The mesh used in Caribbean fish pots is usually galvanized hexagonal-weave chicken wire with 4 cm (11/4 inch) openings. In some parts of the Caribbean, mainly Jamaica, finely woven bamboo cane is used to replace the wire over the wooden frame. Steel reinforcing bars are sometimes used to make pot frames.
Changes to the trap design and modification to the entrance funnel have been found to make big differences to the catch rates of these traps. Straight funnels seem to have higher catch rates (and escape rates) than those with a “horse-neck”. “S” traps were found to outfish “Z” traps by a factor of about 25 percent, while both were found to perform better than arrowhead traps.
Recently, modified arrowhead traps have been introduced into Australia. The trap frame is made from 10 mm mild steel which is covered with 50 x 75 mm rectangular 1 to 3 mm diameter mesh. The buoy lines are made from 12 mm rope adjusted to one-and-a-half times the depth of the water being fished. The traps are set with the point towards the tide.
As with other types of trap, the size and height of round traps vary with the area being fished, the type of fish being targeted and the availability of trap-making materials. The number of funnels in round traps varies, but one, two or three are usual. Additional funnels can increase the catch rates by allowing fish to enter the trap more quickly, but there is a higher escape rate and the additional internal projections from the extra funnels cause greater damage to the fish in the trap.
The western Australian snapper trap is a typical commercial round trap. It is also popular in northern Australia and has been used in the development of the tropical snapper fishery in that area. The dimensions and construction details of these traps can vary. A version of the western Australian trap has three funnels and a frame made from 10 mm mild steel rod. This frame is 180 cm in diameter, 70 cm high and has three braces top and bottom to support the funnels and the attached buoy ropes. In this trap the funnels are straight, tapered to a 25 x 11 cm opening. The frame is usually covered with welded wire mesh of about 75 x 50 mm but it can be covered with other types of wire, heavy nylon netting, etc. Similarly, the funnels can be made from steel rod and covered with heavy nylon mesh or the same material as the body of the trap. In some traps, the funnel is shaped from welded mesh without a frame. A door is normally placed in the side of the trap to make it easier to take the catch. As with other traps with more than one funnel, the catch rates increase with the number of funnels but damage to the fish is increased by the extra projections from the funnels inside the trap.
The main fish caught in tropical Australian waters with round traps are tropical snappers ( Lutjanidae ), emperors (Lethrinidae) and groupers (Epinephlidae).
A simple round trap can be made from a horizontal cylinder of wire netting with a wire mesh funnel at one end or funnels at both ends . A similar trap can be made of nylon mesh covering a steel frame constructed from hoops and steel rods. These simple traps are often referred to as “drum nets”. They are used in rivers, streams and lakes to catch fish moving close to the bank. A freshwater fish pot or drum net used in Germany for catching tench, roach and carp.
Drum nets are normally set by rolling them into the water from the bank and down the underwater slope to the preferred fishing place. A line attached to the trap winds round its centre as it is rolled down the slope . The trap is taken from the water by pulling on the line, which rolls it back up to the bank. Drum nets can either be baited or placed unbaited in an area where fish swim in currents.