The Scottish Sea Angling Conservation Network

            A charity registered in Scotland - RegNo:: SC039015

28
Nov

Thornback Ray discard survival rates

Update :: The report is available here in pdf format.

CEFAS have completed a project which was developed to estimate the survival of rays, which are caught commercially in a trawl and subsequently discarded.

The trial was held in the Bristol Channel and its’ objectives were to

  1. Estimate the short-term discard survival rates of thornback rays
  2. Estimate the long-term discard survival rates of the most commercially important ray species
  3. Investigate the effect of codend weight on ray discard survival.

For every three thornback rays returned to the sea in the Bristol Channel ray fishery, around two survive for at least 3 days (range 50-74% survival).

In a previous study conducted by Cefas, the survival rates of only commercially discarded rays was investigated which showed a survival rate of 55%; this  was comparable with the results of this study.

Unsurprisingly, the study showed that as total catch weight and tow duration
increase, the survival rate of rays decreases.

It has been suggested that a maximum landing length be introduced for rays in order to allow the largest and most fecund fish to survive.

For this to be successful, trawlers would have to cut there tow duration in order to increase the survival rate. This was not supported by the fishers involved in the study, their preferred management measure was the use of area closures.

To do nothing should not be an option.

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