Gear Description

In order to sample the upper few (10-50) centimeters of the water column where the eggs and larvae of a wide variety of fishes reside as either obligate or facultative components of the neuston special nets have been designed (e.g. Sameoto and Jaroszynski 1969, Brown and Cheng 1981). They generally have a rectangular mouth opening and are towed so that they ride with only the lower half of the opening below the surface. Some are equipped with floatation, and most have wings that enable them to track at the surface and away from the ship. Flowmeters can be used with them to measure the distance traveled. They are deployed from amidships, as far forward as possible to keep them in undisturbed water out of the wake of the ship. A tag line is frequently used to deploy and retrieve the nets. They are generally towed for a predetermined length of time, at a speed of 2-5 knots. Catchability must be considered in analyzing neuston data, since the occurrence of larvae in the neuston is a function of their behavior. For example, marked diel differences in catches are often seen. A limited size range of larvae of a species may occur in the neuston, reflecting changes in vertical distribution with growth.