RICHARDSON and PEARC Y: COASTAL AND OCEANIC FISH LARVAE 



TABLE 9. — Ranges and modal lengths (mm) for dominant fish larvae in the offshore assemblage (stations 37 to 111) in 1971. Asterisks 

 indicate month in which average abundance per cruise was greatest. Parentheses are used where more than one modal peak occurred. 



quite large (>40 mm) before metamorphosis and 

 have an extended pelagic life (Pearcy et al. 1977). 

 Some taxa were taken throughout most of the year 

 and showed no strong evidence for a definite 

 spawning period, e.g., the multispecies group 

 Sebastes spp., T. crenularis, and Protomyctophum 

 thompsoni (Table 9). Intermediate to these were 

 species which occurred over a rather long period 

 but did show some indication of seasonality based 

 on larval lengths, e.g., Stenobrachius leucopsarus 

 and Bathylagus ochotensis. Cyclopteridae spp. 1 

 was taken over a long time period from February 

 through September. No trends in growth were 

 evident probably because it is a multispecies 

 group. 



Distribution Trends 



Peak abundances occurred 46 to 65 km offshore 

 for some species, e.g., L. exilis, G. zachirus, and 

 some Sebastes spp. (Figure 8). Spawning pre- 

 sumably took place near the outer shelf-upper 

 slope region where depths were —200-300 m. 

 Sebastes spp. also had an abundance peak further 

 offshore, possibly the result of offshore drift of 

 larvae. 



A more oceanic distribution was characteristic 

 of larvae of mesopelagic fishes such as the myc- 

 tophids Stenobrachius leucopsarus, T. crenularis, 

 and P. thompsoni (Figure 8). Peak abundances 

 occurred at the 74- to 111-km stations with a 

 decline in abundance toward the coast, although a 

 few myctophid larvae were taken over the shelf at 

 18 to 28 km offshore. 



Larvae of E. mordax occurred in large numbers 

 (147/under 10 m 2 ) only once in 1971, at the 65-km 

 station in July. In 1972, peak abundance also 

 occurred in July but at 74, 93, and 111 km offshore 

 (236, 297, and 124/under 10 m 2 , respectively). 



These peaks may be associated with spawning in 

 the relatively warm waters of the Columbia River 

 plume (Richardson 1973). 



Year to Year Variation 



In March-April, no major differences in 

 abundance or species richness occurred between 

 1971 and 1972 (Figure 5, Table 7). The dominant 

 taxa were reasonably similar, although there was 

 some decline in abundance in S. leucopsarus and 

 T. crenularis and some increase in Sebastes spp. 

 and Hemilepidotus spinosus in 1972. 



In the May-July period, however, mean larval 

 abundance was higher in 1971 (Figure 5, Table 7). 

 Four of the five dominant taxa were more abun- 

 dant in 1971. A major decline occurred in S. 

 leucopsarus catches in 1972. A major increase in 

 abundance occurred inEngraulis mordax in 1972; 

 six times more larvae were taken than in 1971. 

 This may have been due to increased sampling in 

 Columbia River plume water (Richardson 1973). 

 Species richness values were similar in both years. 



DISCUSSION 



Coastal and Offshore Larval 

 Fish Distributions 



There was a marked inshore-offshore separa- 

 tion of larval fish assemblages. Little overlap in 

 distribution occurred between coastal and offshore 

 larvae. Most (99%) larvae designated as coastal 

 were collected within 28 km of shore and most 

 (96%) larvae designated as offshore were found 

 beyond 28 km. The 28-km station consistently had 

 low larval abundances (Figure 5) and appeared to 

 be a transitional zone between coastal and 

 offshore waters. The biomass of fishes, shrimps, 



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