Northeast Pacific Coast Research Articles

Why less complexity produces better forecasts: an independent data evaluation of kelp habitat models

Understanding how species are distributed in the environment is increasingly important for natural resource management, particularly for keystone and habitat – forming species, and those of conservation concern. Habitat suitability models are fundamental to developing this understanding; however their use in management continues to be limited due to often‐vague model objectives and inadequate evaluation methods. Along the Northeast Pacific coast, canopy kelps (Macrocystis pyrifera and Nereocystis luetkeana) provide biogenic habitat and considerable primary production to nearshore ecosystems. We investigated the distribution of these species by examining a series of increasingly complex habitat suitability models ranging from process‐based models based on species’ ecology to complex generalised additive models applied to purpose‐collected survey data. Seeking empirical limits to model complexity, we explored the relationship between model complexity and forecast skill, measured using both cross‐validation and independent data evaluation. Our analysis confirmed the importance of predictors used in models of coastal kelp distributions developed elsewhere (i.e. depth, bottom type, bottom slope, and exposure); it also identified additional important factors including salinity, and potential interactions between exposure and salinity, and slope and tidal energy. Comparative results showed how cross‐validation can lead to over‐fitting, while independent data evaluation clearly identified the appropriate model complexity for generating habitat forecasts. Our results also illustrate that, depending on the evaluation data, predictions from simpler models can out‐perform those from more complex models. Collectively, the insights from evaluating multiple models with multiple data sets contribute to the holistic assessment of model forecast skill. The continued development of methods and metrics for evaluating model forecasts with independent data, and the explicit consideration of model objectives and assumptions, promise to increase the utility of model forecasts to decision makers.

An overview of non-governmental organization, passive acoustic, ocean observatory data available on the North East Pacific Coast

There are governmental (DFO, DND, NOAA, USN), commercial (typically proprietary), and non-governmental organization (NGO) passive acoustic ocean observing systems installed on the North East Pacific Coast. The NGO passive acoustic datasets span many years, four decades for OrcaLab. This presentation provides an overview of the data collected at various NGO acoustic observatories on the North East Pacific Coast. The dataset time windows, sampling rates, formats, and ancillary data are given for each NGO. Data availability, searchability, data use restrictions, and contact information are given to allow acoustic researchers to access this treasure of acoustic observatory data. NGO’s include Fin Island Marine Institute, CetaceaLab, Pacific Wild, OrcaLab, Ocean Networks Canada, Saturna Island Marine Research and Education Society, Orcasound, and the Monterey Bay Aquarium Research Institute.There are governmental (DFO, DND, NOAA, USN), commercial (typically proprietary), and non-governmental organization (NGO) passive acoustic ocean observing systems installed on the North East Pacific Coast. The NGO passive acoustic datasets span many years, four decades for OrcaLab. This presentation provides an overview of the data collected at various NGO acoustic observatories on the North East Pacific Coast. The dataset time windows, sampling rates, formats, and ancillary data are given for each NGO. Data availability, searchability, data use restrictions, and contact information are given to allow acoustic researchers to access this treasure of acoustic observatory data. NGO’s include Fin Island Marine Institute, CetaceaLab, Pacific Wild, OrcaLab, Ocean Networks Canada, Saturna Island Marine Research and Education Society, Orcasound, and the Monterey Bay Aquarium Research Institute.

Vertical Zonation and Niche Breadth of Tidal Marsh Plants Along the Northeast Pacific Coast

