Sixty-five years of northern anchovy population studies in the southern California Current: a review and suggestion for sensible management

Sydeman, William J.; Dedman, Simon; García‐Reyes, Marisol; Thompson, Sarah; Thayer, Julie A.; Bakun, Andrew; MacCall, Alec D.

doi:10.1093/icesjms/fsaa004

Cited by 20 publications

(56 citation statements)

References 63 publications

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“…Sardine and anchovy fluctuations have been a major focus of fisheries research since the 1950s because of their commercial value and/or they are prey for other high-value fishery species and species of management concern (Checkley et al, 2017). Our model estimates are consistent with other studies (Sydeman et al, 2020; Thompson et al, 2022a) that documented a decline in both sardines and anchovy beginning in 2005. In the wake of the marine heatwave, anchovy continued to be abundant while sardine remained low (Figure 3).…”

Section: Discussionsupporting

confidence: 91%

“…Although anchovy larvae abundance was low in spring during the 2014–2016 marine heatwave, anchovy recruitment was high in the summer of 2015 (Thompson, Schroeder, et al, 2019). Anchovy mature in approximately one to two years (Parrish et al, 1986; Sydeman et al, 2020), and thus the 2015 class likely began spawning in mid-2016 (Thompson et al, 2022a), leading to high anchovy spawning stock biomass and larval abundances by 2016 and lasting into at least 2021 (Thompson et al, 2022b; Weber et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…However, our findings and others (Checkley et al, 2017; McClatchie, 2012; Nielsen et al, 2021; Thompson, Harvey, et al, 2019) suggest that the mechanisms that govern the population dynamics of these species are not a mere function of temperature, but that more complex factors drive recruitment dynamics of these species (Thompson et al, 2022a). For example, despite largely synchronous responses of fish assemblages to the marine heatwave, sardine declines were not consistent across the CCLME (Figure 3), with refugia of localized abundance in nearshore waters potentially driven by distinct, favorable conditions (Checkley et al, 2017; Sydeman et al, 2020; Thompson et al, 2022a).…”

Section: Discussionmentioning

confidence: 99%

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Message in a Bottle: Archived DNA Reveals Marine Heatwave-Associated Shifts in Fish Assemblages

Gold

Kelly

Shelton

et al. 2022

Preprint

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Marine heatwaves can drive large-scale shifts in marine ecosystems but studying their impacts on whole species assemblages can be difficult. Here, we leverage the taxonomic breadth and resolution of DNA sequences derived from environmental DNA (eDNA) in the ethanol of a set of 23-year longitudinal ichthyoplankton samples, combining these with microscopy-derived ichthyoplankton identification to yield higher-resolution, species-specific quantitative abundance estimates of fish assemblages in the California Current Large Marine Ecosystem during and after the 2014-16 Pacific marine heatwave. This integrated dataset reveals patterns of tropicalization with increases in southern, mesopelagic species and associated declines in important temperate fisheries targets (e.g., North Pacific Hake (Merluccius productus) and Pacific Sardine (Sardinops sagax)). We observed novel assemblages of southern, mesopelagic fishes and temperate species (e.g., Northern Anchovy, Engraulis mordax) even after the return to average water temperatures. Our innovative preservative derived eDNA metabarcoding and quantitative modeling approaches open the door to reconstructing the historical dynamics of assemblages from modern and archived samples worldwide.

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Section: Discussionsupporting

confidence: 91%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Message in a Bottle: Archived DNA Reveals Marine Heatwave-Associated Shifts in Fish Assemblages

Gold

Kelly

Shelton

et al. 2022

Preprint

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“…In addition, a negative relationship between upwelling and sardine recruitment can generally be explained by the transfer of fish larvae to offshore areas where they have low chance of survival during periods of strong equatorward flow and upwelling [78,79]. Our understanding of the mechanisms driving anchovy population dynamics is limited [80].…”

