In 2022 the presence of the Japanese sardine, Sardinops melanosticta (Temminck and Schlegel), was detected in the eastern Pacific Ocean, far outside its known western North Pacific range. The species was collected along with the Pacific sardine, Sardinops sagax (Jenyns), which is native to the eastern Pacific Ocean. Here, we report the first direct evidence for spawning by S. melanosticta in the eastern Pacific Ocean.

Changing ocean conditions are leading to spatial redistribution of many marine species, including those that support fisheries. A combination of gradual climate trends and shorter-lived extreme events, such as marine heatwaves, can change the availability of species or stocks to fishing ports, impacting fishing communities and challenging fisheries management frameworks. Pacific sardine (Sardinops sagax) in the California Current System are currently considered as two subpopulations for management purposes. They are separated from each other using oceanographic conditions, based on the assumption that each subpopulation is associated with different habitats and geographic areas. However, as climate change and marine heatwaves lead to increasingly novel environmental conditions in the region, habitat-based assignments may become impractical or unrealistic. In this study, we use generalized additive models to define sea surface temperature and surface chlorophyll conditions associated with the occurrence of multiple sardine life stages in fishery-independent surveys conducted in the California Current System. We then show how the spatial distribution of habitats across life stages and putative subpopulations may be influenced by both gradual climate change and marine heatwaves. Our results highlight the potential impacts of changing ocean conditions near major sardine landing ports. During recent marine heatwaves, habitat associated with the northern subpopulation became less available to southern California Current ports, and this trend is projected to continue through the end of the 21st century. Future spatial shifts in sardine habitat may increasingly challenge the practicality of habitat-based subpopulation separation and introduce more uncertainty into management frameworks.

Effects of climate change on ocean ecosystem dynamics are widespread. Oceanographic conditions vital to biological communities have already shown changes, resulting in negative impacts on several of the world’s largest fisheries. The Northern California Current (NCC) is a highly productive system that supports many important fisheries. In addition to large-scale oceanographic forcing and seasonal up- and downwelling cycles, in the last decade, the NCC also experienced two distinct marine heatwaves (MHWs) that resulted in pervasive ecosystem alterations. The 2014–16 and 2019 MHWs had contrasting oceanic and atmospheric origins and different effects on ocean temperature, providing the opportunity to identify the mechanisms important to juvenile fish recruitment processes and how they may be differentially impacted by future warming scenarios. We utilized a five-year time series (2014, 2015, 2016, 2018, and 2019) of larval fish concentration, growth, and diet as a natural experiment to investigate the impact of MHWs as well as two neutral years on cabezon (Scorpaenicthys marmoratus). Findings include the first published measurement of larval cabezon daily growth rates. Mean growth rates were higher during MHWs, suggesting that elevated temperatures did not pose a major growth or survival challenge. Cabezon’s fast growth response to MHW conditions demonstrates that larval cabezon were able to sustain fast growth in warmer temperatures, and were not likely prey limited. Further, larval cabezon gut fullness did not differ significantly among years. Instead, differences in diet composition and prey quality varied with larval growth. Relative to slower-growing larvae, larval cabezon with high growth rates consumed larger prey items, including larval euphausiids and amphipods. Consistent with these patterns of larval growth, nearshore recruitment of juvenile cabezon was also high during MHW years. Our findings highlight the importance of phenological coupling, or matches in timing, between cabezon and euphausiid population dynamics in that larval cabezon exhibited fast growth when the timing of flexion was coupled with the euphausiid population transition to a larger, omnivorous larval stage. Results of this study suggest that larval cabezon’s variable growth and broad diet coupled with selection for large, nutrient dense prey may be a source of resilience for its population dynamics.

