Draft Lower Columbia River White Sturgeon Current Stock Status and Management Implications

The white sturgeon population residing in the lower Columbia River downstream from Bonneville Dam (LCR) is the most productive in the species’ range. Harvest of white sturgeon in LCR sport and commercial fisheries has averaged over 42,000 annually. Currently, harvest management of white sturgeon is predicated on the precepts outlined in the �"Olympia Accord”, a management plan jointly developed by the Washington and Oregon Departments of Fish and Wildlife. As part of that plan, allowable harvest is based on estimates of optimal sustainable yield for the legal-sized population. Managers understood that periodic updates of stock status and management goals were needed in the face of uncertainty when setting levels of allowable harvest. Therefore, the initial harvest levels specified in the �"Olympia Accord” had a duration of only three years (1997-1999).

New stock status updates are now available for developing new harvest guidelines for the management plan. In-river abundance of legal-sized (42-60”) white sturgeon has declined since 1995. Abundance of this size class was estimated to be 227,700 in 1995. The abundance in 1997 is estimated to be 157,100. It appears that the decline is not a result of overharvest, but attributable to a decrease in recruitment to the legal-sized population and a mass emigration from the Columbia River system. These theories are corroborated by a significant increase in out-of-system tag recoveries and harvest, as well as a shift in size composition in sturgeon research fisheries.

In light of this change in stock status, we are recommending that total allowable harvest of white sturgeon in the LCR be decreased in 1999 and in the next management period starting in 2000. Decision-makers and the public should weigh the current management objectives relative to the year-round LCR sport fishery and the current sport and commercial allocation. With a lower total allowable harvest, these two objectives will probably be in conflict.

This document is intended to provide the latest stock assessment data and analyses to stimulate discussion prior to a decision on new management guidelines later this year. Copies of this document will be mailed out to interested parties and provided on the Washington Department of Fish and Wildlife internet web site (http://wdfw.wa.gov). The Washington and Oregon Departments of Fish and Wildlife will be hosting public meetings this summer to solicit management recommendations from the public for the year 2000 and beyond. The decision for the new management plan will be made after November when the respective state commissions will be briefed by staff on stock status and public feedback regarding management options. It is expected that separate meetings will be conducted this spring to discuss management options for the remainder of 1999. Please refer any questions to the authors.

Introduction

The lower Columbia River downstream from Bonneville Dam (abbreviated LCR in this report) white sturgeon population is the most productive in the species’ range (DeVore et al. 1995). This high productivity supports healthy sport and commercial fisheries that have averaged an annual harvest of over 42,000 white sturgeon in the last ten years. The sturgeon fishery ranks as the largest sport fishery in the Columbia Basin in terms of effort with a ten year annual average of over 175,000 angler trips. Factors most responsible for the favorable production potential of the population are access to marine areas, abundant food resources, and consistently favorable hydrologic conditions during the spawning timeframe which enhances recruitment (Parsley and Beckman 1994, DeVore et al. 1995, Counihan et al. In Press). This high productivity can only be sustained in the long term with careful, scientifically based management.

The longevity, slow growth, and delayed maturation of sturgeon makes them susceptible to overexploitation (Rieman and Beamesderfer 1990, Rochard et al. 1990, Birstein 1993). Excessive harvest in the 19th century collapsed Columbia River sturgeon stocks. Intensive sturgeon fishing on the Columbia River began in 1889 and peaked in 1892 with about 2,500,000 kg of sturgeon landed. The stock was depleted by 1899 after a ten year period of unregulated exploitation (Craig and Hacker 1940). Season, gear, and minimum size restrictions failed to bring about an increase in sturgeon production as evidenced by poor yields during the first half of this century.

The sturgeon population rebounded after a maximum size regulation designed to protect sexually mature sturgeon was enacted in 1950. Annual harvests doubled by the 1970's and doubled again by the 1980's. Increased interest in the recreational sturgeon fishery was due to decreased salmon fishing opportunities, increased stock size, and greater appreciation of sturgeon as gourmet fare. In 1987 a recent year record 72,100 white sturgeon were harvested in the LCR. Research indicated that the harvest rate of 30% of the 3-6 foot population, estimated to have occurred during 1985-1987, was twice what the population could sustain in the long term.

A series of management actions ensued between 1988 and 1997 to reduce the annual harvest rate in LCR sturgeon fisheries to a long term, sustainable level. The legal size slot for LCR white sturgeon was eventually reduced to 42-60 inches for sport fisheries and 48-60 inches for commercial fisheries. The daily bag limit in the sport fishery was reduced to one fish and the annual possession limit to ten fish. Harvest guidelines were also placed on LCR sport and commercial fisheries.