TRUMBLE ET AL.: STRAIT OF GEORGIA HERRING FISHERY 



Table 1. — Results from hydroacoustic-midwater trawl 

 surveys in the Strait of Georgia, Wash, (weights in short tons), 

 1976. 



5 10 15 20 25 30 5 



April 



IO 15 20 25 30 4 

 May June 



Figure 2.— Biomass estimates of adult roe-herring in the 

 Strait of Georgia, 1976. 



Fifty-nine spawning ground surveys were con- 

 ducted between 8 April and 8 June. The total 

 spawning biomass from these surveys was 

 estimated to be 9,590 tons (Fig. 2). The fishery 

 extended from 25 April to 23 May with a total 

 catch of 2,190 tons. 



The highest point estimate of total adult 

 herring biomass, on 21-22 April, was slightly 

 over 14,000 tons and was predominately from the 

 acoustic-trawling data. The last estimate, 11,800 

 tons, was from the spawning escapement esti- 

 mate plus the total catch. The average of the five 

 estimates between 21-22 April and 3-4 June was 

 12,700 tons. The fishery harvested 17.4% of the 

 maturing adult biomass, well within the 20% 

 limit. 



1977 Surveys 



Fish abundance in the study area in 1977 fol- 

 lowed the general pattern of 1976, building up to 

 a peak and then declining as the herring moved 

 inshore to spawn. The total acoustic biomass esti- 

 mates in the study area ranged from a peak value 

 of 10,090 tons on 25-26 April to a minimum value 

 of 3,410 tons on 17-18 May (Table 2). The trawl 



catches were again predominately herring. The 

 proportion of maturing adult herring ranged 

 from 69% to 84% of the total catch during the first 

 half of the survey period when the acoustic-trawl 

 estimate composed the major component of the 

 total biomass; later in the season proportions de- 

 creased. The acoustic-trawling estimate of spawn- 

 er herring reached a peak of 7,900 tons (Fig. 3). 



Seventy-seven spawning ground surveys were 

 conducted from 7 April to 9 June. The estimated 

 spawning escapement was 8,800 tons (Fig. 3). 

 The fishery extended from 11 April to 12 May 

 with a total catch of 2,300 tons. 



The timing of the migration differed slightly 

 from 1976. Significant amounts of spawning and 

 substantial catches occurred before the peak of 

 the acoustically measured biomass. Consequent- 

 ly, the first total biomass point estimate after 

 presumably full recruitment, 11,300 tons, 

 included substantial inputs from the spawning 

 ground surveys and catch data, as well as the 

 acoustic (Fig. 3). The last estimate was 11,100 

 tons, composed of the 8,800 ton spawning escape- 

 ment estimate and the 2,300 ton catch. The mean 

 of the final catch plus escapement and the five 

 surveys from presumably full recruitment was 

 11,040 tons. The harvest rate reached 20.8% for 

 1977. 



Table 2.— Results from hydroacoustic-midwater trawl 

 surveys in the Strait of Georgia, Wash, (weights in short tons), 

 1977. 



Date 



Total 



Maturing 



adult 



herring 



Juvenile 

 or spent 

 herring 



Miscella- 

 neous 



% 

 spawners 



IO 15 20 25 30 5 



April 



IO 15 20 25 30 4 

 May June 



Figure 3.— Biomass estimates of adult roe-herring in the 

 Strait of Georgia, 1977. 



385 