Changing environmental conditions are leading to shifts in the timing of seasonal events globally. In the ocean, environmental cues affecting larval fish (ichthyoplankton) abundance may not be synchronized with factors optimizing larval and juvenile survival, making the study of ichthyoplankton phenology in the context of a changing environment critical. In the southern California Current Ecosystem (CCE), a major eastern boundary current upwelling system, significant long-term shifts in larval fish phenology have been previously observed. To assess the stability of these estimates and extend them to the northern CCE, we evaluated multidecadal trends in ichthyoplankton abundance for 57 species from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) and 25 species from the Newport Hydrographic Line (NH Line). We show that on average, larval fish phenology in the southern CCE has continued to advance with an estimated rate of -0.18 ± 0.05 day year-1 from 1951 to 2022, while phenology in the northern CCE has advanced at a rate of -0.48 ± 0.26 day year-1 from 1996 to 2023. Thirty-nine percent of species showed significant advancing phenology, 12% exhibited delayed phenology, and 49% showed no long-term linear change. A comparison analysis showed that species in these groups had similar rates of change between the two locations for the 1997-2017 period. Phenological shifts in the southern CCE tracked changes in the phenology of upper ocean temperature, zooplankton, and upwelling. These variables poorly explained shifts in the northern CCE, where short-term effects of the El Niño-Southern Oscillation and the 2014-2016 marine heatwave on ichthyoplankton phenology were observed for some species. This research highlights regional variability and continuing phenological shifts in one of the world's most productive marine ecosystems.

As global climate change reorganizes marine ecosystems, understanding how predators will respond to variable prey resources is critical to forecasting future community dynamics. Prey traits that affect the foraging process and recur across unrelated taxa offer a means to better anticipate predator resource use by simplifying complex foraging dynamics. Here we compare taxonomic and trait-based indicators of resource use and selection for albacore tuna (Thunnus alalunga), a commercially valuable pelagic predator undergoing climate-driven range shifts. We synthesized datasets from 2005 to 2019 to evaluate diets of albacore tuna in relation to prey availability estimates from shipboard surveys in the California Current Large Marine Ecosystem. Analyses with these data reveal that albacore and trawl surveys sample different aspects of the pelagic system, with albacore consuming a subset of taxa identified within trawls. Albacore consistently selected coastal prey that are schooling, undefended, silvered and countershaded, and have high energy density — suggesting that ecological mechanisms driving albacore foraging outcomes may be conserved across time and space. Ecological traits mediating predator-prey interactions consistently distinguished albacore diets from assemblages sampled by trawls across years and regions. We demonstrate that a traits-based approach simplifies taxonomically diverse predator-prey interactions and may be a valuable tool to facilitate predictions of prey resource use in changing environments.

2022 marked the third consecutive La Niña and extended the longest consecutive stretch of negative Oceanic Niño Index since 1998-2001. While physical and biological conditions in winter and spring largely adhered to prior La Niña conditions, summer and fall were very different. Similar to past La Niña events, in winter and spring coastal upwelling was either average or above average, temperature average or below average, salinity generally above average. In summer and fall, however, upwelling and temperature were generally average or slightly below average, salinity was close to average and chlorophyll a was close to average. Again, as during prior La Niña events, biomass of northern/southern copepods was above/below average off Oregon in winter, and body size of North Pacific krill in northern California was above average in winter. By contrast, later in the year the abundance of northern krill dropped off Oregon while southern copepods increased and body sizes of North Pacific krill fell in northern California. Off Oregon and Washington abundances of market squid and Pacific pompano (indicators of warm, non-typical La Niña conditions) were high. In the 20th century, Northern anchovy recruitment tended to be high during cold conditions, but despite mostly warm conditions from 2015-2021 anchovy populations boomed and remained high in 2022. Resident seabird reproductive success, which tended in the past to increase during productive La Niña conditions was highly variable throughout the system as common murre and pelagic cormorant, experienced complete reproductive failure at Yaquina Head, Oregon while Brandt’s cormorant reproduction was average. At three sampling locations off central California, however, common murre reproduction was close to or above average while both pelagic and Brandt’s cormorant were above average. California sealion reproduction has been above average each year since 2016, and pup weight was also above average in 2022, likely in response not to La Niña or El Niño but continuous high abundance of anchovy. The highly variable and often unpredictable physical and biological conditions in 2022 highlight a growing recognition of disconnects between basin-scale indices and local conditions in the CCE. “July-December 2022 is the biggest outlier from individual “strong” La Niña (events) ever going back to the 50s.” – Nate Mantua