The distribution patterns of sessile organisms in coastal intertidal habitats typically exhibit vertical zonation, but little is known about variability in zonation among sites or species at larger spatial scales. Data on such heterogeneity could inform mechanistic understanding of factors affecting species distributions as well as efforts to assess and manage coastal species and habitat vulnerability to sea-level rise. Using data on the vertical distribution of common plant species at 12 tidal marshes across the US Pacific coast, we examined heterogeneity in patterns of zonation to test whether distributions varied by site, species, or latitude. Interspecific zonation was evident at most sites, but the vertical niches of co-occurring common species often overlapped considerably. The median elevation of most species varied across marshes, with site-specific differences in marsh elevation profiles more important than differences in latitude that reflect regional climate gradients. Some common species consistently inhabited lower or higher elevations relative to other species, but others varied among sites. Vertical niche breadth varied more than twofold among species. These results indicate that zonation varies by both site and species at the regional scale, and highlight the potential importance of local marsh elevation profiles to plant vertical distributions. Furthermore, they suggest that coastal foundation species such as marsh plants may differ in their vulnerability to sea-level rise by being restricted to specific elevation zones or by occurring in narrow vertical niches.

Are the ghosts of nature’s past haunting ecology today?

Humans have decimated populations of large-bodied consumers and their functions in most of the world's ecosystems. It is less clear how human activities have affected the diversity of habitats these consumers occupy. Rebounding populations of some predators after conservation provides an opportunity to begin to investigate this question. Recent research shows that following long-term protection, sea otters along the northeast Pacific coast have expanded into estuarine marshes and seagrasses, and alligators on the southeast US coast have expanded into saltwater ecosystems, habitats presently thought beyond their niche space. There is also evidence that seals have expanded into subtropical climates, mountain lions into grasslands, orangutans into disturbed forests and wolves into coastal marine ecosystems. Historical records, surveys of protected areas and patterns of animals moving into habitats that were former hunting hotspots indicate that - rather than occupying them for the first time - many of these animals are in fact recolonizing ecosystems. Recognizing that many large consumers naturally live and thrive across a greater diversity of ecosystems has implications for setting historical baselines for predator diversity within specific habitats, enhancing the resilience of newly colonized ecosystems and for plans to recover endangered species, as a greater range of habitats is available for large consumers as refugia from climate-induced threats.

Impact of multiple stressors on juvenile fish in estuaries of the northeast Pacific.

A key step in identifying global change impacts on species and ecosystems is to quantify effects of multiple stressors. To date, the science of global change has been dominated by regional field studies, experimental manipulation, meta-analyses, conceptual models, reviews, and studies focusing on a single stressor or species over broad spatial and temporal scales. Here, we provide one of the first studies for coastal systems examining multiple stressor effects across broad scales, focused on the nursery function of 20 estuaries spanning 1,600km of coastline, 25years of monitoring, and seven fish and invertebrate species along the northeast Pacific coast. We hypothesized those species most estuarine dependent and negatively impacted by human activities would have lower presence and abundances in estuaries with greater anthropogenic land cover, pollution, and water flow stress. We found significant negative relationships between juveniles of two of seven species (Chinook salmon and English sole) and estuarine stressors. Chinook salmon were less likely to occur and were less abundant in estuaries with greater pollution stress. They were also less abundant in estuaries with greater flow stress, although this relationship was marginally insignificant. English sole were less abundant in estuaries with greater land cover stress. Together, we provide new empirical evidence that effects of stressors on two fish species culminate in detectable trends along the northeast Pacific coast, elevating the need for protection from pollution, land cover, and flow stressors to their habitats. Lack of response among the other five species could be related to differing resistance to specific stressors, type and precision of the stressor metrics, and limitations in catch data across estuaries and habitats. Acquiring improved measurements of impacts to species will guide future management actions, and help predict how estuarine nursery functions can be optimized given anthropogenic stressors and climate change scenarios.

