Factors affecting bycatch in a developing New Zealand scampi potting fishery

Published source details Major R.N., Taylor D.I., Connor S., Connor G. & Jeffs A.G. (2017) Factors affecting bycatch in a developing New Zealand scampi potting fishery. Fisheries Research, 186, 55-64.
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This study is summarised as evidence for the following.

	Action	Category
	Use different bait species in traps Action Link
	Modify the design of traps Action Link
	Use a different bait type Action Link

Use different bait species in traps

A replicated, controlled study in 2014–2015 in two seabed areas in the South Pacific Ocean, New Zealand (Major et al. 2017) found that the type of bait used in the New Zealand scampi Metanephros challengeri pot fishery did not change the amount of unwanted invertebrates caught, in either area. The amount of unwanted invertebrates caught was similar in pots baited with mackerel Scomber australasicus, barracouta Thyrsites atun, or squid Nototodarus sloanii (abundance data not shown). In two areas, three bait species were tested: mackerel vs squid, and barracouta vs squid (mackerel vs barracouta not tested). At Chatham Rise from November–December 2014, traps baited with either mackerel or squid (equal number of traps) were tested during three deployments (three 500 m lines of 30 traps/deployment). At Cape Palliser in April 2015, traps baited with either barracouta or squid (equal number of traps) were tested during three deployments (one 500 m line of 30 traps/deployment). Traps were recovered after 18 hours, and unwanted invertebrate catch identified and counted.

(Summarised by: Anaëlle Lemasson)
Modify the design of traps

A replicated, controlled study in 2014–2015 in two areas of seabed in the South Pacific Ocean, New Zealand (Major et al. 2017) found that four different trap designs used to catch New Zealand scampi Metanephros challengeri caught different amount of unwanted catch of combined invertebrates and fish, but the effects varied between areas. In one area, rectangular traps caught more unwanted catch (2 individuals/trap) than box traps and standard traps (1 individual/trap; no difference between the two designs). In the other site, rectangular traps caught more unwanted catch (8 individuals/trap) than boxed traps (3 individuals/trap), and both caught more than domed plastic traps and standard traps (1 individual/trap; no difference between the two designs). Four different trap designs were tested in two areas: a standard creel trap, a box shaped creel trap, a rectangular shaped creel trap and a domed plastic trap. At Chatham Rise from November–December 2014, three designs (rectangular, box, standard) were tested during three deployments (three 500 m lines of 30 baited traps/deployment; 10 traps/design/line). At Cape Palliser in April 2015, all four designs were tested during three deployments (one 500 m line of 30 baited traps/deployment; 7–10 traps/design/line). Traps were recovered after 18 hours, and unwanted catch identified and counted.

(Summarised by: Anaëlle Lemasson)
Use a different bait type

A replicated study in 2014 of two areas of seabed in the South Pacific Ocean, New Zealand (Major et al. 2017) found that using different bait types in crustacean traps did not reduce the catches of unwanted fish. In the first trial testing mackerel Scomber australasicus and squid Nototodarus sloanii baits, there was no significant difference in the amount of unwanted fish catch between baits (mackerel: 0.6 fish/trap, 0.2 fish/trap). In the second trial, unwanted fish catch again was similar using barracouta Thyrsites atun bait (3.7 fish/trap) compared to squid bait (2.2 fish/trap). Bait species were tested in two trials on grounds fished for New Zealand scampi Metanephrops challengeri. In November/December 2014, a total of 140 traps baited with squid and 139 baited with mackerel were deployed at Chatham Rise. In April 2015 at Cape Palliser, 46 traps baited with squid and 45 with barracoota were deployed. Four types of traps were used, equal numbers baited with each bait species. All traps were deployed on the seabed and left for 18 hours before retrieval. All unwanted catch was identified and counted.

(Summarised by: Rosslyn McIntyre)