Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior Dipl.-Geogr. Peter Michael Link, BA Research Unit Sustainability & Global Change Center for Marine and Climate Research University of Hamburg, Germany

Outline of the presentation Context of the study Characteristics of the bioeconomic model Simulations with adaptive harvesting strategies: What are the impacts of changes in reproductive rates or carrying capacities? Simulations with rational behavior: To what extent are stocks and harvest amounts affected by changes in population dynamics? Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior How does the economic impact change depending on the harvesting strategies of the fishermen?

The research project INTEGRATION INTEGRATION looks at the impacts on ecosystems and society caused by a regional or global breakdown of the thermohaline circulation. This is done along two paths: 1.ocean circulation  climate change in Europe  agriculture and forestry  economy and society 2.ocean circulation  plankton  fish  fisheries (economy and society) Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Structure of the model covering two fish species and three fleet types environmental change cod: age 0 recruitment cod: age 1 cod: age 2 cod: age N capelin: age 0 recruitment capelin: age 1 capelin: age 2 capelin: age N fishing effort fixed costs, variable costs profits revenue total catch fishing effort fixed costs, variable costs profits revenue total catch fishing effort fixed costs, variable costs profits revenue total catch cod stock capelin stock coastal fisheries trawlerspurse seine fisheries Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Adaptive strategies: development of the cod stock for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Adaptive strategies: development of the capelin stock for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Adaptive strategies: development of total cod catches for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Adaptive strategies: development of total capelin catches for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Adaptive strategies: net present value of profits for different levels of reduction of reproductive rates Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Impacts of changes in fish population dynamics when fishermen follow adaptive strategies The stock sizes of cod and capelin decrease over time if the population dynamics of the species are negatively affected. This in turn leads to smaller total annual catches. Therefore, there is a negative long-term development of the fisheries. This trend is in some cases masked by the short-term increase of the the returns from fishing which occurs despite a continued decrease of the stock sizes. The net present value of profits in years changes only marginally since the significant effect on catches occurs mainly in the second half of this period of interest. Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Rational behavior: development of the cod stock for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Rational behavior: development of total cod catches for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Rational behavior: development of the capelin stock for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Rational behavior: development of total capelin catches for different reductions of the rate of reproduction Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Impacts of changes in fish population dynamics when fishermen seek profit maximization The stock sizes of cod and capelin show no clear trend with decreasing rate of reproduction. A smaller reproductive rate in the capelin stock can be offset by a reduced predation pressure. The extent of the impact on the cod stock depends on how heavily exploited the fish stock is. Catches of cod can fluctuate drastically, indicating that fishing operations take place on the edge of profitability. Capelin catches generally follow the development of the stock, taking advantage of less predation by cod. Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Comparison of the observed effects with regard to the harvesting strategy emloyed (1) Fishing with the goal of profit maximization removes all old age classes. With adaptive strategies all age classes remain present in the stock throughout the simulation period. Adaptive strategies: trawlers and coastal vessels share cod fishery with coastal vessel share increasing over time Profit maximization: change of age structure practically forces coastal vessels out of the market. Almost the entire share of cod catches come from trawlers. Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Comparison of the observed effects with regard to the harvesting strategy emloyed (2) The overall profits of trawlers are similar when population dynamics are affected only marginally. For large reductions of the reproductive rate the cod fishery becomes unprofitable under profit maximization. Changes in the rate of reproduction have a slightly higher impact on the capelin fishery under profit maximization except for the cases in which larger and less predated stock leads to a increased landings and therefore higher returns from fishing. Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

Comparison of the observed effects with regard to the harvesting strategy emloyed (3) Changes in population dynamics would only affect stocks marginally without the presence of fisheries. The absence of harvesting activities can lead to a stable stock size despite a significantly lower rate of reproduction. Complete stock failures only occur in simulations with a drastically reduced carrying capacity and significant fishing activity. Economic impacts of changes in fish population dynamics: the role of the fishermen’s behavior

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