Section: Environmental Covariatesmentioning

confidence: 99%

Tracking and forecasting community responses to climate perturbations in the California Current Ecosystem

et al. 2022

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Ocean ecosystems are vulnerable to climate-driven perturbations, which are increasing in frequency and can have profound effects on marine social-ecological systems. Thus, there is an urgency to develop tools that can detect the response of ecosystem components to these perturbations as early as possible. We used Bayesian Dynamic Factor Analysis (DFA) to develop a community state indicator for the California Current Ecosystem (CCE) to track the system’s response to climate perturbations, and to forecast future changes in community state. Our key objectives were to (1) summarize environmental and biological variability in the southern and central regions of the CCE during a recent and unprecedented marine heatwave in the northeast Pacific Ocean (2014–2016) and compare these patterns to past variability, (2) examine whether there is evidence of a shift in the community to a new state in response to the heatwave, (3) identify relationships between community variability and climate variables; and (4) test our ability to create one-year ahead forecasts of individual species responses and the broader community response based on ocean conditions. Our analysis detected a clear community response to the marine heatwave, although it did not exceed normal variability over the past six decades (1951–2017), and we did not find evidence of a shift to a new community state. We found that nitrate flux through the base of the mixed layer exhibited the strongest relationship with species and community-level responses. Furthermore, we demonstrated skill in creating forecasts of species responses and community state based on estimates of nitrate flux. Our indicator and forecasts of community state show promise as tools for informing ecosystem-based and climate-ready fisheries management in the CCE. Our modeling framework is also widely applicable to other ecosystems where scientists and managers are faced with the challenge of managing and protecting living marine resources in a rapidly changing climate.

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“…However, their population sizes fluctuate enormously in response to environmental conditions that control recruitment variability (Baumgartner et al, 1992;Lluch-Belda et al, 1992;McClatchie et al, 2017). The sardine population has been very low since 2015 (Hill et al, 2015), and the anchovy population reached record lows from 2013 to 2015 (Sydeman et al, 2020). These conditions resulted in very poor conditions for upper-trophic-level predators and caused the closure of the commercial sardine fishery, which has not yet reopened.…”

Section: Introductionmentioning

confidence: 99%

State of the California Current 2019–2020: Back to the Future With Marine Heatwaves?

Weber

Auth²,

Baumann‐Pickering

et al. 2021

Front. Mar. Sci.

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The California Current System (CCS) has experienced large fluctuations in environmental conditions in recent years that have dramatically affected the biological community. Here we synthesize remotely sensed, hydrographic, and biological survey data from throughout the CCS in 2019–2020 to evaluate how recent changes in environmental conditions have affected community dynamics at multiple trophic levels. A marine heatwave formed in the north Pacific in 2019 and reached the second greatest area ever recorded by the end of summer 2020. However, high atmospheric pressure in early 2020 drove relatively strong Ekman-driven coastal upwelling in the northern portion of the CCS and warm temperature anomalies remained far offshore. Upwelling and cooler temperatures in the northern CCS created relatively productive conditions in which the biomass of lipid-rich copepod species increased, adult krill size increased, and several seabird species experienced positive reproductive success. Despite these conditions, the composition of the fish community in the northern CCS remained a mixture of both warm- and cool-water-associated species. In the southern CCS, ocean temperatures remained above average for the seventh consecutive year. Abundances of juvenile fish species associated with productive conditions were relatively low, and the ichthyoplankton community was dominated by a mixture of oceanic warm-water and cosmopolitan species. Seabird species associated with warm water also occurred at greater densities than cool-water species in the southern CCS. The population of northern anchovy, which has been resurgent since 2017, continued to provide an important forage base for piscivorous fishes, offshore colonies of seabirds, and marine mammals throughout the CCS. Coastal upwelling in the north, and a longer-term trend in warming in the south, appeared to be controlling the community to a much greater extent than the marine heatwave itself.

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Sixty-five years of northern anchovy population studies in the southern California Current: a review and suggestion for sensible management

Cited by 20 publications

References 63 publications

Message in a Bottle: Archived DNA Reveals Marine Heatwave-Associated Shifts in Fish Assemblages

Message in a Bottle: Archived DNA Reveals Marine Heatwave-Associated Shifts in Fish Assemblages

Tracking and forecasting community responses to climate perturbations in the California Current Ecosystem

State of the California Current 2019–2020: Back to the Future With Marine Heatwaves?

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