STCEL STRIPS 

 6 «5 r 1419 CM, 

 ('4<2<l6l'2lN I 



DIVING PLANE 



I 3-CM ( S'j-IN 1 MARINE PLYWOOD 



STEEL RUNNERS - 

 3 < 51 > 63 5 CM. 



(>/.« 2«25 IN ) 



^TUBING 2 5 CM DIAMETER tl IN ) 



Figure 26. — Framework of benthlc sampling sled with approximate dimensions. Gulf of 



Mexico, 1968. 



and the Columbia River Plume. The first 

 cruise to study environmental conditions off 

 Oregon was completed. 



William G. Pearcy, Project Leader 



Oregon State University 

 (Contract No. 14-17-0002-333) 



Preparation of a Bibliography of Ocean - 

 Surface Features Significant to Fisheries 



We prepared a preliminary 78-page bibli- 

 ography of evaluated references pertaining to 

 sea conditions that restrict fishing, ocean 

 features that delineate high- seas fisheries, and 

 environmental deviations that affect the size 

 of a year-class of fish. 



Richard D. Terry, Project Leader 



Seaonics International Inc. 

 (Contract No. 14-17-0002-357) 



SPECIAL REPORT: A MODIFIED BENTHIC 

 SAMPLING SLED 



To study the distribution of postlarval penaeid 

 shrimp in relation to different types of sedi- 

 ments and to establish indices of postlarval 

 abundance, we modified the quantitative benthic 

 sampler originally described by Macer ( 1967) . 

 Although the dimensions of our gear (fig. 26) 



^Macer, C. T. 1967. A new bottom-plankton sampler. 

 J. Cons. 31: 158-163. 



were similar to those of the sampler designed 

 by Macer, modifications included a different 

 opening and closing mechanism; a flowmeter; 

 and two attachments- -a roller and a digger 

 bar--designed to disturb the substrate (fig. 27). 

 Because our gear was designed to catch post- 

 larvae in the surface layer of the sediment as 

 well as from the water immediately above the 

 bottom, the net opening was lowered to a posi- 

 tion just off the bottom. 



Figures 27 and 28 show the design of the 

 opening and closing mechanism. The door is 

 welded to a horizontal shaft that projects 

 1.3 cm. (0.5 inch) on each side of the box, and 

 both ends of which are secured to support 

 arms. These arms are attached to supports 

 which are welded to the two shoes that are 

 held in position by a guide on each side of the 

 box. In the closed position, the door is held 

 shut by springs connected to each support arm. 

 When the sled is not resting on the shoes, the 

 spring holds them in the lowered position with 

 the door closed. When the sled touches bottom, 

 the shoe is raised and the door opens. If the 

 sled loses contact with the sea floor at any 

 time, the door closes until the sled is again on 

 the bottom in an upright position. 



Towing procedures are as follows. To pre- 

 pare the sled for sampling, we set the diving 

 plane at an angle of about 30°. If the sled is 

 to be towed faster than 3.7 km. per hour (2 

 knots) or if the sea is rough, the angle may 

 have to be increased to keep the sled on the 

 bottom. The appropriate bottom-disturbing 

 attachment is secured in place, and the flow- 

 meter reading is recorded. A line is then 

 fastened to the sled with a 1.5-m. (5-ft.) 



37 



