A methodology for quantifying and valuing the impacts of flow changes on a fishery

Abstract

A quasi-population model for adult brown trout was developed for the Taylor River below the Taylor Park Reservoir in Colorado. This model allows the population to be predicted under alternative flow management regimes. The predicted population effects of two different flow release patterns were compared with the predicted population for the current reservoir operation regime. Changes in angler catch were imputed for these scenarios. The changes in catch were valued using estimates of willingness to pay obtained from anglers fishing at the site. Total angling effort was held constant. For both of the flow scenarios examined the difference in economic use value was limited. The relatively small changes in value predicted were shaped by the small changes in catch predicted and the high number of fish caught under current conditions. INTRODUCTION Releases from storage reservoirs have traditionally been made for agricultural purposes, mining and manufacturing, municipal water supply, and other off-stream uses. Now, however, management strategies which favor these traditional water uses are being questioned and operation regimes which recognize the importance of fisheries, habitat maintenance, and other uses requiring adequate stream flow are being formulated. In Colorado, as in other western states, the question of how to balance reservoir releases between traditional water uses and instream uses such as maintaining recreational fisheries has become the subject of considerable debate. While there are numerous political, legal, and philosophical aspects to this debate, objective economic analysis hinges on the development of tools for quantifying and valuing the impacts on recreational fisheries which result from changes in flow regimes. At a minimum, these tools must allow for the prediction of fish populations under differing flow regimes, linkage of these fish populations to fish catch, and estimation of the economic value of this catch. The three objectives of this study were (1) to develop a framework for predicting fish population as a function of stream discharge, (2) to estimate the economic use value of these fish, and (3) to demonstrate the use of this framework for the analysis of alternative reservoir release regimes. RELATED STUDIES capture the effect of stream flow and lend themselves to the analysis of different flow management regimes. Recently, however, two studies based on flow-driven models have appeared in the literature. Cheslak and Jacobson [1990] employed a fisheries population model based on the method used in the present study: the Instream Flow Incremental Methodology (IFIM). Cheslak and Jacobson predicted the flow impacts of a proposed hydroelectric project on fish populations in the Clavey River in California. The results reported by the authors and the population response predicted in this analysis are similar. The Cheslak and Jacobson model is not linked to fish catch or economic value.Another study by Fisher et al. [1991] is based on a rather sophisticated biological modeling effort and ...

Recreational anglers’ willingness to pay for increased catch rates of Pacific threadfin (Polydactylus sexfilis) in Hawaii

“…In this case, anglers would answer yes or no to whether they would be willing to pay the stated dollar amounts for changes in daily catch rates and catch size of trout in Colorado. Harpman et al (1993) used the dichotomous choice CVM to estimate anglers' WTP for increases in average catch rate of trout in Colorado. Dichotomous choice CVM poses dichotomous questions to survey respondents, e.g.…”

Estimating the Economic Value of Improved Trout Fishing on Wyoming Streams

“…Johnson (1989) found the marginal economic benefit to anglers for catching one additional fish to be $1.11 and the marginal value of a tenth additional fish was $0.46. Harpman et al (1993) studied trout fishing on the Taylor River in Colorado. Four hypothetical scenarios with different catch rates were described to mail survey respondents.…”

“…A dichotomous-choice CVM approach was used. Results of Harpman et al (1993) indicated the marginal economic benefit of increasing catch per day by two fish to be $1.89 per fish. Using these benefit estimates, Johnson et al (1995) concluded that stocking catchable rainbow trout in Colorado needed to be reduced.…”

REVIEW OF DETERMINATION OF INSTREAM FLOW REQUIREMENTS WITH SPECIAL APPLICATION TO AUSTRALIA1

“…More recently, Harpman et al (1993) used an extended version of IFIMnamely, the effective habitat model -to simulate the impact of two regimes of operation of Taylor Park Reservoir on fish population in Colorado. Their results predicted improvement in habitat conditions due to the operational strategy in place.…”