Fish and Wildlife Responses to Prolonged Heatwaves: A Window to the Future?

Prolonged periods of anomalously warm temperatures are increasing in frequency, intensity, and duration world-wide. These events can have far-reaching influence on food webs from primary producers to predators and operate over wide temporal and spatial scales. For example, the NE Pacific marine heatwave of 2014–2016 was an unusually strong (Category III) and lengthy (24 mo.) heatwave spanning at least 3 large marine ecosystems: Bering Sea, Gulf of Alaska, and California Current. Mass mortality events and reproductive failures of seabirds and marine mammals provided some dramatic indications of ecosystem perturbation, but effects of the heatwave were also noted in the abundance and biology of phyto- and zooplankton communities, some species of forage fish, salmon, and groundfish, including >70% decline in Pacific cod. Understanding how fish and wildlife populations respond to these events allows us to identify key ecosystem relationships affected by warming, re-evaluate current assumptions embedded in ecosystem models, and provides a window to future conditions that may guide management strategies. This session provides an opportunity to describe observations, discuss linkages among taxa, and consider the risks posed by prolonged heatwaves to fisheries, wildlife, and economies. Those studying similar phenomena in freshwater and terrestrial ecosystems are also encouraged to participate.

8:20AM Understanding the Effects of a Prolonged Marine Heatwave on Biota in the California Current
  Ric Brodeur
The Northern California Current is a highly productive region that has undergone substantial interannual and decadal-scale variability in recent decades. Forage taxa play a central role in the transfer of energy from lower to higher trophic levels. Ocean conditions may influence this energy pathway in the northern California Current (NCC) ecosystem. The recent unprecedented prolonged warming in the NCC provided unique opportunities to examine connections between ocean conditions and forage taxa abundance and distribution patterns and feeding. Findings from several studies that suggest that the recent warming period associated with the ‘Warm Blob’ and El Niño affected zooplankton and forage fishes over the last several years resulting in dramatic changes in species composition and phenology. Food habits of forage fishes examined from June during recent warm years compared to previous average or cool years varied significantly between these periods. Crustaceans were the main prey items of the forage fishes in cool years, but gelatinous zooplankton were consumed in higher quantities in warm years. This substantial reorganization of the pelagic forage community has the potential to lead to major alterations in trophic functioning in this normally productive ecosystem, which were exhibited in reproductive failures and decreased productivity of top predators.
8:40AM Life on the Edge: The Phenological Response of a Critical-Endangered Fish to a Rapidly Changing Climate
  Christian Denney, Malte Willmes, Levi Lewis, Wilson Xieu, Rachel Fichman, Feng Zhao, James Hobbs
Climate change is causing ever greater variability in the frequency of floods, droughts, and heat waves, however less attention has been focused on estuaries and freshwaters which could be even more sensitive to climate change than other ecosystems. Delta Smelt (Hypomesus transpacificus) is a small endemic estuarine species nearing extinction in the wild due to a variety of factors such as loss of habitat, reduction in freshwater flows, changing food webs, and entrainment into water diversions. Climate change is likely to exacerbate these problems and lead to new challenges for the management of this imperiled species. In this study we documented changes to the estuarine thermal regime over the last 20-years, including a period of extreme heat wave in 2014 and 2015, causing Delta Smelt to reproduce earlier and contributing to a miss-match with prey and decreased recruitment. Furthermore, using a 20-year otolith dataset, we’ve documented an effect of early warming on the dispersal history causing fish to shift habitat use towards areas of the estuary with cooler temperatures but less food. Combined, these changes appear to be pushing the species ever closer to extinction, and emphasize the need to consider thermal management strategies in future conservation efforts
9:00AM Extreme Reduction in Nutritional Value of a Key Forage Fish during the Pacific Marine Heatwave of 2014–2016
  Vanessa R. von Biela, Mayumi Arimitsu, John Piatt, Brielle Heflin, Sarah Schoen, Jannelle Trowbridge, Chelsea Clawson
Pacific sand lance (Ammodytes personatus) are a key forage fish in the North Pacific for many predators and have historically been important in relatively warm years. However, extreme declines in the nutritional value of sand lance in Prince William Sound, Alaska, during 2012–2016 indicate that energy transfer from lower trophic levels to predators may have been disrupted during the North Pacific marine heatwave in 2015 and 2016. Nutritional value (length, energy density, and whole-body energy) was measured in age-1 sand lance collected during July in cool (2012–2013) and increasingly warm (2014–2016) years. The value of age-1 fish significantly declined in 2015, and by 2016 they were 38% shorter and 13% lower in energy density compared to cooler years. This contributed to significant declines in whole body energy of 44% in 2015 and 89% in 2016 compared to cooler years (2012–2014). The 2015 sand lance cohort experienced little growth or lipid accumulation from July 2015 at age-0 to July 2016 at age-1. This effective disruption of energy through pelagic food webs probably contributed to population declines and/or breeding failures observed among several predators in the Gulf of Alaska and suggests tipping points were reached during the heatwave.
