Salmon and jellies and herring, oh my! Abiotic and biotic-dependent trends in abundance and distribution of pelagic critters in Skagit Bay across 17 years

As a large fjord, the Salish Sea exhibits strong spatiotemporal variation in temperature and salinity due to various marine and freshwater inputs. These patterns are particularly evident in Skagit Bay where water conditions are influenced by marine inputs from Deception Pass and Saratoga Passage and seasonal pulses of fresh water from Skagit River. We investigated how abundance and community composition in pelagic surface waters of Skagit Bay varied from 2001-2017, and how temperature and salinity patterns can influence which species predominate in particular years. Data come from long-term monitoring of Skagit Bay using a Kodiak surface trawl that sweeps the uppermost 10 feet of the water column. We evaluated how temperature and salinity influenced species abundance and distribution and tested whether distributions were likely influenced by biotic interactions (e.g. predation, competition), focusing on diadromous species (e.g., salmon, lamprey, starry flounder), forage fish (e.g., Pacific herring, surf smelt, Pacific sandlance), and gelatinous zooplankton (e.g., ctenophores, scyphozoan and hydrozoan medusae). Our results provide evidence for strong abiotic structuring and weaker effects from biotic interactions, although certain species appeared to interact more than others. These results may help us understand how long-term increases in regional and local temperatures and freshening waters will affect Salish Sea ecology

Comparing marine survival among Chinook and coho salmon and steelhead trout in the Salish Sea

Recent work on marine survival in Chinook and coho salmon and steelhead trout has shown a decline in marine survival in the Salish Sea that was not evident in other regions. For Chinook, the decline was not explained well by oceanographic patterns, and for coho, regional-scale patterns were suggested as important in understanding survival. Recent work on the development of indicators of Puget Sound steelhead survival has shown that predator abundance and patterns in hatchery releases, as well as oceanographic conditions are informative in predicting marine survival. While the three species of focus for the Salish Sea Marine Survival Project have different life-histories, and are therefore subjected to variable pressures at multiple scales, this current analysis aims to answer three questions: 1.) Are there similarities in survival trends among the three species? 2.) Do regional patterns in survival emerge when survival trends are evaluated concurrently across the three species? 3.) Does release strategy (yearling or subyearling) confer a survival advantage, and if so, is this consistent across all species? To evaluate survival time series, we used multivariate time series analysis with multiple groupings (species, spatial, and release strategy) to identify commonalities among species. Observed commonalities will aid in the development of indicators of marine survival for coho and Chinook by focusing efforts on appropriate spatial or temporal attributes. A hypothesis-driven approach similar to that employed for the development of indicators for steelhead survival will be used to relate coho and Chinook to environmental, biological, and anthropogenic factors influencing survival

Introduction

Introduction to the assessing, planning and adapting to climate change Impacts in Skagit River watershed session of the Salish Sea Conference

Reconstructing historical patterns of primary production in Puget Sound using growth increment data from shells of long-lived geoducks (Panopea generosa)

Bottom-up hypotheses predict that changes in primary production affect marine survival of species like Pacific salmon. Long term records of primary production would provide important data to test these predictions. However, direct observations of primary production (in situ fluorometers, water chemistry, and satellite observations of color back-scatter) have relatively short time series (\u3c 30 years). We investigated whether growth increments of geoduck clams (Panopea generosa) are correlated with primary production in different sub-basins of greater Puget Sound. Geoduck are long-lived (older specimens live \u3e100 years), widely distributed throughout the Salish Sea, and deposit annual growth rings in their shells. Shell samples from aged geoducks were by the Washington Department of Fish and Wildlife in four sub-basins within greater Puget Sound (Strait of Jan de Fuca, Southern Strait of Georgia, South Puget Sound, and Central Basin). Geoduck shells from Saratoga passage were provided by the Tulalip Tribe. Using growth indices, the known correlation of growth indices with sea surface temperature and other long-term measurements, and existing basin-level records of temperature and primary production, we modeled historical patterns of primary production in different regions of greater Puget Sound. Analyses show that the relationship between geoduck growth, temperature, and primary production varies between sub-basins, and stable isotope analysis suggests that geoducks may be more than just primary consumers. These issues make reconstruction of a historical record of primary production from growth increments challenging. Nevertheless, analyses suggest that residual growth (after accounting for temperature variation) can explain variation in annual marine survival of local coho and chinook salmon stocks. This indicates the method has promise for retrospective hypothesis testing

Density-dependent and landscape effects upon estuary rearing in Chinook salmon: insights from long-term monitoring in four Puget Sound estuaries

