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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 100-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.

Historically, gelatinous zooplankton have been considered important consumers or predators in marine food webs, but more recently they have also been recognized as important prey for many marine species. Here, we summarized data obtained from >100 Northeast Pacific fish predators based on extensive gut content analysis (~450000 stomachs examined) from broad-scale demersal trawl surveys ranging from the Bering Sea to Southern California. In the Bering Sea, we identified 27 predators on jellyfish and 23 on urochordates. In the Aleutian Islands, 14 and 18 predators were identified, respectively, and for the Gulf of Alaska, a total of 23 and 32 such predators were documented. Off the West Coast of the contiguous USA, we identified 16 coelenterate predators and 7 urochordate predators. Many of these predators were not previously known to prey on gelatinous zooplankton. Dominant consumers of coelenterates include prowfish, rockfishes, walleye pollock, sablefish, and grenadiers, and primary consumers of urochordates included rockfishes, Atka mackerel, and sablefish. Pronounced seasonal and interannual variability in gelatinous taxa occurrence was observed in several dominant fish predators. The occurrence of jellyfish prey was generally much higher in diets of fishes examined fresh at sea when compared with diets of the same species examined in the laboratory following preservation. Differences in occurrence were less pronounced with the more durable urochordate prey. We suggest that many existing estimates of predation on easily dissolved gelatinous prey may underestimate the true predation rate and the importance of these organisms in marine food webs.

During 2016-2018, unprecedented aggregations of the colonial pelagic tunicate Pyrosoma atlanticum were observed in the Northern California Current (NCC). Pyrosomes are common in tropical and sub-tropical ocean waters, but little is known about their abundance, distribution, and trophic ecology in mid-latitude systems. To assess these factors, pyrosomes were collected during cruises in the NCC in May and August 2017. A generalized additive model (GAM) was used to identify relationships between in situ environmental variables (temperature, salinity, fluorescence) and distribution and abundance patterns of pyrosomes in May 2017. Fatty acid (FA) profiles were then characterized as diet indicators, and bulk stable isotope analysis of carbon and nitrogen was used to examine spatial variations in potential food sources and trophic level. The GAM identified sea surface temperature and surface salinity as significant variables related to pyrosome densities. The most abundant FA in the pyrosomes was docosahexanoic acid (22:6ω3), which serves in pelagic systems as a biomarker for dinoflagellates. Common FA biomarkers for bacteria, carnivory, and dinoflagellates differed by latitude, suggesting that pyrosomes have different diets over a broad latitudinal range. The δ15N values of P. atlanticum indicate that pyrosomes may be feeding at a relatively low trophic level compared to other zooplankton groups in this region. Offshore pyrosomes had lower δ13C values than those collected on the shelf, suggesting incorporation of nearshore carbon in pyrosome tissues. Previously documented rapid reproduction and growth of pyrosomes coupled with efficient feeding behavior for common NCC plankters may support their continued presence in this mid-latitude region.

Tidally controlled river plumes form distinct frontal boundaries that can alter the spatial distributions of larval fishes and their planktonic prey and predators. Variable in nature, they may expose larval fishes to different trophic environments over small spatio-temporal scales, with unknown consequences for survival and recruitment. In the northern California Current, the Columbia River Plume is strongly influenced by twice-daily freshwater injections that create a highly dynamic coastal environment. Using the In situ Ichthyoplankton Imaging System, we examined changes in the fine-scale horizontal and vertical distributions of larval fishes, their prey, and their predators over space and time (ebb/flood tide). In total, 6095 fish larvae and ~1.5 million prey/predator zooplankton were imaged and measured. Plume regions provided substantially higher concentrations of prey and enhanced spatial overlap between larval fishes and their prey relative to oceanic waters. The functionality of river plumes as a refuge from predators was less clear. Predator concentrations were also higher in plume regions, but overlap with larval fishes was taxon-specific and varied with the tide. Notably, regions of high zooplankton concentrations did not necessarily confer high spatial overlap on small scales (meters vertical, kms horizontal) relevant to trophic interactions. Surface salinity and chlorophyll a were the most important factors influencing the spatial overlap of zooplankton with larval fishes. In the vicinity of river plumes, larval fishes experience a diversity of unique prey and predator fields over short spatio-temporal scales, which likely contribute to variable growth and mortality patterns at much finer scales than previously thought.

