Bristol Bay Research Articles

Body size as a leading indicator of run size and application to in-season forecasting of sockeye salmon in Bristol Bay, Alaska

Bristol Bay supports the world’s largest fishery for sockeye salmon which are harvested during an extremely condensed time period as fish return to their natal rivers. Uncertainties in preseason forecasts of run size challenge managers and the fishing community because of limited time to adapt strategies within a season. Preseason forecast errors from 2000 to 2023 were as large as 29%, with a mean absolute % error (MAPE) of 15%. We used autoregressive models including mean size-at-age of returning sockeye salmon, along with other environmental covariates, and weighted these models by the inverse of their MAPE to produce an ensemble in-season model that was subsequently weighted with preseason forecasts. This methodology improved forecasts of run size substantially earlier in the fishing season than currently possible and had an average MAPE of 12% (∼6 million fish), approximately 1 week into the fishing season. This level of error is not met by current in-season methods until approximately 2 weeks later after the season has peaked, and is better than current preseason methods in most years.

Reproductive potential of red king crab (Paralithodes camtschaticus) across warm and cold stanzas in Bristol Bay in southwestern Alaska: Supplementary Figure

Reproductive potential of red king crab (Paralithodes camtschaticus) across warm and cold stanzas in Bristol Bay in southwestern Alaska: Supplementary Figure

Reproductive potential of red king crab (Paralithodes camtschaticus) across warm and cold stanzas in Bristol Bay in southwestern Alaska: Supplementary Table

Reproductive potential of red king crab (Paralithodes camtschaticus) across warm and cold stanzas in Bristol Bay in southwestern Alaska: Supplementary Table

Reproductive potential of red king crab (Paralithodes camtschaticus) across warm and cold stanzas in Bristol Bay in southwestern Alaska

Reproductive potential of red king crab (Paralithodes camtschaticus) across warm and cold stanzas in Bristol Bay in southwestern Alaska

Shrinking suitable habitat of a sub-Arctic foundation kelp under future climate scenarios.

Climate change has profound effects on the distribution of kelp forests in the Arctic and sub-Arctic. However, studies on the responses of kelps to climate change, particularly along the sub-Arctic regions of the Alaska coast, are limited. Eualaria fistulosa is a foundational kelp species in the Aleutian Islands, with an east-west distribution that extends from Japan to southern southwest Alaska. In this study, we utilized a species distribution model (SDM) to explore changes in the future habitat suitability of E. fistulosa under contrasting Shared Socioeconomic Pathway (SSP) scenarios. Our model exhibited relatively high predictive performance, validating our SDM predictions. Notably, the SDM results indicate that minimum sea surface temperature, annual range in sea surface temperatures, and annual mean current velocities are the three most important predictor variables determining E. fistulosa's distribution. Furthermore, the projected geographic distribution of Eualaria is generally consistent with its observed occurrence records. However, under high emission scenarios (SSP5-8.5), E. fistulosa is predicted to contract its distribution range by 9.0% by 2100, with widespread disappearance along the southeast Alaskan coast and limited northward migration to Kamchatka Krai in Russia and Bristol Bay in Alaska. These findings contribute valuable insights for conservation strategies via addressing climate-induced alterations in sub-Arctic kelp distribution.

Predicting the distribution of red king crab bycatch in Bering Sea flatfish trawl fisheries

Declining Bristol Bay red king crab (BBRKC) abundance has triggered recent closures of this iconic Bering Sea fishery and raised interest in bycatch in non-directed fisheries as a possible conservation concern. One particular concern is the effectiveness of static closed areas for bycatch fisheries in an era of climate warming and widespread distribution shifts. However, spatial data for supporting management decisions concerning bycatch is lacking, as fisheries-independent data are collected only in the summer, and the relationship to BBRKC distribution in the fall/winter/spring, when most bycatch occurs, is unknown. We filled this information gap by using fishery-dependent data to build predictive models of BBRKC bycatch distribution in non-pelagic trawl groundfish fisheries in the data-poor seasons. We trained Boosted Regression Tree models for bycatch occurrence and abundance of four BBRKC sex-size/maturity categories, and evaluation metrics indicated good to excellent predictive ability across all models. We found that flatfish directed-fishery CPUE, summer survey CPUE for BBRKC and flatfish, and depth were important predictors for bycatch occurrence and abundance. Physical variables (ice cover and temperature) were generally less important. We also found strong correlations between the mean latitude of observed bycatch and the summer survey for BBRKC, highlighting the ability of summer survey data to predict non-summer bycatch distributions. BBRKC bycatch prediction is a tractable problem, and our results are the first step towards operating models that may be used to evaluate proposed management actions. We also conclude that northward shifts in fishery-independent and -dependent data suggest the possible value of reassessing decades-old static closure areas for managing BBRKC bycatch.

