Assessment of a juvenile and trash excluder device in a Vietnamese shrimp trawl fishery

Published source details Eayrs S., Hai N.P. & Ley J. (2007) Assessment of a juvenile and trash excluder device in a Vietnamese shrimp trawl fishery. ICES Journal of Marine Science, 64, 1598-1602.
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This study is summarised as evidence for the following.

	Action	Category
	Fit a size-sorting escape grid (rigid or flexible) to a prawn/shrimp trawl net Action Link

Fit a size-sorting escape grid (rigid or flexible) to a prawn/shrimp trawl net

A replicated study of an area of shallow water in the Gulf of Thailand, Vietnam (Eayrs et al. 2007) found that shrimp trawl nets fitted with a rigid size-sorting excluder grid resulted in the escape of a high proportion of immature unwanted fish and sub-legal sizes of three of three fish of value, in a Vietnamese shrimp Penaeidae fishery. Overall, the grid excluded by weight 73% of the immature fish and 16% of the valuable fish catches (data not reported). For three of three fish species of commercial value (Japanese threadfin bream Nemipterus japonicus, bartail flathead Platycephalus indicus and snakefish Trachinocephalus myops) numbers of fish below the 150 mm length minimum landing size were reduced by 70–78% by the grid compared to the total codend catch (grid: 4,885–8,593 fish, codend: 1,767–3,706 fish). Lengths at which 50% of fish escaped were 124–134 mm across the three species. In addition, 8% of the target shrimp species were excluded by the grid. Data were collected over five days from 15 × 3 h trawl deployments at 12–15 m depth near Phu Quoc Island. A grid of three rectangular hinged panels, two of steel construction with 20 mm bar spacing, and one of small mesh to stop fish re-entering the net, was fitted to a 15 mm diamond mesh codend shrimp trawl net. Fish escaping from the grid were collected in a small-mesh cover installed over the panels. Both cover and codend catches were sorted separately by species, weighed and fish lengths recorded. The year the study took place was not reported.

(Summarised by: Chris Barrett)