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Open Access Publications from the University of California

Scholarly Works (15 results)

  • Article
Research Summaries (2008)

In this project, researchers compiled information on Common Murre (Uria aalge) population size, diet, field metabolic rate, prey energy densities and assimilation efficiency to estimate the bird’s annual prey consumption between Cape Blanco, Ore. and Point Conception, California.

    Cover page: Annual prey consumption of the Common Murre, a Dominant Seabird in the California Current
    • Article
    Research Final Reports (2008)

    Adult Chinook Salmon returns (ocean catch plus escapement) to the Sacramento River watershed in 2007 were the second lowest on record. This prompted severe management actions, as well as a great deal of speculation into possible causes. In response to the unpredicted and precipitous decline, the Pacific Fisheries Management Council (PFMC) closed the fishery for the 2008 season, the most drastic management measure in the history of West Coast salmon fisheries. The socioeconomic impacts of this measure will be extreme for fishers and coastal communities.

      Cover page: California Central Valley Chinook Salmon: A Comparison of Statistical Forecasts for 2007 and 2008
      • Article
      Research Final Reports (2010)

      Matches and mismatches in predator needs and prey availability account for changing reproductive success of top predators (fish and seabirds) in the California Current Large Marine Ecosystem (CCLME).

        Cover page: Tackling Ecological Complexity and Climate Change: Matches and Mismatches in the Seasonal Cycle of California's Marine Flora and Fauna
        • Article
        Research Final Reports (2008)

        We collated information on population size, diet composition, energy requirements, energy densities of prey species, and assimilation efficiency from the literature to estimate annual prey consumption by Common Murres (Uria aalge) between Cape Blanco, Oregon and Point Conception, California in 2004. We estimated that the population consumed approximately 242,250 metric tons of prey, including 70,500 metric tons consumed by breeding adults, 51,920 metric tons consumed by nonbreeding adults and subadults during the breeding season (March-August), 119,620 metric tons consumed by all birds during the wintering period (September –February), and 214 metric tons consumed by dependent chicks prior to leaving breeding colonies. Pacific hake (Merluccius productus) and market squid (Loligo opalescens) each made up over 20% of annual prey consumption. Other species making up at least 10% of annual consumption included shiner surfperch (Cymatogaster aggregata), northern anchovy (Engraulis mordax), and rockfish (Sebastes spp.). Chick diet was dominated by anchovy/sardine (Sardinops sagax; 63%), rockfish (21%), and smelt (Osmeridae spp.; 7%). Understanding these prey requirements is important for understanding the dynamics of predator and prey populations and for effective management of ocean resources.

          Cover page: Annual prey consumption of a dominant seabird, Common Murre, in the California Current
          • Article
          Research Final Reports (2009)

          We will test the primary hypothesis that coastward advection of bottom cold-salty water during intense wind-driven upwelling provides conditions conducive forE. pacifica(the more oceanic species) to move onto the continental shelf where they become abundant and available to predators “early” in the season each year. As a corollary, we will test the hypothesis that as upwelling relaxes “later” in the season each year,E. pacificamoves offshore where it is less available to predators, andT. spinifera(the more coastal species) develops, becoming the dominant euphausiid in shelf waters and predator diets. 

