BIONESS

BIONESS

BIONESS (Bedford Institute of Oceanography Net and Environmental Sampling System) is a multiple-net sampler for ZOOPLANKTON and micronekton (pelagic animals 1-10 cm in length). It uses a new design concept, with nets arranged horizontally rather than vertically, as in earlier multiple-net samplers. The 10 one metre-square nets open sequentially and are towed from a ship at a speed of 3-6 knots on a conductor cable that transmits and receives information. The sampler supports sensors for temperature, conductivity, depth, illumination, pitch, roll, yaw and net closure, together with internal and external flowmeters and a 35 mm camera with a strobe light.

This system can collect biological samples and environmental data simultaneously and can photograph animals in front of the sampler. The sampler can operate to depths of 2500 m.It weighs 782 kg and is best handled from an A-frame or large crane on a ship's stern. The towing wire and depressor attachments can be adjusted so that, at any towing speed up to 4 knots, the mouth is vertical. The sampler's weight, combined with the depressor, makes the depth variation during towing small, 0.2 m up or down in seas with waves of 1-2 m. The mouth area to surface area of the nets is 1:10; the mesh size, normally 243µm. Nets are dark green and all surfaces are painted dark grey to make the sampler as inconspicuous as possible. Catches consist of animals ranging from 0.3 mm copepods to krill, squid and fish up to 20 cm long.

Advantages of BIONESS include its ease of handling, its steep towing angle at high speeds and its reduced front profile. Data first collected by this sampler have made it possible to explain the ecological relationships between zooplankton, the micronekton that prey on them and the physical environment. For example, a dense layer of zooplankton at 500 m depth will not be preyed upon by a population of fish at 700 m depth because of the 200 m separation. Older methods of sampling did not reveal this fact. Such information is being used to explain the abundance and distribution of commercial species of fish.