The Northern California Current is a highly productive marine upwelling ecosystem that is economically and ecologically important. It is home to both commercially harvested species and those that are federally listed under the U.S. Endangered Species Act. Recently, there has been a global shift from single-species fisheries management to ecosystem-based fisheries management, which acknowledges that more complex dynamics can reverberate through a food web. Here, we have integrated new research into an end-to-end ecosystem model (i.e., physics to fisheries) using data from long-term ocean surveys, phytoplankton satellite imagery paired with a vertically generalized production model, a recently assembled diet database, fishery catch information, species distribution models, and existing literature. This spatially-explicit model includes 90 living and detrital functional groups ranging from phytoplankton, krill, and forage fish to salmon, seabirds, and marine mammals, and nine fisheries that occur off the coast of Washington, Oregon, and Northern California. This model was updated from previous regional models to account for more recent changes in the Northern California Current (e.g., increases in market squid and some gelatinous zooplankton such as pyrosomes and salps), to expand the previous domain to increase the spatial resolution, to include data from previously unincorporated surveys, and to add improved characterization of endangered species, such as Chinook salmon ( Oncorhynchus tshawytscha ) and southern resident killer whales ( Orcinus orca ). Our model is mass-balanced, ecologically plausible, without extinctions, and stable over 150-year simulations. Ammonium and nitrate availability, total primary production rates, and model-derived phytoplankton time series are within realistic ranges. As we move towards holistic ecosystem-based fisheries management, we must continue to openly and collaboratively integrate our disparate datasets and collective knowledge to solve the intricate problems we face. As a tool for future research, we provide the data and code to use our ecosystem model.

Small pelagic fish are important marine ecosystem components and highly variable fisheries resources. In the California Current upwelling system, Pacific sardine (Sardinops sagax) has supported important fisheries in the past, but contrary to expectations, remains at low biomass despite recent warm ocean conditions. We developed a data-driven, process-based population model that reproduces fluctuations of the US Pacific sardine population based on ocean temperature, early life stage and adult food, and upwelling strength. The lack of sardine recovery after 2014 can be explained by reduced food availability. Ensemble projections for the 21st century driven by downscaled ocean-biogeochemical simulations under three Earth system models (ESMs) show a likely recovery to early 2000s sardine abundance and catch by mid-century, due to increased recruitment. Ecological process uncertainty (ensemble configuration range) is of the same magnitude as uncertainty among ESM projections, and uncertainty related to the thermal optimum of early life stages dominates after 2070. Even for a fish species presumably favoured by warmer conditions, future climate projections entail risks of stock declines in food-limited years and when passing unknown thermal optima. Quantification of combined environmental driver impacts and sources of uncertainty to projections under novel conditions open new pathways for environment-responsive fisheries management strategies.

In late 2020, models predicted that a strong La Niña would take place for the first time since 2013, and we assessed whether physical and biological indicators in 2021 were similar to past La Niñas in the California Current Ecosystem (CCE). The Pacific Decadal Oscillation and Oceanic Niño Index indeed remained negative throughout 2021; the North Pacific Gyre Oscillation Index, however, remained strongly negative. The seventh largest marine heatwave on record was unexpectedly present from April to the end of 2021; however, similar to past La Niñas, this mass of warm water mostly remained seaward of the continental shelf. As expected from past La Niñas, upwelling and chlorophyll were mostly high and sea surface temperature was low throughout the CCE; however, values were close to average south of Point Conception. Similar to past La Niñas, abundances of lipid-rich, northern copepods off Oregon increased. In northern California, unlike past La Niñas, the body size of North Pacific krill (Euphausia pacifica) was close to average. Predictably, overall krill abundance was above average in far northern California but, unexpectedly, below average south of Cape Mendocino. Off Oregon, similar to past La Niñas, larval abundances of three of six coastal species rose, while five of six southern/offshore taxa decreased in 2021. Off California, as expected based on 2020, Northern Anchovy (Engraulis mordax) were very abundant, while Pacific Sardine (Sardinops sagax) were low. Similar to past La Niñas, market squid (Doryteuthis opalescens) and young of the year (YOY) Pacific Hake (Merluccius pacificus), YOY sanddabs (Citharichthys spp.), and YOY rockfishes (Sebastes spp.) increased. Southern mesopelagic (e.g., Panama lightfish Vinciguerria lucetia, Mexican lampfish Triphoturus mexicanus) larvae decreased as expected but were still well above average, while northern mesopelagic (e.g., northern lampfish Stenobrachius leucopsarus) larvae increased but were still below average. In line with predictions, most monitored bird species had above-average reproduction in Oregon and California. California sea lion (Zalophus californianus) pup count, growth, and weight were high given the abundant Anchovy forage. The CCE entered an enduring La Niña in 2021, and assessing the responses of various ecosystem components helped articulate aspects of the system that are well understood and those that need further study.

