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Published byGertrude Montgomery Modified over 9 years ago
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Bridging from single species tactical advice to ecosystem-based strategic advice Lesson 1: We should expect our models to fail, sometimes spectacularly so. But when we do we should take the opportunity to learn from the failure
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Traditional approach to fisheries management Management approach focuses on F via catch & effort regulation – Stock assessments recommend B and F reference points – SSC recommend ABC (<=OFL) that includes scientific uncertainty –tactical advice – Council recommend ACT (<=ABC) that includes management uncertainty (implementation uncertainty) Stakeholders limited to – Commercial fishery interests – Managers (protecting societal interest)
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Approach to incorporating scientific uncertainty Select %ile of probability distribution Lack of data in many systems means that P* is becoming ordinal as cF lim But this assumes that all stakeholders will want a maximal F
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4 Stakeholders can be responsible Council recommendation 10M Lbs quota 3 fish bag limit >24 in min size Stakeholder choice 8M Lbs quota 2 fish bag limit >28 in min size How and why did recreational anglers, CCA, and NGOs become more conservative than managers?
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5 Stakeholder-centered approach Stakeholders propose objectives, options and performance measures Revise options and performance measures Model development and modification Stakeholders Review model results Recommendations
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6 Model Schematic “Natural” Deaths Reproduction Growth & Maturity Fishing Migration
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7 Model Structure Abundance Mortality Catch N = AbundanceF = Inst. Fishing mort. Rate M = Natural mort.Z = Total mort. p = migration rate y = years = season a = agex = sex o = areaf = fishery
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8 Parameter uncertainty Simulations drew from parameter distributions that reflected either – Scientific uncertainty – System uncertainty Recreational F – used 3 scenarios: either increasing, constant and decreasing scenarios with white noise variability (lognormal CV 10%) Ran multiple simulations to yield distributions of outcomes
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9 Recommended options SSB F Season closure 8M, 2 Fish, 28in 8M, 2 Fish 8M, 32in Status Quo 8M, 2 Fish, 28in 8M, 2 Fish 8M, 32in Status Quo 8M, 2 Fish, 28in 8M, 2 Fish 8M, 32in Status Quo
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Lesson 2 Don’t under-estimate the ability of stakeholders to understand complicated management questions and processes. Stakeholder involvement is critical at all stages of management – Objectives – Management alternatives – Evaluation
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EAM Strategic advice: Management policies that support long term fishery and ecosystem sustainability
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What kind of EAM do you want? Lesson 3: Understanding of EAM by managers and stakeholders is at a infant’s level - education is critical
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Case Study: Chesapeake Bay Fishery Ecosystem Plan Ecosystem boundaries – ~350 fishes described in Chesapeake Bay – Variation in life history causes boundary problems
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FEP: Boundary issues Biological – 2 Large marine ecosystems Human – 11 states – 3 multi-jurisdictional commissions – 2 regional management councils – 2 nations
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FEP: Simple strategic advice Patterns based on total removals Empirical evidence suggests ~250,000 mt may be sustainable 75,000 mt of non- menhaden harvest has been sustained
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Ecosystem dynamics Used to examine ecosystem context of single species management decisions – What would happen if the region achieved a goal of a 10-fold increase in oyster biomass? Concerns Fisheries model in a “microscopic” ecosystem My species wasn’t included Are we modeling the tail or the dog? Modeling effort was not integrated into management Maryland Sea Grant asked to facilitate an ecosystem based process for the Chesapeake Bay
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Single-species ecosystem-based FMPs
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Single-species ecosystem-based reference points Striped bass
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Case study: Atlantic menhaden Estuarine-dependent pelagic planktivore that provides ecosystem-services – by filtering phytoplankton – important prey resource for charismatic piscivores Stock migrates along coast from Florida to Maine Juveniles use estuarine nursery areas Stock assessment (2006) indicates neither stock is not overfished, nor experiencing overfishing. Yet concerns expressed over “localized” depletion in Chesapeake Bay
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Localized depletion? A spatially-restricted decline in abundance that impairs ecological function – Predator production – Nutrient export Otolith chemistry evidence suggests spatial structure
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Nutrient export services
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MS-models Predator-prey model – Climate-driven recruitments are strongly negatively correlated – Stochastic, correlated SR function PaPa
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MS – models: effects of recruitment correlation on depletion
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Biophysical EM Luo et al.
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Biophysical EM Sample output
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Lesson 3 Defining the question is essential – What is localized depletion? Models with different outputs can’t be compared – What are the common metrics Reference points for non fishery endpoints are needed
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Case study: Regime shifts in the northwest Atlantic Dramatic shift from a groundfish-dominated community to an elasmobranch-dominated community Multiple explanatory hypotheses
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Winter skate length frequencies Frisk et al. 2008
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Closed Ecosystem? Could broadscale movement of adult skate from Scotian Shelf be responsible
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Ecosystem change on the Scotian Shelf Figures from Frank, 2003
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Lesson 4: Even the most successful EM may not forecast the future state of the ecosystem – CBO budget forecasts have all been wrong, but that doesn’t mean that they haven’t been useful. Managing expectation is critical
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Recommendations Given a goal, what approaches are feasible or useful? – There needs to be a clear statement of what question is the model being used to ask – Not all ecosystem questions require an EM What comes first – goal or stakeholders? – The stakeholders you have in the room will affect the stated goal or vision – Engage stakeholders early and often Strategic advice may not be of the form of control rules, e.g., ecosystem services – How then do EM feed into the management process, particularly ?
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