Predation is a major source of mortality in the early life stages of fishes and a driving force in shaping fish populations. Theoretical, modeling, and laboratory studies have generated hypotheses that larval fish size, age, growth rate, and development rate affect their susceptibility to predation. Empirical data on predator selection in the wild are challenging to obtain, and most selective mortality studies must repeatedly sample populations of survivors to indirectly examine survivorship. While valuable on a population scale, these approaches can obscure selection by particular predators. In May 2018, along the coast of Washington, USA, we simultaneously collected juvenile quillback rockfish Sebastes maliger from both the environment and the stomachs of juvenile coho salmon Oncorhynchus kisutch. We used otolith microstructure analysis to examine whether juvenile coho salmon were age-, size-, and/or growth-selective predators of juvenile quillback rockfish. Our results indicate that juvenile rockfish consumed by salmon were significantly smaller, slower growing at capture, and younger than surviving (unconsumed) juvenile rockfish, providing direct evidence that juvenile coho salmon are selective predators on juvenile quillback rockfish. These differences in early life history traits between consumed and surviving rockfish are related to timing of parturition and the environmental conditions larval rockfish experienced, suggesting that maternal effects may substantially influence survival at this stage. Our results demonstrate that variability in timing of parturition and sea surface temperature leads to tradeoffs in early life history traits between growth in the larval stage and survival when encountering predators in the pelagic juvenile stage.

Within the Eastern Bering Sea, the jellyfish Chrysaora melanaster has fluctuated widely over recent decades. We examined the role of C. melanaster as an ecosystem-structuring agent via application of ecosystem models representing inner-, mid-, and outer-shelf regions of comparable areal coverage. Chrysaora melanaster utilize 1% of total mid-shelf consumer production, or 1/4th the energy required by forage fish (capelin Mallotus villosus, Pacific herring Clupea pallasii, age-0 Pacific cod Gadus macrocephalus, age-0 walleye pollock Gadus chalcogrammus). Model simulations show the impacts of C. melanaster are broadly distributed across consumer groups with increasingly negative impacts with higher jellyfish biomass. Age-0 pollock represent the greater part of the forage fish biomass, and observed pollock biomass during low jellyfish years (2004–2007) was significantly greater than during high jellyfish years (2009–2014). However, sensitivity among consumer groups to observed jellyfish variability is small, within 5% of baseline (2004–2015) conditions. Estimates using similar models for the Coastal Gulf of Alaska (CGoA) and Northern California Current (NCC) suggest large differences in the role of scyphozoans among northern Pacific shelf ecosystems. Only 0.1% of total summer consumer production is required to support CGoA Chrysaora, while the coastal NCC population uses 19%.

Determining how energy flows through ecosystems reveals underlying ecological patterns that drive processes such as growth and food web dynamics. Models that assess the transfer of energy from producers to consumers require information on the energy content or energy density (ED) of prey species. ED is most accurately measured through bomb calorimetry, but this method suffers from limitations of cost, time, and sample requirements that often make it unrealistic for many studies. Percent dry weight (DW) is typically used as a proxy for ED, but this measure includes an indigestible portion (e.g., bones, shell, salt) that can vary widely among organisms. Further, several distinct models exist for various taxonomic groups, yet none can accurately estimate invertebrate, vertebrate and plant ED with a single equation. Here, we present a novel method to estimate the ED of organisms using percent ash‐free dry weight (AFDW). Using data obtained from 11 studies diverse in geographic, temporal and taxonomic scope, AFDW, DW as well as percent protein and percent lipid were compared as predictors of ED. Linear models were produced on a logarithmic scale, including dummy variables for broad taxonomic groups. AFDW was the superior predictor of ED compared to DW, percent protein content and percent lipid content. Model selection revealed that using correction factors (dummy variables) for aquatic animals (AA) and terrestrial invertebrates (TI) produced the best‐supported model—log10(ED) = 1.07*log10(AFDW) − 0.80 (R 2 = 0.978, p 0.97), suggesting that AFDW can be used with high degrees of certainty to predict the ED of taxonomically diverse organisms. Our AFDW model will allow ED to be determined with minimal cost and time requirements and excludes ash‐weight from estimates of digestible mass. Its ease of use will allow for ED to be more readily and accurately determined for diverse taxa across different ecosystems., Determining how energy flows through ecosystems reveals underlying ecological patterns that drive processes such as growth and food web dynamics. Models that assess the transfer of energy from producers to consumers require information on the energy density (ED) of prey species, however, measuring this value carries limitations of cost, time, and sample requirements. Here, we present a novel method to accurately estimate the ED of invertebrates, vertebrates, and plants using a single equation, with minimal cost and time requirements using percent ash‐free dry weight.

