Ecological risk assessment for seabirds in New Zealand fisheries

We examined the risk of fisheries incidental mortality causing population declines for a suite of seabird species in 14 New Zealand fisheries using trawl and longline methods. We applied a method developed by Sharp et al. (2009) that used the available data on species biology, fisheries interactions, and fishing effort in a semi-quantitative Ecological Risk Assessment framework. Data quality was a strong pre-occupation in the study, with species abundance and productivity data being of extremely variable quality. Fishery data on captures were relatively sparse for small longline fisheries. Therefore, the results should be interpreted with caution, and are best used to guide the setting of research and management priorities. Sixty-three species were studied, but the final analysis reports on data for 39, the remainder being excluded due to lack of data in the relevant fisheries at this time.

The primary statistic generated by the study is the risk score, which describes the risk of adverse effects at species level from fishing mortalities — it is the number of likely captures in New Zealand commercial fisheries, over the species-specific index of population productivity. Our primary findings in relation to the likely impacts of fishing mortality on species, by fishery and area were: 1. Nineteen of 39 species (19 species, 90%Confidence Limit (CL)) had risk scores of 0.01 or above, which we define as having more-than-negligible levels of fisheries interaction. 20 species had negligible levels of interactions.

2. For 4 species (7 species, 90%CL) there could be cause for concern as the likely captures exceed the Potential Biological Removals (PBR) index (very high risk) and one other species (4 species, 90% CL) showed high risk. The species of greatest concern, in descending order were: Westland petrel, Chatham albatross, black-browed albatross, northern royal albatross, and southern Buller’s albatross.

3. The following species had risk scores of moderate risk for the median value of the risk score, but these changed to high or very high risk with the 90% CL. This indicates considerable uncertainty around the risk scores, and which warrants further research: Kermadec white-faced storm petrel, southern royal albatross, Antipodean albatross (both populations), Salvin’s albatross, Campbell albatross, and black petrel.

4. The suite of species identified in points 2 and 3 above are a high priority for research that helps define input parameters to the analysis. In some cases, this may be a greater knowledge of the species-specific catch rates, and for others, of basic biological attributes such as abundance and population growth rate. For some of these species, research is underway that will lead to better definition of biological parameters.

5. Warp strike affecting small albatrosses in trawl fisheries can result in birds being killed but not brought on board the vessel. These cryptic kills are not recorded by fisheries observers. When cryptic kills from trawl warp strike were included, at rates of 2 times (and 10 times) the likely capture values, the following seven species achieved very high risk rankings: Chatham albatross, black-browed albatrosses, southern Buller’s albatross, Salvin’s albatross, Campbell albatross, northern Buller’s albatross, and white-capped albatross. There is considerable uncertainty around the effect that warp-strikes may have on the risk levels for these birds, which may increase the priority for research on cryptic kills.

6. Four fisheries were identified as having the largest overall impact at species level, both in terms of captures of species with high to very high risk, and the number of overall captures throughout the NZEEZ. These were inshore trawl, small vessel bottom longline, squid trawl, and small vessel surface longline fisheries.

7. The greatest risk overall was in Fishery Management Areas (FMAs) 1 and 2, with high risk for some fisheries in FMAs 3, 4, 5, 6, and 7 and lower risk in FMAs 8,9, and 10.

8. Five fishing groups made little or no contribution to the total seabird bycatch (<1% of the total captures each) or to risk to individual species (<4% for any species each). These were bottom longline autoline, middle depths fresher trawl, southern blue whiting trawl, mackerel trawl, and deepwater trawl fisheries.

9. Those five species ranked with very high or high risk in the study have IUCN threat rankings of Critical to Vulnerable. Of the six species ranked of moderate risk, all were listed by the IUCN as Vulnerable. This indicates that at an international level, conservation concern for the species is high. Of these 11 species, ten breed only in New Zealand. Local loss of these species’ populations would lead to global extinction.

10. The species identified as having high to very high risk in the analysis are affected by a number of fisheries. Bycatch management measures currently apply in only a proportion of those fisheries. Monitoring of seabird catch has previously been focused in high-value and mainly southern fisheries, while the areas of greatest risk identified here occur in small vessel fisheries in both trawl and longline fleets, and predominantly in northern areas (in particular FMAs 1 and 2).

11. While ongoing research of this issue is recommended, the current results present the culmination of research and development of methods over several years in Ecological Risk Assessment for seabirds in New Zealand and Pacific fisheries, and make use of the available data. It needs to be acknowledged that the data quality is variable across species, but data were relatively robust for albatross and Procellaria petrel species. These were the species identified as most likely to be suffering population effects from fisheries mortality in the study.

12. The study presents the most recent in a series of comprehensive assessments of seabird risk from fishing mortality in New Zealand fisheries. The methods used are responsive to changes in fishing practice, distribution of effort, and improved knowledge of species biology. They will provide a useful tool for assessing risk and targeting measures to manage it in New Zealand fisheries through time.

13. Other fisheries, such as flatfish trawl, set net, troll and purse-seine could be treated with the methods explored in this study as observer data become available for these fisheries. Improved information about a number of species included in the analyses is expected over the next 2-3 years, as long-term research programmes deliver their findings. Therefore, we can optimistically expect improved information, understanding, and finer-scale management of this important environmental risk.