Codends modified with rectangular mesh panels (one oriented length-wise in the cod end and one oriented width-wise, each measuring 7 x 11 bars) reduced the weight of discarded bycatch by 46% and 38% respectively but did not significantly reduce the catch of targeted prawns. A haulback delay of 10-15 seconds allowed juvenile red spot to escape through the square mesh panels, while trawls with no delay showed no significant reduction in the bycatch of this species.
Gillnets with three difference mesh sizes (2 7/8", 3" and 4") were modified to use 200 lbs/200 yard lead line and 11 oz buoyancy floats (versus 50lbs/200 yard lead line and 3 oz floats) to increase the tension in the net. Catch rates of Atlantic sharpnose and bonnethead sharks were significantly lower in the 4" modified net. The proportion of hammer-wrapped bonnethead sharks was significantly higher in the 4" unmodified net and significantly less blacktip sharks were wrapped in the 3" modified net. Selectivity of blacknose sharks varied between the modified and unmodified nets.
White Dukane pingers with a fundamental frequency of 10kHz and harmonies of up to 160 kHz, elicited the strongest response from Hector's dolphins, compared to the black Pice and red Dukane pingers. More than half (62.5%) of the dolphins exhibited avoidance when exposed to the white pinger. However, no significant differences between pingers were found in the rate of echolocation clicks per dolphin or dolphin group, or among the peak frequencies of subset clicks.
Tests were conducted to determine if twin trawl nets containing a Turtle Excluder Device (TED) and a Popeye Fishbox caught less bycatch then nets fitted only with a TED. Nets that had the Popeye Fishbox located 70 meshes from the codend draw strings had a 48% reduction in the weight of small bycatch, an 87% reduction in number of sea snakes and a 35% reduction in the number of sharks and rays caught. When the Popeye Fishbox was placed 100 meshes from the codend draw strings, the weight of small bycatch was reduced by 28% and the number of sharks and rays was reduced by 27%.