Seismic and Potential Field Constraints on Upper Crustal Architecture of Inner Bering Shelf, Offshore Southwestern Alaska

Southwestern Alaska encompasses a group of fault-bounded tectonostratigraphic terranes that were accreted to North America during the Mesozoic and Paleogene. To characterize the offshore extension of these terranes and several significant faults identified onshore, we reprocessed three intersecting multichannel deep seismic reflection profiles totaling ∼750 line-km that were shot by the R/V Ewing across part of the inner Bering continental shelf in 1994. Since the uppermost seismic section is often contaminated by high amplitude water layer multiples from the hard and shallow seafloor, the migrated reflection images are supplemented with high-resolution P wave velocity models derived by traveltime tomography of the recorded first-arrivals to depths of up to 2000 m. Additionally, other geophysical datasets such as seismicity, well logs, high resolution satellite-altimetry gravity, air-borne magnetics, ship-board gravity and magnetics, are also incorporated into an integrated regional interpretation. We delineate the offshore extension of the major mapped geological elements, including the Togiak fault (TGF), East Kulukak fault (EKF), Chilchitna fault (CF), Lake Clark fault (LCF), Togiak terrane (TT), Goodnews terrane (GT), Peninsular terrane (PT), Northern Kahiltna flysch (NKF) and Southern Kahiltna flysch (SKF) deposits, and the regional suture zone. The geophysical evidence from this study suggest that the major faults and terrane boundaries of southwestern Alaska, excluding the LCF, not only extend beneath the Bering shelf offshore but also appear to rotate, forming a trend parallel to the inactive Beringian margin. The LCF extends offshore but likely terminates in the northeastern part of the Bristol Bay basin. Additionally, the constraints from seismicity data indicates that while the major faults in southwestern Alaska exihibit some activity onshore, they remain dormant in the offshore region. These new findings will contribute to a better understanding of terrane accretion processes and existing fault models of southwestern Alaska.

Estimation of pop-up satellite archival tag initial surface position: applications for eastern Bering Sea crab research

BackgroundClimate change is reshaping Bering Sea crab distributions and recent population declines have elevated the urgency in understanding spatial dynamics in relation to management boundaries. While pop-up satellite archival tags (PSATs) can provide fishery-independent movement information, a high level of spatial resolution is needed to evaluate small-scale (i.e., 10 s of km) movements of crabs. Because PSATs drift at the surface prior to acquisition of a satellite-estimated location (via Argos), the accuracy of pop-up location (i.e., animal terminal position) estimates depends on the ability to accurately estimate drift error. We deployed PSATs (n = 36) on fixed-position moorings in Bristol Bay and Marmot Bay, Alaska to validate a new method to estimate tag pop-up location and an associated error ellipse that uses in situ drift data from surfaced tags to estimate drift error. Estimated pop-up location was compared to the location of tag surfacing (i.e., the tag’s fixed position) and to an alternative estimate (i.e., an early satellite-estimated location). Additional tags were deployed on mature male red king crab (Paralithodes camtschaticus) in Bristol Bay during 2020 (n = 84) and 2021 (n = 90) to compare estimates of tag drift error and crab displacement derived using the method.ResultsFor red king crab tags with pop-up location estimates in 2020 (n = 79) and 2021 (n = 46), mean drift error was 9% and 44% of mean crab displacement, respectively. For fixed-position PSATs with pop-up location estimates (n = 27), mean distance between the estimated pop-up location and the tag’s fixed position was 2.0 km, representing a mean improvement in accuracy of 51% over alternative estimates. Corresponding error ellipse estimates either encompassed the tag’s fixed position (n = 11) or their boundaries were a mean distance of 1.3 km (n = 16) from the fixed position.ConclusionsOur method improves pop-up location estimates for PSAT-tagged animals and is particularly well suited for crabs and other slow-moving benthic marine species. The improved estimates enhance PSAT utility for addressing management and ecological questions that require a fine spatial resolution, such as movement near management boundaries or defining essential habitat for important life history events.

