Combining Alaska forage fish data from research surveys and predator diets to assess forage fish response to climatic regime shifts

Turner, Lindsay

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Author

Turner, Lindsay

Chair

Cunningham, Curry

Committee

Arimitsu, Mayumi
Eckert, Ginny

Abstract

Forage fish play a crucial role in the marine ecosystems of Alaska through the transfer of energy from lower trophic levels to marine predators. Understanding and quantifying Alaskan forage fish responses to rapid climatic shifts is needed to inform adaptive management strategies under a warmer and more variable future in Alaska. However, data on the occurrence and abundance of forage fish in Alaska are limited due to the diversity of life history strategies and patchy distribution that make their capture in fisheries-independent surveys difficult. In this thesis, I address current gaps in the data available on forage fish through the publication of an Alaska Forage Fish Database (AFFD) comprised of data from trawls, beach seines, and the diets of predator consuming forage fish, collected by a variety of contributing agencies and organizations. This data compilation effort resulted in a database containing forage fish abundance data from 461,449 sampling events spanning the years 1953 - 2023. Using the compiled dataset, I then assess large-scale spatial and temporal patterns in the occurrence of Pacific capelin (Mallotus catervarius), Pacific herring (Clupea pallasii), and sand lance (Ammodytes spp.) in the Bering Sea and Gulf of Alaska. Interannual trends in the encounter probability for each species, based on models fit to data from fisheries surveys, groundfish diets, and seabird diets, exhibit coherence in large-scale changes among observation types in the Gulf of Alaska (1972 - 2023) and Bering Sea (1980 - 2023). I compare the distribution of species’ encounter probability across decadal climate stanzas and demonstrate the differences in distribution of species during the 2014 - 2019 heatwaves compared to prior stanzas, as well as reoccurring distribution patterns in response to similar climatic characteristics among stanzas. Findings from this thesis facilitate an expanded understanding of forage fish population dynamics and spatial distribution in response to rapid climatic shifts.

Description

Thesis (M.S.) University of Alaska Fairbanks, 2024

Chapter 1: General introduction -- 1.1 References. Chapter 2: Expanding data availability of Alaska forage fish -- 2.1 Abstract -- 2.2 Introduction -- 2.3 Methods -- 2.3.1 Study areas -- 2.3.2 Species -- 2.3.3 Database structure -- 2.3.4 Quality control -- 2.3.5 Datasets -- 2.3.5.1 Surface trawls -- 2.3.5.2 Groundfish bottom trawl survey -- 2.3.5.3 Nearshore fish atlas -- 2.3.5.4 Inshore trawl surveys -- 2.3.5.5 Southeast Alaska Steller Sea Lion Prey Project -- 2.3.5.6 Late-summer, small-mesh trawl survey -- 2.3.5.7 Small-mesh shrimp bottom trawl survey -- 2.3.5.8 Seabird diets -- 2.3.5.9 Groundfish diets -- 2.4 Results -- 2.4.1 Spatial and temporal overview -- 2.4.1.1 Bering Sea -- 2.4.1.2 Gulf of Alaska -- 2.4.1.3 Aleutian Islands -- 2.4.1.4 Arctic -- 2.4.2 Species distribution -- 2.5 Discussion -- 2.5.1 Variability in data -- 2.5.2 Caveats and considerations -- 2.5.3 Future work -- 2.6 References -- 2.7 Figures -- 2.8 Supplementary information -- 2.8.1 Supplementary tables -- 2.8.2 Supplementary figures. Chapter 3: Integrating multiple data sources for spatial and temporal dynamic assessments of forage fish in Alaska -- 3.1 Abstract -- 3.2 Introduction -- 3.3 Methods -- 3.3.1 Data -- 3.3.2 Case studies -- 3.3.2.1 Eastern Bering Sea -- 3.3.2.2 Gulf of Alaska -- 3.3.3 Decadal climate stanzas -- 3.3.4 Estimation models -- 3.3.5 Model performance -- 3.4 Results -- 3.4.1 Model performance -- 3.4.2 Temporal trends -- 3.4.2.1 Capelin -- 3.4.2.2 Herring -- 3.4.2.3 Sand lance -- 3.4.3 Decadal stanzas -- 3.4.4 Spatial distribution -- 3.4.4.1 Pacific capelin -- 3.4.4.2 Pacific herring -- 3.4.4.3 Sand lance (Ammodytes spp.) -- 3.5 Discussion -- 3.5.1 Trends amongst models -- 3.5.2 Climate response -- 3.5.2.1 Pacific capelin: Bering Sea -- 3.5.2.2 Pacific capelin: Gulf of Alaska -- 3.5.2.3 Pacific herring: Bering Sea -- 3.5.2.4 Pacific herring: Gulf of Alaska -- 3.5.2.5 Sand lance (Ammodytes spp.): Bering Sea -- 3.5.2.6 Sand lance (Ammodytes spp.): Gulf of Alaska -- 3.5.3 General conclusions -- 3.6 References -- 3.7 Tables -- 3.8 Figures -- 3.9 Supplementary information -- 3.9.1 Supplementary tables -- 3.9.2 Supplementary figures. Chapter 4: General conclusions -- 4.1 References.

Date

2024-12

Type

Thesis

Collections

Fisheries