Juvenile Chinook salmon are well known for utilizing estuarine habitats within the tidal delta for rearing during outmigration. Several studies have linked population responses to availability of estuary habitat, and support the hypothesis that estuarine habitats are vital rearing areas for juvenile Chinook salmon. However, these coarse-scale studies provide little insight on how specific estuarine habitats contribute to rearing potential for salmon. We integrate long-term monitoring data from four estuaries of Puget Sound (Nooksack, Skagit, Snohomish, and Nisqually) to examine whether 1) Chinook populations in these rivers are limited by restricted estuary habitat, 2) hatchery releases can influence density dependent relationships in estuaries, 3) highly connected sites support higher densities of salmon, and 4) different habitat types support higher rearing densities of Chinook salmon. Across sampling locations within estuary systems, average annual rearing densities varied over four orders of magnitude. We found strong support for density dependence, habitat type, landscape connectivity, and hatchery release numbers influencing rearing densities, although all factors were not necessarily as important within each system, and effects of habitat type were particularly variable. Further work using bioenergetics models suggest that habitat-dependent variation in temperature can strongly influence growth in different systems, and that multiple habitats are likely important to provide suitable habitat for extended estuary rearing. These analyses are useful for determining the relative contribution of connectivity, cohort population size, and local habitat conditions for growth potential of Chinook salmon using estuarine habitats at early life stages, and shed light on likely impacts of climate change upon rearing conditions

Trophic structure of pelagic fish and jellyfish across spatial and seasonal gradients in the greater Puget Sound

Recent analysis of community structure in the pelagic ecosystem of the greater Puget Sound has revealed a shift in species composition and abundance in some areas from those dominated by fish to those dominated gelatinous mesozooplankton (“jellyfish”). Unfortunately, the mechanisms behind these shifts are unclear due to a deficit of ecological understanding of this system. The analysis of foodweb structure, which reflects the flow of carbon and nutrients, is useful to complement composition and abundance information in order to understand the energetic processes underlying pelagic communities and why they may be changing. In this talk, we examine foodweb structure and trophic ecology of middle trophic level pelagic fish and jellyfish in six oceanographic sub-basins in Puget Sound from April to October 2011. Specifically, we assessed spatial and seasonal variation in 1) the isotopic composition of abundant species of salmonids, forage fish and jellyfish, 2) the trophic overlap between fish and jellyfish and 3) foodweb attributes of whole pelagic communities including niche width, trophic length and basal resource diversity. At the species level, there were strong spatial differences in isotopic composition among sub-basins. Seasonal patterns, possibly suggesting ontogenetic diet shifts or changes in basal carbon sources, were also evident but were more pronounced in fish than jellyfish. The degree of trophic overlap between fish and jellyfish varied among sub-basins and generally decreased seasonally. At the community level, overall community niche width was higher in Whidbey basin in spring and summer months then switched to a north-south gradient in fall months with the highest value in South Sound. Both the trophic length and basal resource diversity exhibited contrasting seasonal patterns among basins with values decreasing seasonally in northern basins (Whidbey and Rosario) and increasing in southern basins (Central and South Sound). Taken as a whole, our observations suggest that the trophic ecology and overall structure of pelagic fish and jellyfish are heavily influenced by local processes at the sub-basin scale as well as temporally dynamic biotic processes such as changes in body size. Our analysis provides an important groundwork to understand how Puget Sound’s pelagic ecosystem is structured and why it may be changing

Temporal and spatial variation in springtime ichthyoplankton assemblages in Puget Sound: the search for an ecological baseline

Our knowledge of historical baselines for many marine fisheries is scant, making it difficult to determine the extent of change in commercial and non-commercial stocks alike. Providing a unique glimpse at entire communities and relatively easy to sample, ichthyoplankton surveys are a valuable tool for assessing change in populations. Our study evaluates the degree of spatial and temporal variation in larval fish assemblages across the sub-basins of Puget Sound by comparing historical and current surveys. Historical data for comparison was drawn from a study in 1967 conducted throughout the sub-basins (Waldron 1972). Larval fish were also collected in April of 2011, using a combination of horizontal and vertical tows, at 77 sample sites across a similar spatial extent. Although densities were fairly constant in both studies, we found a region-wide decrease in the density of previously dominant families, most notably in Merluccidae (hake) and Gadidae (cod) which experienced a 98% and 85% decrease, respectively, as well as the total disappearance of smaller, poorly understood families like Cyclopteridae (lumpsuckers). Within sub-basins, a substantial change at a compositional level was observed, shifting away from few, dominant families to more diverse assemblages. These findings reflect significant temporal and spatial changes in ichthyoplankton assemblages over the past 44 years that parallel changes in commercial harvest practices. When examined alongside coastal larval data over the same time frame, we found coastal stocks do not follow trends observed in Puget Sound in terms of changes in species composition or disappearances. In demonstrating the value of larval studies as a tool to assess long-term composition and density changes, we call for additional efforts to describe and monitor larval fish densities in Puget Sound to better our understanding of adult population dynamics