Inconsistency for the niche breadth invasion success hypothesis in aquatic invertebrates

AbstractComparison of highly successful and less successful invasive species can highlight traits that are associated with invasion success, and indicate the associated risk of further establishment or invasion from novel species. We compared variation in δ13C and δ15N, or isotopic niche, in the tissues of matched pairs of highly successful and less successful (respectively) freshwater and marine aquatic invasive species: violet tunicate Botrylloides violaceus and golden star tunicate Botryllus schlosseri from the northwest Atlantic coast; spiny waterflea Bythotrephes longimanus and fishhook waterflea Cercopagis pengoi from the Great Lakes basin; and Pacific oyster Crassostrea gigas and eastern oyster Crassostrea virginica from the northeast Pacific coast. Individual (δ13C and δ15N) and population (Bayesian ellipses of δ13C and δ15N) level comparisons of isotopic niche revealed, in most cases, greater niche breadth in the more successful species of tunicate but the less successful species of waterflea and oyster. Comparison with the literature suggested that a broad dietary niche is less crucial for widespread distribution of aquatic invasive invertebrates than it is for vertebrates (i.e., fishes). Inconsistency in the association between isotopic niche breadth and invasion success could be due to a greater influence of habitat suitability on variation in invertebrate diets. These findings challenge the common assumption that a broader niche promotes invasion success, and thus, have implications for invasive species risk assessment, management, and our understanding of species spread and distribution.

Seasonal and interannual variability in along‐slope oceanic properties off the US West Coast: Inferences from a high‐resolution regional model

AbstractA 6 year, 2009–2014 simulation using a 2 km horizontal resolution ocean circulation model of the Northeast Pacific coast is analyzed with focus on seasonal and interannual variability in along‐slope subsurface oceanic properties. Specifically, the fields are sampled on the isopycnal surface kg m−3 that is found between depths of 150 and 300 m below the ocean surface over the continental slope. The fields analyzed include the depth , temperature , along‐slope current , and the average potential vorticity PV between 26.5 and 26.25 kg m−3. Each field is averaged in the cross‐shore direction over the continental slope and presented as a function of the alongshore coordinate and time. The seasonal cycle in shows a coherent upwelling‐downwelling pattern from Mexico to Canada propagating to the north with a speed of 0.5 m s−1. The anomalously deep ( m) displacement in spring‐summer 2014 is forced by the southern boundary condition at 24°N as a manifestation of an emerging strong El Niño. The seasonal cycle in is most pronounced between 36°N and 53°N indicating that subarctic waters are replaced by warmer Californian waters in summer with the speed close 0.15 m s−1, which is consistent with earlier estimates of the undercurrent speed and also present analyses. The seasonal patterns and anomalies in and find confirmation in available long‐term glider and shipborne observations. The PV seasonality over the slope is qualitatively different to the south and north of the southern edge of Heceta Bank (43.9°N).

Largest baleen whale mass mortality during strong El Niño event is likely related to harmful toxic algal bloom.

While large mass mortality events (MMEs) are well known for toothed whales, they have been rare in baleen whales due to their less gregarious behavior. Although in most cases the cause of mortality has not been conclusively identified, some baleen whale mortality events have been linked to bio-oceanographic conditions, such as harmful algal blooms (HABs). In Southern Chile, HABs can be triggered by the ocean–atmosphere phenomenon El Niño. The frequency of the strongest El Niño events is increasing due to climate change. In March 2015, by far the largest reported mass mortality of baleen whales took place in a gulf in Southern Chile. Here, we show that the synchronous death of at least 343, primarily sei whales can be attributed to HABs during a building El Niño. Although considered an oceanic species, the sei whales died while feeding near to shore in previously unknown large aggregations. This provides evidence of new feeding grounds for the species. The combination of older and newer remains of whales in the same area indicate that MMEs have occurred more than once in recent years. Large HABs and reports of marine mammal MMEs along the Northeast Pacific coast may indicate similar processes in both hemispheres. Increasing MMEs through HABs may become a serious concern in the conservation of endangered whale species.

Plastic in Cassin's Auklets (Ptychoramphus aleuticus) from the 2014 stranding on the Northeast Pacific Coast

Oceanic plastic debris found in the digestive tracts of seabirds includes industrial plastic pellets and post-consumer user plastics. We examined whether the amount and type of plastic ingested by Cassin's Auklets (Ptychoramphus aleuticus) is changing by surveying the stomach contents of 171 Cassin's Auklets stranded along the Washington and Oregon coasts in 2014. We found that 41.5% of the birds contained plastic in their ventriculi, similar to values from the North Subarctic Pacific reported in the 1980s. Industrial pellets were found in 22.8% of our samples, and accounted for 28.1% of all the plastic pieces found. Industrial pellets tended to be larger than pieces of user plastic and accounted for 40.2% of total plastic weight. These industrial pellets were significantly smaller than those found in other species, suggesting either that Cassin's Auklets selected smaller plastic particles or that plastic was retained in ventriculi and worn down.

