A swath across the great divide: Kelp forests across the Samalga Pass biogeographic break

Konar, Brenda; Edwards, Matthew S.; Bland, Aaron; Metzger, Jacob; Ravelo, Alexandra M.; Traiger, Sarah B.; Weitzman, Benjamin P.

doi:10.1016/j.csr.2017.06.007

Cited by 11 publications

(14 citation statements)

References 65 publications

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“…Within the BSAI region, Pacific halibut tagged in the Central and Western Aleutian Islands remained within their island groups (i.e., within the Andreanof and Near-Rat Islands, respectively), while those tagged on and along the EBS continental shelf moved among Bering Sea regulatory areas and from Alaskan to Russian waters. These dispersal patterns are consistent with summer-to-winter PAT-tagging studies that have indicated basin-scale reproductive segregation with considerable mixing within those basins [4]; research that has shown Samalga Pass to be an oceanographic [39] and ecological [40][41][42] boundary within the Aleutian Island ecosystem; and population-genetic analyses that suggest relative isolation of Pacific halibut in the Aleutian Islands westward of Amchitka Pass [7]. In addition, light-based geolocation demonstrates that connectivity among regulatory areas may be seasonally cyclic, with fish emigrating from their tagging region for the winter and returning the following spring.…”

Section: Discussionsupporting

confidence: 85%

Dispersal and seasonal movements of Pacific halibut (Hippoglossus stenolepis) in the eastern Bering Sea and Aleutian Islands, as inferred from satellite-transmitting archival tags

Loher

2022

Anim Biotelemetry

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Background Understanding connectivity is critical to the management of exploited fish stocks, but migratory dynamics of Pacific halibut (Hippoglossus stenolepis) in the Bering Sea and Aleutian Islands region are not well-understood. In the current study, 145 Pacific halibut ≥ 82 cm fork length were tagged with Pop-up Archival Transmitting (PAT) tags to evaluate interannual dispersal, seasonal migration, and depth-specific habitat use. Results Endpoint locations obtained after 1 year at liberty (n = 79), fishery recoveries after 2–3 years at liberty (n = 5), and at-liberty geopositions based on light data (n = 5313 estimates from 109 fish) indicated geographically distinct movement patterns: Pacific halibut tagged in the Western and Central Aleutian Islands remained within the island groups in which the fish had been tagged; fish in the eastern Bering Sea remained in that ocean basin, moving among International Pacific Halibut Commission (IPHC) regulatory areas and into Russian waters; those tagged south of Unimak Pass in IPHC Regulatory Area 4A displayed the greatest amount of emigration, dispersing eastward both seasonally and interannually to as far south as Washington State. Analysis of daily maximum depth and temperature data from 113 individuals demonstrated group-level variation in summer temperatures experienced by the fish and in the timing, duration, and synchrony of movement to deep-water wintering grounds. Conclusions Depth-specific habitat use was suggestive of regionally explicit migratory contingents, while interannual dispersal patterns were consistent with the existence of multiple functional spawning units. The results may guide future research to examine cross-basin connectivity in the Northern Bering Sea and provide inputs for numerical modelling of individual movements, larval advection, and recruitment analyses.

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Section: Discussionsupporting

confidence: 85%

Dispersal and seasonal movements of Pacific halibut (Hippoglossus stenolepis) in the eastern Bering Sea and Aleutian Islands, as inferred from satellite-transmitting archival tags

Loher

2022

Anim Biotelemetry

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“…S4). Our results conform to Konar et al (2017) who found that kelp forests are significantly more abundant east of Samalga Pass than west. Given that kelp forests in this region are strongly associated with sea otter presence (Estes et al 1978, Estes and Duggins 1995, our results combined with the results of Konar et al (2017) imply that otters, at a minimum, continue to be a functioning component of the ecosystem here.…”

Section: Discussionsupporting

confidence: 92%

A hierarchical distance sampling model to estimate spatially explicit sea otter density

