Advances in Understanding the Drivers of Change and Potential Conservation Actions for Pacific Herring in the Salish Sea

Advances in Understanding the Drivers of Change and Potential Conservation Actions for Pacific Herring in the Salish Sea This session offered the latest results from researchers in the USA and Canada based upon cutting-edge approaches to understanding what limits Pacific herring populations in the Salish Sea, which are in decline in many places, and what management actions can be taken to ensure their recovery and conservation. Margaret (Megsie) Siple described the importance of population diversity in Pacific herring for maintaining their overall stability (i.e., portfolio effects), and presented population model results showing increased adult mortality and age truncation (i.e., loss of older ages) over recent decades. Lorenz Hauser showed the most recent genetic microsatellite support for metapopulation structure in Puget Sound herring, i.e., subpopulations going extinct and recolonizing, driven by a combination of spawn timing and geographic distance, potentially with learned social migration behavior. Herring genetic diversity based upon spawn timing was further supported by Eleni Petrou’s work; Petrou used an advanced restriction site-associated (RAD) sequencing approach to determine that genetic differentiation increases with difference in spawn timing. Petrou’s results also supported the idea that populations with similar spawn timing are connected by migration. Finally, two presentations shed new light on potential challenges to early life stages of herring. Brooke Love presented recent research showing that high temperatures result in larval mortality and abnormalities, while adding acidified conditions (high pCO2 levels) to high temperatures additionally led to respiratory difficulties, suggesting that both warming and acidification are factors that negatively affect herring development. Louisa Harding presented results showing for the first time that herring are also negatively impacted by stormwater runoff: inability to mobilize yolk energy stores, and cardiac stress when exposed to stormwater. Together, these results fill some major gaps in our understanding about limitations to recovery for herring in the Salish Sea, and suggest potential ways forward

Key factors influencing change in Pacific herring populations: a qualitative network model approach

Pacific herring are a foundational species in the Salish Sea, providing important cultural, social, economic, and ecological benefits throughout the ecosystem. While herring are common across the Salish Sea, patterns of their abundance in recent years vary spatially. Herring are subject to many factors that may influence their abundance and distribution, but there is no agreement on what the key factors are or, therefore, how to address local declines and support herring resilience. Here, we present results from a qualitative network model of the herring ecological system evaluating the relative support for the influence of different possible factors on herring populations in the Salish Sea. Expert elicitation and data synthesis were used to develop a conceptual model of herring, their food web, environmental drivers (including plankton), and hypotheses about key stressors on herring populations, including shoreline development, disease, predation, fishing, and prey limitation. Based on this conceptual model, a qualitative network model is developed, which directly connects ecosystem components using positive, negative, or neutral links. By simulating perturbations via an increase in one or more nodes, and comparing predicted outcomes to data observations, the model evaluates the relative support for each potential stressor, and multiple stressors in aggregate, as limiting factors for herring populations in the Salish Sea. By accounting for indirect effects and positive and negative feedbacks, the qualitative network model allows for comparisons between scenarios under which individual and multiple factors have direct impacts on herring at different life stages. This tool will thus identify which are the key factors linked to observed changes in the abundance and distribution of herring, and therefore what management actions can be taken to ensure the resilience of this critical resource

Synthesis of Results from Twelve Puget Sound Regulatory Effectiveness and Incentive Investigations

Between 2011 and 2014, the Puget Sound Marine and Nearshore Grant Program funded twelve projects relating to shoreline regulatory and incentive programs. Here we provide an overview of overarching themes that emerged from a review of the projects in aggregate. Despite the different approaches to problem identification, data collection, and analysis in these investigations, the conclusions reached and recommendations made are remarkably similar. Key findings and implications of our analysis relate to: (1) armoring compliance rates; (2) compliance monitoring methodologies; (3) local Shoreline Master Program (SMP) capacity limitations; (4) SMP implementation improvements; and (5) incentive programs to encourage the use of alternative shore protection techniques. This type of synthesis and analysis of program results is a critical component of adaptive management. Findings are being used to inform next steps for Puget Sound recovery efforts funded under the National Estuary Program

Biocomplexity in Pacific herring (Clupea pallasii) of Puget Sound, USA

Small-scale genetic and demographic diversity can stabilize populations on a larger scale. However, subpopulations of pelagic fish species can be difficult to distinguish. Here, we examine demographic diversity in 21 stocks of Pacific herring (Clupea pallasii) in Puget Sound, USA using a multivariate auto-regressive state-space (MARSS) model, and data from both acoustic surveys paired with trawls, and subtidal egg surveys to estimate population growth trends. Herring populations associated with individual spawning beaches are asynchronous, but share a common negative growth rate across the Puget Sound estuary. We found that both survey techniques observe the same underlying demographic processes, and that egg surveys are a more accurate estimator of total spawning biomass. We used states obtained from MARSS analysis to measure portfolio effects in Puget Sound herring, and found that the Puget Sound population as a whole is stabilized by the presence of several separate spawning subpopulations. Available environmental data was not sufficient to explain variations in spawning biomass; however, herring may respond to spawning site conditions that aren’t currently measured

Incorporating Science into the Environmental Policy Process: a Case Study from Washington State

