37 



this symposium. Most of our standard sampling gear is of venerable age. 

 Except for gear used in commercial fishing, there has been no economic incen- 

 tive to develop biological collecting gear. Unfortunately, biologists are not as 

 mechanically inclined as many other scientists. 



PLANKTON SAMPLING EQUIPMENT 



As I have been miore directly concerned with the problems of plankton 

 sampling, I will discuss first the new developments in this field. 



In quantitative plankton research, considerable effort has been expended 

 in finding reliable methods for collecting plankton samples from the sea, and in 

 working up the material. Due to the limitations of any type of sannpler em- 

 ployed in collecting plankton, as well as to the actual dumpiness of plankton 

 distribution in the sea, no instrument will obtain a fully representative sample 

 of the organisms present in the water. Most samplers are selective in one 

 way or another. The selection may be a size selection, resulting from loss of 

 organisms through the meshes of the net employed. The selection may be due 

 to the avoidance of the sampler by the more agile planktonic organisms --a 

 motility -- influenced selection. The selection may result from mechanical 

 limitations of the gear, from limitations in its operation, or from many other 

 causes. 



I wish to discuss three of the more outstanding instruments designed for 

 the quantitative collection of plankton. These are by no means the only new 

 plankton collecting devices that could be included. 



Hardy Plankton Recorder - Although the Hardy plankton recorder is not a new 

 instrument, it has not been used by workers in this country until recently. It 

 was demonstrated at several institutions during the past year by K. M. Rae. 

 This instrument has been used so continuously and effectively in research on 

 the plankton of the North Sea and other areas, that it certainly ranks as one of 

 the most important instruments for plankton sampling now in use. 



The Hardy plankton recorder was used for the first time during the Dis- 

 covery Expedition to the Antarctic in 1925-27, but it was not described in any 

 detail until 1936. It was designed to take a continuous sample over distances 

 as great as several hundred miles. It is ordinarily towed at a depth of about 

 10 meters at a vessel speed of 8 to 16 knots. 



The front end of the recorder is provided with a small orifice (about li" 

 square) which may be reduced, if desired, to j" or less. The water, after en- 

 tering the body of the recorder, is led through a wider tunnel, across which is 

 stretched a band of silk or nylon gauze. The gauze band is slowly wound across 

 the water tunnel and into a preservative chamber where it is spooled and stored 

 in a bath of formalin. The spooling mechanism is geared to an external pro- 

 peller which is turned by passing water, hence the spooling is in direct relation 

 to the distance travelled. Because of this, it is possible to determine the ap- 

 proximate locality where each portion of the continuous plankton sample was ob- 

 tained. To facilitate working with the material ashore, the straining band is 

 graduated into numbered divisions. 



The instruments have been made sufficiently fool-proof, so that they 

 can be used on merchant vessels on routine runs between ports. Most of the 

 sampling is done on such vessels. The sampling done in a year by these in- 

 struments now amounts to about 30,000 miles of plankton records, an impres- 

 sive total. The use of the plankton information by the herring fishery in in- 