            Cover page: Krill and Krill Predators: Ecosystem-Based Management in the Gulf of the Farallones-Cordell Bank Krill Production Domain
            • Article
            • Peer Reviewed
            UC San Diego Previously Published Works (2015)
            Climate change may increase both stratification and upwelling in marine ecosystems, but these processes may affect productivity in opposing or complementary ways. For the Southern California region of the California Current Ecosystem (CCE), we hypothesized that changes in stratification and upwelling have affected marine bird populations indirectly through changes in prey availability. To test this hypothesis, we derived trends and associations between stratification and upwelling, the relative abundance of potential prey including krill and forage fish, and seabirds based on the long-term, multi-disciplinary CalCOFI/CCE-LTER program. Over the period 1987 through 2011, spring and summer seabird density (all species combined) declined by ~2% per year, mostly in the northern sector of the study region. Krill showed variable trends with two species increasing and one deceasing, resulting in community reorganization. Nearshore forage fish, dominated by northern anchovy (Engraulis mordax) as well as offshore mesopelagic species, show declines in relative abundance over this period. The unidirectional decline in springtime seabird density is largely explained by declining nearshore fish abundance in the previous season (winter). Interannual variability in seabird density, especially in the 2000s, is explained by variability in krill abundance. Changes in the numerical responses of seabirds to prey abundance correspond to a putative ecosystem shift in 1998-1999 and support aspects of optimal foraging (diet) theory. Predator-prey interactions and numerical responses clearly explain aspects of the upper trophic level patterns of change in the pelagic ecosystem off southern California.
              Cover page: Climate–ecosystem change off southern California: Time-dependent seabird predator–prey numerical responses
              • Article
              • Peer Reviewed
              UC San Diego Previously Published Works (2014)
              The link between ocean temperature and spatial and temporal distribution patterns of 8 species of small cetaceans off Southern Cali- fornia was examined during the period 1979-2009. Averages and anomalies of sea-surface temperatures (SSTs) were used as proxies for SST fluctua- tions on 3 temporal scales: seasonal, El Niño-Southern Oscillations (ENSO), and Pacific Decadal Oscillations (PDO). The hypothesis that cetacean species assemblages and habitat associations in southern California waters co-vary with these periodic changes in SST was tested by using generalized additive models. Seasonal SST averages were included as a predictor in the models for Dall's porpoise (Phocoenoides dalli), and common dolphins (Delphinus spp.), northern right whale dolphin (Lisso-delphis borealis), and Risso's dolphin (Grampus griseus). The ENSO index was included as a predictor for north- ern right whale, long-beaked common (Delphinus capensis), and Risso's dol-phins. The PDO index was selected as a predictor for Dall's porpoise and Pacific white-sided (Lagenorhynchus obliquidens), common, and bottlenose (Tursiops truncatus) dolphins. A metric of bathymetric depth was included in every model, and seafloor slope was included in 5 of the 9 models, an indi-cation of a distinctive spatial distribu-tion for each species that may repre-sent niche or resource partitioning in a region where multiple species have overlapping ranges. Temporal changes in distribution are likely a response to changes in prey abundance or dis-persion, and these patterns associated with SST variation may foreshadow future, more permanent shifts in dis-tribution range that are due to global climate change.
                Creative Commons 'BY' version 4.0 license
                • Article
                • Peer Reviewed
                UC Santa Cruz Previously Published Works (2023)
                The world's eastern boundary upwelling systems (EBUSs) contribute disproportionately to global ocean productivity and provide critical ecosystem services to human society. The impact of climate change on EBUSs and the ecosystems they support is thus a subject of considerable interest. Here, we review hypotheses of climate-driven change in the physics, biogeochemistry, and ecology of EBUSs; describe observed changes over recent decades; and present projected changes over the twenty-first century. Similarities in historical and projected change among EBUSs include a trend toward upwelling intensification in poleward regions, mitigatedwarming in near-coastal regions where upwelling intensifies, and enhanced water-column stratification and a shoaling mixed layer. However, there remains significant uncertainty in how EBUSs will evolve with climate change, particularly in how the sometimes competing changes in upwelling intensity, source-water chemistry, and stratification will affect productivity and ecosystem structure. We summarize the commonalities and differences in historical and projected change in EBUSs and conclude with an assessment of key remaining uncertainties and questions. Future studies will need to address these questions to better understand, project, and adapt to climate-driven changes in EBUSs.
                  Cover page: Climate Change Impacts on Eastern Boundary Upwelling Systems
                  • Article
                  • Peer Reviewed
                  UC San Diego Previously Published Works (2006)
                  In spring-summer 2005, anomalous atmospheric-oceanographic coupling caused unprecedented reproductive failures and redistribution of a planktivorous marine bird in both central California (37°N) and southern British Columbia (50°N). At SE Farallon Island, CA, the birds abandoned the breeding colony en masse between 10-20 May, a unique behavioral response; for the first time in 35 years, reproductive success was zero. At Triangle Island, B.C., only 8% of the nesting pairs were successful, the worst year on record. Surveys of birds at sea revealed a peak in relative abundance south of Point Conception (34°N) in summer and fall, suggestive of emigration from the north. Prey (euphausiid crustacean) biomass in the Gulf of the Farallones was reduced, but remained high south of Point Conception. Change in predator and prey may be explained, in part, by unusual atmospheric blocking in the Gulf of Alaska in May, which caused the jet stream to shift southwards resulting in poor upwelling-favorable winds and anomalously warm SST. This study demonstrates the deleterious consequences of this climate event for a top marine predator in the central-northern California Current System. Copyright 2006 by the American Geophysical Union.
                    Cover page: Planktivorous auklet Ptychoramphus aleuticus responses to ocean climate, 2005: Unusual atmospheric blocking?
                    • Article
                    • Peer Reviewed
                    UC Davis Previously Published Works (2010)
                    This report summarizes observations of the California Current System (CCS) from Baja California, Mexico to Oregon for the period from spring 2009 through spring 2010. During this period, changes in the state of the CCS reflected a transition from cool La Niña conditions into and through a short-lived, relatively weak El Niño event. Weaker than normal upwelling and several extended relaxation events contributed to warming over much of the CCS during summer 2009, especially in the north. Moderation of La Niña conditions in the CCS coincided with the development of El Niño conditions in the equatorial Pacific, yet manifested well in advance of any evidence for direct effects of El Niño on the CCS. Responses to El Niño in fall 2009 and winter 2009-2010 appear to have varied substantially with latitude: conditions off southern California returned to near climatological values with the decline of La Niña, and did not indicate any subsequent response to El Niño, yet the northern CCS warmed subtantially following the decline of La Niña and was strongly affected by intense downwelling during winter 2009-2010. The 2009-2010 El Niño diminished rapidly in early 2010, and upwelling off central and southern California resumed unusually early and strongly for a spring following an El Niño, but recovery from El Niño in early 2010 appears to be less robust in the northern CCS. Thus, despite dynamic changes in the overall state of the California Current, 2009-2010 continued the recent pattern of strong regional variability across the CCS.
                      Cover page: STATE OF THE CALIFORNIA CURRENT 2009-2010: REGIONAL VARIATION PERSISTS THROUGH TRANSITION FROM LA NINA TO EL NINO (AND BACK?)
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