New Net for Sampling the Ocean Surface

Abstract

The 'Manta Net', a new design capable of con-tinuous-flow collect~on of organisms and flotsam at the sea surface, is described and compared to the Neuston Net. The Manta Net stays reliably at the surface during the entire sample period; ~ t s handling requires 2 persons. During the past several decades, increased attention has been given to nets for sampling the surface of the ocean. The most important feature distinguishing these from conventional plankton nets is some kind of flotation device to keep the front opening of the net at the water surface. Some of the problems associated with sampling of ocean surfaces and the designs of several early neuston samplers have been briefly dis-cussed by David (1965), who designed a net ('David Sampler') with a rectangular mouth opening, kept afloat by a pair of wooden skis. The David Sampler and modifications of it (nets stacked vertically for sampling different strata of the surface water) have been used rather extensively, especially in studies of ichthyo-plankton and surface zooplankton (e.g. Hartmann, 1970; Zaitsev, 1970; Hempel and Weikert, 1972; John, 1976). Several other nets, all more or less variations of the David Sampler, have been proposed over the years; e.g. the Otter Surface Sampler (Sameoto and Jaros-zynski, 1969), the Norwegian multi-layered sampler (Ellertsen, 1977), an integrating sampler for collecting small planktonic organisms (Hinton and Boney, 1979), and a Boothbay neuston net for catching live fish (Hettler, 1979). Almost all of these nets are rather clumsy to use and relatively ineffective in following the undulations of the sea surface in a manner that would yield quantitative data. Miller (1973) designed a 'push-net' reasonably capable of quantitative samp-ling, but its use is mostly limited to inshore waters as it has to be operated from twin-hulled boats. In this paper we describe a newly designed net, the Manta Net, capable of continuous-flow collection of organisms and flotsam (tar lumps, etc.) at the ocean surface, and we compare some of its features with the