1. Technical Challenges and Tradeoffs of Managing Multi-species Fisheries in the Northeast US Mission 2011: Can we save our oceans? Massachusetts Institute of Technology September 28, 2007 Paul J. Rago National Marine Fisheries Service Northeast Fisheries Science Center Woods Hole, Massachusetts

2. Putting the cart before the horse isn’t the only problem to worry about. Why is Fisheries Management so Difficult? Common Property Resource No ownership Shifting Baselines History is lost Allocation Fisheries, States, Ports Inelastic demand Pay any price Increases in Fishing Power Electronics Speed, Capacity Multiple Jurisdictions Fed,State,Local Law suits ~100 pending Multiple Species Non-selective harvest Varying Productivity

3. Technical challenges are pervasive “An Indian fisherman speaks on his cellphone to other fishermen as he moves toward a large school of fish. Fishermen are also using cellphones while at sea to call traders and check prices for their catch”. Andy Mukherjee, National Post, 2/24/05 Photos by Deshakalyan Chowdhury A panoramic view of the New Bedford waterfront

4. Can we engineer our way out of the problem? Are closed areas effective? Is there a downside to closing areas without additional controls?--Jensen Inequality How do we deal with environmental change? How do we deal with tradeoffs among non- commensurate quantities? Note that closed areas do not correct the conditions that led to need of closed areas in the first place — excess effort. Closed areas can reduce dependency on effort reductions, and provide “ insurance ” policy but response is necessary “life does not stand still while specialists put their minds in order” Michael Graham, 1950. Address to United Nations Technical Challenges

5. Large Scale Experiments Foreign Fleets EEZ and Increase in Domestic Fleet Closed Areas Effort Reductions Foreign Domestic

6. Large Scale Changes in Species Assemblages

7. Surplus Production Models Limited Population Growth –Logistic growth: populations increase proportional to their biomass, but the rate of increase slows as the population approaches its carrying capacity. –Rate of change (production) is maximum when the population is at half of its carrying capacity. Carrying Capacity Rate of Growth Time Stock Biomass ‘all models are wrong, some are useful’. G.E.P. Box

8. Graham-Schaefer Model: Discrete Time Surplus Production (1) B t = stock biomass in year t K = unfished stock biomass at carrying capacity r = intrinsic rate of stock growth. Now Catch C can be written as the product of fishing mortality F and stock size B or more generally as a function of stock biomass, fishing effort E, and a constant, known as the “catchability coefficient” q Substituting for C t gives--

9. Graham-Schaefer Model: Discrete Time Surplus Production E t = Effort in year t q = catchability coefficient (fraction of resource removed per unit of effort. At equilibrium, biomass B* can be written as a function of Effort such that

10. Production Models Graham’s Theory of Sustainable Fishing (1935): –If removals can be replaced by stock production each year, the fishery is sustainable. –If stock size is maintained at half its carrying capacity, the population growth rate is fastest, and sustainable yield is greatest (Maximum Sustainable Yield). Stock Biomass Sustainable Yield Maximum Sustainable Yield = MSY Biomass at MSY 0 K MSY=rK/4 K/2

11. Managing at the Margins Balancing a population at B MSY can be precarious Changes in stock size can occur due to many factors—many of which cannot be controlled. Targeting for a population size greater than B MSY creates a “reserve” that reduces yield slightly and protects against changes in stock status Stock Biomass Sustainable Yield Maximum Sustainable Yield = MSY Biomass at MSY Not Overfished Overfished K K/2 0

12. Managing at the Margins Balancing a population at F MSY can be precarious also Changes in fishing mortality can arise form several sources Targeting for a fishing mortality rate LESS than F MSY leads to higher biomass, a slight reduction in yield and reduces the need for future reductions in effort. Fishing Mortality Rate Sustainable Yield Maximum Sustainable Yield = MSY Fishing Mortality Rate at MSY Overfishing Not Overfishing r/2 r 0

13. Status determination is based on a comparison of current estimates of fishing mortality and spawning stock biomass with their respective biological reference points. The comparison is based on the ratio of the current value to the reference value. There are 4 possible categories based on overfishing and overfished status.

14. Where do you want to manage the resource? Managing at the margin makes changes in stock status very likely given the expected variation in assessments. In this instance, 75% of the outcomes are bad.

15. Where do you want to manage the resource? Managing AWAY from the margin makes changes in stock status less likely and increases planning time for management and business

16. Graham-Schaefer Model: Extension to multiple species B s,t = stock biomass of species s in year t K s = unfished stock biomass at carrying capacity r s = intrinsic rate of stock growth. E t = Effort in year t At equilibrium, biomass B s * can be written as a function of Effort such that

17. Extension to multiple species. Which species will be overfished? Overfishing will occur whenever A stock is overfished when B<1/2 K. Using the equilibrium formulation, then the effort sufficient to create an over fished status is

18. Haddock: The Agony of Recovery Cod: The Misery of Decline

19. Results of 2005 Groundfish Assessment Review Meeting: Comparisons with Reference Points Species Key AbbreviationStock/Species GBYT1Georges Bank Yellowtail Fl. “Base Model” GBYT2 Georges Bank Yellowtail Fl. “Major Change Model” CCYTCape Cod/Gulf of Maine Yellowtail Fl. SNEYTS. New England/Mid Atlantic Yellowtail Fl GM CodGulf of Maine Cod W HakeWhite Hake GG CodGeorges Bank Cod SNE WinterS. New England Winter GM HadGulf of Maine Haddock GB HadGeorges Bank Haddock PlaiceAmerican Plaice S WindowSouthern Windowpane Fl. PoutOcean Pout GB WintGeorges Bank Winter Flounder WitchWitch Flounder Pollock GM WinterGulf of Maine Winter Flounder RedfishAcadian Redfish N WindowNorthern Windowpane Fl.

20. Is the single species surplus production paradigm applicable to multispecies management? Well, only if intrinsic rates of population increase r, carrying capacity K and catchability q are the same. Otherwise, stocks will respond differently to a common level of effort E. If it is undesirable to create an overfished condition then total effort must be lower than THEREFORE — Weakest Link Management Manipulations of q s via gear modifications etc may be possible but such changes will affect other species.