evelyn D Biggs’s scientific contributions

A herring spawn deposition survey program employing underwater techniques,similar to the survey program in Southeast Alaska (Blankenbeckler,1987), was re-implemented in Prince William Sound in 1988. Surveys of this kind had not been conducted in the Sound since 1983 and 1984, when feasibility studies had been completed. The program was re-initiated due to an increase in funding and a need for an increase in accuracy of herring biomass forecasting in Prince William Sound. The Sound was divided into four areas (Figure1) and biomass estimates were calculated for each area. Survey transects were randomly selected from mapped spawning areas derived from aerial surveys. Quadrants of l/10th square meter within each transect were haphazardly sampled for egg density every 5 meters along the transect; the contents of 38 quadrants were collected for determination of diver estimate correction factors or divercalibration. It was discovered from the Prince William Sound data and from Southeast Alaska data (Funk,1988) that diver error is not a constant and is affected by substrate type and egg density; a model was derived to employ a diver error correction that takes into account substrate, year, diver, and density effects. Fecundities were determined from 315 weighed females over a range of 10mm lengths in order to provide egg numbers per female, as a parameter in the biomass estimate model. AWL samples representative of the timing of spawn for each area examined were selected to obtain average fish weight and sex ratio; the numbers were then employed for back-calculation of spawner biomass. In addition, a skiff survey was conducted in two of the four areas to examine the accuracy of mapping from aerial surveys and major discrepancies were discovered. In 1988, a total of 166.3 miles of spawn was mapped, with an average spawner density of .56 million pounds of spawners per mile. The resulting spawner biomass estimate for the Sound was 43,581 tonnes or 48,047 short tons. With the commercial catch of 11,731 short tons, the total herring pre-spawning biomass was estimated at 59,778 short tons which is 17,778 tons over the Prince William Sound stock threshold of 42,000 tons. The resulting exploitation rate for 1988 was approximately 19.6% KEYWORDS: Pacific herring, Clupea harengus pallasi, spawn deposition surveys, biomass, diver calibrations, fecundity, aerial survey.