essentially an asymetrical cone with a pentagonal mouth opening and 

 a round cod end. Additional netting of half- inch stretch is attached as 

 a lining for the after end of the net. A steel ring is fastened in the 

 cod end to maintain its tubular shape. A cup attached to the cod end 

 retains the sample in a relatively undamaged condition. In front of the 

 net a spread-V depressor- vane is rigged, and a spreader bar is attached 

 to the leading edge of the top panel of the net. This device, however, 

 is cumbersome to rig and difficult to stabilize in the water unless it 

 is towed at a constant speed. 



6. Fouling plates 



At the present time, fouling programs are largely restricted to 

 quantitative studies of fouling plates. These plates are submerged to 

 allow attachment of the fouling organisms and are analyzed on a month- 

 ly or seasonal schedule. Determination of species, growth rate, and 

 growth pattern, as influenced by environmental conditions and time, 

 are the aims of these programs. Supplementary visual and photo- 

 graphic observations are made of pilings, buoys, and other fouled 

 objects in areas where no fouling plates are being studied. 



7. Noise level meters 



These meters, although not specifically designed for this use, 

 are being used successfully in studying sonic animals. Noises from 

 these animals often are noted during underwater noise level measure- 

 ments or seen as anomalous rises in the noise spectrum during 

 frequency analyses. 



8. Echo sounders and rangers 



These instruments also are not designed specifically for biologi- 

 cal measurements. However, scattering layer studies are made by 

 using them. It is assumed that most of the sound scattering is of 

 biological origin, since the scattering layers perform daily verti- 

 cal migrations in much the same manner as many planktonic animals 

 nearer the surface. 



9. Nannoplankton samplers 



Nannoplankton collections are difficult and time consuming to 

 make. Their use in military oceanographic problems is extremely 

 limited, and no descriptions of or recommendations concerning such 

 samplers are included in this section. 



IX- 4 



