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Fishery Bulletin 90(2). 1992 



(Table 5). Individuals appear to require about 45 days 

 to progress through Stage 3. Our laboratory -held 

 specimen progressed through Stage 4 in 43 days. 

 Overall, the progression through Stages 2-4 appears 

 to require about 1 year for the population as a whole 

 and about 9 months for an individual. 



The length and weight of benthic Stage 3 larvae were 

 compared between January and March 1989. Mean 

 length in March (51.5mmSL) was significantly smaller 

 than the mean length in January (56.3 mm SL, P< 

 0.00001). March specimens were also significantly 

 lighter (2.0 g) than January specimens (2.7 g, P< 

 0.0001). A similar pattern (earliest individuals in a 

 stage being largest) was seen in Stage-2 larvae. The 

 mean length of Stage-2 larvae captured between 

 January and March Gate in the season. Table 4) was 

 smaller (53.0mm vs. 54.3mmSL) and lighter (2.4 vs. 

 2.8 g) than Stage-2 larvae captured between June and 

 December (early in the season. Table 4), but the dif- 

 ferences were not significant (length P< 0.4642; weight 

 P<0.1227). 



Habitat of stages 



On average, Stage-1 specintens were caught in nets 

 fished to a maximum depth of 338 m, Stage-2 specimens 

 in nets fished to 538 m, and planktonic Stage-3 speci- 

 mens in nets fished to 293 m. All planktonic Stage-3 

 larvae were caught at night, between 1835 and 0544 

 hours, and 93% of Stage-2 larvae were caught at night, 

 between 1802 and 0748 hours. Sampling effort was also 

 greatest at night (Table 1; opening-closing nets col- 

 lected 516 Dover sole but most (509) were Stage 1). The 

 minimum depth of capture in the discrete depth 

 samples was < 100m for 82%, and <300m for 95%, of 

 Stage-1 specimens. Only six Stage-2 specimens were 

 caught in discrete depth samples, and only two of these 

 in nets not fishing the surface. One Stage-2 larva was 

 caught at 100-150m and the other at 400-500m. The 



Depth of Capture (m) 



Figure 14 



Relationship between standard length and depth of capture 

 of developing Dover sole Microstomus pacificus, caught in 

 bottom trawls off Oregon, January and March 1989: (A) scat- 

 terplot of data points. Stages 3-5; (B) polygons circumscribing 

 areas bounded by specimens in Stages 3-5. 



single Stage-3 larva collected in a discrete depth sample 

 was collected at 0-330 m. 



Benthic specimens were caught at depths shallower 

 than the maximum depth fished by non-closing mid- 

 water nets. Based on our stratified sampling, a com- 

 parison of depth of capture of stages shows that 

 Stage-3 specimens were caught at an average depth 

 of 146 m (SE 2.65, range 55-377 m), Stage-4 specimens 

 in January and March at an average depth of 118 m (SE 

 0.68, range 40-170m), and Stage-5 specimens in 

 January and March at an average depth of 110 m (SE 



