Fishing methods for sustainable shrimp fisheries in the Canary Islands (North-West Africa)

Published source details Arrasate-López M., Tuset V., Santana J., García-Mederos A., Ayza O. & González J. (2012) Fishing methods for sustainable shrimp fisheries in the Canary Islands (North-West Africa). African Journal of Marine Science, 34, 331-339.
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This study is summarised as evidence for the following.

	Action	Category
	Modify the position of traps Action Link
	Deploy fishing gear at selected depths to avoid unwanted species Action Link
	Modify fishing trap/pot configuration Action Link

Modify the position of traps

A replicated, controlled study in 2003–2004 at four different water depths in areas of rocky seabed around the Canary Islands, North Atlantic Ocean, Spain (Arrasate-López et al. 2012) found that using semi-floating shrimp traps instead of traditional bottom traps appeared to reduce the catch and biomass of unwanted non-commercial species (discards) and unwanted commercial species (here referred to as bycatch), consistently across water depths. Results were not tested for statistical significance. Across water depths, semi-floating traps tended to catch fewer discard species of lower biomass (1–3 species; 0.006–0.6 g/trap/day) compared to bottom traps (2–4 species; 1–23 g/trap/day), and fewer bycatch species of lower biomass (semi-floating: 0–4 species, 0–18 g/trap/day; bottom: 1–6 species, 59–363 g/trap/day). The overall number and biomass of commercially targeted prawn species caught tended to be similar using semi-floating traps (2–6 species; 20.5–135 g/trap/day) and bottom traps (3–5 species; 16.6–107.3 g/trap/day), but the trap types caught different species. Four surveys were undertaken between October 2003 and October 2004. During each survey, an unspecified number of baited bottom traps and semi-floating traps (2 m above the seabed) were deployed at 100 m depth intervals between 120 and 1,300 m depths for 15–25 h. The number and biomass of bycatch, discard, and commercially targeted species were recorded. Data for a total of 487 bottom traps and 1,971 semi-floating traps were collected.

(Summarised by: Anaëlle Lemasson)
Deploy fishing gear at selected depths to avoid unwanted species

A replicated, controlled study in 2003–2004 of seabed and near seabed in the Atlantic Ocean off the Canary Islands, Spain (Arrasate-López et al. 2012) reported that shrimp traps fished above the seabed (semi-floating) caught less unwanted fish catch (non-commercially targeted or discarded) catch than traditional bottom traps set on the seabed, and the difference decreased with overall depth. Data were not statistically tested. At 100–400 m depths, semi-floating traps caught 18 unwanted species of fish at catch rates between <0.1–858.9 g/trap/day, and bottom traps caught eight species at <0.1–24.9 g/trap/day. Between 401–800 m depth, semi-floating traps caught eight unwanted fish species (<0.1–2,241.0 g/trap/day) while bottom traps caught four species (0.4–140.6 g/trap/day). At the deepest depths (801–1,130 m), semi-floating traps caught five unwanted fish species (<0.1–186.4 g/trap/day) and four were caught in bottom traps (0.5–41.9 g/trap/day). At all but the deepest depths, conger eels Conger conger accounted for a large proportion of the unwanted catch in bottom traps and in semi-floating traps at the intermediate depths (see paper for species individual data). Target shrimp Plesionika spp. catches between floating and bottom traps varied with species and depth (see paper for data). Four research surveys were done around the Canary Islands in 2003–2004 at depths of 100–1,300 m. Two types of traps were used to target shrimp: semi-floating traps of plastic mesh (20 ×15 mm) covering a conical cylinder (56 × 57 cm), and bottom traps made of wire mesh (19 × 19 mm) and an iron rectangular frame (100 × 100 × 50 cm). Semi-floated traps were set in groups of 75 traps, 15 m apart and 2 m above the seabed (total 1,971). Bottom traps were deployed in lines of 10 traps, 50 m apart (total 487). All traps were deployed in daylight hours and baited with mackerel Scomber colias.

(Summarised by: Leo Clarke)
Modify fishing trap/pot configuration

A replicated, controlled study in 2003–2004 of seabed and near seabed in the Atlantic Ocean off the Canary Islands, Spain (Arrasate-López et al. 2012) reported that semi-floating shrimp traps caught less unwanted fish catch (non-commercially targeted or discarded) catch than traditional bottom traps, and the difference decreased with depth. Data were not statistically tested. At 100–400 m depths, semi-floating traps caught 18 unwanted species of fish at catch rates between <0.1–858.9 g/trap/day, and bottom traps caught eight species at <0.1–24.9 g/trap/day. Between 401–800 m depth, semi-floating traps caught eight unwanted fish species (<0.1–2,241.0 g/trap/day) while bottom traps caught four species (0.4–140.6 g/trap/day). At the deepest depths (801–1,130 m), semi-floating traps caught five unwanted fish species (<0.1–186.4 g/trap/day) and four were caught in bottom traps (0.5–41.9 g/trap/day). At all but the deepest depths, conger eels Conger conger accounted for a large proportion of the unwanted catch in bottom traps and in semi-floating traps at the intermediate depths (see paper for species individual data). Target shrimp Plesionika spp. catches between floating and bottom traps varied with species and depth (see paper for data). Four research surveys were done around the Canary Islands in 2003–2004 at depths of 100–1,300 m. Two types of traps were used to target shrimp: semi-floating traps of plastic mesh (20 ×15 mm) covering a conical cylinder (56 × 57 cm), and bottom traps made of wire mesh (19 × 19 mm) and an iron rectangular frame (100 × 100 × 50 cm). Semi-floated traps were set in groups of 75 traps, 15 m apart and 2 m above the seabed (total 1,971). Bottom traps were deployed in lines of 10 traps, 50 m apart (total 487). All traps were deployed in daylight hours and baited with mackerel Scomber colias.

(Summarised by: Leo Clarke)