FISHERY BULLETIN: VOL. 80, NO. 2 



1978 Surveys 



Herring abundance estimated through the 

 1978 season showed considerably more variabil- 

 ity than in other years of the surveys (Fig. 4, 

 Table 3). As expected, abundance was low at the 

 time (11-12 April) of the first acoustic-trawl 

 survey. The following week, 16-22 April, 

 acoustic-trawl estimates of maturing adult 

 herring increased to approximately 13,400 tons 

 in each of two surveys, and the total estimate 

 exceeded 16,000 tons. For the next three surveys, 

 24 April-1 May, acoustic-trawl estimates of 

 maturing adult herring biomass in the survey 

 corridor dropped considerably, and correspond- 

 ing total abundance declined to 10,000-11,000 

 tons. On 4-5 and 8-9 May estimates of total 

 maturing herring increased to 13,000 tons; these 

 latter estimates included 3,500-6,000 tons from 

 acoustic surveys. 



The highest biomass estimate occurred just 

 after complete immigration when the estimate 

 comprised mostly acoustic data. The original 

 high values, midseason low values, and inter- 



Table 3. — Results from hydroacoustic-midwater trawl 

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

 1978. 



Date 



Total 



Maturing 



adult 



herring 



Juvenile 

 or spent 

 herring 



Miscella- 

 neous 



% 

 spawners 



■B e 



CUMULATIVE 



SPAWNING 



ESCAPEMENT 



CUMULATIVE 

 CATCH 



.-•-•" 



5 IO 15 20 25 30 5 IO 15 20 25 30 4 



April May June 



FIGURE 4.— Biomass estimates of adult roe-herring in the 

 Strait of Georgia, 1978. 



mediate values at the end of the season were com- 

 posed of at least two similar estimates, which 

 suggests that the changes represent actual 

 occurrences. 



The final spawning escapement estimate, 

 based on 67 spawning ground surveys was 8,840 

 tons. Total catch was 2,120 tons. Cumulative 

 escapement plus catch equaled 10,960 tons. 

 Mean value of the eight population estimates 

 made from the time of completed immigration to 

 the survey area was 12,700 tons. The 16.7% 

 harvest rate, lowest of this 4-yr series, was due to 

 a reduced quota during the midseason period of 

 low abundance estimates. 



1979 Surveys 



Total all-species acoustic abundance estimates 

 (Table 4) increased from a normal low value of 

 about 3,000 tons in mid-April to a peak of 8,150 

 tons following presumed full recruitment on 27 

 April. By the end of the season, estimates were 

 less than 3,000 tons. Maturing adult herring 

 comprised 50-70% of acoustic biomass until the 

 last survey of the season. Early season estimates 

 of 1,000-2,000 tons of adult herring increased to 

 about 5,600 at the peak, and declined to 890 tons 

 on 7-8 May. 



Seventy-two spawning ground surveys con- 

 ducted during 1979 provided an escapement esti- 

 mate of 8,040 tons. Total harvest was 1,920 tons. 



Variation in 1979 seasonal abundance esti- 

 mates for adult (spawner) herring showed a 

 pattern similar to those observed in 1976 and 

 1977: biomass increased rapidly early in the 

 season, and remained fairly constant for the 

 duration of sampling (Fig. 5). From the time of 

 full recruitment, total adult herring estimates 

 ranged from 8,000 to 10,000 tons. As in 1977, con- 

 siderable spawning and catch occurred prior to 

 the peak acoustic estimate, and added consider- 

 ably to the first estimate following presumed full 



Table 4.— Results from hydroacoustic-midwater trawl 

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

 1979. 



Date 



Total 



Maturing 



adult 



herring 



Juvenile 

 or spent 

 herring 



Miscella- 

 neous 



% 

 spawners 



386 