Forage fishes are ecologically and economically important in marine ecosystems worldwide and thus are a focal topic for ecosystem-based fisheries management. In the California Current Large Marine Ecosystem (CCLME), the community dynamics of forage populations have been studied at regional spatial scales, but not across regions. To evaluate indicators of the forage community at the ecosystem-wide scale, we examine temporal variability of forage assemblages in Northern (Oregon/Washington), Central (California; Point Reyes to Monterey Bay) and Southern (southern California) regions of the CCLME from 1998 through 2016 which include years with unprecedented climate variability. Forage communities fluctuated greatly between years within each region owing to regionally low abundances of common taxa in at least some years (e.g., rockfishes Sebastes spp. in each region). Comparison of species assemblages among regions indicate that that temporal shifts in assemblage structure were largely synchronous throughout the CCLME. However, dynamics of most individual taxa were out of phase between regions, indicating that different taxa drove the variability in each region. Within regions, taxa with similar adult ecological niches tended to co-vary, suggesting synchronous responses to environmental forcing. Major changes in forage assemblage structure are descriptively linked to large oceanographic perturbations such as the transition from El Nino to La Nina conditions in 1998, anomalous upwelling in 2005, and the onset of a large marine heatwave in fall-winter 2013–2014. Changes in forage assemblage structure are reflected in prey switching in the diet of California sea lions, Zalophus californianus, in the Southern region. The multivariate forage indices that we develop can serve as effective indicators of regional forage community composition shifts in the CCLME and provide managers with context on spatio-temporal changes in the structure of forage fish communities important to top predators in this system.

Ecologically important juvenile groundfishes and salmon co-occur in the upper water column of the eastern Gulf of Alaska during the summer, a period when growth is critical to their survival. We quantified fine-scale spatial and trophic overlap of juvenile groundfishes (arrowtooth flounder, Pacific cod, walleye pollock, and rockfish) and salmon (piscivorous coho and Chinook as well as planktivorous pink, chum, and sockeye) to examine trophic structuring and potential survival bottlenecks for these fishes in the Gulf of Alaska between 2010 and 2014. In general, juvenile groundfish catches had low coherence with station environmental variables with the exception that across the years, rockfish were correlated with deeper station bottom depths. Juvenile salmon catches were correlated with station environmental variables such as shallower station depth and where the pycnocline was closer to the surface, higher chlorophyll levels, and lower salinities. The overall fish community in 2011 was disorganized compared to 2010 and 2012–2014 based on higher ordination stress and had poorer environmental correlations. Fine-scale spatial overlap among juvenile groundfishes and salmon populations was highest in 2011 and 2012 and lowest in 2013 and 2014. Juvenile rockfish had the least spatial overlap with the juvenile salmon due to their offshore distribution. Fine-scale diet overlap between juvenile groundfishes and planktivorous juvenile salmon species ranged from 0% to 78%, was highest in 2012, and was lowest in 2011. Fine-scale diet overlap among juvenile groundfishes and piscivorous juvenile salmon occurred but was typically lower than that with planktivorous juvenile salmon. Additionally, juvenile groundfishes were directly consumed by juvenile salmon. Neither the abundance nor stomach fullness of the juvenile planktivorous groundfishes or salmon correlated with station-level zooplankton biomass in 2012–13, suggesting a lack of a resource bottleneck for these planktivores in these 2 years. Juvenile groundfishes were less frequently caught at stations where the highest catches of juvenile piscivorous salmon occurred, which could be due to predation. Overall, during years when juvenile groundfishes survival was high, juvenile salmon survival was also high, suggesting sufficient food resources in the GOA. Alternatively, when food resources are low in the GOA, as seen in 2011, competition for resources by groundfish and salmon was likely, and both appeared to be negatively impacted.

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 vast spatial extent of the ocean presents a major challenge for monitoring changes in marine biodiversity and connecting those changes to management practices. Remote-sensing offers promise for overcoming this problem in a cost-effective, tractable way, but requires interdisciplinary expertise to identify robust approaches. In this study, we use generalized additive mixed models to evaluate the relationship between an epipelagic fish community in the Northeastern Pacific Ocean and oceanographic predictor variables, quantified in situ as well as via remote-sensing. We demonstrate the utility of using MODIS Rrs555 fields at monthly and interannual timescales to better understand how freshwater input into the Northern California Current region affects higher trophic level biology. These relationships also allow us to identify a gradient in community composition characteristic of warmer, offshore areas and cooler, nearshore areas over the period 2003–2012, and predict community characteristics outside of sampled species data from 2013 to 2015. These spatial maps therefore represent a new, temporally and spatially explicit index of community differences, potentially useful for filling gaps in regional ecosystem status reports and is germane to the broader ecosystem-based fisheries management context.