A comparison of epifaunal invertebrate communities in native eelgrass Zostera marina and non-native Zostera japonica at Tsawwassen, BC

The introduction of non-native species can alter the structure of local communities and ecosystems. Although there is concern over the negative effects imposed by introduced species, positive effects are also possible. Introduced species may facilitate local resident species by providing or modifying habitat; these positive effects are sometimes overlooked, but are important for decisions about the local management of non-native species. The introduction of Zostera japonica to the Northeast Pacific coast is a case of a non-native foundation species that appears to expand total eelgrass habitat area, potentially facilitating local eelgrass-inhabiting species. In this study, we asked whether the non-native Z. japonica provides habitat for eelgrass-dwelling invertebrates that is similar to its native congener, Z. marina. We systematically quantified invertebrate assemblages in the two eelgrass species and quantified eelgrass characteristics that are relevant to epifaunal habitat quality (e.g. shoot density and surface area). We found that Z. japonica supports a greater total abundance of the same invertebrate species found in Z. marina meadows; however, the relative abundance of invertebrate species differed between Z. japonica and Z. marina. This result is consistent with differences in the two congeners’ morphological characteristics, density of vegetative and reproductive shoots, and total blade surface area per square metre. We conclude that the expansion of total eelgrass habitat due to the introduction of Z. japonica appears to increase the available habitat for local epifaunal invertebrate communities.

Densovirus associated with sea-star wasting disease and mass mortality.

Populations of at least 20 asteroid species on the Northeast Pacific Coast have recently experienced an extensive outbreak of sea-star (asteroid) wasting disease (SSWD). The disease leads to behavioral changes, lesions, loss of turgor, limb autotomy, and death characterized by rapid degradation ("melting"). Here, we present evidence from experimental challenge studies and field observations that link the mass mortalities to a densovirus (Parvoviridae). Virus-sized material (i.e., <0.2 μm) from symptomatic tissues that was inoculated into asymptomatic asteroids consistently resulted in SSWD signs whereas animals receiving heat-killed (i.e., control) virus-sized inoculum remained asymptomatic. Viral metagenomic investigations revealed the sea star-associated densovirus (SSaDV) as the most likely candidate virus associated with tissues from symptomatic asteroids. Quantification of SSaDV during transmission trials indicated that progression of SSWD paralleled increased SSaDV load. In field surveys, SSaDV loads were more abundant in symptomatic than in asymptomatic asteroids. SSaDV could be detected in plankton, sediments and in nonasteroid echinoderms, providing a possible mechanism for viral spread. SSaDV was detected in museum specimens of asteroids from 1942, suggesting that it has been present on the North American Pacific Coast for at least 72 y. SSaDV is therefore the most promising candidate disease agent responsible for asteroid mass mortality.

Evidence-Based Analysis of Search and Rescue Operations Following the Great East Japan Earthquake

The March 11, 2011 earthquake off Japan’s northeast (Tohoku) Pacific coast and the resulting gigantic tsunamis took the lives of nearly 18,000 people in the devastated coastal communities. In the immediate aftermath of the disaster, now called Great East Japan Earthquake, search and rescue (SAR) for those who were trapped in tsunami waters and debris and who were missing was the top priority in the integrated emergency response. Eventually, SAR operations were performed on an unprecedented scale and complexity. This being the case, a strong interest in the details of these activities has surfaced and frequent enquiries have often been made both from within Japan and from overseas. Still, few studies have been conducted to-date on how SAR operations were performed and what lessons have been learned as a result. By analyzing the experiences of fire service rescue workers, this paper identifies challenges and gaps that the SAR system – institutions, policy frameworks and instruments, skills and techniques, equipment, etc. – could not fully deal with. This paper also looks at the lessons learned to examine the reasons behind them and to explore ways forward that may enable us to be better prepared for future disasters of a similar kind.

