ORCID ID
https://orcid.org/0000-0003-1436-2291
Date Awarded
2024
Document Type
Dissertation
Degree Name
Doctor of Philosophy (Ph.D.)
Department
Virginia Institute of Marine Science
Advisor
Robert J Latour
Committee Member
Mary C Fabrizio
Committee Member
Andrew M Scheld
Committee Member
Donglai Gong
Committee Member
Sarah K Gaichas
Abstract
Extensive and largely unregulated fisheries operating on the Northeast US continental shelf during the 20th century resulted in widespread overfishing. Single-species stock assessments and management have been used to end overfishing and rebuild these resources, yet as stocks recover the influences of biophysical forcing and trophic interactions play a greater role in shaping their dynamics. Infrastructure for including these ecosystem processes into assessment and management activities began emerging during the 1990s and has led to a gradual transition toward Ecosystem Approaches to Fisheries Management (EAFM) in the Northeast. By creating spaces to improve communication, enhancing data collection, synthesizing ecosystem indicators, developing system-level caps on harvest, and monitoring outcomes, management agencies should be well-positioned to accelerate this evolution to EAFM.Operationalizing EAFM requires quantifying community ecology with a focus on developing ecosystem indicators. Northeast shelf coastal ecosystems have received little attention, so 12 years (2008 – 2019) of fisheries-independent bottom trawl survey data were used to characterize and synthesize the spatiotemporal patterns of species assemblages inhabiting the nearshore Mid-Atlantic Bight (MAB). All 178 species collected by the survey were allocated among nine ecomorphotype (EMT) groups: demersal fishes; pelagic fishes; flatfishes; skates; rays; dogfishes; other sharks; cephalopods; and benthic arthropods. Univariate hurdle models were used to quantify annual time-series and seasonal, spatial distributions of EMT relative biomass, and a multivariate state-space model revealed that the nine time-series were effectively summarized by three common trends. Model fits to the EMT time-series represented a new suite of indicators for this ecosystem. MAB winter sea surface temperature was a significant predictor of relative biomass trends for several EMTs, suggesting that winter environmental conditions structure this system on an annual scale. Multivariate ordination uncovered a north-to-south gradient in EMT seasonal, spatial distributions and a distinct area of elevated biomass for several assemblages along Long Island, NY. Exploited forage species support directed fisheries and predator productivity, so both harvest and trophic removals should be considered when developing EAFM. Shelf-wide predator catch and stomach content data collected by two fisheries-independent bottom trawl surveys over 42 years (1978 – 2019) were combined within multivariate spatiotemporal models to estimate consumptive removals during spring and fall each year for four commercially-exploited prey; Atlantic herring (Clupea harengus), silver hake (Merluccius bilinearis), butterfish (Peprilus triacanthus), and longfin squid (Doryteuthis pealeii). Seasonal consumption trends were mostly synchronous for Atlantic herring and silver hake and were asynchronous for butterfish and longfin squid. Consumption increased since the 1990s for most prey, which coincided with the widespread implementation of harvest constraints meant to rebuild fisheries resources. State-space regression models linking these time-series with hypothesized drivers revealed that prey availability (bottom-up; positive relationships) and commercial catch (top-down; primarily negative relationships) were the strongest predictors of consumption. Overall, this body of research yielded novel insights on the community and predator-prey dynamics of the Northeast shelf ecosystem by illuminating key linkages with biophysical, trophic, and harvest processes that govern fisheries resource productivity. Such information could be used by managers to further advance EAFM strategies meant to improve resource sustainability and stakeholder outcomes.
DOI
https://dx.doi.org/10.25773/v5-6e4f-nb81
Rights
© The Author
Recommended Citation
Gartland, James, "Linking Fish Community Dynamics And Trophic Interactions With Ecological Processes On The Northeast Us Continental Shelf" (2024). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1717521786.
https://dx.doi.org/10.25773/v5-6e4f-nb81
