Sea otter carrying capacity in a soft- and mixed-sediment benthic habitat

Davis, Ian P.; Dellapenna, Timothy M.; Maale, Gary; Gelwick, Francis P.; Weltz, Frederick; Davis, Randall W.

doi:10.1016/j.jembe.2021.151602

Cited by 2 publications

(3 citation statements)

References 54 publications

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“…Sea otter populations in California and the Aleutian Islands, Alaska, show a greater preference for sea urchins compared with those in eastern Hokkaido (Estes et al, 1978; Estes et al, 1980; LaRoche et al, 2021; Watt et al, 2000). Sea otter dietary preference correlates with prey abundance, and they do not necessarily require a wide range of prey to thrive (Ostfeld 1982; Tinker et al 2008; Wolt et al 2012; Davis et al 2021). The unusual HAB (Gail, 1950; Orlova et al, 2002) in eastern Hokkaido provided an opportunity to observe the ecosystem effects at two trophic levels (Hasegawa et al, 2022; Iwataki et al 2022; Kuroda et al 2021; Kuroda et al, 2022).…”

Section: Discussionmentioning

confidence: 99%

The effect of a harmful algal bloom (Karenia selliformis) on the benthic invertebrate community and the sea otter (Enhydra lutris) diet in eastern Hokkaido

Johnstone,

Suzuki,

Konno

et al. 2024

Preprint

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In recent decades, the locally extinct sea otter (Enhydra lutris lutris) has been recolonizing the coast of eastern Hokkaido. Their diet includes benthic invertebrates such as bivalves, sea urchins, snails, and chitons. In the fall of 2021, a harmful algal bloom (HAB) of Karenia selliformis occurred across Hokkaido's northern and eastern coasts, leading to a massive mortality of sea urchins. This dinoflagellate produces a neurotoxin (gymnodimine) implicated in shellfish poisoning. To determine the effect of the HAB on the marine community, we conducted benthic surveys using SCUBA and visually monitored the prey items of the sea otters in the affected area from 2020 to 2023. Following the HAB, we observed an 82% decrease in benthic sea urchin density (number m2), leading to their complete absence from the diet of sea otters. Conversely, bivalve density increased six-fold, accompanied by a nearly two-fold rise in their percentage in the sea otters' diet. Minimal changes were observed in the density of chitons and snails, with no significant alteration in the sea otters' diet. Despite these changes, the impact of the HAB on otters' dietary preferences was temporary, as the percentage of dietary sea urchins began recovering one year later. Sea otters augmented their diet with bivalves to compensate for the reduced availability of sea urchins during the HAB with no apparent effects on the number of sea otters or their health. Our results highlight the adaptability of sea otters to adjust their diet according to prey availability.

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Section: Discussionmentioning

confidence: 99%

The effect of a harmful algal bloom (Karenia selliformis) on the benthic invertebrate community and the sea otter (Enhydra lutris) diet in eastern Hokkaido

Johnstone,

Suzuki,

Konno

et al. 2024

Preprint

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“…This study is a step forward in exploring additional habitat features that may be important for estimating sea otter carrying capacity in southcentral Alaska, as has been done in California with southern sea otters (Tinker et al., 2021 ). However, a component necessary for carrying capacity estimates is prey availability data, which influences equilibrium densities of sea otters (Davis et al., 2021 ; Dean et al., 2002 ). Despite large efforts to model carrying capacity in other regions, many studies (Eisaguirre et al., 2021 ; Hale et al., 2022 ; Lu et al., 2020 ; Tinker et al., 2019 , 2021 ; Williams et al., 2019 ), including the one presented here, have not incorporated sea otter prey information directly, which is recommended for future modeling efforts (Davis et al., 2019 ).…”

Section: Discussionmentioning

confidence: 99%

“…Including estimates of available prey energy is also critical for accurately estimating equilibrium density of sea otters. Regions with stable sea otter populations have been found to increase in abundance after being considered standards for equilibrium densities, pointing to prey availability as a more reliable metric (Davis et al., 2021 ; Hale et al., 2019 , 2022 ). We recommend combining a suite of known sea otter‐associated metrics in future studies to improve model AUC.…”

Section: Discussionmentioning

confidence: 99%

Species distribution modeling of northern sea otters (Enhydra lutris kenyoni) in a data‐limited ecosystem

Hasan,

Gorman,

Coletti

et al. 2024

Ecology and Evolution

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Species distribution models (SDMs) are used to map and predict the geographic distributions of animals based on environmental covariates. Typically, SDMs require high‐resolution habitat data and time series information on animal locations. For data‐limited regions, defined as having scarce habitat or animal survey data, modeling is more challenging, often failing to incorporate important environmental attributes. For example, for sea otters (Enhydra lutris), a federally protected keystone species with variable population trends across the species' range, predictive modeling of distributions has been successfully conducted in areas with robust sea otter population and habitat data. We used open‐access data and employed a presence‐only model, maximum entropy (MaxEnt), to investigate subtidal habitat associations (substrate and algal cover, bathymetry, and rugosity) of northern sea otters (E. lutris kenyoni) for a data‐limited ecosystem, represented by Kachemak Bay, Alaska. Habitat association results corroborated previous findings regarding the importance of bathymetry and understory kelp as predictors of sea otter presence. Novel associations were detected as filamentous algae and shell litter were positively and negatively associated with northern sea otter presence, respectively, advancing existing knowledge of sea otter benthic habitat associations useful for predicting habitat suitability. This study provides a quantitative framework for conducting species distribution modeling with limited temporal and spatial animal distribution and abundance data. Utilizing drop camera information, our novel approach allowed for a better understanding of habitat requirements for a stable northern sea otter population, including bathymetry, understory kelp, and filamentous algae as positive predictors of sea otter presence in Kachemak Bay, Alaska.

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Sea otter carrying capacity in a soft- and mixed-sediment benthic habitat

Cited by 2 publications

References 54 publications

The effect of a harmful algal bloom (Karenia selliformis) on the benthic invertebrate community and the sea otter (Enhydra lutris) diet in eastern Hokkaido

The effect of a harmful algal bloom (Karenia selliformis) on the benthic invertebrate community and the sea otter (Enhydra lutris) diet in eastern Hokkaido

Species distribution modeling of northern sea otters (Enhydra lutris kenyoni) in a data‐limited ecosystem

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