Spatial distribution and reproductive phenology of sexual and asexual Mastocarpus papillatus (Rhodophyta)

Fierst J.L., Kübler J.E. and Dudgeon S.R. 2010. Spatial distribution and reproductive phenology of sexual and asexual Mastocarpus papillatus (Rhodophyta). Phycologia 49: 274–282. DOI: 10.2216/09-41.1Species of the genus Mastocarpus exhibit two distinct life cycles, a sexual alternation of generations and an obligate, asexual direct life cycle that produces only female upright fronds. In the intertidal red alga, M. papillatus (Kützing) sexual fronds dominate southern populations and asexual fronds dominate northern populations along the northeast Pacific coast, a pattern of spatial separation called geographic parthenogenesis. Along the central coast of California, sexual and asexual variants occur in mixed populations, but it is not known whether they are spatially separated within the intertidal zone at a given site. We investigated reproductive phenologies and analyzed patterns of spatial distributions of sexual and asexual M. papillatus at three sites in this region. Sexual M. papillatus were aggregated lower on the shore at two sites and only reproduced during part of a year, while asexual M. papillatus occurred throughout the intertidal range at all sites and reproduced throughout the year. The distribution patterns of sexual and asexual M. papillatus are consistent with a hypothesis of shoreline topography influencing their dynamics of dispersal and colonization. Spatial and temporal partitioning may contribute to the long-term coexistence of sexual and asexual life histories in this, and other, species of Mastocarpus. The occurrence of geographic parthenogenesis at multiple spatial scales in M. papillatus provides an opportunity to gain insight into the phenomenon.

Extensive hybridization with minimal introgression in Mytilus galloprovincialis and M. trossulus in Hokkaido, Japan

Species in the Mytilus edulis complex (M. edulis, M. galloprovincialis and M. trossulus) hybridize in nature but, depending on the species pair involved, hybridization can range from mini- mal to very common with extensive introgression. Since M. galloprovincialis has been introduced within the geographic range of M. trossulus in several locations, this system provides the opportunity to determine whether the propensity for hybridization and the resulting level of introgression depends upon environmental circumstances in which the 2 species become sympatric. Contact between these 2 species on the Northeast Pacific coast and within the Puget Sound results in low lev- els of hybridization with little to no introgression. The present study examines the level of hybridiza- tion and introgression between M. galloprovincialis and M. trossulus around Hokkaido, Japan, where these species are also sympatric. We show that 2 independent hybrid zones exist in Hokkaido, each having distinct genetic architectures. The hybrid zone formed along the northern coast of Hokkaido is similar in structure to those reported in the northeast Pacific. The second hybrid zone formed along the southern coast of Hokkaido differs markedly from these other hybrid zones by exhibiting an exceptionally high propensity for hybridization, but, like other hybrid zones between these 2 species, it generates minimal levels of introgression. The mechanism(s) producing high levels of hybridization between M. galloprovincialis and M. trossulus in southern Hokkaido may include some form of apparent outcrossing or hybrid vigor for survival but not for fertility.

First Occurrence of A Pacific Crevalle Jack, Caranx caninus, North of San Diego, California