Citation: Weber ED, Auth TD, Baumann-Pickering S, Baumgartner TR, Bjorkstedt EP, Bograd SJ, Burke BJ, Cadena-Ramírez JL, Daly EA, de la Cruz M, Dewar H, Field JC, Fisher JL, Giddings A, Goericke R, Gomez-Ocampo E, Gomez-Valdes J, Hazen EL, Hildebrand J, Horton CA, Jacobson KC, Jacox MG, Jahncke J, Kahru M, Kudela RM, Lavaniegos BE, Leising A, Melin SR, Miranda-Bojorquez LE, Morgan CA, Nickels CF, Orben RA, Porquez JM, Portner EJ, Robertson RR, Rudnick DL, Sakuma KM, Santora JA, Schroeder ID, Snodgrass OE, Sydeman WJ, Thompson AR, Thompson SA, Trickey JS, Villegas-Mendoza J, Warzybok P, Watson W and Zeman SM (2022) Corrigendum: State of the California Current 2019–2020: Back to the Future With Marine Heatwaves? Front. Mar. Sci. 9:863176. doi: 10.3389/fmars.2022.863176 Corrigendum: State of the California Current 2019–2020: Back to the Future With Marine Heatwaves?

The effects of climate warming on ecosystem dynamics are widespread throughout the world's oceans. In the Northeast Pacific, large‐scale climate patterns such as the El Niño/Southern Oscillation and Pacific Decadal Oscillation, and recently unprecedented warm ocean conditions from 2014 to 2016, referred to as a marine heatwave (MHW), resulted in large‐scale ecosystem changes. Larval fishes quickly respond to environmental variability and are sensitive indicators of ecosystem change. Categorizing ichthyoplankton dynamics across marine ecosystem in the Northeast Pacific can help elucidate the magnitude of assemblage shifts, and whether responses are synchronous or alternatively governed by local responses to regional oceanographic conditions. We analyzed time‐series data of ichthyoplankton abundances from four ecoregions in the Northeast Pacific ranging from subarctic to subtropical: the Gulf of Alaska (1981–2017), British Columbia (2001–2017), Oregon (1998–2017), and the southern California Current (1981–2017). We assessed the impact of the recent (2014–2016) MHW and how ichthyoplankton assemblages responded to past major climate perturbations since 1981 in these ecosystems. Our results indicate that the MHW caused widespread changes in the ichthyoplankton fauna along the coast of the Northeast Pacific Ocean, but impacts differed between marine ecosystems. For example, abundances for most dominant taxa were at all‐time lows since the beginning of sampling in the Gulf of Alaska and British Columbia, while in Oregon and the southern California Current species richness increased as did abundances of species associated with warmer waters. Lastly, species associated with cold waters also increased in abundances close to shore in southern California during the MHW, a pattern that was distinctly different from previous El Niño events. We also found several large‐scale, synchronized ichthyoplankton assemblage composition shifts during past major climate events. Current climate projections suggest that MHWs will become more intense and thus our findings can help project future changes in larval dynamics, allowing for improved ecosystem management decisions.

