Bio economic Simulations of Management Measures Contributing to Restoration of a Crustacean Shellfish Stock: the Case of the Nephrops in the Bay of Biscay Claire Macher (1), Olivier Guyader (2), Catherine Talidec (3) (1) UBO, Brest, Centre de Droit et d Economie de la Mer/ Ifremer, Brest, Département d Economie Marine (2) Ifremer, Brest, Département d Economie Maritime (3) Ifremer, Lorient, Département Sciences et Technologies Halieutiques, Laboratoire de Biologie des Pêcheries tons 6 5 4 3 2 1 7h1 8c1 7g1 7h3 8a2 7g2 7h2 8d1 7f1 7e2 8c2 7e1 8a1 7d2 8b1 7d1 Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 scenario 6 age 6
STRUCTURE OF THE COMMUNICATION The problem of discards The bio economic model Results of the simulations of selectivity measures Discussion and conclusion
PROBLEM OF DISCARDS N (') 12 1 8 6 4 2 grade 4 grade 3 23 grade 2 Discards Landings grade 1 grades and prices 1 2 3 4 5 6 7 8 9+ High level of discards: 1875 tons in 23, 6% of the Nephrops caught in number, 3% in weight (Talidec et al., 25) responsible for both stock and economic impact (prices increase with ages) Need to modify the exploitation pattern through selectivity measures To reduce discards To conserve the stock To improve sustainability of the exploitation (dependence on recruitment) 14 12 1 8 6 4 2 euros/kg
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant ECONOMIC MODEL
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Fishing effort: number of days at sea Nds ECONOMIC MODEL 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Fishing mortality Selectivity factor % and discards mortality Fishing effort: number of days at sea Nds ECONOMIC MODEL 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Nephrops Stock Biomass Fishing mortality Selectivity factor % and discards mortality Catches Fishing effort: number of days at sea Nds ECONOMIC MODEL 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Nephrops Stock Biomass Fishing mortality Selectivity factor % and discards mortality Discards Catches Landings Fishing effort: number of days at sea Nds ECONOMIC MODEL 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Nephrops Stock Biomass Fishing mortality Selectivity factor % and discards mortality Discards Price model F(quantity and grades) Catches Landings Total revenue Nephrops Fishing effort: number of days at sea Nds ECONOMIC MODEL 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Nephrops Stock Biomass Fishing mortality Selectivity factor % and discards mortality Discards Price model F(quantity and grades) Catches Landings Total revenue Nephrops Total revenue other species Fishing effort: number of days at sea Nds ECONOMIC MODEL 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Nephrops Stock Biomass Fishing mortality Selectivity factor % and discards mortality Discards Price model F(quantity and grades) Catches Landings Total revenue Nephrops Total revenue other species Fishing effort: number of days at sea Nds wages Profits Rent ECONOMIC MODEL STATIC : constant effort 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE BIO ECONOMIC MODEL : annual simulation model BIOLOGICAL MODEL R constant Nephrops Stock Biomass Fishing mortality Selectivity factor % and discards mortality Discards Price model F(quantity and grades) Catches Landings Total revenue Nephrops Total revenue other species Fishing effort: number of days at sea Nds wages Profits Rent ECONOMIC MODEL DYNAMIC :Nds n= f(profit n-1) Variable effort 1 sub-fleets Criteria: - 2 Geographic segments - 5 crew categories Costs structure (variable and fixed costs)
THE SCENARIOS OF SELECTIVITY MEASURES Scenario 1 statu quo Scenario 2 Age 2 6.3 cm Scenario 3 Age 3 8.8 cm min landings size Scenario 4 Age 4 1.4 cm Scenario 5 Age 5 11.8 cm Analysis of the potential impacts of these scenarios on discards, biomass, landings and economic indicators Scenario 6 (alternative gear) Age 6 13.1 cm
THE STATIC MODEL : constant effort 14 12 1 8 6 4 2 45 4 35 3 25 2 15 1 Discards in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scénario 6 âge 6 Biomass in tons Scenario 1 Age 1 Statu quo Scenario 2 Age 2 (6.3cm) Scenario 3 Age 3 (8.8cm) 6 5 4 3 2 1 Potential impacts of selective devices adoption : preliminary results on discards, biomass, landings Landings in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scenario 6 age 6 Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 scenario 6 age 6
THE STATIC MODEL : constant effort 14 12 1 8 6 4 2 45 4 35 3 25 2 15 1 Discards in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scenario 6 age 6 Biomass in tons Scenario 4 Age 4 (1.4 cm) 6 5 4 3 2 1 Potential impacts of selective devices adoption : preliminary results on discards, biomass, landings Landings in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scenario 6 age 6 Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 scenario 6 age 6
