Figure 2. — Starbuuiil winch on NMFS rest-arcli vl-ssuI David Starr Jurdaii used for 

 plankton tows and Nansen bottle casts (see Table 1). Details on drum size, wire, boom, 

 and block are described in the text. 



hydrographic winch starboard and its conductor- 

 cable winch aport. Additional winches for trawl- 

 ing operations or very heavy gear are located be- 

 low decks with their wire coming above decks 

 to be fairleaded astern to a powered H-frame and 

 a stern ramp. Although the hydrographic-net 

 tow wire is capable of the strain noted above, 

 the boom supporting it (Figs. 2 and 3) can and 

 need only support 5,000 lb. (2,200 kg). The 

 block (Fig. 3) through which the wire is run 

 also is capable of supporting 5,000 lb. and has 

 three wheels of which one is a tensiometer. 



To enable handling gear clear of the side of 

 the ship, an overside platform (the "bucket") — 

 Figures 4 and 5 — is another essential aid to data 

 collection. It may be designed to be swung lat- 

 erally outboard as on the Jordan or swung up- 

 ward and outboard onto a ship's rail to be fas- 

 tened and kept there while at sea. The bucket 

 is constructed of heavy steel, and its bottom is 

 usually a steel grill which can drain immediately 

 if water is shipped into it. A 100-lb. weight (45 

 kg) — Figure 4 — is always attached to the end 

 of the cable to aid in lowering the plankton net 

 and the hydrographic cast of Nansen bottles. 



Laboratory space on a research vessel may be 

 of varying degrees of sophistication in size and 



equipment. On a small ship, one space may serve 

 for all functions but must be of sufficient size to 

 accommodate a number of Nansen bottles with 

 thermometers and space to read them, an area 

 with running salt and fresh water and sink for 

 preserving biological specimens and an area for 

 preserving water samples and determining their 

 chemical constituents. 



A survey for plankton sampling, extending to 

 14 or more days, will yield large numbers of bi- 

 ological samples for processing ashore. Ade- 

 quate storage facilities must be available to keep 

 them until off-loaded. 



The Plankton Tow 



The objective of the plankton tow is to obtain 

 qualitative and quantitative samples of the zoo- 

 plankton to the depth sampled at the time and 

 place of the tow. Most important to the objective 

 are the proper readings and recordings of the 

 flowmeter, the recordings of the various parts 

 of the towing times and wire angles, the neces- 

 sity for the smooth paying out and retrieval of 

 the net, rinsing the net, and the preservation 

 and labelling of the sample. 



