Catch Efficiency Of Gillnets Research Articles

Effect of Hang‐in Percentage on Catch Rates of Flounder in the North Carolina Inshore Gill‐Net Fishery

AbstractThe effects of hang‐in percentage (degree of tautness) on the catch efficiency of gill nets for paralichthine flounders in North Carolina were examined using monofilament gill nets with 5.75‐in stretched mesh. Nets with hang‐in percentages of 33% and 60% were fished in pairs and were separated by a single monofilament gill net of 5.50‐in stretched mesh. Catches of the paired test nets were significantly different, with the catches obtained by the looser nets (60% hang‐in) exceeding the catches in the more tightly hung nets (33% hang‐in) by 37% in number of fish and 46% in estimated weight. Length‐frequency distributions of the catch were not significantly different between the paired nets with different hang‐in percentages. Length‐frequency distributions of legal‐sized fish taken in 5.50‐ and 5.75‐in stretched‐mesh nets were significantly different, with the smaller mesh size resulting in a smaller (left‐shifted) length‐frequency distribution. Thus, hang‐in percentage can be manipulated to alter flounder harvest rates per unit of net, and small changes in mesh size can alter the size distribution of the catch.

Outdoor tank experiments on the influence of soaking time on the catch efficiency of gillnets and entangling nets

An outdoor tank experiment was conducted to study the influence of soaking time on the catch efficiency of gillnets and entangling nets (trammel and semi-trammel nets). The catch efficiency of the nets was also compared with detecting the difference between entangling nets and gillnets in relation to soaking time. Nets of the same mesh sizes were set simultaneously in separate outdoor tanks containing 200 rainbow trout ( Oncorhynchus mykiss) whose composition size was known. The experiment was carried out at night using four soaking times; 0.5, 1, 3 and 5 h. The variations of the catch efficiency of all nets had a U-shaped trend, showing that the efficiency increased at the shortest time (0.5 h), decreased at the intermediate time (1 h), and increased again at the longest soaking time. The average catch efficiency of the semi-trammel net appeared to be slightly higher than that of the gillnet.