second set of attachment points from the front of 

 the sled. From these towing points the sled proved 

 to be stable, never landing on the bottom upside 

 down. It could be launched and recovered by two 

 people in moderate-to-rough seas. The sled was 

 launched while underway at 2 knots. A 20-min tow 

 (bottom time) at 2 knots was calculated to be 

 sufficient to filter 500 m' of water. Presence on the 

 bottom was detected by the winch potentiometer. 



Filtering efficiency of the sampler, based on the 

 degree of clogging, was never markedly reduced 

 over this time interval. However on soft muddy- 

 sand bottoms, characteristic of P. Jordan i grounds, 

 bottom times were reduced to 10 min because of 

 the amount of fine sediment and meiofauna 

 stirred up and retained in the cod end. Large 

 organisms, including adult P. jordani, as well as 

 the fragile urchin, Alloceutrotus fragilis, and 

 slender sole, Lyopsetfa exilis, were effectively 

 retained in the coarse mesh liner and prevented 

 from reaching the sample in the cod end. Flow- 

 meter readings indicated that at no time did the 

 number of animals retained in the liner seriously 

 occlude the mouth of the plankton net and affect 

 its efficiency. On coarse sand bottoms, the samples 

 were very clean, with little sediment and 

 meiofauna retained, even when the net was only 

 5-8 cm off the bottom. 



Though the sled was never observed firsthand 

 while on the bottom, evidence from skid marks on 

 the runners and shoe, behavior of the poten- 

 tiometer while the sled was on the bottom, and the 

 relationship between flowmeter readings and 

 bottom time indicated that the epibenthic sampler 

 was stable and not prone to dig in or bounce off the 

 bottom while being towed. 



Vertical Distribution of 

 Larval Pandalus jordani 



On 30 and 31 May 1972 the epibenthic sampler 

 was used to sample near-bottom fauna and open 

 bongo nets were used to obtain a series of quasi- 

 vertically stratified plankton samples 10 nautical 

 miles off Cascade Head, on the central Oregon 

 coast (lat. 45°04.0'N, long. 124°15.rW). The 0.7-m 

 diameter bongo frames had paired cylidner/cone 

 571-/xm Nitex nets, 5.1 m in length with an 

 effective filtering area to mouth area ratio of 8:1. A 

 scope to depth ratio of 2:1 was maintained by using 

 a 40-kg multiplane kite otter as a wire depressor 

 (Colton 1959). All nets contained TSK flowmeters. 

 A time-depth recorder was fixed to the wire just 



above the bongo nets. Tows were made at four 

 strata (0-10, 11-50, 51-100, 101-150 m) with the 

 open bongo nets, and a bottom sample was taken 

 with the epibenthic sampler at 160 m. Replicate 

 tows were taken at each depth interval, both day 

 (1200-1930 h) and night (2105-0400 h). Contamina- 

 tion in the open bongo net was minimized by 

 lowering to the depth interval as fast as possible, 

 doing a stepped oblique tow through the horizon, 

 and then raising the net as quickly as possible. 

 Towing time at depth was long enough to keep the 

 period of contamination below 20% of the total 

 sampling time for the deepest tows. 



The vertical distribution of P. jordani larvae 

 and juveniles is summarized in Figure 2. During 



' , , w , w 



5- 



E 





5- 



300- 



200- 



100- 



DAY 



NIGHT 



lOm 



n-50m 



51-IOOm 



101 150m 



' I 1 I I I I 



BOTTOM (160m) 



Q TOW 1 

 Q TOW 2 



VI VIII X XII JUV VI VIII X XII JUV 



LARVAL STAGE 



Figure 2.-Vertical distribution of lar\ae and early juvenile 

 Pandalus jordani, during one day and one night period. All tows 

 were replicated. 



996 