Edited By: S. J. Hawkins, A. J. Lemasson, A. L. Allcock, A. E. Bates, M. Byrne, A. J. Evans, L. B. Firth, E. M. Marzinelli, B. D. Russell, I. P. Smith, S. E. Swearer, P. A. Todd., The productive eastern boundary current (EBC) systems provide significant sources of global marine protein and have been subject to intense research over the last 50 years. Yet large jellyfish, which are present in all four major systems, have seldom been included in otherwise comprehensive reviews. This undoubtedly reflects their lack of intrinsic commercial value, and the consequently slow pace of knowledge generation. We attempt to redress that imbalance here and to consolidate disparate information on the macromedusae of EBC systems. With the exception of the Canary Current system, which supports a generally low biomass of mostly subtropical taxa, 372jellyfish assemblages in the Benguela, Humboldt and California Current systems are dominated by cool water taxa that can occur at high abundances. While there are large gaps in knowledge, which are highlighted, it is clear that jellyfish can play significant ecological roles in each system. Although there may be strong similarities in faunal composition among the different systems, there are pronounced differences in population responses to the environment and in system resilience and these are reviewed and discussed., Variously, we would also like to thank the Namibian government for access to data and to the National Research Foundation (South Africa), the Royal Society (London), the EAF Nansen Programme and the University of the Western Cape for financial support over the years. We are grateful to the Chilean government and the Agencia Nacional de Investigación y Desarrollo de Chile – formerly Comisión Nacional de Investigación Científica y Tecnológica, and IMARPE for their financial support, and would like to acknowledge grants awarded by the Inter-American Institute for Global Change Research in Montevideo (GEO-0452325, EXA 470/10, PIP 12-201101-00892; CRN3070), as well as the Ministerio de Ciencia, Tecnología e Innovación Productiva in Argentina (FONCyT 01553, FONCyT PICT 2006 No. 1553). Funding was provided by NOAA Fisheries through the Northwest and Southwest Fisheries Science Centers. The CSIC research was supported by projects P07-RNM-02976 (Junta de Andalucía), CTM2011-22856 (Spanish Ministry of Science and Innovation) and 2019AEP203 (CSIC).

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 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 Nino/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 Nino 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.

A micronekton intercalibration experiment was conducted off the southwest coast of Oahu Island, Hawaii in October 2004. Day and night samples were collected in the epipelagic and mesopelagic zones using three micronekton sampling gears: the Cobb Trawl, the Isaacs-Kidd Midwater Trawl (IKMT), and the Hokkaido University Frame Trawl (HUFT). Taxonomic composition and contribution by main size groups to total catch varied among gear types. However, the three gears exhibited similar taxonomic composition for macrozooplankton and micronekton ranging from 20 to 100 mm length (MM 20–100 ). The HUFT and IKMT captured more mesozooplankton and small MM 20–100 , while the Cobb trawl selected towards larger MM 20–100 and nekton. Taxonomic composition was described and inter-compared among gears. The relative efficacy of the three gears was assessed, and size dependent intercalibration coefficients were developed for MM 20–100 .

Refugia are areas relatively buffered from contemporary climate change that enable the persistence of valued physical, ecological or socio-cultural resources. Spatially identifying refugia is important for conservation and applied management. Yet the concept of refugia has not been broadly extended to marine ecosystems. Here, we analyze data from a unique and long-term (1999-2015) standardized survey of pelagic marine and anadromous species off Oregon and Washington in the northern California Current to identify such refugia. We use quantitative approaches to assess locations with high species richness and assemblage persistence relative to local and basin-scale environmental fluctuations. We have identified a potential climate change refugial zone along the continental shelf of Washington State in the Northeastern Pacific Ocean, characterized by a species-rich assemblage with low interannual temporal community change. This region contrasts with adjacent areas to the south and offshore that have lower species richness, and higher temporal species assemblage change. Also, using spatially variant generalized additive mixed models, we identify areas with species assemblages that are be more influenced by basin-scale climatic fluctuations than others. We propose that upwelling regions with retentive topographic features, such as wide continental shelves, can function as marine refugia for pelagic fauna, whereas offshore locations are potentially more climatically sensitive and experience high temporal change in species composition. Further identification of these marine refugia using in-situ data for pelagic biodiversity and climatically sensitive areas can help guide management in the face of inevitable climatically driven change. This article is protected by copyright. All rights reserved.

Gelatinous zooplankton can dominate the dynamics of marine ecosystems; can have major ecological, social, and economic impacts; are often indicative of broader ecosystem perturbations; and are increasingly being harvested by humans. Yet fisheries scientists typically do not monitor these taxa on a regular basis, despite the existence of clear rationales and even mandated authorizations to do so. Notably, the costs of monitoring jellyfish during regular fisheries research cruises would be a small increase over the cost of running a large fishery survey and a small fraction of the costs caused by impacts from these taxa. As ecosystems experience increasing pressures from climate change and fisheries, we recommend considering routine monitoring before some future jellyfish-associated crisis arises.