Introducing subplot in policy narratives: A structural narrative analysis of the debate over the Pebble Mine project in Bristol Bay in Alaska, United States

AbstractPolicy narrative research focuses on one story/plot that forms narratives in policy controversies without attention to the subplot, picturing a reduced policy narrative structure. Subplots are studied in literary narratives as secondary plots to main plots and in terms of their structures, differences with, and similarities to plots, with both pursuing individual objectives toward common goals. Subplots enhance policy narratives’ structures through enlargement and enrichment. Neglecting the subplot impedes knowledge about their contributions and potentially limits narrative analyses. This article introduces the subplot in policy narratives through a descriptive account, proposes an expanded structural definition, and structurally analyzes the policy narratives in the debate over a mining project in Bristol Bay, Alaska, United States. The opposing narrative's plot is cultural with political, legal, and environmental subplots, while the supporting narrative's plot is developmental with legal and political subplots. The study offers perspectives for advancing subplot research and narrative policy analysis.Related ArticlesBrekken, Katheryn C., and Vanessa M. Fenley. 2021. “Part of the Narrative: Generic News Frames in the U.S. Recreational Marijuana Policy Subsystem.” Politics & Policy 49(1): 6–32. https://doi.org/10.1111/polp.12388.Chang, Katherine T., and Elizabeth A. Koebele. 2020. “What Drives Coalitions’ Narrative Strategy? Exploring Policy Narratives around School Choice.” Politics & Policy 48(4): 618–65. https://doi.org/10.1111/polp.12367.Shanahan, Elizabeth A., Mark K. McBeth, and Paul L. Hathaway. 2011. “Narrative Policy Framework: The Influence of Media Policy Narrative on Public Opinion.” Politics & Policy 39(3): 373–400. https://doi.org/10.1111/j.1747‐1346.2011.00295.x.

Always and forever: Materializing an environmental public in Bristol Bay, Alaska

In this article, we examine how residents of the Bristol Bay region of southwest Alaska, an area known for its vibrant salmon fishery, have mobilized to oppose the longstanding threat of large-scale mining in the Bay's headwaters. Drawing on ethnographic research in the region, we show how organizers and activists working to defeat the proposed Pebble Mine respond to unceasing if often unpredictable pressures that arrive in a distinctively erratic, fast-yet-slow fashion. Our analysis explores the implications of this condition for everyday efforts to bring together and maintain what we conceptualize as an environmental public: a community whose composition speaks to certain spatial, temporal, and material features associated with natural resources as well as to the bureaucratic demands of the resource-regulating, extraction-oriented state. By joining scholarship on resource temporalities with that on material publics, we add to studies of action in the face of extractivism in highlighting the tremendous behind-the-scenes labor and dexterity required to sustain an environmental public through the vicissitudes of a drawn-out struggle, requirements that in this case give rise to an always-and-forever political subjectivity primed for perpetual vigilance. While we focus on the specificities of the Pebble fight, we argue that this subjectivity and its burdens are central to a growing number of environmental contests today, as conditions of vulnerability are broadened at the same time that responsibility for confronting them proves unevenly distributed.

Along‐Strike Variations of Alaska Subduction Zone Structure and Hydration Determined From Amphibious Seismic Data

AbstractWe develop a 3‐D isotropic shear velocity model for the Alaska subduction zone using data from seafloor and land‐based seismographs to investigate along‐strike variations in structure. By applying ambient noise and teleseismic Helmholtz tomography, we derive Rayleigh wave group and phase velocity dispersion maps, then invert them for shear velocity structure using a Bayesian Monte Carlo algorithm. For land‐based stations, we perform a joint inversion of receiver functions and dispersion curves. The forearc crust is relatively thick (35–42 km) and has reduced lower crustal velocities beneath the Kodiak and Semidi segments, which may promote higher seismic coupling. Bristol Bay Basin crust is relatively thin and has a high‐velocity lower layer, suggesting a dense mafic lower crust emplaced by the rifting processes. The incoming plate shows low uppermost mantle velocities, indicating serpentinization. This hydration is more pronounced in the Shumagin segment, with greater velocity reduction extending to 18 ± 3 km depth, compared to the Semidi segment, showing smaller reductions extending to 14 ± 3 km depth. Our estimates of percent serpentinization from VS reduction and VP/VS are larger than those determined using VP reduction in prior studies, likely due to water in cracks affecting VS more than VP. Revised estimates of serpentinization show that more water subducts than previous studies, and that twice as much mantle water is subducted in the Shumagin segment compared to the Semidi segment. Together with estimates from other subduction zones, the results indicate a wide variation in subducted mantle water between different subduction segments.

