Ecosystem modelling to quantify the impact of ecosystem interactions on species’ harvest rates and dynamics Alida Bundy (BIO) and Stratis Gavaris (SABS)

Ties into recent DFO initiatives DFO 5-year Research Agenda – –research program to create new knowledge and methods that will support the development of better advice required for policy and decision making and in particular, ecosystem-based management (EBM) Ecosystem Science Framework –integrates existing knowledge about ecosystem dynamics and the effects of human activities on them, assesses the aspects that are most important to that ecosystem, and interprets the trends and patterns in ways that can be applied to risk assessment and management of human activities in aquatic ecosystems.

Addresses what DFO has been missing Conceptual, strategic and tactical ecosystem modelling in support of EAM

ERI’s and opportunity to fill this GAP Use ecosystem models of differing complexity to explore our understanding of: –ecosystem dynamics and functioning –implications of change in structure and energy flow of ecosystems for harvest rates and management strategies Input into EAM decision making

Stock/Single Species EcosystemMulti-speciesAggregate Biomass SS models, no ecosystem issues Messy Picture Here Gadids Flatfish Pelagics Gradient of Possibilities Multiple SS assessments in “harmony” SS assessments with explicit M2 or habitat or climate considerations Multi-species assessments Aggregate Biomass Models Whole System Models Slide courtesy of Jason Link, NMFS

GOM BOF WSS GB

Initial focus on 2 modelling approaches MSVPA minimum realistic model VPA plus an equation describing predation Ecopath with Ecosim mass balance ecosystem model Herring

MSVPA – Herring (SW Nova Scotia/BoF spawning component) How would management strategies and harvest rates be affected if the simplifying assumptions of single species models were replaced by dynamical processes? Specifically, Explore the impact on management strategies and harvest rates for herring due to variation in predation mortality due to changes in abundance of principal predators.

Ecopath with Ecosim Bay of Fundy and WSS Explore our understanding of ecosystem dynamics and the implications of change in structure and energy flow for harvest rates and management strategies. –Questions about ecosytem structure and functioning –Questions about impact of ecosystem and environmental dynamics on harvest rates –Use a comparative approach

EAM Framework MSVPA EwE Other ATTRIBUTES STRATEGIES Productivity  Keepfishing mortality moderate - Promote positivebiomass change when biomass is low - Managediscarded catch for all harvested species  Allow sufficient escapement from exploitation of spawning biomass  Limit disturbingactivity in spawning areas/seasons  Control alteration of nutrient concentrations affecting primary production at the base of the food chain by algae Biodiversity  Controlincidental mortality for all non-harvested species  Minimize unintended transmission of invasive species  Distribute populationcomponent mortality in relation to component biomass Habitat  Managearea disturbed of bottom habitat  Limit introduction ofpollutants in habitat  Minimize deaths from structures/equipment/ ost gear yield biomass recruitment size/age structure spatial extent spatial occupancy population richness predator forage community assemblage trophic structure habitat type spectrum breeding behavior  Control noiseand lightdisturbance

Progress to date Econet Ecosystem Modelling Wkshp (Victoria, 2007) Formation of CanUSE Modelling WG –WG Meeting, Woods Hole March 2008 –2 Papers at ICES Spatial synchrony in major ecological and commercial fish species of the Northwest Atlantic You are what you eat … whenever you eat it: an integrative analysis of fish food habits across different seasons in eastern US and Canadian waters Post-doc (Júlio Neves de Araujo) at BIO Post-doc to be hired at SABS for MSVPA modelling

Any questions?

Develop Ecopath (energy budget models) for the western Scotian Shelf and Bay of Fundy for Begin development of MSVPA model for herring in NAFO Division 4X to Review range of further ecosystem models to be investigated

Comparison of WSS and BoF models with EMAX (US) models for GoMA Further development of Ecopath models for the WSS and BoF for the early 1970s Time-series fitting of Ecopath with Ecosim trophodynamic simulations for Bay of Fundy and Western Scotian Shelf in preparation for exploring climate change scenarios from Theme 1 Further development of MSVPA model for herring in NAFO Division 4X and initial evaluation of results. Revise/refine model setup as required. Develop aggregate biomass models of Bay of Fundy and western Scotian Shelf (with Can USE WG).

Compare results between models, within and across regions: –With respect to relative performance of alternative fishing mortality and incidental mortality reference values for the GoMA –With respect to impact of changes in energy flow on harvest rates –With respect to the relative importance of ecosystem structure on ecosystem dynamics and harvest rates Summarize implications of MSVPA model on management strategies and reference harvest rates for herring in NAFO Division 4X. Synthesis of results and recommendations for future work

Broad Categories of Information Conceptual –Understanding Ecosystem Functioning –Relative Importance of Different Processes –Advancing Scientific Theory –Forms underlying context for management planning and decision making Strategic –Generally long-range, broadly-based and inherently adaptable –Linked to policy goals –What if scenarios, gaming, trade-offs, reference directions, long term trends Tactical –Aimed at short term –Stock assessment advice (TACs, Reference Points) –Linked to an operational objective

Use of model(s) depends on the questions being asked, data availability, time frame, resources All the models explored are useful!

MSVPA = VPA plus an equation describing predation mortality Where is the number of individuals that have died from predation, s is species, a is age, and t is time step (often quarter) Predation mortality Slide from Henrik Gislason