2021

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Wildlife managers often rely on analyses conducted prior to the widespread adoption of hierarchical models which can lead to questions about the accuracy of previous inferences. Hierarchical models allow observed data to be partitioned into factors that influenced the collection of the data such as detectability of animals (i.e., observation processes) and factors that influence the ecology of a population such as features that affect the distribution of animals (i.e., ecological processes). Population surveys for sea otters in the Aleutian Islands, Alaska, have historically been conducted by conflating the observation and ecological processes potentially leading to inaccurate population estimates. Based on boat and planebased sea otter survey data collected in 2017, we sought to overcome many problems of previous sea otter surveys in southwestern Alaska. We developed a spatially explicit hierarchical distance sampling model to estimate the abundance of sea otters in the Eastern Aleutians Management Unit while explicitly accounting for factors that affect the ability to detect sea otters during surveys (i.e., group size, ocean conditions). We also sought to account for the environmental factors leading to the non-uniform distribution of sea otter groups by identifying relationships between otter group abundance and environmental attributes (i.e., ocean depth, presence of kelp, underwater substrate). Detection of sea otter groups was related to group size, and ocean conditions (e.g., ocean swell size). After accounting for detection, we estimated a mean population size of 8593 individual sea otters (95% CI: 7450-9984) which is considerably higher than previous estimates, although comparisons are difficult given divergent methodologies. Sea otter group density was negatively related to ocean depth and the presence of rock and gravel as underwater substrates. Conversely, sea otter group density was positively related to the presence of kelp and mud as an underwater substrate. Our hierarchical distance sampling model accounted for the observation process which allowed better estimates of the environmental attributes affecting otter abundance. Our research can serve as a template for other study systems requiring spatially explicit density estimates from a distance sampling framework and can help provide a new baseline for managers to gauge future population changes in sea otters.

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“…In the Arctic, the loss of sea ice (and consequently increased light availability) and warming temperatures are predicted to increase the geographic extent and depth range of marine vegetation, with 145,093 km 2 of suitable habitat projected for this type of species (Krause-Jensen et al, 2020). Coastal erosion from melting sea ice, fragmenting permafrost, and unusually high glacial inputs are, however, increasing sediment loads and freshwater inputs in high-latitude coastal zones (Fritz et al, 2017), which could result in direct kelp die-offs (Konar et al, 2017;Filbee-Dexter et al, 2019) or offset positive impacts of increased light and warmer temperatures (Bonsell and Dunton, 2018). Long-term research from Greenland, Russia, and Norway suggests a warmer Arctic with less sea ice may support higher kelp productivity and biomass by expanding the northern range and lower depth limit of these species (Filbee-Dexter et al, 2019;Krause-Jensen et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Kelp in the Eastern Canadian Arctic: Current and Future Predictions of Habitat Suitability and Cover

et al. 2021

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Climate change is transforming marine ecosystems through the expansion and contraction of species’ ranges. Sea ice loss and warming temperatures are expected to expand habitat availability for macroalgae along long stretches of Arctic coastlines. To better understand the current distribution of kelp forests in the Eastern Canadian Arctic, kelps were sampled along the coasts for species identifications and percent cover. The sampling effort was supplemented with occurrence records from global biodiversity databases, searches in the literature, and museum records. Environmental information and occurrence records were used to develop ensemble models for predicting habitat suitability and a Random Forest model to predict kelp cover for the dominant kelp species in the region – Agarum clathratum, Alaria esculenta, and Laminariaceae species (Laminaria solidungula and Saccharina latissima). Ice thickness, sea temperature and salinity explained the highest percentage of kelp distribution. Both modeling approaches showed that the current extent of arctic kelps is potentially much greater than the available records suggest. These modeling approaches were projected into the future using predicted environmental data for 2050 and 2100 based on the most extreme emission scenario (RCP 8.5). The models agreed that predicted distribution of kelp in the Eastern Canadian Arctic is likely to expand to more northern locations under future emissions scenarios, with the exception of the endemic arctic kelp L. solidungula, which is more likely to lose a significant proportion of suitable habitat. However, there were differences among species regarding predicted cover for both current and future projections. Notwithstanding model-specific variation, it is evident that kelps are widespread throughout the area and likely contribute significantly to the functioning of current Arctic ecosystems. Our results emphasize the importance of kelp in Arctic ecosystems and the underestimation of their potential distribution there.

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A swath across the great divide: Kelp forests across the Samalga Pass biogeographic break

Cited by 11 publications

References 65 publications

Dispersal and seasonal movements of Pacific halibut (Hippoglossus stenolepis) in the eastern Bering Sea and Aleutian Islands, as inferred from satellite-transmitting archival tags

Dispersal and seasonal movements of Pacific halibut (Hippoglossus stenolepis) in the eastern Bering Sea and Aleutian Islands, as inferred from satellite-transmitting archival tags

A hierarchical distance sampling model to estimate spatially explicit sea otter density

Kelp in the Eastern Canadian Arctic: Current and Future Predictions of Habitat Suitability and Cover

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