Rockfish are an important component of West Coast fisheries and California Current food webs, and recruitment (cohort strength) for rockfish populations has long been characterized as highly variable for most studied populations. Research efforts and fisheries surveys have long sought to provide greater insights on both the environmental drivers, and the fisheries and ecosystem consequences, of this variability. Here, variability in the temporal and spatial abundance and distribution patterns of young-of-the-year (YOY) rockfishes are described based on midwater trawl surveys conducted throughout the coastal waters of California Current between 2001 and 2019. Results confirm that the abundance of winter-spawning rockfish taxa in particular is highly variable over space and time. Although there is considerable spatial coherence in these relative abundance patterns, there are many years in which abundance patterns are very heterogeneous over the scale of the California Current. Results also confirm that the high abundance levels of YOY rockfish observed during the 2014-2016 large marine heatwave were largely coastwide events. Species association patterns of pelagic YOY for over 20 rockfish taxa in space and time are also described. The overall results will help inform future fisheries-independent surveys, and will improve future indices of recruitment strength used to inform stock assessment models and marine ecosystem status reports.

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.

Spatial distributions of marine fauna are determined by complex interactions between environmental conditions and animal behaviors. As climate change leads to warmer, more acidic, and less oxygenated oceans, species are shifting away from their historical distribution ranges, and these trends are expected to continue into the future. Correlative Species Distribution Models (SDMs) can be used to project future habitat extent for marine species, with many different statistical methods available. However, it is vital to assess how different statistical methods behave under novel environmental conditions before using these models for management advice, and to consider whether future projections based on these techniques are biologically reasonable. In this study, we built SDMs for adults and larvae of two ecologically important pelagic fishes in the California Current System (CCS): Pacific sardine (Sardinops sagax) and northern anchovy (Engraulis mordax). We used five different SDM methods, ranging from simple [thermal niche model (TNM)] to complex (artificial neural networks). Our results show that some SDMs trained on data collected between 2003 and 2013 lost substantial predictive skill when applied to observations from more recent years, when ocean temperatures associated with a marine heatwave were outside the range of historical measurements. This decrease in skill was particularly apparent for adult sardine, which showed non-stationary relationships between catch locations and sea surface temperature (SST) through time. While sardine adults and larvae shifted their distributions markedly during the marine heatwave, anchovy largely maintained their historical spatiotemporal distributions. Our results suggest that correlative relationships between species and their environment can become unreliable during anomalous conditions. Understanding the underlying physiology of marine species is therefore essential for the construction of SDMs that are robust to rapidly changing environments. Developing distribution models that offer skillful predictions into the future for species such as sardine and anchovy, which are migratory and include separate sub-stocks, may be particularly challenging.

The bay anchovyAnchoa mitchilliis the most abundant fish in Chesapeake Bay (USA) and is a vital link between plankton and piscivores within the trophic structure of this large estuarine ecosystem. Baywide distributions and abundances of bay anchovy eggs and larvae, and larval growth, were analyzed in a 5 yr program to evaluate temporal and spatial variability based on research surveys in the 1995-1999 spawning seasons. Effects of environmental variability and abundance of zooplankton that serve as prey for larval bay anchovy were analyzed. In the years of these surveys, 97.6% of eggs and 98.8% of larvae occurred in the polyhaline lower bay. Median egg and larval abundances differed more than 10-fold for surveys conducted in the 5 yr and were highest in the lower bay. Within years, median larval abundance (ind. m-2) in the lower bay was generally 1-2 orders of magnitude higher than upper-bay abundance. Salinity, temperature, and dissolved oxygen explained 12% of the spatial and temporal variability in egg abundances and accounted for 27% of the variability in larval abundances. The mean, baywide growth rate for larvae over the 5 yr period was 0.75 ± 0.01 mm d-1, and was best explained by zooplankton concentration and feeding incidence. Among years, mean growth rates ranged from 0.68 (in 1999) to 0.81 (in 1998) mm d-1and were fastest in the upper bay. We identified environmental factors, especially salinity, that contributed to broadscale variability in egg and larval production.

