THE STRAIT OF GEORGIA HERRING FISHERY: 

 A CASE HISTORY OF TIMELY MANAGEMENT AIDED BY 



HYDROACOUSTIC SURVEYS 



Robert J. Trumble, 1 Richard E. Thorne, 2 and Norman A. Lemberg 1 



ABSTRACT 



A stock assessment program which combines hydroacoustic biomass estimates with midwater trawl 

 sampling, spawning escapement estimates, and daily catch reporting has provided a timely method 

 of managing an intensively fished, Pacific herring population in Puget Sound, Wash. Since 1976, 

 these techniques have been implemented through the spawning season to estimate adult herring 

 biomass, and to set quotas consistent with the biomass. The estimates become available for manage- 

 ment use less than a day following completion of an acoustic-trawl survey, which allows for in-season 

 adjustments in fishing. 



Acoustic-trawl surveys carried out at regular intervals during the spawning season monitored 

 declines of prespawning adult herring biomass; the declines corresponded to cumulative increases 

 of catch and spawning escapement. After full recruitment to the fishery, the sum of catch, escape- 

 ment, and acoustic-trawl estimates provided a point estimate of total available adult herring. 

 Within a season, these point estimates varied less than 15%. This stability is a check on the accuracy 

 of acoustic surveys, and confirms that accuracy is sufficient for management purposes. 



Management of virtually all fisheries requires 

 information on the abundance of the resource 

 with which to set catch quotas, limit effort, or 

 determine stock condition. The effectiveness of 

 fishery management is often hampered by the 

 need to make decisions based on stock assess- 

 ment requiring long time periods or doubtful 

 assumptions, or both. 



Fisheries on the west coast of the United States 

 and Canada for sac-roe (egg skein) of Pacific 

 herring, Clupea harengus pallasi, have a need 

 for rapid management response. The herring 

 migrate from offshore waters to subtidal and 

 intertidal spawning grounds. The fish are 

 harvested just prior to spawning and the sac-roe 

 is subsequently prepared as a caviar product. 

 Total allowable harvests can be taken in very 

 short times, from minutes to days, and prolonged 

 fishing time easily leads to overharvest. An ob- 

 jective of sac-roe herring management is to 

 obtain real time estimates of abundance prior to 

 and during the fishery so that quotas compatible 

 with abundance may be established. Spawning 

 escapement goals must be met without losing the 

 opportunity to catch harvestable fish. 



Traditional methods of determining abun- 



'Washington Department of Fisheries, M-l Fisheries Center 

 WH-10, University of Washington, Seattle. WA 98195. 



fisheries Research Institute WH-10, University of Wash- 

 ington. Seattle, WA 98195. 



Manuscript accepted November 1981. 

 FISHERY BULLETIN: VOL. 80, NO. 2, 1982. 



dance or setting fishing rates are inadequate for 

 the short-duration sac-roe herring fisheries. 

 Catch per unit effort (CPUE), virtual population 

 analysis/cohort analysis (VPA), or yield per 

 recruit (Y/R) provide postharvest information, 

 and often with lags of several years. Problems 

 with effort standardization and harvesting 

 aggregated fish (CPUE), the need for independ- 

 ent estimates of highly variable recruitment 

 (VPA), and sexual maturity being reached after 

 maximum cohort biomass (Y/R) make these 

 methods difficult to apply to in-season sac-roe 

 herring management even without the timeli- 

 ness factor. 



Sac-roe herring management relies heavily on 

 catch records and on spawning escapement 

 estimates. Even though these values ultimately 

 combine to estimate total abundance, they are 

 too late for in-season estimates and in-season 

 management modifications. Abundance esti- 

 mates before and during the spawning/fishing 

 season can be obtained by use of hydroacoustic 

 techniques, as are used in Washington, Alaska, 

 and British Columbia. 



Successful management of the sac-roe herring 

 fishery in the Strait of Georgia, Wash., requires 

 timely information on the abundance of the 

 fishable stock during the fishing season. A fleet 

 composed of purse seiners and gill netters has the 

 capacity to harvest the available quota within 1 



381 



