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Fishery Bulletin 105(3) 



[day]; 0.21/1000 m^ [nightD, C. macouui (1.74/1000 m^ 

 [day]; 1.07/1000 m-' [night]), and total eggs (13.43/1000 

 m'3 [day]; 3.65/1000 m'^ [night]), although differences 

 were not significant (ANOVA, P>0.05). However, I. lock- 

 ingtoni eggs occurred in slightly higher concentrations 

 in the water column at night (2.21/1000 m'M than dur- 

 ing the day (1.83/1000 m-'). Egg concentrations were 

 generally higher during the day than at night at each 

 depth stratum for most taxa (Table 2). 



Larval concentrations and distributions 



A total of 1571 fish larvae representing 20 taxa from 

 11 families were collected throughout the study. Three 

 families accounted for 97.4% of the total standard- 

 ized larval concentration: Scorpaenidae (55.6%), Myc- 

 tophidae (35.6%), and Pleuronectidae (6.2%.). Within 

 these families, four taxa were dominant based on total 

 mean concentration and frequency of occurrence from 

 all depth-stratified samples: Sebastes spp. (57.75/1000 

 m3; 0.42), S. leucopsarus (25.23/1000 m^; 0.45), T. crenu- 

 laris (8.81/1000 m3; 0.35), and L. exilis (3.78/1000 m^; 

 0.15). Several other taxa were documented at relatively 

 high frequencies but at lower mean concentrations: 

 Glyptocephalus zachirus (rex sole) (2.10/1000 m^; 0.18), 

 Protomyctophum thompsoni (northern flashlightfish) 

 (1.17/1000 m3; 0.16), 7. lockingtoni (1.01/1000 m^; 0.11), 

 Diaphus theta (California headlightfish) (0.91/1000 m^; 

 0.11), and Liparis fucensis (slipskin snailfish) (0.66/ 

 1000 m3; 0.11). 



Larval concentrations varied across depth-stratified 

 and diel scales (Table 3). For S. leucopsarus larvae, both 

 factors and their interaction term (depth, diel presence, 

 and depthxdiel presence) in the type-II ANOVA model 

 were significant (P<0.05). However, depth stratum was 

 the only significant factor explaining variation in L. 

 exilis, Sebastes spp., T. crenularis, and total larval den- 

 sities in the model. More than 96%^ of the total larval 

 abundance was distributed in the upper 100 m of the 

 water column. Mean concentrations of Sebastes spp., S. 

 leucopsarus, T. crenularis, and total larvae generally 

 increased from the surface to the 20-50 m depth, then 

 declined steadily as depth increased. No Sebastes spp. 

 larvae were collected below 100 m. In addition, L. exilis 

 larvae were found only in the 20-100 m depth range, 

 where concentrations were greater than 3x higher in 

 the 20-50 than in the 50-100 m depth stratum. 



Mean larval densities were generally greater at night 

 than during the day at all but one depth stratum for 

 Sebastes spp., S. leucopsarus, T. crenularis, and total 

 larvae (Table 3). These differences were significant for 

 S. leucopsarus and total larvae at the 0-10 and 10-20 

 m depth strata (ANOVA, P<0.05). However, higher lar- 

 val densities were found during the day than at night 

 for Sebastes spp., S. leucopsarus, and total larvae at the 

 50-100 m depth stratum. In addition, L. exilis larvae 

 were found at higher densities during the day than at 

 night at all depths at which they were collected. 



Analysis of the dominant larval taxa depth distribu- 

 tions over a 16-h period revealed evidence of diel verti- 



cal migration (Fig. 2). Weighted mean depth (WMD) 

 of L. exilis and Sebastes spp. larvae increased from 

 2324 to 1550 PDT, whereas larval S. leucopsarus WMD 

 decreased slightly between 2324 and 0303 PDT be- 

 fore increasing as the day progressed. In contrast, T. 

 crenularis larvae appeared to move up in the water 

 column from 2324 to 0604 PDT but were not found in 

 any sample from the haul conducted at 1550 PDT. 



Weighted mean standard lengths (SL) of L. exilis, 

 Sebastes spp., S. leucopsarus, and T. crenularis larvae 

 generally increased with depth (Table 4). Mean SL for 

 S. leucopsarus larvae collected during night and during 

 both day and night combined was significantly greater 

 at the 20-100 m than at the 10-20 m depth stratum 

 (ANOVA, P<0.05). Lyopsetta exilis, Sebastes spp., and T. 

 crenularis larvae collected at night were generally the 

 same size or larger than those collected during the day 

 at each depth stratum, although these differences were 

 not significant (ANOVA, P>0.05). 



Diversity and evenness 



Larval and egg diversity and evenness varied across 

 depth strata. Larval diversity generally increased with 

 depth. Egg diversity increased from the surface to 20 

 m then declined with increasing depth. Egg and larval 

 evenness generally increased with depth before declining 

 slightly at the 200-350 m depth stratum. Egg diversity 

 and evenness could not be assessed at the 100-150 and 

 150-200 m depth strata because no eggs were found 

 between 100 and 150 m, and only one egg (Microstomus 

 pacificus [Dover sole]) was found at the 150-200 m 

 depth stratum. There was no appreciable difference in 

 egg and larval diversity and evenness between day and 

 night samples. 



Assemblages 



Several taxa and depth assemblages were identified on 

 the basis of cluster analyses and MDS, although no diel 

 assemblages were apparent (Fig. 3, A-C). Larval taxa 

 separated out into four assemblages (Fig. 3A). In more 

 than 5% of the samples too few egg taxa (m = 4) were pres- 

 ent to permit identification of any assemblages. Cluster 

 analyses and MDS also indicated the presence of two 

 egg and larval depth assemblages: <100 m and >100 m 

 (Fig. 3, B and C). 



Environmental relationships 



BIO-ENV and correlation analyses revealed significant 

 relationships between several environmental factors and 

 egg and larval mean concentrations. A depth-stratified 

 BIO-ENV analysis, which included mean depth (m), mean 

 temperature (°C), and mean salinity of each depth-strati- 

 fied sample, showed that depth alone explained 46% of 

 the variability in mean egg concentrations and 44% in 

 larval concentrations. No multiple-factor combination 

 explained more variability in egg or larval concentration 

 data. Pairwise correlation analyses revealed significant 



