Updated fisheries risk assessment framework for seabirds in the Southern Hemisphere

Edwards CTT, Peatman T, Roberts JO, et al (2023) Updated fisheries risk assessment framework for seabirds in the Southern Hemisphere. New Zealand Aquatic Environment and Biodiversity Report No. 321:103

The Spatially Explicit Fisheries Risk Assessment (SEFRA) framework has been developed in
New Zealand for quantitative assessment of the risk to a variety of megafauna, including seabirds. It
uses spatial and temporal overlap between the distribution of seabirds and fishing effort to construct
a measure of the opportunity for interaction. The relationship between this opportunity and actual
captures is estimated using a regression, with observed captures providing the response variable and
overlap providing the input covariate. The regression of captures onto overlap is described by an
estimated term known as the catchability. This catchability can then be applied to the total overlap
(from observed and unobserved fishing effort) to predict total captures. Captures are converted to
death via a mortality multiplier, and this in turn is used to estimate the risk. Species for which the
number of fishery related deaths exceeds capacity of the population to regenerate are considered to
be at risk.

Many of the New Zealand endemic and indigenous seabird species are subject to incidental catch by
fisheries outside the New Zealand Exclusive Economic Zone (EEZ). A comprehensive assessment
of the risk therefore needs to include these global pressures. The current project represents the
most recent iteration of attempts to quantify the risk to New Zealand’s seabirds in the entire
Southern Hemisphere. In order to expand its relevance, species of interest to the Commission for
the Conservation of Southern Bluefin Tuna (CCSBT) and the Agreement on the Conservation of
Albatrosses and Petrels (ACAP) have also been included.

Compared with previous iterations, the most significant advance is that bottom longline and trawl
effort data have been represented, rather than focusing on surface longline effort only. However,
observer capture data were only available from within the New Zealand EEZ, meaning that
catchability could only be estimated from a very small fraction of the possible captures. Because
of strong mitigation measures within the New Zealand EEZ, the application of this catchability
to fishing effort globally is likely not representative of the global captures and risk. The results
presented here should therefore only be considered preliminary. Given this caveat, the current
project identifies Westland petrel (Procellaria westlandica), White-chinned petrel (Procellaria
aequinoctialis), New Zealand white-capped albatross (Thalassarche cauta steadi), Southern Buller’s
albatross (Thalassarche bulleri bulleri), Salvin’s albatross (Thalassarche salvini), Northern royal
albatross (Diomedea sanfordi), and Amsterdam albatross (Diomedea amsterdamensis), as the
species at highest risk.

A number of other features of the SEFRA framework have been updated, based on recent updates
to the domestic seabird risk assessment. They are described here with the intention of providing a
foundation for future work.