A Sled-Mounted Suction Sampler 

 for Benthic Organisms 



By 



DONALD M. ALLEN and J. HAROLD HUDSON 

 Fishery Biologists 



Bureau of Commercial Fisheries 



Tropical Atlantic Biological Laboratory 



Miami, Florida 33149 



ABSTRACT 



The sampler is an underwater vacuum device mounted on a sled; a venturi-type 

 water dredge provides suction. This equipment collects quantitative samples of young 

 pink shrimp, Penaeus duorarum duo r a rum , and is effective in capturing other small 

 benthic organisms. 



INTRODUCTION 



Pink shrimp, Penaeus duorarum duorarum , 

 are the basis of an important commercial 

 fishery on the offshore Tortugas grounds, 

 northwest of Key West, Fla. We measured the 

 abundance of juvenile shrimp in the shallow 

 coastal waters before their offshore migration, 

 to predict and evaluate fluctuations in the yield 

 of the adult pink shrimp. 



Longhurst (1964) described problems in- 

 volved in obtaining quantitative samples of 

 benthic organisms. Pink shrimp are particu- 

 larly difficult to sample because of variations 

 in their burrowing habits . Although they usually 

 remain burrowed in the substrate during day- 

 light and become active at night, certain en- 

 vironmental conditions can disrupt this pattern 

 (Fuss and Ogren, 1966). 



Conventional shrimp sampling gear, such as 

 trawls or pushnets, primarily capture only 

 unburrowed shrimp. Obviously, a different 

 type of gear is needed to capture both un- 

 burrowed and burrowed shrimp. Various 

 suction devices have been used to remove 

 organisms or eggs from the substrate. Brett 

 (1964) used a hydraulic suction dredge to 

 sample benthic macrofauna encircled by a 

 shallow cylinder. We believed, however, that 

 active animals, such as shrimp, would escape 

 from a cylinder and for reasons described 

 later, we preferred to have samples that were 

 taken continuously along a transect. Manz 

 (1964) collected eggs of walleyes, Stizostedion 

 vitreum vitreum , by using a sled to transport 

 a suction hose across the bottom. His device 

 was not designed for quantitative sampling of 

 infauna, however, and his pumping system was 

 too bulky for our use and tended to clog on 



mud, silt, or sand bottoms. To overcome 

 those deficiencies, we developed the sled- 

 mounted suction sampler described briefly 

 by Costello and Allen (1966). 



DESIGN 



The suction sampler has three main com- 

 ponents: (1) winch assembly; (2) vacuum sled; 

 and (3) raft-mounted water dredge (fig. 1). 



Winch Assembly 



A hand-operated wincn is bolted to amount- 

 ing flange on a 112-cm. upright stand of 3. 2- cm. 

 aluminum pipe. Welded to the base of the stand 

 for stability is an "H" shaped platform of 0.6- 

 by 5.1-cm. aluminum flatstock. About 18.3 m. 

 of 0.3-cm. nylon parachute cord is wound on 

 the winch drum. The cord is led through a 

 block affixed to the stand, 45.7 cm. below the 

 drum, to ensure a low angle of pull. A snap 

 is fastened to the cord end for ready attachment 

 to the sled bridle. 



Vacuum Sled 



The sled is composed of two major parts: 

 the sled frame and the suction head (fig. 2). 

 The sled frame, 0.3-cm. aluminum stock, is 

 made of four curved vertical runners welded 

 at each end to a 1 1.3- by 45.7-cm. transverse 

 plate. Gussets are welded at the angles between 

 the vertical runners and transverse plates for 

 rigidity. The two outside runners are welded 

 to the ends of the plate and have 3.8-cm. 

 wide strips welded to their undersides to 

 form skis that prevent the sled from sinking 



