A MODEL FOR THE PRELIMINARY-ANALYSIS OF THE ECONOMIC-FEASIBILITY OF ATLANTIC COD ENHANCEMENT IN THE GULF OF MAINE (USA)

The 116th Maine state legislature created the Groundfish Hatchery Stud y Commission in 1993 to investigate the economic feasibility of stock enhancement. The commission generated a model that balanced the costs of hatchery operations against the income realized from an augmented A tlantic cod (Gadus morhua) fishery. Because the most problematic data were those on mortality after the fish were released into the ocean bu t before their recruitment into the fishery, the model results are exp ressed as a required survival rate for fish, from the time of release from the hatchery until their recruitment into the fishery, necessary for an economic break-even, i.e., neither profit nor loss. The model, which was constructed with the STELLA programming language, can be cha racterized as a dynamic net-present-value model consisting of two conc eptual layers. The first is a simulation of hatchery operations, a wil d population into which the fish are released, and a market in which f ish are caught and sold. The second layer checks the economic results for each hatchery cohort of fish by comparing the value of the catch a ttributable to hatchery-raised fish with the cost of producing those f ish. If profits differ from zero, the survival rate is adjusted, and t he model is rerun until the break-even point is found. Because experie nce rearing Atlantic cod selecting their location for release, and tim ing their release in the wild will alter the initial survival rate est imates, the intelligent use of the model is to use sensitivity analysi s to produce a range of answers that depend on circumstances. This app roach allows for the identification of economic or biological bottlene cks that might be addressed through research and/or policy development . To illustrate possible outcomes, we have generated a range of surviv al rates for the release of three different life-history stages. The l owest required rate of survival for example, of 0.19%, was for the rel ease of fertilized eggs. In contrast, release of 36-wk-old juveniles w ould require a survival rate of at least 28% from their time of releas e until recruitment into the fishery.