have been proposed to explain the underlying mechanisms (7) or question the existence of such patterns (8). A comprehensive review of …