FISHERY BULLETIN: VOL. 75, NO. 3 



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FIGURE 2. — Top. Stations in the survey area where eggs of 

 thread herring were collected at least once during 1971-74. 

 Stations where eggs did not occur are indicated by dots. Bottom. 

 Stations in the survey area where larvae of thread herring were 

 collected at least once during 1971-74. Stations where larvae did 

 not occur are indicated by dots. 



sorted from 867 samples. Number of thread her- 

 ring larvae totalled 11,255, 7.87% of the 143,004 

 total larvae collected throughout the survey. 

 Thread herring eggs constituted 13.20% of the 

 total clupeid eggs collected, and thread herring 

 larvae constituted 39.69% of the clupeid larvae. 

 Mean abundances of thread herring eggs under 

 10 m 2 of sea surface ranged from 0.00 to 60.53 for 

 the 17 cruises (Table 1). At positive stations, 

 cruise means ranged from 14.39 to 999.46 under 

 10 m 2 . Most egg abundances at individual stations 

 were <100 under 10 m 2 of sea surface, but abun- 



dances ranged from 101 to 1,000 under 10 m 2 on 

 eight occasions and > 1,000 under 10 m 2 on four 

 occasions (Figures 3-6). 



Thread herring larvae mean abundances for the 

 17 cruises ranged from 0.00 to 172.28 under 

 10 m 2 of sea surface (Table 1). At positive stations, 

 mean cruise abundances ranged from 2.43 to 

 229.37 under 10 m 2 . Larval abundances exceeded 

 1 ,000 under 10 m 2 on three occasions ( Figures 3- 6) 

 and frequently were in the range of 101 to 1,000 

 under 10 m 2 . Detailed summaries of station and 

 cruise data for both larvae and eggs of thread 

 herring were recently published (Houde et al. 

 1976). 



Spawning intensity appeared to vary within the 

 observed spawning area. The logio mean egg 

 abundance under 10 m 2 for positive stations from 

 all cruises was 1.3837 at stations =£30 m deep but 

 was only 1.2750 at stations >30 m. The means did 

 not differ significantly U-test, P>0.50). But, the 

 surface area encompassed by the ^30-m depth 

 zone was 76.03 x 10 9 m 2 as opposed to only 30.69 x 

 10 9 m 2 in the 30- to 50-m depth zone, beyond which 

 virtually no spawning was observed (Figure 2). 

 Most eggs were spawned where depth was <30 m. 



There was no evidence that spawning intensity 

 increased nearer to the coast than measured by 

 our usual survey stations, based on cruise CL7412 

 (Figure 6, Table 1), when 12 nearshore stations 

 were added to the usual stations. Thread herring 

 eggs were collected at three of the nearshore sta- 

 tions and at seven of the regular, more offshore 

 stations (Figure 6) on that cruise. The log 10 mean 

 catch under 10 m 2 was higher at the offshore sta- 

 tions, but due to the small number of stations it did 

 not differ significantly (P>0.10) from the near- 

 shore stations' mean: 



A^o. of stations 

 with thread 

 Stations herring eggs Log 10 x Log 10 S* 



Regular 7 1.5272 0.5064 



Nearshore 3 0.5525 0.3101 



t ca]c = 1.69 * .05C2,8) = 2.306 



Temperature and Salinity Relations 



Thread herring eggs were collected where sur- 

 face temperatures ranged from 22.5° to 30.3°C and 

 surface salinities from 32.4 to 36.8%<>. From May to 

 September temperatures from surface to 15 m 

 were nearly homothermous, but temperatures at 

 the 30-m depth often differed from the surface by 



496 