CYCLICAL MIGRATION IN ALASKA NATIVE ELDERS AND ITS IMPACT ON ELDERS’ IDENTITY AND LATER LIFE WELL-BEING

Abstract This paper outlines a unique culturally driven cyclical migration of Alaska Native Elders. This Indigenous cyclical migration is distinct from other previously described mobility observations in that Elders spend extended time in more than one community. We describe the cyclical migration of Alaska Native (AN) Elders and its influence on the Elders’ identity, health, and well-being. Employing a life course perspective and social theory of migration, inductive content analysis was employed to identify themes related to Elders’ cyclical migration between rural and urban communities and the impact on their identity, health, and well-being. Interviews with 125 AN Elders were conducted across five regions of Alaska: Bristol Bay, Interior, Norton Sound, Aleutian Pribilof Islands, and Southcentral. AN Elders traveled between rural and urban communities to access resources and connections critical to their identities, health, and well-being. Urban Elders maintained a connection to rural villages because they perceive them as healthier places to age based on access to traditional practices, land, and the community. Rural Elders spent extended time in urban settings to access health care services, be closer to family, and to benefit from the lower costs of living. This study builds upon existing migration theories by introducing a cyclical pattern uniquely driven by AN identity, culture, and traditional practices. Findings illustrate how AN communities can support Elders who experience cyclical migration patterns to ensure they age successfully in both locations. Future recommended research should explore cyclical migration patterns among other Indigenous populations with histories of migration.

Applying the ideal free distribution to the movement of a highly mobile gillnet fishery for Pacific salmon

Ecological models are used to understand where fishing vessels operate, improving fisheries management success. The ideal free distribution (IFD) predicts equalization of catch across locations in response to distributions of fish and competing vessels. We applied the IFD as a null model to investigate the movement and catch per vessel (CPUE) of the sockeye salmon drift gillnet fleet in Bristol Bay, AK, from 1980 to 2019. The IFD prediction of equal CPUE across areas was not supported, so we explored violations of two assumptions of the theory. We categorized each vessel according to its mobility, highlighting the “free to move” assumption, and found that when we removed nonmobile vessels, some districts had fewer vessels than predicted from their high CPUE. We examined the “equal competitive ability” assumption by calculating the average CPUE, relative to success of other vessels. The underutilization of profitable districts persisted. Overall, the fleet underused high CPUE areas when considering differences in mobility and relative fishing success, indicating that unmeasured safety concerns, travel costs, knowledge of fishing grounds, or other factors could be preventing an IFD.

COVID-19 transmission in a resource dependent community with heterogeneous populations: An agent-based modeling approach

Outbreaks of COVID-19 in crowded work locations led to mass infection events during the pandemic that stressed health capacity in rural communities. This led to disparate responses – either isolating and restricting workers to facilities and potentially amplifying spread between them, more intense community wide restrictions, or an acceptance of higher disease spread. An extreme case is the salmon fishery in Bristol Bay, Alaska, where fishermen, factory workers, and residents all interact during the summer fishing season. During the pandemic, policy measures were debated, including community mask mandates, restricting workers to their boats and factories, and even closing the valuable seasonal fishery. We develop an agent-based SIR model (ABM) to examine COVID-19 transmission in a resource-dependent community populated by distinct subgroups. The model includes a virus spreading within and between three heterogenous populations who interact with other members of their type in their home location, and with different types of agents when out in the community. We simulate various non-pharmaceutical interventions and vaccination rates across these groups. Results demonstrate the efficacy of non-pharmaceutical interventions and vaccinations, as well as tradeoffs between duration and intensity and tradeoffs between groups impacted by the outbreak. This ABM demonstrates the impact of public policy mechanisms on health outcomes in resource-dependent communities with distinct populations.