9:20AM Mass Mortality and Breeding Failure of Seabirds during and after the 2014-2016 Marine Heat Wave
  John Piatt, Mayumi Arimitsu, Sarah Schoen, Vanessa R. von Biela, Julia K. Parrish, Heather Renner
More than 60,000 common murres, the dominant breeding seabird of the Northern Hemisphere, washed ashore between summer 2015 and spring 2016 along the west coast of North America. Starvation was the apparent cause of most mortality. Total mortality was centered in the Gulf of Alaska and likely exceeded one million birds. In addition, breeding failures were observed at colonies in the region before and for years after the mass mortality. The magnitude of these events is globally unprecedented and was associated with the northeast Pacific marine heat wave that developed during winter 2014 and intensified through 2015-2016. This prolonged heating apparently increased metabolic demands of ectothermic forage fish but reduced primary production and restructured zooplankton communities in favor of lower calorie species, thereby reducing the quality and abundance of forage fish to seabirds. At the same time, the metabolic rates of large ectothermic groundfish increased, thereby increasing competition with seabirds and mammals. Together, these bottom-up and top-down forces created an “ectothermic vise” on forage fish leading to a system-wide scarcity of food and mass mortality of murres and at least eight other upper-trophic-level fish, bird and mammal species in the region during 2014-2017.
09:40AM Break
1:10PM How “the Blob” Affected Groundfish Distributions in the Gulf of Alaska
  Qiong Yang, Edward Cokelet, Phyllis Stabeno, Lingbo Li, Anne Hollowed, Wayne Palsson, Nick Bond, Steve Barbeaux, PhD
We investigated the distributional shifts of groundfish in response to the recent anomalously warm period (2014–2016;“The Blob”), based on ten Gulf of Alaska (GOA) bottom trawl surveys during 1996–2015. Six groundfish species were considered: Pacific cod, arrowtooth flounder, walleye pollock, Pacific ocean perch, northern rock sole, and southern rock sole. Our study demonstrated that after accounting for size‐specific depth preferences, the spatial responses of groundfish to anomalous ocean conditions differed by species and foraging guild in the central GOA. Pacific cod and arrowtooth flounder showed similar responses to ocean warming, but different responses to cooling. In general, Pacific cod moved to deeper depths in warmer years and moved to shallower depths in colder years. Arrowtooth flounder also moved deeper in warmer years. However, in colder years, large arrowtooth flounder (>40 cm) shifted toward shallower depths while smaller‐sized fish shifted toward deeper depths. In warmer years, large pollock (>30 cm) moved to deeper waters while smaller pollock (10–20 cm) moved to shallower waters. Pacific ocean perch exhibited an opposite response to thermal changes in habitat. They moved deeper in colder years, but there was no clear change in depth as a function of size in response to warmer habitat.
1:30PM The 2014–2016 Gulf of Alaska Marine Heatwave and the Cod Crisis That Followed
  Steve Barbeaux, PhD, Stephani Zador, Kirstin Holsman
The 2014–2016 marine heatwave in the eastern North Pacific Ocean triggered changes in ecosystem productivity in the Gulf of Alaska (GOA). The marine heatwave was noteworthy in its geographical extent, depth range, and persistence, with evidence of shifts in species distribution and reduced productivity of lower-trophic and upper-trophic organisms. In 2017 groundfish surveys indicated that GOA Pacific cod (Gadus macrocephalus) experienced a greater than 70% decline in abundance from 2015. The GOA Pacific cod fishery supports 29% of the total groundfish harvest in the GOA ($103 million). In this study, we demonstrate that an increase in metabolic demand during the heatwave as well as a reduced prey supply explains the decline in abundance. Although increased mortality likely led to the decline, historically low recruitment concurrent with the heatwave portends a slow recovery for the stock and gives a preview of impacts facing this region due to climate change. We evaluate the intersection of climate change with ecosystem-based fisheries management in context of GOA Pacific cod with a description of the sensitivities of the ecosystem, how changes in the ecosystem affected the Pacific cod stock, and a description of how the management system in the North Pacific handled this shock.
1:50PM Declining Abundance, Reproduction, Calf Survival, and Body Condition in Humpback Whales during and after the North Pacific Marine Heatwave
  Janet Neilson, Christine Gabriele, Mayumi Arimitsu
Migratory humpback whales forage seasonally on small schooling fish and zooplankton in Glacier Bay and Icy Strait in southeastern Alaska. The National Park Service has conducted annual individual identification-based population monitoring since 1985. The longevity and consistency of this study offer a unique opportunity to examine this population’s response to the recent North Pacific marine heatwave. This population increased at ~5%/yr and peaked in abundance in 2013. In 2014-2018 we documented abrupt declines in abundance, reproduction, calf survival, site fidelity, and body condition coinciding with the onset of the marine heatwave. By 2018, 1) abundance had declined by 58%; 2) we documented total reproductive failure for the first time in this 34-year study; 3) many (56%) of the whales with uninterrupted site fidelity in 2004-2013 were missing; and 4) 17% of the remaining whales appeared abnormally thin. We also documented changes in forage fish abundance and body condition in the region during 2018. For example, key whale prey species had significantly lower body condition in 2018 than in previous years. Our findings are consistent with humpback whale declines elsewhere in the North Pacific and indicate that significant and lasting changes in the whales’ prey base began during the heatwave.