The spatial distribution, abundance, and size variability of two pelagic tunicate species, Thetys vagina and Pyrosoma atlanticutn, were examined from midwater trawl surveys to assess the historical context and geographical aspects of a major mass occurrence event throughout the California Current Large Marine Ecosystem during 2012-19. Off central California, abundance of both species were significantly greater in 2012-19 compared to 1983-2001, and their recent persistent multiyear abundance peaks were unprecedented. Coastwide abundance and distribution of T. vagina during 201319 was patchy, with no discernible shifts in distribution or changes in mean length. From 2013-18, abundance and distribution of P. atlanticum demonstrated a temporal trend of increasing abundance from south to north, and in northern areas, average P. atlanticum colony length increased over time. In 2019, high abundances of P. atlanticum occurred south of Monterey Bay, but were not found in the northern California Current. We discuss how in situ and regional-scale environmental drivers may have contributed to this recent multiyear gelatinous mass occurrence, and potential consequences to forage community structure and ecosystem function.

The California Current Ecosystem (CCE) has been in a primarily warm state since 2014, and this pattern largely continued into 2019. The CCE experienced a mild El Nino from late 2018 into 2019, and basin-scale indicators reflected this condition (elevated Oceanic Nitio Index and Pacific Decadal Oscillation; table 1). Despite the El Nino, spring upwelling was above average between southern California and Washington but below average in Baja California. Sea surface temperature (SST) was mostly near the long-term average between Washington and southern California, while surface chlorophyll a was above average in Oregon/Washington and slightly below average in most of California in spring/early summer 2019. SST changed dramatically by fall 2019, however, as a marine heat wave (MHW) that formed in May 2019 in the Gulf of Alaska impinged upon the West Coast of the United States. The expansion of the 2019 MHW followed a similar pattern to the 2014-15 MHW. Off Oregon, the zooplankton assemblage was in a mixed state as southern copepods were close to average while northern copepod abundances were positively anomalous in 2019. Off northern California, Euphausia pacifica body size was smaller than average. Euphausid abundances were well below average in both central and southern California in 2019. In the north, winter 2019 larval fish abundances were high and dominated by offshore taxa that are associated with warm conditions; spring larval and post-larval biomass were close to average; and spring surface trawls observed record-high market squid (Doryteuthis opalescens) abundances. The single most important finding in 2019 was that northern anchovy (Engraulis tnordax) adults and larvae were at record-high abundances in central and southern California. In central California, market squid and Pacific sardine (Sardinops sagax) were also abundant. In southern California warm-water mesopelagic fishes have been very abundant since 2014, and this trend continued into 2019. Indicators for future salmon returns were mixed in 2019. The abundance of northern copepods, which correlate positively with returns, was high. However, abundances of yearling Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch), which also correlate positively with returns, were slightly below average. Winter ichthyoplankton was comprised mostly of southern or offshore taxa, which bodes poorly for future salmon returns. Seabird (common murre [Urfa aalge]; Brandt's cormorant [Phalacrocorax penidllatus]; and pelagic cormorant [Phalacrocorax pelagicus]) productivity off Oregon was the highest in years in both 2018 and 2019. In 2018, common murre chicks in Oregon consumed large amounts of young-of-the-year flatfish, a prey item known to be conducive to chick survival. Despite the prevalence of northern anchovy in central California, common murre and Brand's cormorant production was low in Southeast Farallon Island as these birds were unable to feed optimally on northern anchovy, and there was a scarcity of more appropriate prey such as young-of-the-year flat-fishes or rockfishes. California sea lions (Zalophus californianus), by contrast, benefitted greatly from the large northern anchovy forage base. In 2018, live pup count, weight, and growth rate were anomalously high, and northern anchovy remains occurred in >85% of scat samples. Humpback whale (Megaptera novaeangliae) sightings were also very high in 2019, likely because humpback whales congregated near shore to feed on northern anchovy.