THE STATIC MODEL : constant effort 14 12 1 8 6 4 2 45 4 35 3 25 2 15 1 Discards in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Biomass in tons Scenario 5 Age 5 (11.8 cm) 6 5 4 3 2 1 Potential impacts of selective devices adoption : preliminary results on discards, biomass, landings Landings in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scenario 6 age 6 Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 scenario 6 age 6
THE STATIC MODEL : constant effort 14 12 1 8 6 4 2 45 4 35 3 25 2 15 1 Discards in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scénario 6 âge 6 Biomass in tons Scenario 6 Age 6 (13.1 cm) 6 5 4 3 2 1 Potential impacts of selective devices adoption : preliminary results on discards, biomass, landings Landings in tons Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 Scenario 6 age 6 Scenario 1 statu quo Scenario 2 age 2 Scenario 3 age 3 Scenario 4 age 4 Scenario 5 age 5 scenario 6 age 6
million euros illion euros 45 4 35 3 25 2 15 1 5-5 45 4 35 3 25 2 15 1 5-5 THE STATIC MODEL : constant effort Potential impacts of selective devices adoption : preliminary results on fleets profits Scenario 3 Scenario 5 Scenario 1 statu quo Scenario 3 age 3 Scenario 1 statu quo Scenario 5 age 5 The long term gains offset the short term losses Million euros Million euros 45 4 35 3 25 2 15 1 5-5 45 4 35 3 25 2 15 1 5-5 Scenario 4 Scenario 6 Scenario 1 statu quo Scenario 4 age 4 Scenario 1 statu quo Scenario 6 age 6 Restoring the stock does not necessarily induce a negative net benefit Rent formed by adopting scenario 3 would be a profit of 25 euros per vessel ( actualization rate 4% on 24-215)
THE DYNAMIC MODEL : variable effort Scenario 3 at constant effort and with an endogenous effort are compared tons Million euros 3 25 2 55 5 45 4 35 3 Landings Scenario 1 statu quo Scenario 3 age 3 constant effort Scenario 3 age 3 variable effort Rent of the fishery euros 6 55 5 45 4 35 3 Profit per effort unit Scenario 1 statu quo Scenario 3 age 3 constant effort Scenario 3 age 3 variable effort Dissipation of rent occurs when the number of days at sea increases Traduces a loss of fleet economic performance 15 Scenario 1 statu quo Scenario 3 age 3 constant effort Scenario 3 age 3 variable effort underlines the need to control effort
DISCUSSION AND CONCLUSION Restoring the biomass thanks to technical measures does not mean negative net benefit (high proportion of discards of small individuals). Long term gains offset short term losses ex scenario 3 By taking into account economic dynamics of increasing effort we show however that selectivity measures are insufficient to ensure the restoration of the stock. An individual access regulation to the fishery is required (Individual quotas, licences with nb of days at sea )
mean nb of days at sea per vessel 3 25 2 15 1 THE DYNAMIC MODEL Taking into account the increasing effort dynamic for the evaluation of the potential impacts of improving selectivity scenario nb of days at sea profit year t-1 When a rent is formed, the ship-owner is incited to increase his fishing effort 13 12 11 1 9 8 7 6 5 in keuros per middle vessel 21 23 25 Do not disseminate 27without author authorization 29 211 213 215 Endogenous fishing effort: nb days at sea year n= f(profit of year n-1)
1 euros maintenant n a pas la même valeur que 1 euros dans dix ans exemple: 1 placé à un taux d intérêt fixe de 5% vaut 1,63 en période 1 Inversement, recevoir 1 actuellement est équivalent à recevoir 1,63 dans 1 ans avec un taux d intérêt de 5% période période 1 période 2 période 3 période 4 période 5 période 6 période 7 période 8 période 9 période 1 1. 1.5 1.1 1.16 1.22 1.28 1.34 1.41 1.48 1.55 1.63
tons 23 22 21 2 19 18 17 16 15 Biomass Scenario 1 statu quo Scenario 3 age 3 constant effort Scenario 3 age 3 variable effort
THE BIO ECONOMIC MODEL An annual simulation model on the 24-215 period, to analyze the transition phases and perform a cost-benefit analysis of the adoption of different selectivity measures A biological structural model based on an hypothesis of a constant recruitment Stock Dynamic of Nephrops is taking into account Other species are supposed to be exogenous An economic model - static to compare the profit of the different scenarios - dynamic to take into account an increasing effort
Nb Nephrops trawlers (VIIIa,b) 234 Crew Number Vessel Average Categories of Vessels Length Class Gross Revenue ]1-2] 33 [9-12[ mètres 1.64 ]2-3] 64 [12-16[ mètres 3.15 ]3-4] 59 [16-2[ mètres 4.56 ]4-5] 6 [2-24[ mètres 5.41 ]5-1] 18 Landings 39 t Gross revenue from Nephrops 33.2 M Total gross revenue 82.4 M