Study

Escape response of juvenile fish in a shaking codend determined from tank experiments

  • Published source details Kim Y. (2015) Escape response of juvenile fish in a shaking codend determined from tank experiments. Fisheries Research, 161, 273-279.

Actions

This study is summarised as evidence for the following.

Action Category

Fit a moving device to a trawl net to stimulate fish escape response (stimulator device)

Action Link
Marine Fish Conservation
  1. Fit a moving device to a trawl net to stimulate fish escape response (stimulator device)

    A replicated, controlled study in 2012 at an experimental tank facility in Tongyoung, South Korea (Kim 2015) found that trawl net codends fitted with moving devices (two types) to stimulate fish escape response (active stimulating devices) increased the escape of young red seabream Pagrus major compared to conventional codends, but for young olive flounder Paralichthys olivaceus they were only effective when used in combination with an additional device that generated an active shaking motion of the net. For seabream, overall escape rates from the codend were higher with a stimulator device than without (with: 40–62%, without: 13–43%), but there was no difference for olive flounder (with: 55–88%, without: 60–87%). However, for both species the escape rates were greater in codends, with or without stimulator devices, fitted with another device that made the nets shake (seabream, shaking: 38–62%, steady: 13–40%; flounder, shaking: 55–63, steady: 85–88%), with the exception of seabream in a shaking codend with stimulator device at the faster of two flow rates (shaking: 38%, steady: 32%). In October 2012, seven separate experiments were done in circular water tanks to test a new method (shaking of the codend generated by a cap-like canvas fitted at the end) of increasing the escape of young fish from three types of codend: two with active stimulator devices (a fluttering flag-like netting panel and a double conical rope array – see paper for specifications); and one conventional codend without a device. In each experiment, a group of 200 hatchery-reared fish were released into the water flow at the front of the codend and the number of fish retained/escaped were recorded. Three flounder experiments with all three types of codend and shaking or steady motion were tested at the same water flow rate (0.6 m/s). For seabream, a conventional codend and a net stimulator device were each tested at two different water flow rates (0.5 and 0.7 m/s).

    (Summarised by: Natasha Taylor)

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