Marine reptiles, a review of interactions and populations

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Summary

Five species of marine turtles and four species of sea snakes and kraits have been recorded in New Zealand waters. These species are susceptible to adverse effects from commercial fisheries to varying degrees.

This project investigated commercial bycatch data to describe the nature and extent of marine reptile interactions in New Zealand's Exclusive Economic Zone from 2008 to 2015.

Existing population information was reviewed to assess potential risks to fisheries, to identify information gaps, and ultimately make recommendations to mitigate impacts. In total, 120 marine turtle bycatch records were reported while no bycatch of sea snakes or kraits were documented.

Leatherback turtles were most frequently captured comprising 75% (n = 90) of all records. In contrast, green turtles, hawksbill turtles, and loggerhead turtles were captured in relatively low numbers, comprising 10% (n = 12), 5% (n = 6) and 2% (n = 2), respectively.

The large majority of all bycatch events occurred in fisheries management areas off northeastern New Zealand (74%) and during summer (51%, n = 61) and autumn (38%, n = 45).

Surface longline (SLL) activities targeting swordfish and tunas posed the greatest risk to marine turtles, recording the highest number of bycatch overall (91%, n = 109). In particular, leatherback turtles were most frequently captured in this fishery, accounting for 73% (n = 88) of total bycatch.

The potentially significant threat of SLL activities to marine turtles is reflected by the annual bycatch rate (for all species combined) which, in some years, exceeded the Western and Central Pacific Fisheries Commission recommended minimal marine turtle interaction rate of 0.019 turtles per 1000 hooks. In addition, very low observer coverage was allocated to fisheries and management areas where marine turtle bycatch was most likely to occur. Overall, very little local population information is available for marine reptile species in New Zealand.

Ultimately, given the potential impacts to marine turtles and information gaps identified, several recommendations are made in order to mitigate bycatch risk in New Zealand.

Publication information

Godoy, D. 2016. Marine reptiles - review of interactions and populations, Final report. Report prepared by Karearea Consultants for the New Zealand Department of Conservation. 53p.