Kylie L Scales

Juvenile salmon Oncorhynchus spp. experience variable mortality rates during their first few months in the ocean, and high growth during this period is critical to minimize size-selective predation. Examining links between the physical environment and foraging ecology is important to understand mechanisms that drive growth. These mechanisms are complex and include interactions among the physical environment, forage availability, bioenergetics, and salmon foraging behavior. Our objectives were to explore how seascape features (biological and physical) influence juvenile Chinook salmon O. tshawytscha foraging at annual and feeding-event scales in the California Current Ecosystem. We demonstrate that forage abundance was the most influential determinant of mean salmon stomach fullness at the annual scale, while at the feeding-event scale, fullness increased with greater cumulative upwelling during the 10 d prior and at closer distances to thermal fronts. Upwelling promotes nutrient enrichment and productivity, while fronts concentrate organisms, likely resulting in available prey to salmon and increased stomach fullness. Salmon were also more likely to consume krill when there was high prior upwelling, and switched to non-krill invertebrates (i.e. amphipods, decapods, copepods) in weaker upwelling conditions. As salmon size increased from 72-250 mm, salmon were more likely to consume fish, equal amounts of krill, and fewer non-krill invertebrates. Broad seascape processes determined overall prey availability and fullness in a given year, while fine- and meso-scale processes influenced local accessibility of prey to individual salmon. Therefore, processes occurring at multiple scales will influence how marine organisms respond to changing environments.

Shark-control nets pose an entanglement risk to East Australian humpback whales during their annual northward and southward migrations between the Southern Ocean and the Coral Sea. Rates of whale entanglement exhibit seasonal and interannual variation, suggesting that an understanding of the influence of variability in the broad-scale physical environment along the migratory route would be useful in assessing risk of entanglement. This study provides a quantitative spatio-temporal analysis of the probability of whale entanglement in shark-control nets relative to the position and characteristics of the East Australian Current (EAC), the dominant oceanographic feature of the region. We use satellite-derived sea-surface temperature, and outputs from a data-assimilating ocean model, to develop multivariate, data-driven algorithms for detecting the edge of the EAC using Principal Components Analysis. We use outputs from these algorithms to model the likelihood of humpback entanglements in South-east Queensland. We find that the likelihood of entanglement increases when the EAC edge is locally less structured and closer to shore in the vicinity of the corresponding net, or when the EAC is well resolved over the entire study domain. Our results suggest that migrating humpbacks use the gradient in physical characteristics that marks the EAC inner edge as a navigational aid. Thus, when the EAC inner edge encroaches on the coast, the whales' migration range is compressed into nearshore waters, increasing the risk of entanglement. Our findings can help predict periods of elevated entanglement risk, which could underpin a more data-driven approach to the management of shark-control programs, and other activities that involve static fishing gear.

The rapid pace of environmental change in the Anthropocene necessitates the development of a new suite of tools for measuring ecosystem dynamics. Sentinel species can provide insight into ecosystem function, identify hidden risks to human health, and predict future change. As sentinels, marine apex (top) predators offer a unique perspective into ocean processes, given that they can move across ocean basins and amplify trophic information across multiple spatiotemporal scales. Because use of the terms "ecosystem sentinel" and "climate sentinel" has proliferated in the scientific literature, there is a need to identify the properties that make marine predators effective sentinels. We provide a clear definition of the term "sentinel", review the attributes of species identified as sentinels, and describe how a suite of such sentinels could strengthen our understanding and management of marine ecosystems. We contend that the use of marine predators as ecosystem sentinels will enable rapid response and adaptation to ecosystem variability and change.

Advances in ocean observing technologies and modeling provide the capacity to revolutionize the management of living marine resources. While traditional fisheries management approaches like single-species stock assessments are still common, a global effort is underway to adopt ecosystem-based fisheries management (EBFM) approaches. These consider changes in the physical environment and interactions between ecosystem elements, including human uses, holistically. For example, integrated ecosystem assessments aim to synthesize a suite of observations (physical, biological, socioeconomic) and modeling platforms (ocean circulation models, ecological models, short-term forecasts, management strategy evaluations) to assess the current status and recent and future trends of ecosystem components. This information provides guidance for better management strategies. A common thread in EBFM approaches is the need for high-quality observations of ocean conditions, at scales that resolve critical physical-biological processes and are timely for management needs. Here we explore options for a future observing system that meets the needs of EBFM by i) identifying observing needs for different user groups, ii) reviewing relevant datasets and existing technologies, iii) showcasing regional case studies, and iv) recommending observational approaches required to implement EBFM. We recommend linking ocean observing within the context of GOOS and other regional ocean observing efforts with fisheries observations, new forecasting methods, and capacity development, in a comprehensive ocean observing framework.

Environmental Impact Assessments (EIAs) are at the frontline of balancing economic, societal and environmental needs. With the world expected to invest around $90 trillion in infrastructure in the next 15 years, resulting in more new infrastructure than is currently in existence globally (Jan Corfee-Morlot et al., 2016), there has never been a more critical time for EIAs to get it right. Yet even in Australia, a wealthy, economically and politically stable nation with multiple environmental laws and comparatively effective governance, environmental legislation has failed to effectively protect wildlife (McDonald et al., 2015). By and large, the same story holds true worldwide (Laurance, 2018a). For some species, current failings to halt their trajectory toward extinction have been directly linked to inappropriate EIAs (Reside et al., 2019).