Juvenile Chinook salmon feed primarily on late larval and early juvenile fishes when they enter coastal waters (Daly and Brodeur 2015).The late larval and early juvenile life stage of most marine fishes are difficult to sample effectively (Brodeur et al. 2011), which led us to explore alternative indices of potential fish prey abundance.The majority of marine fishes in the northern California Current (NCC) spawn in late winter and early spring (Brodeur et al. 2008).Winter-spawned fish larvae that grow and survive through spring provide a food base for juvenile coho, steelhead, and Chinook salmon during their first marine summer.Therefore, we used the winter ichthyoplankton biomass as a proxy for potential salmon food during this critical growth period (Daly et al. 2013).The five most dominant fish prey consumed by juvenile yearling and subyearling Chinook salmon, and yearling coho salmon in May-September 1998-2010 were originally chosen as the taxa to calculate the winter ichthyoplankton biomass (i.e., Pacific sand lance, sculpins, smelts, northern anchovy, and rockfishes).Biomasses of these taxa were significantly correlated with adult salmon return abundance (Daly et al. 2013).The ichthyoplankton data used for the index come from five stations sampled bi-weekly along the Newport Hydrographic (NH) line in January-March 1998-2019.The stations in the index are fixed and are located from 9.3 km offshore to just off the shelf at 46.3 km (Peterson et al. 2014).Rarely sampled ichthyoplankton taxa (present in < 2.5% of the samples) and rarely-(or never-) eaten taxa (e.g., myctophids) were omitted from the biomass index.With inconsistent station and bi-weekly sampling, the biomass of each taxon was first averaged by station within each month/year, then by each month/year, and finally by each year for an overall annual average for each taxon.The biomass of the five taxa was summed to get one annual value and ln-transformed and entered into a Principal Coordinate analysis (PCO) and the axis-1 scores from that analysis were used as the index for each year.Ocean regimes of 'cold' and 'warm' were established based upon NOAA's Ocean Indicator stoplight chart where the mean of the ranks were divided into two ranked groups (lower rank half = cold, higher rank half = warm; https://www.nwfsc.noaa.gov/research/divisions/fe/estuarine/oeip/g-forecast.cfm#TableSF-02).During 'cold' regimes, the colder and more productive ocean conditions coincided with higher winter ichthyoplankton biomass and a community dominated by coastal fish larvae such as Pacific sandlance, smelts, and various sculpins, salmon showed higher marine survival (Daly et al. 2017).In contrast, during the warm ocean periods, the winter ichthyoplankton biomass was low and primarily comprised of offshore taxa such as rockfishes and winter-spawned northern anchovy.The five taxa index was a combination of both coastal and offshore taxa, which related well to salmon returns for the first 17 years the index was used.

The community structure of pelagic zooplankton and micronekton may be a sensitive indicator of changes in environmental conditions within the California Current ecosystem. Substantial oceanographic changes in 2015 and 2016, due to the anomalously warm ocean conditions associated with a large-scale marine heatwave perturbation, resulted in onshore and northward advection of warmer and more stratified surface waters resulting in reduced upwelling. Here we quantify changes in the macrozooplankton and micronekton community composition and structure based on five highly contrasting ocean conditions. Data from fine-mesh pelagic trawl surveys conducted off Oregon and Washington during early summer of 2011 and 2013-2016 were examined for interannual changes in spatial distribution and abundance of fish and invertebrate taxa. Overall species diversity was highest in 2015 and lowest in 2011, but 2016 was similar to the other years, although the evenness was somewhat lower. The community of taxa in both 2015 and 2016 was significantly different from the previously sampled years. Crustacean plankton densities (especially Euphausiidae) were extremely low in both of these years, and the invertebrate composition became dominated mostly by gelatinous zooplankton. Fishes and cephalopods showed mixed trends overall, but some species such as age-0 Pacific hake were found in relatively high abundances mainly along the shelf break in 2015 and 2016. These results suggest dramatically different pelagic communities were present during the recent warm years with a greater contribution from offshore taxa, especially gelatinous taxa, during 2015 and 2016. The substantial reorganization of the pelagic community has the potential to lead to major alterations in trophic functioning in this normally productive ecosystem.