The spatial analysis of bottom-contacting trawl effort by commercial trawlers within the New Zealand Territorial Sea and 200 n. mile Exclusive Economic Zone (TS+EEZ), in waters open to trawling down to 1600 m depths, is presented in this report, for different time periods during the 1990–2019 fishing years, based on available data. Separate summaries are presented for inshore and deepwater fisheries. A summary of shellfish dredging is also included.

The extent of the bottom-contacting trawl footprint in New Zealand waters open to trawling is updated by this report to include the 2018 (1 October 2017 to 30 September 2018) fishing year, where data are available for the commercial inshore (fishing years 2008–2018) and deepwater trawl fisheries (1990–2018). Effort data for other bottom-contacting fishing methods, Danish seine and shellfish dredge, are also summarised by fishery, for 1990 to 2018 (1989–90 to 2017–18).

The present study provides estimates of seabird bycatch in commercial fisheries in New Zealand waters. Estimates were derived using statistical models that integrated fishing effort and observer data up to the 2017–18 fishing year. In 2017–18, there were 3328 (95% credible interval, c.i.: 2971–3782) estimated seabird captures, including 1506 (95% c.i.: 1344–1696) captures in trawl, and 1186 (95% c.i.: 913–1589) and 635 (95% c.i.: 536–758) captures in bottom and surface longline, respectively.

Commercial catch-effort data and fisheries observer records of catch and discards by species were used to estimate the rate and level of non-target catch and discards in the ling longline fisheries for the fishing years 2002–03 to 2017–18. Estimates were made for broad categories of catch and discards including target species, QMS species, non-QMS fish, and non-QMS invertebrate species, and estimates of annual catch were made for several of the major individual non-target species.

This report presents an updated assessment of the risk of commercial fisheries in New Zealand for 71 seabird taxa breeding in this region, including data to the 2016–17 fishing year. The risk for seabirds was estimated as the ratio of total fishery-related deaths to the Population Sustainability Threshold, with 18 species having an estimated risk ratio that was non-negligible. Black petrel continued to be identified as the species most at risk from commercial fisheries in New Zealand waters.

The present report details the preparation of data for the estimation of protected species captures in New Zealand commercial fisheries, including data from 2002–03 to 2017–18. Protected species captures included seabirds, marine mammals and turtles. The data preparation included the linking of observer records and fisher-reported data and updates, including changes to the fisher-reported purse-seine effort data, resulting in a decrease in the latter compared with the previous data preparation.

This report documents the preparation of data for the estimation of protected species captures in New Zealand commercial fisheries, up to the end of the 2016–17 fishing year. Recorded captures included captures of seabirds, marine mammals and turtles. The report describes the rationale for and impact of changes that were made to the processing of these data, when compared with the processing carried out in previous years.

The deepwater Tier 1 and Tier 2 target fishstock footprint for fishing years 2008–17 was estimated at 180 100 km2. This 10-year footprint contacted 4.4% of the Territorial Sea and EEZ seafloor area and 13% of the seafloor open to fishing, down to 1600 m. Tier 1 fisheries accounted for 87%, with hoki effort contributing 42%. The 2017 footprint covered 48 203 km2, lower than the 10-year median of 49 845 km2. The aggregated swept area from all bottom-contacting trawls for 2017 was 94 500 km2.

The present study provides estimates of seabird captures in commercial trawl and longline fisheries in New Zealand’s Exclusive Economic Zone. Estimates were obtained from statistical models that integrated fishing effort and observer data. The current estimates update previous analyses to the 2016–17 fishing year. In this most recent fishing year, an estimated total of 4210 (95% credible interval: 3508–5296) seabirds were captured in New Zealand’s trawl and longline fisheries.

A SEFRA model was developed for female New Zealand sea lions at the Auckland Islands. Inputs to the model included: the estimated at-sea spatial density of female sea lions, and cryptic mortality priors relating to SLED use. Across the last 3 years assessed, the estimated annual risk ratio across all Auckland Islands fisheries was 0.24 (95% credible interval (CI) = 0.11–0.47); consistent with population recovery to 97.5% of unimpacted status when assuming deaths at the upper 95% CI level.

This report summarises bycatch and discards in hoki, hake, ling, silver warehou, and white warehou trawl fisheries for 1990–91 to 2016–17, based on analysis of fisheries observer and commercial catch effort data. Javelinfish, other rattails, and spiny dogfish were the main bycatch species recorded by observers. Total annual bycatch for the period ranged from 17 500 t to 49 000 t; total annual discards (for 2002–03 to 2016–17) were 5000 t to 25 000 t and decreased significantly after 2002–03.

New Zealand Aquatic Environment and Biodiversity Report No. 216.

An individual-based population model was fitted to genetic capture-recapture data collected during 2001-16 from Māui dolphins (Cephalorhyncus hectori maui), to estimate population size and trends. The population is estimated to be declining despite declining mortality rates. Forward projections under various scenarios imply that a further reduction of anthropogenic mortality of at least 50% is required to arrest population decline and avert extinction, regardless of the main source of the mortality, which is suspected to be fisheries bycatch and/or disease.

New Zealand Aquatic Environment and Biodiversity Report No. 215. 18 p.

A Bayesian Māui dolphin population model was developed integrating information from genetic “mark-recapture” and population size estimates. Model runs incorporated estimates of historical annual deaths from commercial fisheries and toxoplasmosis obtained from a separate spatial risk assessment. These models were then used to simulate the effects of estimated threat-specific mortality rates on future population growth.

New Zealand Aquatic Environment and Biodiversity Report No. 214. 168 p.
(Manuscript 3334)

A spatial risk assessment of threats was undertaken for Hector’s and Māui dolphins, to inform a revised Threat Management Plan (TMP) for the species. A Bayesian risk model was developed using the spatially-explicit fisheries risk assessment (SEFRA) approach, incorporating revised estimates of Hector’s and Māui dolphin spatial density and intrinsic population growth rate. The risk model was used to estimate spatial overlap, annual deaths and risk for commercial fisheries and lethal non-fishery threats, including toxoplasmosis. Spatial overlap was estimated for other threats.

Francis, M.P.; Hoyle, S.D. (2019). Estimation of fishing effort in the Southern Hemisphere.

New Zealand Aquatic Environment and Biodiversity Report No. 213. 24 p.

This report estimates the high seas fishing effort expended in the Southern Hemisphere by the main methods likely to impact seabirds (surface and bottom longline, and trawl). Data were sourced from 10 Regional Fisheries Management Organisations. Effort totals are biased low (sometimes substantially) in some regions and times, although the degree of under-estimation has probably declined through time. These estimates will be used in a subsequent quantitative risk assessment of seabirds.

978-1-98-859461-3

(Manuscript 3308)