Protected rays – occurrence and development of mitigation methods in the New Zealand tuna purse seine fishery

Two species of rays in the Family Mobulidae are known to occur in New Zealand waters – spinetail devilray (Mobula japanica) and manta ray (Manta birostris).
In New Zealand, fisheries bycatch of mobulid rays have been reported from the domestic skipjack tuna (Katsuwonus pelamis) purse seine fishery, which has operated since the mid 1970s. The fishery occurs around the northern North Island in summer and autumn, with the key areas being the Bay of Plenty, east Northland, west Northland and North Taranaki Bight.
This paper looks to identify successful mitigation methods for captures of manta and devil rays by investigating current fishing practices aboard New Zealand vessels, and reviewing existing information worldwide on release methods for these and similar species.
Based on the existing evidence from diaries, photos and discussions, it is possible that a proportion of manta rays caught may suffer post-release mortality as a result of the conditions and injuries sustained during purse seining. Recommendations are made for the handling and live release of bycaught rays to maximise their survival rate.