Acute Toxicity of Copper to Three Species of Pacific Salmon Fry in Water with Low Hardness and Low Dissolved Organic Carbon.

Proposed development of a mine within Alaska's Bristol Bay watershed (USA) has raised concerns about the potential impact of copper (Cu) on Pacific salmon (Oncorhynchus spp.). We conducted 96-h flow-through bioassays using low-hardness and low dissolved organic carbon water to determine the acute lethal toxicity of Cu to sockeye (Oncorhynchus nerka), Chinook (Oncorhynchus tshawytscha), and coho salmon (Oncorhynchus kisutch) fry. We aimed to determine Cu toxicity under field-relevant water quality conditions and to assess three methods of calculating ambient Cu criteria: the biotic ligand model (BLM), a multiple linear regression model endorsed by the US Environmental Protection Agency, and the hardness-based model currently used by the State of Alaska. The criteria generated by all models were below 20% lethal Cu concentrations by factors ranging from 2.2 to 54.3, indicating that all criteria would be protective against mortality. The multiple linear regression-based criteria were the most conservative and were comparable to BLM-based criteria. The median lethal concentrations (LC50s) for sockeye, Chinook, and coho were 35.2, 23.9, and 6.3 µg Cu/L, respectively. We also used the BLM to predict LC50s for each species. Model predictions differed from empirical LC50s by factors of 0.7 for sockeye and Chinook salmon, and 1.1 for coho salmon. These differences fell within the acceptable range of ±2, indicating the model's accuracy. We calculated critical lethal Cu accumulation values for each species to account for differing water chemistry in each bioassay; the present study revealed that coho salmon were most sensitive to Cu, followed by sockeye and Chinook salmon. Our findings underscore the importance of considering site- and species-specific factors when modeling Cu toxicity. The empirical data we present may enhance Cu risk assessments for Pacific salmon. Environ Toxicol Chem 2023;42:2440-2452. © 2023 SETAC.

Cyclical Migration in Alaska Native Elders and Its Impact on Elders' Identity and Later Life Well-Being.

This paper outlines the unique culturally driven cyclical migration of Alaska Native (AN) Elders, distinct from previously described migration patterns in that Elders spend extended time in more than one community. We describe this Indigenous cyclical migration of AN Elders and its influence on their identity and later life health and well-being. Interviews with 124 AN Elders were conducted across 5 regions of Alaska: Bristol Bay, Interior, Norton Sound, Aleutian Pribilof Islands, and Southcentral. Within this sample, 87 participants engaged in cyclical migration. Thematic analysis was employed to identify themes related to Elders' cyclical migration between rural and urban communities and the impact on their identity and later life health and well-being. We identified 2 distinct patterns of Indigenous cyclical migration-Elders living primarily in rural communities migrating to urban communities and Elders living primarily in urban communities migrating to rural communities. Elders engaged in these 2 patterns of cyclical migration to maintain cultural practices, access social, and health care services to maintain their physical health and well-being, and continue their community roles contributing to their AN Elder identity. This study builds upon existing migration theories by introducing a cyclical pattern uniquely driven by AN identity, culture, and traditional practices. Findings illustrate how AN communities can support Elders who experience cyclical migration patterns to ensure they age successfully in both locations. Future research should explore cyclical migration patterns among other Indigenous populations with migration histories.

Trend in aerial counts of beluga or white whales (Delphinapterus leucas) in Bristol Bay, Alaska, 1993-2005

Thirty-eight aerial surveys of beluga or white whales (Delphinapterus leucas) were conducted in Bristol Bay, Alaska, during six different years between 1993 and 2005. Belugas were sighted mainly close to shore in the upper parts of Nushagak and Kvichak bays, as well as along the coast between these bays and in the lower parts of major rivers. Data from 28 complete counts made in good or excellent survey conditions were analysed for trend. Counts ranged from 264 to 1,067. The estimated rate of increase over the 12-year period was 4.8%/year (95% CI = 2.1%-7.5%). Such a rate of increase suggests that either the population was below the environmental carrying capacity in the early 1990s or, alternatively, that factors that had been limiting population increase were alleviated after that time. A review of possible changes in human-caused mortality, predation and prey availability did not reveal a single likely cause of the increase. Among the factors that could have played a role are recovery from research kills in the 1960s, a modest decline in subsistence removals and a delayed response to increases in Pacific salmon (Oncorhynchus spp.) abundance in the 1980s. The positive growth rate for this population shows that in recent years there has been no substantial negative impact of human or natural factors, acting either alone or in combination, and there is no need for changes to the current management regime