Potential for ecological nonlinearities and thresholds to inform Pacific salmon management

AbstractEcology is often governed by nonlinear dynamics. Nonlinear ecological relationships can include thresholds—incremental changes in drivers that provoke disproportionately large ecological responses. Among the species that experience nonlinear and threshold dynamics are Pacific salmon (Oncorhynchus spp.). These culturally, ecologically, and economically significant fishes are in many places declining and management focal points. Often, managers can influence or react to ecological conditions that salmon experience, suggesting that nonlinearities, especially thresholds, may provide opportunities to inform decisions. However, nonlinear dynamics are not always invoked in management decisions involving salmon. Here, we review reported nonlinearities and thresholds in salmon ecology, describe potential applications that scientists and managers could develop to leverage nonlinear dynamics, and offer a path toward decisions that account for ecological nonlinearities and thresholds to improve salmon outcomes. It appears that nonlinear dynamics are not uncommon in salmon ecology and that many management arenas may potentially leverage them to enable more effective or efficient decisions. Indeed, decisions guided by nonlinearities and thresholds may be particularly desirable considering salmon management arenas are often characterized by limited resources and mounting ecological stressors, practical constraints, and conservation challenges. More broadly, many salmon systems are data‐rich and there are an extensive range of ecological contexts in which salmon are sensitive to anthropogenic decisions. Approaches developed to leverage nonlinearities in salmon ecology may serve as examples that may inform analogous approaches in other systems and taxa

Climate vulnerability assessment for Pacific salmon and steelhead in the California Current Large Marine Ecosystem.

Major ecological realignments are already occurring in response to climate change. To be successful, conservation strategies now need to account for geographical patterns in traits sensitive to climate change, as well as climate threats to species-level diversity. As part of an effort to provide such information, we conducted a climate vulnerability assessment that included all anadromous Pacific salmon and steelhead (Oncorhynchus spp.) population units listed under the U.S. Endangered Species Act. Using an expert-based scoring system, we ranked 20 attributes for the 28 listed units and 5 additional units. Attributes captured biological sensitivity, or the strength of linkages between each listing unit and the present climate; climate exposure, or the magnitude of projected change in local environmental conditions; and adaptive capacity, or the ability to modify phenotypes to cope with new climatic conditions. Each listing unit was then assigned one of four vulnerability categories. Units ranked most vulnerable overall were Chinook (O. tshawytscha) in the California Central Valley, coho (O. kisutch) in California and southern Oregon, sockeye (O. nerka) in the Snake River Basin, and spring-run Chinook in the interior Columbia and Willamette River Basins. We identified units with similar vulnerability profiles using a hierarchical cluster analysis. Life history characteristics, especially freshwater and estuary residence times, interplayed with gradations in exposure from south to north and from coastal to interior regions to generate landscape-level patterns within each species. Nearly all listing units faced high exposures to projected increases in stream temperature, sea surface temperature, and ocean acidification, but other aspects of exposure peaked in particular regions. Anthropogenic factors, especially migration barriers, habitat degradation, and hatchery influence, have reduced the adaptive capacity of most steelhead and salmon populations. Enhancing adaptive capacity is essential to mitigate for the increasing threat of climate change. Collectively, these results provide a framework to support recovery planning that considers climate impacts on the majority of West Coast anadromous salmonids

Landmark geometry and identity controls spatial navigation in rats

In three experiments, a new reference memory procedure was used to examine how male rats search for consistently located food in a cue-controlled spatial environment. The animals searched the tops of 24 poles for six hidden baits in an enclosed circular arena containing a fixed configuration of six object landmarks. In Experiment 1, acquisition was faster and overall performance better for the consistent group (lO rats), in which the six baited poles were fixed relative to the landmarks for each session, than for the random group (4 rats), in which baited poles were randomly configured, Cue-control tests and computer simulations suggested that the consistent group relied on the landmarks to directly go to the baited poles, whereas the random group used them to employ a response strategy for searching the arena. Experiments 2 and 3 revealed that the number, identity, and geometric configuration of the landmarks were important to the consistent group's search performance, Overall, these results are most consistent with the use of a geometric representation by male rats which includes information about both the identity and the relative geometry of discrete landmarks in the surrounding spatial environment. In searching for food, many animals demonstrate an accurate working knowledge oftheir surrounding environment. Two general questions have been of interest in the investigation of this spatial behavior: What stimuli in the environment govern this behavior, and how are these stimuli encoded and used by animals for navigation? Although research addressing these basic questions has in