Riverine plumes in nearshore coastal waters are areas of enhanced production and accumulation of prey and may increase availability of food during a critical period of juvenile salmon survival and hence serve as a nursery area for these juveniles. Physical and biological sampling was conducted along a cross-shelf transect through the Columbia River plume during May 1999. Based on cluster analyses of physical variables, stations considered to be within the core of the plume, at 27.8–46.3 km from shore, were distinct from inshore (7.4–18.5 km) and offshore (55.6–92.7 km) stations. Five variables (temperature at 10 m, salinity at 3 and 10 m, silicate, and chlorophyll) accounted for 92 % of this difference. Both surface neuston and subsurface plankton tows revealed differences in plankton composition at the plume core stations compared to non-plume stations. However, stomach contents of juvenile Chinook salmon were not significantly different inside and outside the plume core. Comparison of similarity indices showed that the stomach composition was more similar to the catch composition in the neuston than the meter net. Fishes, decapod larvae, and hyperiid amphipods occurred in greater proportions and copepods and euphausiids in lesser proportions in the stomachs than in the plankton. There appeared to be a distinctive plume signal, evident in both the physical environment and zooplankton resources sampled inside and outside the plume core, but the plume signature was not as evident in the salmon diets, possibly due to their higher mobility and shorter residence time within the plume.

The Northern California Current (NCC) is a complex, dynamic system experiencing distinctly different levels of upwelling and downwelling, ranging from intermittent upwelling in summer to downwelling in winter. In recent years, warm water anomalies along the Oregon coast have had significant effects on coastal plankton assemblages. To resolve some of the fine-scale responses to these conditions, we used a towed, undulating underwater imaging system to investigate fine-scale (1 m vertical) zoo- and ichthyoplankton distributions along a 57-km section parallel to the Newport Hydrographic Line encompassing the shelf, shelf break, and slope off the central coast of Oregon. A sparse Convolutional Neural Network was used to automate the identification of 52 million plankton images of 64 plankton taxa, ranging from protists to copepods, larval fishes, and gelatinous organisms. Taxa distributions were interpolated over the whole transect, providing unprecedented insight into their horizontal and vertical distributions and revealing seven broad patterns of distribution. Additional fine-scale distribution data enable examination of some of the physical and biological processes underlying these fine-scale distribution patterns, building upon the historical time series data that exists for this region and advancing our knowledge of planktonic processes in this productive region of the NCC.

Coinciding with the marine heat wave in 2014 and a strong El Nino in 2016, blooms of the tropical-temperate pelagic colonial tunicate, Pyrosoma atlanticum, expanded into the Northern California Current (NCC). Given the high densities of P. atlanticum colonies observed in the NCC, and their potential for high grazing rates, we hypothesized that the species could have a substantial negative effect on the phytoplankton standing stock in the Northeastern Pacific Ocean. In the late winter, spring and early autumn of 2018, we measured abundances and length frequencies of P. atlanticum colonies off the coast of Oregon and estimated their spring grazing impact on the local phytoplankton standing stock. Abundances of P. atlanticum peaked in late winter (0.7 colonies m−3), dropped off in spring (0.42 colonies m−3), and declined to near-absent in early autumn (0.07 colonies m−3). We observed a doubling in the median size of P. atlanticum colonies from late winter to spring, followed by a decline in size in early autumn. With their high individual colony gut pigment contents and bloom densities, the overall spring grazing impact of P. atlanticum was substantial, reaching a maximum of 22% of the available phytoplankton standing stock.

Aggregations of the neustonic hydrozoan Velella velella occur periodically in the northern California Current. Despite the regular occurrence of notable bloom events in this productive upwelling zone, little is known about their trophic ecology. We used gut content and stable isotope analyses (SIA) to elucidate V. velella prey selectivity and trophic niche to address their potential impacts on the marine ecosystem. The dominant prey items ingested by V. velella colonies were non-motile prey including cladocerans and northern anchovy (Engraulis mordax) eggs, though copepods were also common in gut contents. Removal rates of northern anchovy eggs could be magnified in bloom years and in areas of high spawning biomass. Stable isotope analysis revealed differences in isotopic niche width and overlap among V. velella based on latitudinal gradients and to a lesser extent on V. velella size and demonstrates the need for continued work to fully understand the trophic ecology of this unique neustonic organism.