Pacific crevalle jack (Caranx caninus) is common throughout the tropical waters of the eastern Pacific Ocean (Eschmeyer et al. 1983, Nelson et al. 2004). It was believed that a single crevalle jack species (C. hippos) was circumglobal in its distribution, but SmithVaniz and Carpenter (2007) divided the species into three taxa, C. hippos (Atlantic, mainly western), C. caninus (eastern Pacific), and C. fischeri (eastern Atlantic). They described numerous meristic differences between the three species while maintaining them under the C. hippos complex. Throughout their tropical range, Pacific crevalle jack are often found in shallow inshore areas, including brackish waters (Eschmeyer et al. 1983). Along the eastern Pacific boundary, the northern range limit extends to San Diego Bay, California (Miller and Lea 1972; Eschmeyer et al. 1983; Love et al. 2005). The northern range limit for Pacific crevalle jack was established with the collection of an individual in south San Diego Bay in March 1972 (Miller and Lea 1972; SIO [Scripps Institution of Oceanography] 72–69) during a period of warmer than normal sea surface temperatures (Lea and Rosenblatt 2000). Lea and Rosenblatt (2000) report a total of four individuals collected from southern California, all within San Diego Bay, with the last individual collected on 21 January 1998 (SIO 98–119), during the one of the most intense El Nino events of the twentieth century. The remaining two individuals were collected in May 1975 (SIO 75–383) and September 1984 (SIO 84–251), both in San Diego Bay. El Nino Southern Oscillation (ENSO) events commonly transport more tropical species northwards along the Northeast Pacific Coast (Lea and Rosenblatt 2000), especially species known to aggregate around flotsam, such as jacks (Hunter and Mitchell 1966). While two carangid species (yellowtail jack [Seriola lalandi] and jack mackerel [Trachurus symmetricus]) are common to the Southern California Bight, Lea and Walker (1995) noted the record of 12 novel carangid species collected within southern California. Most of these occurrences were attributed to natural migrations associated with warmwater oceanographic events, although they did note the potential for anthropogenic introductions, especially of juveniles or adults carried north aboard sportfishing vessels, either as bait or alive within their holds. On 5 December 1982, M. D. Curtis collected one juvenile Pacific crevalle jack during an impingement survey at Huntington Beach Generating Station in Huntington Beach, California. Initially preserved in 10% formalin, the specimen was later transferred to 90% ethanol for archiving in the MBC Applied Environmental Sciences voucher collection. The individual measured 83 mm standard length, with a total length of 100 mm (Table 1). Morphometric analysis compared favorably to measurements in Miller and Lea (1972) with the current specimen exhibiting the following fin spine/ray counts: anal fin III, 18, pectoral fin I, 21, and dorsal fin VII, 21 (Table 2). Furthermore, a high arch in

Covariation between the average lengths of mature coho (Oncorhynchus kisutch) and Chinook salmon (O. tshawytscha) and the ocean environment

AbstractWe used the average fork length of age‐3 returning coho (Oncorhynchus kisutch) and age‐3 ocean‐type and age‐4 stream‐type Chinook (Oncorhynchus tshawytscha) salmon along the northeast Pacific coast to assess the covariability between established oceanic environmental indices and growth. These indices included the Multivariate El Niño‐Southern Oscillation Index (MEI), Pacific Decadal Oscillation (PDO), Northern Oscillation Index, and Aleutian Low Pressure Index. Washington, Oregon, and California (WOC) salmon sizes were negatively correlated with the MEI values indicating that ultimate fish size was affected negatively by El Niño‐like events. Further, we show that the growth trajectory of WOC salmon was set following the first ocean winter. Returning ocean‐type British Columbia‐Puget Sound Chinook salmon average fork length was positively correlated with the MEI values during the summer and autumn of return year, which was possibly a result of a shallower mixed layer and improved food‐web productivity of subarctic Pacific waters. Size variation of coho salmon stocks south of Alaska was synchronous and negatively correlated with warm conditions (positive PDO) and weak North Pacific high pressure during ocean residence.

First record of Plakortis Schulze (Porifera: Homosclerophorida) from the Northeast Pacific coast, with the description of Plakortis albicans sp. nov.

