Managing a Fishery under Moratorium: Assessment Opportunities for Virginia's Stocks of American Shad

Virginia's river fisheries for American shad have been under moratorium since 1994. The moratorium is partial since the three stocks (in the James, York, and Rappahannock rivers) are harvested to an unknown degree in an offshore mixed-stock fishery. Current research efforts have three objectives: (1) to determine current status of the stocks relative to historical levels, (2) to determine appropriate target catch-rate levels for restoration, and (3) to develop new assessment tools so that a future moratorium can be avoided. Current status is being evaluated by monitoring catch rate of commercial fishers who are paid to fish with historical methods in historical locations; the contemporary catch rates are compared to those recorded in logbooks completed voluntarily by fishers prior to the closure. We propose to define restoration targets in terms of historic catch rates recorded in logbooks. This requires determination of relative catching power of historic (multifilament) and modern (monofilament) nets. Two novel assessment methods are being evaluated: index-removal and change-in-ratio methods. These are based on comparing the catch rate and catch composition, respectively, of ripening fish and spent fish near the mouth of the river. During a moratorium, the parameters should be the same for ripening and spent fish, thus providing a critical check on the model assumptions. Maturity information is needed to forecast recruitment but previous estimates of maturity-at-age schedules are biased. Improved estimates can be obtained using a new statistical method which requires that there be a moratorium. It is unfortunate for society when a fish population declines to the point where a moratorium must be declared but a moratorium can provide important opportunities for testing methods and estimating parameters.