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« Food Web Dynamics Program

Projects: Products and Analyses

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There are four levels of products and analyses conducted by FWDP:

  1. Basic
  2. Inferential/Retrospective
  3. Predictive/Modeling
  4. Theoretical

We examine the relative importance of fishery and natural mortality, identify critical life stages, evaluate multi-species yield dynamics, assess the impact of fishery management scenarios based on an understanding of food web connectivity, relate fish feeding dynamics to environmental and anthropogenic conditions, and simply answer questions of "what does that fish eat?".

See our recent American Fisheries Society and National Habitat Assessment Workshop posters regarding A Program Overview, QA/QC Stomach Sampling Comparison, Fish Feeding and Chronic Bottom Fishing, and How Didemnum vexillum Effects Fish Diets.

  1. Basic:   We produce species profiles (descriptors of who's eating who) across life histories of these fish including simple diet parameters (e.g. frequency of occurrence for particular prey, diet composition, total amount of food consumed, diet overlap matrices, guilds, clustering by diet, etc.). These are basically data summaries, exploratory, and observational analyses, and provide most of the information included in multi-species comparisons and similar reports (see Staff Publications).
  2. Feeding Guild ClusteringClick image to enlarge. From Garrison, L.P. and J.S. Link. 2000. Dietary guild structure of the fish community in the Northeast United States Continental Shelf Ecosystem. Mar. Ecol. Prog. Ser. 202:231-240. Diet OverlapClick image to enlarge. From Smith, B.E. and Link, J.S. 2010. The trophic dynamics of 50 finfish and 2 squid species on the Northeast US continental shelf. NOAA Tech. Memo. NMFS-NE-216; 640 p.

  3. Inferential / Retrospective:   We examine what has happened to the fish community of the northeast U.S. continental shelf with time-series modeling; hypothesis testing for differences across geographic regions, decades, depths, size classes, predators, etc.; and multivariate analyses. Examples include:
    • Changes in diet overlap and other estimates of competition among selected species
    • Community interaction matrices
    • The association between select benthivores and benthic habitats on Georges Bank in response to bottom fishing disturbance
    • Life history phases of key fish (in terms of trophic ecology) and essential fish habitat
    • The magnitude of predation on larval fish, especially gadids, by Atlantic herring (Clupea harengus) and Atlantic mackerel (Scomber scombrus)
    • Differential (predation) mortality based upon size
    • Consumption estimates of the fish community, contrasted with fishery landings

  4. Predictive / Modeling: Based upon our knowledge of the fish community, what will likely happen to the multi-species yield dynamics and community composition? We use short-term forecasts, time series forecasts, empirical / statistical modeling, and develop mechanistic / deterministic models. These methods are both static and dynamic to provide instantaneous solutions and to link growth with predation and fishing to assess yield across time. A major objective is to contrast fishing versus natural mortality. One goal is to produce predictive models of fish biomass to address "What if..?" scenarios.

    Examples include:
    • Generalized Consumption Models
    • Cross-linking population dynamics between predator and prey populations (F versus M for key species)
    • Predator-prey interaction models

  5. Theoretical:   The current structure of the fish community of this continental shelf region has responded to multiple perturbations (e.g. harvesting and habitat degradation) over time. Why has the fish community responded the way it has? We produce generalized consumption estimates for key species with a theoretical examination of several approaches verified with field data. We are also interested in monitoring patterns that contribute to basic ecological principles observed from fish trophic interactions.
Food Web

Click image to enlarge.

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