The incorporation of science into environmental policy is a key concern at many levels of decision making. Various institutions have sought to standardize the protection of natural resources by requiring that decisions be made based on the best available science. Here we present empirical data describing the incorporation of best available science in the land-use policy process on a local scale. Results are based on interviews with planners and others who conducted scientific reviews associated with a Washington State Growth Management Act amendment that requires the inclusion of best available science in protecting critical areas. Our results show that jurisdictions varied with respect to how they included science in their land-use policies. Specifically, we found that smaller jurisdictions were very reliant on scientific information provided by state agencies, communicated frequently with other jurisdictions and agencies, and most often let scientific information guide the policy development process. Medium-sized jurisdictions, in contrast, were more inwardly focused, relied predominantly on local information, communicated little with outsiders, and more often looked to political influences to guide the policy process. Large jurisdictions, including most counties, often generated their own best science, communicated with and often informed state agencies and other jurisdictions, and more often considered science first during the policy development process. Jurisdictions also differed in terms of how best available science was defined, and how jurisdictions dealt with conflicting scientific information. Our results provide empirical evidence of the variation with which best available science is used in environmental policies

Effects of stochasticity on the length and behaviour of ecological transients

There is a growing recognition that ecological systems can spend extended periods of time far away from an asymptotic state, and that ecological understanding will therefore require a deeper appreciation for how long ecological transients arise. Recent work has defined classes of deterministic mechanisms that can lead to long transients. Given the ubiquity of stochasticity in ecological systems, a similar systematic treatment of transients that includes the influence of stochasticity is important. Stochasticity can of course promote the appearance of transient dynamics by preventing systems from settling permanently near their asymptotic state, but stochasticity also interacts with deterministic features to create qualitatively new dynamics. As such, stochasticity may shorten, extend or fundamentally change a system\u27s transient dynamics. Here, we describe a general framework that is developing for understanding the range of possible outcomes when random processes impact the dynamics of ecological systems over realistic time scales. We emphasize that we can understand the ways in which stochasticity can either extend or reduce the lifetime of transients by studying the interactions between the stochastic and deterministic processes present, and we summarize both the current state of knowledge and avenues for future advances

Age truncation and portfolio effects in Puget Sound Pacific herring

Forage fish undergo dramatic changes in abundance through time. Long-term fluctuations, which have historically been attributed to changes in recruitment, may also be due to changes in adult mortality. Pacific herring, a lightly exploited forage fish in Puget Sound, WA, have exhibited shifts in age structure and decreases in spawning biomass during the past 30 years. Here, we investigate changes in adult mortality as a potential explanation for these shifts. Using a hierarchical, age-structured population model, we indicate that adult natural mortality for Puget Sound Pacific herring has increased since 1973. We find that natural mortality has increased for every age class of adult (age 3+), especially age 4 fish, whose estimated mortality has doubled over the survey time period (from M=0.84 to M=1.76). We demonstrate that long-term shifts in mortality explain changes in age structure, and may explain biomass declines and failure to reach management thresholds for some spawning sites in Puget Sound. Temporal shifts in natural adult mortality could have negative implications for herring and herring predators. For predators, these implications include a reduction in the stability of the herring resource

Estimating the abundance of marine mammal populations

Support for this project was provided by the Lenfest Ocean Program.Motivated by the need to estimate the abundance of marine mammal populations to inform conservation assessments, especially relating to fishery bycatch, this paper provides background on abundance estimation and reviews the various methods available for pinnipeds, cetaceans and sirenians. We first give an “entry-level” introduction to abundance estimation, including fundamental concepts and the importance of recognizing sources of bias and obtaining a measure of precision. Each of the primary methods available to estimate abundance of marine mammals is then described, including data collection and analysis, common challenges in implementation, and the assumptions made, violation of which can lead to bias. The main method for estimating pinniped abundance is extrapolation of counts of animals (pups or all-ages) on land or ice to the whole population. Cetacean and sirenian abundance is primarily estimated from transect surveys conducted from ships, small boats or aircraft. If individuals of a species can be recognized from natural markings, mark-recapture analysis of photo-identification data can be used to estimate the number of animals using the study area. Throughout, we cite example studies that illustrate the methods described. To estimate the abundance of a marine mammal population, key issues include: defining the population to be estimated, considering candidate methods based on strengths and weaknesses in relation to a range of logistical and practical issues, being aware of the resources required to collect and analyze the data, and understanding the assumptions made. We conclude with a discussion of some practical issues, given the various challenges that arise during implementation.Publisher PDFPeer reviewe

Robustness of potential biological removal to monitoring, environmental, and management uncertainties

Support for this project was provided by the Lenfest Ocean Program.The potential biological removal (PBR) formula used to determine a reference point for human-caused mortality of marine mammals in the United States has been shown to be robust to several sources of uncertainty. This study investigates the consequences of the quality of monitoring on PBR performance. It also explores stochastic and demographic uncertainty, catastrophic events, sublethal effects of interactions with fishing gear, and the situation of a marine mammal population subject to bycatch in two fisheries, only one of which is managed. Results are presented for two pinniped and two cetacean life histories. Bias in abundance estimates and whether there is a linear relationship between abundance estimates and true abundance most influence conservation performance. Catastrophic events and trends in natural mortality have larger effects than environmental stochasticity. Managing only one of two fisheries with significant bycatch leads, as expected, to a lower probability of achieving conservation management goals, and better outcomes would be achieved if bycatch in all fisheries were managed. The results are qualitatively the same for the four life histories, but estimates of the probability of population recovery differ.Publisher PDFPeer reviewe