Subsistence harvest of beluga or white whales (Delphinapterus leucas) in northern and western Alaska, 1987–2006

Four stocks of beluga or white whales (Delphinapterus leucas) are hunted by Alaska Natives in northern and western Alaska. These are the Beaufort Sea, eastern Chukchi Sea, eastern Bering Sea and Bristol Bay stocks. Since 1987, the Alaska Beluga Whale Committee has monitored the subsistence harvests of belugas from these stocks. During this 20 year period, the total landed harvest for the four stocks combined (adjusted for years with missing data) ranged from 208 in 1995 to 494 in 1988, with a 20 year average of 323 per year. For individual stocks the average annual landed harvests for 1987–2006 were: Beaufort Sea – 41; Chukchi Sea – 62; eastern Bering Sea – 191; and Bristol Bay – 20. There was no significant longterm trend (p>0.05) in the rate of harvesting for any stock from 1987–2006. Average landed harvests relative to estimated stock size were: 0.1% for the Beaufort Sea (0.4% including belugas harvested from the Beaufort Sea stock by Canadian hunters); 1.7% for the eastern Chukchi Sea; 1.1% for the eastern Bering Sea; and 1.1% for Bristol Bay. The success of beluga harvest monitoring in Alaska is due to the cooperation of beluga hunters from more than 40 small coastal communities who report their harvests to the Alaska Beluga Whale Committee (ABWC). Through the ABWC, beluga hunters have been able to formalise their role in managing their subsistence resources.

Declines in body size of sockeye salmon associated with increased competition in the ocean

Declining body sizes have been documented for several species of Pacific salmon; however, whether size declines are caused mainly by ocean warming or other ecological factors, and whether they result primarily from trends in age at maturation or changing growth rates remain poorly understood. We quantified changes in mean body size and contributions from shifting size-at-age and age structure of mature sockeye salmon returning to Bristol Bay, Alaska, over the past 60 years. Mean length declined by 3%, corresponding to a 10% decline in mean body mass, since the early 1960s, though much of this decline occurred since the early 2000s. Changes in size-at-age were the dominant cause of body size declines and were more consistent than trends in age structure among the major rivers that flow into Bristol Bay. Annual variation in size-at-age was largely explained by competition among Bristol Bay sockeye salmon and interspecific competition with other salmon in the North Pacific Ocean. Warm winters were associated with better growth of sockeye salmon, whereas warm summers were associated with reduced growth. Our findings point to competition at sea as the main driver of sockeye salmon size declines, and emphasize the trade-off between fish abundance and body size.

Variability of Echolocation Clicks in Beluga Whales (Delphinapterus leucas) Within Shallow Waters

While echolocation is vital to the sensory ecology of odontocetes, we have few data characterizing the signals of most species, limiting our understanding of key attributes of these animals, especially for those with a diverse range of habitats. Beluga whales (Delphinapterus leucas) have successfully overcome the pressures of living in both shallow and deep open water habitats. We characterized the echolocation clicks of 13 wild beluga whales during temporary capture-and-release events in Bristol Bay, Alaska (USA). We extracted and examined 556 high-quality clicks from approximately 22 hours of recordings. As a group, the duration (41.1 ± 17.3 µs; mean ± SD), peak frequency (97.9 ± 34.4 kHz), centroid frequency (101.9 ± 23.9 kHz), -3 dB bandwidth (29.1 ± 14.4 kHz), -10 dB bandwidth (67.7 ± 31.8 kHz), and root mean square (RMS) bandwidth (27.8 ± 8.1 kHz) were assessed. These are the first on-axis data from wild belugas in their natural shallow water habitat within 1 m. Beluga whales emit clicks with high frequency and high source level in extremely shallow waters regardless of the potential strong reverberations and clutter. These results provide a foundation for future studies on how this species manipulates its sonar to successfully operate in acoustically challenging shallow waters.