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Fishery Bulletin 90(2), 1992 



tion depths was 0-6000 m, but 81.8% of the samples 

 were from depths <500m. Eleven different gear types 

 were used: Tucker trawl, Cobb trawl, 0.9 m Isaacs- 

 Kidd midwater trawl (IKMT), 1.8m IKMT, 2.4m 

 IKMT, 3.0 m IKMT, 2.4 m rectangular midwater trawl 

 (RMT), 2.7m RMT, Im^ multiple plankton sampler, 

 65m2 midwater trawl, and lOOm^ midwater trawl. 

 Some gears were operated with and without opening- 

 closing devices (Pearcy 1980). Eighty-eight percent of 

 the collections were made with either a 1.8 m or 2.4 m 

 Isaacs-Kidd midwater trawl (IKMT). All specimens 

 were preserved in 10% formalin and transferred to 

 50% isopropanol. 



Juvenile bottom-trawl collections 



A bottom-trawl survey of juvenile Dover sole was con- 

 ducted bimonthly, January to November 1989, in three 

 areas off Oregon (Fig. 1). In March 1988 and 1990, a 

 more limited survey was conducted in the central 

 (Foulweather) area. Each area was 10 miles wide and 

 oriented to the coast such that the depth range of 

 50-400 m could be covered in the shortest distance. 

 Each area was subdivided into six strata bounded by 

 isobaths at 50, 80, 100, 120, 160, 220 and 400 m. Trawl 

 stations were randomly chosen such that a minimum 

 of three 5-minute trawls were attempted in each 

 stratum. When time permitted, additional stations 

 were added in strata with highest concentrations of 

 Dover sole (100-119 and 120-159m). All trawling was 

 conducted from the FV Olympic during daylight hours. 

 The gear was a commercial, 34.9mm mesh, two-seam 

 shrimp trawl with a 27.4m headrope, rigged with a 

 28.5m footrope and tickler chain. The posterior 3/4 of 



the codend had a 6.4mm liner. The catch was sorted 

 on board, all fish species were counted and measured, 

 and all Dover sole <200mmSL were frozen or fixed 

 in 10% formalin and returned to the laboratory for mor- 

 phological analysis. All formalin-fixed specimens were 

 preserved in 50% isopropanol before measurement. 



Morphological analysis 



All measurements reported herein were made in the 

 laboratory on defrosted or formalin-fixed, isopropanol- 

 preserved specimens. We found no significant differ- 

 ences (P 0.93) between measurements of 89 defrosted 

 juvenile Dover sole (46. 9-71.0 mm SL) when remea- 

 sured over a year after fixation and preservation. 



Measurements were taken on 2220 larvae, juve- 

 niles, and adults. Using the staging system developed 

 herein, the numbers examined in each stage were: 

 Stage 1, 811; Stage 2, 29; Stage 3, pelagic captures, 

 12; Stage 3, benthic captures, 409; Stage 4, pelagic 

 captures, 1; Stage 4, benthic captures, 461; and 

 Stage 5, 497. On all specimens returned to the labor- 

 atory, we measured TL, SL, body depth at anus 

 (BDIA), maximum body depth, snout to posterior 

 extent of intestine length (SINT), and body weight. 

 Length measurements were taken to the nearest 

 0.1mm using an ocular micrometer on specimens 

 <20mmSL and dial calipers on larger specimens. Body 

 weight was determined to the nearest O.OOlg for 

 Stages 1 and 2 and to the nearest O.lg for Stages 3, 

 4, and 5 (see staging description below). Weights were 

 taken from undamaged, pat-dried individuals. Weight 

 loss in isopropanol-preserved larvae was as great as 

 10% after 2 minutes of air exposure due to alcohol 

 evaporation. Although specimens were exposed for less 

 time before weighing, a 10% weighing error was 



