The Role of Fisheries in Optimal Eutrophication Management

Transcription

1 The Role of Fisheries in Optimal Eutrophication Management ECA-project Antti Iho

2 ECA-project Initial plan joint output Iho, A., Ahtiainen, H., Artell, J., Heikinheimo, O., Kauppila, P., Kosenius, A.K., Laukkanen, M., Lindroos, M., Oinonen, S., Ollikka, K. and Parkkila, K., Pavlova, Y. Peltonen, H., Pouta, E. & Uusitalo, L The Role of Fisheries in Optimal Eutrophication Management. Water Economics and Policy, p

3 Main objective Establish a bioeconomic framework capable of anlayzing the efficiency of eutrophication management, acknowledging External load reducion Restoration activities Food web effects Concrete modelling choices Focus on phosphorus (P) Agricultural P loading P removal by fisheries (Poorly understood) food web effects Long term (i.e. steady state) analysis to prevent one-shot tricks to appear optimal

4 A note on fisheries and P removal, Baltic Sea North Sea Fisheries Deep sediments As a system, Baltic Sea has three major outlets for P; rough estimates: Deep sediments (about tonnes per year; not the same as annual net sedimentation to surface sediments) North Sea net exchange (about tonnes per year) Commercial fisheries (about 3000 tonnes per year) P removal of fisheries is significant Relevance for eutrophication management?

5 Main commercial fish stocks (sprat, cod, herring); sum up and use a logistic growth function 3500 Stock and net growth Harvest in tons of P Stock size What if we are at the MSY? Changing the intensity of fisheries

6 Main commercial fish stocks (sprat, cod, herring); sum up and use a logistic growth function 3500 Stock and net growth Harvest in tons of P Stock size Increasing harvesting efforts which would bring the stock down in the long run and decrease P removal

7 Main commercial fish stocks (sprat, cod, herring); sum up and use a logistic growth function 3500 Stock and net growth Harvest in tons of P Stock size Decreasing harvesting efforts which would increase the stock in the long run and decrease P removal

8 Issues in fisheries policies regarding commericially viable fish species Illegal fishing Coordination, cooperation Monitoring, enforcement Free riding A huge existing machinery to design policies: analyze, negotiate TACs Adding nutrient removal as a social benefit would not change the basics of fisheries policies Non-additive measure a good one, but no need to touch

9 How about species that used to have commercial value but today do not? Stock and net growth Harvest in tons of P Stock size Situation 100 years ago. Competion might have brought the stocks below optimum but still significant, annual P removal

10 How about species that used to have commercial value but today do not? Stock and net growth Harvest in tons of P Stock size Situation now. Stocks very high, P removal negligible

11 Low commercial value Why, and what does it mean? Low demand leads to low prices (customer prefers bream or roach over Norwegian salmon or Baltic reinbow trout) Low prices decrease fishing efforts Stylized facts: 1. Changing customers preferences to favour (again) bream & roach is extremely difficult 2. Changing fishermen s efforts to certain fish species happens very quickly fishermen react to prices Price can be changed by subsidies very quickly

12 Could fisheries of non commercial species play a role in long term eutrophication management? The long run model External P loading from agriculture P stock of the water body develops as a function of time, loading and P removal (fisheries one component in removal) Damages from eutrophication, i.e. poor water quality Costs from nutrient abatement from agriculture Costs and revenues from fisheries Fishing efforts set the fish stock in an equilibrium level Equilibrium fish stock may have and effect on water quality (the food web effect) Food web effect unknown

13 Optimality conditions αz = βd Q 1 β(1 ρ) p γ S = βf S p γ X D X βξ(1 βf S ) 1 β(1 ρ) D Q

14 Optimality conditions, external P abatement αz = βd Q 1 β(1 ρ) p γ S = βf S p γ X D X βξ(1 βf S ) 1 β(1 ρ) D Q Marginal abatement costs equals the shadow value (marginal damage) of the P stock, discounted back one period

15 Optimality conditions, fisheries αz = βd Q 1 β(1 ρ) p γ S = βf S p γ X D X βξ(1 βf S ) 1 β(1 ρ) D Q Marginal profits must equal

16 Optimality conditions, fisheries αz = βd Q 1 β(1 ρ) p γ S = βf S p γ X D X βξ(1 βf S ) 1 β(1 ρ) D Q Marginal profits must equal discounted values a change in marginal escapement has on - Profits - Environmental damage via food web effect - Environmental damage via P removal

17 Optimality conditions, fisheries αz = βd Q 1 β(1 ρ) p γ S = βf S p γ X D X βξ(1 βf S ) 1 β(1 ρ) D Q Marginal profits must equal discounted values a change in marginal escapement has on - Profits - Environmental damage via food web effect - Environmental damage via P removal

18 Optimality conditions, fisheries αz = βd Q 1 β(1 ρ) p γ S = βf S p γ X D X βξ(1 βf S ) 1 β(1 ρ) D Q Marginal profits must equal discounted values a change in marginal escapement has on - Profits - Environmental damage via food web effect - Environmental damage via P removal

19 Application, Mynälahti Fixed parameter values in simulations. Parameter/function Value Unit i Interest rate β Discount factor β = 1 1+i Transition of the phosphorus concentration: Q t+1 = 1 ρ Q t + തq z t ξ X t S t ρ Decay rate of the phosphorus stock തq Baseline loading 8.6 ton ξ Phosphorus concentration in cyprinid fish 0.75 per cent Transition of the fish population: X t+1 F S t = S t + rs t 1 St K r Intrinsic growth rate K Carrying capacity of the fish stock 1500 ton Fishery profits: π f = p X t S t γ ln Xt S t p Market price for fish 400 EUR/ton γ Cost parameter for harvesting EUR Profits from agriculture: π a = തπ a 1 2 αz t 2 തπ a Normalized profits with zero abatement 0 EUR α Cost parameter for phosphorus abatement EUR/ton Damage function: D = σ κ + η ln Q t c ω 1 Xt K σ Value of the marginal environmental damage 317,40 κ Intercept of the phosphorus water quality function η Slope of the phosphorus water quality function 19 ω Cyprinid fish stock s direct effect on water quality EUR

20 Results Socially and privately optimal steady state phosphorus abatement and concentration, and fisheries and fish stock Social optimum Sole owner Open access Annual Harvest X S Escapement S Phosphorus z Abatement Phosphorus Stock Q Phosphorus Concentration Q c Profits π f + π a Damage D Welfare W

21 Results

22 Results

23 Results

24 Thank you!