Modify the design of traps
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Traps or pots are static gears often used to fish for crabs or lobsters. They consist of structures into which species of commercial interest enter through funnels. These funnels encourage entry but limit escape, and often catch a large amount of unwanted species (Stevens 1996). Trap design can be modified, such as by using different shape or material for the frame (Amengual-Ramis et al. 2016; Major et al. 2017), to potentially reduce the amount of subtidal benthic invertebrate bycatch (Arrasate-López et al. 2012; Schoeman et al. 2002).
Evidence for related interventions is summarised under “Threat: Biological resource use – Modify the position of traps” and “Use different bait species in traps”.
Amengual-Ramis J.F., Vazquez-Archdale M., Canovas-Perez C. & Morales-Nin B. (2016) The artisanal fishery of the spiny lobster Palinurus elephas in Cabrera National Park, Spain: comparative study on traditional and modern traps with trammel nets. Fisheries Research, 179, 23–32.
Arrasate-López M., Tuset V.M., Santana J.I., García-Mederos A., Ayza O. & González J.A. (2012) Fishing methods for sustainable shrimp fisheries in the Canary Islands (North-West Africa). African Journal of Marine Science, 34, 331–339.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.
Stevens B.G. (1996) Crab bycatch in pot fisheries. Solving bycatch: considerations for today and tomorrow, 151–158.
Schoeman D.S., Cockcroft A.C., Van Zyl D.L. & Goosen P.C. (2002) Changes to regulations and the gear used in the South African commercial fishery for Jasus lalandii. South African Journal of Marine Science, 24, 365–369.
Supporting evidence from individual studies
A replicated, controlled study in 2011–2012 of seabed composed of mud, kelp, and maërl, off the southeastern coast of Mallorca, western Mediterranean Sea, Spain (Amengual-Ramis et al. 2016) found that plastic lobster traps appeared to catch lower amounts of non-commercial unwanted catch (discard) than collapsible traps. Data were not statistically tested. The amount of discard caught in plastic traps (3 individuals/450 m) tended to be lower than in collapsible traps (16). In addition, plastic traps caught some legal-size commercially targeted lobsters (0.3/450 m), while collapsible traps caught none. In May–September 2011, two new designs of traps, plastic and collapsible (900/design), were deployed at 50–100 m depth for 24 h (see original paper for details of each design). Lobsters and discard species caught were counted and measured in each trap. Baited traps were deployed in two 450 m-long strings of 30 traps each (one line/design; >200 m apart).Study and other actions tested
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.Study and other actions tested