A new species of Plakortis Schulze, 1880 from the Pacific coast of Mexico is described, which constitutes the first record of the Plakortis genus in the Northeast Pacific coast, and the first record of Homosclerophorida in the Mexican Pacific coast. Plakortis albicans sp. nov. is characterized by its white or ivory color, by a surface sculpted by subectosomic drainage canals, and by the morphological details of its skeleton, such as the presence of diods and triods in one single class, and a tangential alveolar ectosomal skeleton formed mostly by smaller diods. The only species known in the genus Plakortis from the East Pacific Ocean is Plakortis galapagensis Desqueyroux-Faúndez &amp; van Soest, 1997, which differs from Plakortis albicans sp. nov. mainly by having diods in two distinct size classes. So far, P. albicans is only known in one locality (Mazatlán Bay), where it is relatively abundant in cryptic habitats such as under rock.

Post-glacial population history and genetic structure of the northern clingfish ( Gobbiesox maeandricus ), revealed from mtDNA analysis

Mitochondrial d-loop sequences were analyzed to characterize the phylogeographic and population genetic structure of the northern clingfish (Gobbiesox maeandricus Girard). Sequence analysis of 378 bp from 111 individuals sampled in 14 localities along the northeast Pacific coast and within the Strait of Georgia from 1996 to 1999 revealed marked genetic differentiation (Φct=0.247) among regional population groupings. The gene genealogy distinguished two major clades of haplotypes separated by at least 1.1% sequence divergence. One clade with very low haplotype diversity (h=0.2095, n=18) occurred only within the recently unglaciated Strait of Georgia. The other clade had high haplotype diversity (h=0.8808, n=93) and was found in all populations. High haplotype diversity was found in open coastal populations, both north and south of the maximum extant of the Wisconsin ice sheet, suggesting that the clingfish range was not pushed to a southern refugium during the last glacial maximum. A nested clade analysis also did not detect a large northward expansion from a single southern refugium. The level of sequence divergence and coalescent-based analyses suggest that the observed patterns of polymorphism are the result of Pleistocene diversification within multiple refugia, followed by population expansion and asymmetrical lineage introgression.

Tree-ring estimates of Pacific decadal climate variability

Decadal-scale oscillatory modes of atmosphere-ocean variability have recently been identified in instrumental studies of the Pacific sector. The regime shift around 1976 is one example of such a fluctuation, which has been shown to have significantly impacted climate and the environment along the coastline of the western N and S Americas. The length of meteorological data for the Pacific and western Americas critically limits analyses of such decadal-scale climate variability. Here we present reconstructions of the annual Pacific Decadal Oscillation (PDO) index based on western North American tree-ring records which account for up to 53% of the instrumental variance and extend as far back as AD 1700. The PDO reconstructions indicate that decadal-scale climatic shifts have occurred prior to the period of instrumental record. Evaluation of temperature and precipitation-sensitive tree-ring series from the northeast Pacific as well as these reconstructions reveals evidence for a shift towards less pronounced interdecadal variability after about the middle 1800s. Our analyses also suggest that sites from both the northeast Pacific coast as well as the subtropical Americas need to be included in proxy data sets used to reconstruct the PDO.

Isotopic composition of otoliths as a chemical tracer in population identification of sockeye salmon (Oncorhynchus nerka)

The feasibility of stable oxygen and carbon isotope ratio (δ18O and δ13C) analyses in sagittal otoliths of sockeye salmon (Oncorhynchus nerka) was tested by analyzing the seasonal and annual otolith zones of 44 samples collected from different localities in the northeast Pacific coast. The δ18O and δ13C values of these otoliths ranged from -14.23 to +1.62‰ and from -15.18 to -3.17‰, respectively. The δ18O variations can be divided into two stages from freshwater (-14.2 to -2.5‰) to marine (-2.5 to +1.6‰) that were consistent with the life history of sockeye salmon from juvenile to adult stages. The transition occurred after age 1, during which the timing of seaward migration of smolts was different. The marine component of the isotope variation in sockeye salmon otoliths (ages &gt; 2) was uniform but showed a consistent and strong shift towards oceanic changes around 1996. Thus, δ18O and δ13C values of otoliths can be potentially used as a chemical tracer in population identification, and their marine portions can be used in the study of ocean environmental changes.