Presentation on theme: "1 Ecological and Economic Considerations in Management of the U.S. Pacific sardine Fishery Samuel F. Herrick Jr NOAA Fisheries Southwest Fisheries Science."— Presentation transcript:
1 Ecological and Economic Considerations in Management of the U.S. Pacific sardine Fishery Samuel F. Herrick Jr NOAA Fisheries Southwest Fisheries Science Center
Report on ongoing work in collaboration with Rognvaldur Hannesson, Norwegian School of Economics and Business Administration and John Field, NOAA Fisheries, Southwest Fisheries Science Center Publications: –Hannesson, R., S. Herrick and J. Field Ecological and economic considerations in the conservation and management of the Pacific sardine (Sardinops sagax). Ca. J. Fish. Aquat. Sci. 66: –Hannesson, R. and S.F. Herrick Jr The value of Pacific sardine as forage fish. Marine Policy 34: 935–942 2
3 Account for the total value sardines provide in terms of their function in the California Current Ecosystem Basically a matter of balancing the economic benefits from harvesting sardines against the economic benefits from leaving sardines in the water At this point –Present the analytical framework for evaluating the tradeoffs –Show what has been done with existing data –Draw some conclusions
4 Uses of the Pacific sardine resource in the California Current Ecosystem
5 Summarize as follows
6 The analytical framework to address this issue: –Suppose that the catch of sardines is reduced by S –The value of this incremental sardine stock as forage would be given by (1) Where: – i indexes species that feed on the sardine, –P i is the price (net of fishing costs) of species i, –a i is the share of the incremental sardine stock that is eaten by species i, and –b i is the transfer efficiency, the fraction converted to predator biomass –If the sardine is more valuable as commercial landings than as forage fish the following must hold: (2) Where P s is the market price of sardine, net of fishing costs.
7 The predators of the sardine are not all commercially valuable –Dividing the right hand side of (2) into commercial and non- commercial predators, and canceling the S on both sides, gives (3) Where: v is a non-market average value per unit of biomass growth of non- commercial predators attributable to sardine consumption i is an index for the commercially valuable species j is an index for the non-commercial species The right hand side is the value of the increase in the amount of sardine predators provided by a unit increase in the sardine stock –The P i’ s and v have to be large enough to reverse the inequality for sardine to be more valuable as forage species Calculate the critical value of v, that turns (3) into an equality
8 We used the data published in Field et al. (2006) to identify sardine predators and to calculate values for the parameters a and b for each predator k Prices, P, are real average exvessel prices over the period
9 Critical value of v under different pricing scenarios: 1.Base case, v = $6.78/kg The annual net benefit of a one kg increase in the biomass of all non-commercial predators induced by the incremental supply of sardines as forage. 2.Five-fold increase in the price of sharks to reflect their potential recreational value: from $1.73 to $8.47/kg, v = $0.0/kg The increase in the value of sharks would suffice to make the sardine more valuable as forage. 3.20% increase in salmon and albacore prices with a 20% decrease in price of sardines, v < $0.0/kg These price differences are within the range of prices for the period, indicating that the value of sardine as forage is quite sensitive to realistic changes in its own price and those of commercially relevant predators.
10 Critical value of v under different biological/ecological parameter scenarios: 1.Increase the transfer efficiency, b, to.02 for salmon, albacore and coastal sharks, v = $3.81/kg A higher transfer efficiency by itself would not make sardine sufficiently valuable as forage for the commercial predators alone at the assumed baseline biological parameter values and exvessel prices. 2.Increase the share of sardines in the diets of salmon, albacore and coastal sharks by 40%, v < $0.0 If increased consumption of sardines by commercial predators is realistic, it would imply that the sardine stock is more valuable as forage fish than as commercial catches.
11 Conclusions: –The total value of forage species is derived from their commercial harvest value and their value as prey for commercially, recreationally and ecologically important stocks –To quantitatively model this situation requires a great deal of detailed economic and ecological data On the economic side –Market values »the net benefits of harvesting sardines and their commercial predators rely on market prices and costs associated with their harvest –Non-market values »recreational catches are not sold »ecologically important species are public goods On the ecological side –Identify sardine predators »the proportion of the sardine biomass that is consumed by each predator »transfer efficiencies –The relationships that have been modeled here are likely to be non- linear and dependent on the relative abundance of sardines and their predators –Management strategy likely to vary with the composition of the forage base Composition of forage base determined by environment
Species by trophic level and trophic category. 13
15 Ecological data: –Field, J.C., R.C. Francis and K. Aydin Top-down modeling and bottom-up dynamics: Linking a fisheries-based ecosystem model with climate hypotheses in the California Current. Progress in Oceanography 68:
Predators, ecological parameters, shares of sardine eaten by predators (a), and prices of sardine and its predators. PredatordS/km 2 gba Price ($/kg) Salmon Albacore Coastal sharks Common murres Gulls Orcas Toothed whales Sea lions Fur seals Baleen whales Sardine