Gear Description

20 cm paired nets on circular aluminum or fiberglass frames that are connected to each other by a central yoke or axle (Posgay and Marak 1980). These are usually used to collect zooplankton, but have been used on some cruises for ichthyoplankton. Often used in conjunction with 60 cm bongos to collect simultaneous zooplankton and ichthyoplankton samples. The towing wire and the weight (22-40 kg) are attached to the axle or to the 60 cm frame by and extended wire. The towing frame is fitted with two cylindrical-conical nets. The cylindrical section helps prevent clogging. The ratio of the sum of all openings in the net to the diameter of the opening is at least 8:1 which increases filtration efficiency and prevents clogging. Flowmeters are mounted in the mouth of each net to provide data on the volume of water filtered. Bongo nets are towed at speeds of 1.5 to 2.0 knots. The advantages of bongo nets are that there is no bridle or other obstruction in front of the net as it is being towed, and it is possible to take two samples simultaneously: these can be used for different processing and analysis, or two mesh sizes can be used to collect different size fractions of the plankton.