2:10PM Understanding Population-Level Changes and Response to Ecosystem Perturbations: Humpback Whale Monitoring during the North Pacific Marine Heatwave
  Janice Straley, John Moran, Robert Suryan, Mayumi Arimitsu, Christine Gabriele, Janet Neilson, Rachel Cartwright
After decades of population growth following commercial whaling, some populations of humpback whales were delisted from the Endangered Species Act in 2016. To establish baseline indices for monitoring during the 10-year post-delisting period, we collected photographic mark-recapture data to assess trends in abundance, calf production, spatial and temporal distribution of the whales. We also evaluated prey abundance, composition, and body condition. We documented low numbers of calf sightings, “skinny” whales, and shifts in distribution, suggesting that whales feeding in the Gulf of Alaska may be ending decades of rapid population growth. Additionally, whale researchers on the Hawaiian wintering grounds recently reported a reduction in the number of whales and calves observed. These declines were most pronounced during a marine heatwave in the Alaskan feeding grounds and was coincident with decreased abundance and body condition of key forage species including krill, capelin, herring, and sand lance. The complexity of ecosystem variability under a changing climate highlights the importance of creating monitoring programs as a tool to reliably detect population level changes, and distinguish long-term trends from temporary ecosystem perturbations. We recommend the use of similar low-cost rapid assessment tools for successful management of both listed and recently delisted humpback whale populations.
2:30PM Adaptative Response to an Ecological Perturbation in the Dungeness Crab Fishery
  Mary Fisher, Stephanie Moore, Sunny Jardine, Briana Abrahms, Jameal Samhouri
The massive harmful algal bloom that occurred during the recent Pacific marine heatwave closed the Dungeness crab fishery for up to five months. These closures, implemented during the 2015-16 fishing season, had widespread socioeconomic impacts on fishery-dependent communities along the US West Coast. Characterizing fishers’ adaptive responses to the 2015-16 closures can provide insights into the resilience of the fishery to future ecological perturbations. We evaluated adaptive behavior as shifts in fishery participation and Dungeness crab fishing strategies, using landings-based connectivity networks and vessel monitoring system data. We constructed connectivity networks for West Coast port groups for each Dungeness crab fishing season, from 2008 to 2016. Each season was further split into an immediate and a latent response period. We then used a generalized linear model to quantify the marginal effects of the 2015-16 closures on network structural metrics related to resilience. Changes in Dungeness crab fishing strategies were observed in de novo communities of fishing vessels, clustered according to a pre-2015 baseline of Dungeness crab trip characteristics. Dungeness crab fishing trips after the 2015-16 season re-opened were then compared to this baseline. We interpret our results in the context of economic models and survey data on the 2015-16 season.
2:50PM Refreshment Break
3:20PM Quantifying and Predicting Fisher Responses to Environmentally-Linked Fishery Closures
  Kate Richerson, Dan Holland, Jerry Leonard
The increasing variability of marine systems, including marine heatwaves, is likely to lead to changing fisheries productivity. Such changes are likely to lead not only to direct impacts within a fishery but to economic and ecological effects on other fisheries if there is substantial cross-participation by fishers. We use data from the US West Coast salmon troll fishery before, during, and after large-scale closures to examine how altered resource availability influences the behavior of fishing vessels in heterogeneous ways. We find that vessels are less likely to participate in fishing of any type during the closure, and that closures may lead to fishers permanently exiting the fishery. In spite of a high level of cross-participation, we find limited evidence that vessels increase their participation in other fisheries to offset lost salmon revenue, indicating a limited ability to buffer against reduced salmon availability. We use data from the 2018 partial fishery closure associated with a recent marine heat wave and an input-output model to test whether behavioral models can predict economic impacts of fishery closures. We find that accounting for conditions in other fisheries, particularly the Dungeness crab fishery, may be important in prediction.
3:40PM The Challenges of Complex Environmental Problems
  Lianne Ball
Decision analysis and policy science provide avenues for assessing challenges and developing realistic management options for a new type of environmental problem facing natural resource managers, industries, local communities, and society writ large. Recent marine heat waves have provided us a glimpse into a global complex problem that spans multiple systems and contains complicated inter-dependencies. This type of problem is not within the purview of a single agency, does not fall under an existing regulatory net, nor is captured within existing policy. Phenomena of this scope are public policy challenges in addition to being scientific problems. They require us to struggle with interlocking decisions about conservation, harvest, business, and ultimately global food availability. Stakeholders will have to cooperate in new ways at multiple levels to gain a better understanding of such problems, how they might be approached, and how to identify and facilitate what may be only limited options. The nature of these problems, which includes other challenges such as global poverty, drug trafficking, and political security, is that there will be no magic bullet to solve them, but there may be a path forward.
4:00PM Discussion

Organizers: Vanessa R. von Biela, John Piatt, Mayumi Arimitsu, Lianne Ball

Location: Reno-Sparks CC Date: October 3, 2019 Time: 8:20 am - 5:00 pm