Study

Movement, depth distribution and survival of spinetail devilrays (Mobula japanica) tagged and released from purse-seine catches in New Zealand

  • Published source details Francis M.P. & Jones E.G. (2017) Movement, depth distribution and survival of spinetail devilrays (Mobula japanica) tagged and released from purse-seine catches in New Zealand. Aquatic Conservation: Marine and Freshwater Ecosystems, 27, 219-236

Actions

This study is summarised as evidence for the following.

Action Category

Release protected or species of concern alive after capture

Action Link
Marine Fish Conservation
  1. Release protected or species of concern alive after capture

    A replicated study in 2013–2015 in coastal pelagic waters of the Tasman Sea, off northern New Zealand (Francis & Jones 2017) found that some individuals of the protected and endangered spinetail devilray Mobula japonica survived release after accidental capture in purse-seine nets and normal handling practices, but survival was decreased in rays brought aboard entangled in the net. Three of seven data tagged devilrays survived capture and release, two over monitoring lengths of 30 days and one with a monitoring length of 82 days. Four rays died within 1–2 days of release, indicated by rapid descents in the data to ~1,800 m. All three rays that survived had been brought onboard from the purse-seine in a convey net, or brailer, and released directly from the convey net or using a rope and winch. All rays that died had been entangled in a part of the net (bunt) and hauled onboard in the final section of the main purse-seine net. Rays were tagged by observers aboard commercial skipjack purse-seine vessels after being lifted on deck. Only rays hauled onboard were tagged as those released whilst in the water were all expected to survive. Satellite-archival tags were anchored in the central part of the wing musculature using an umbrella anchor with eight plastic barbs. Anchors were attached to tags by 10-11 cm monofilament nylon or stainless-steel tethers. Tags were secondarily attached to the wing with a numbered conventional plastic tag and had a release device that triggered at 1,700–1,800 m.

    (Summarised by: Leo Clarke)

Output references

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