Characterisation of seabird captures in New Zealand fisheries

Project: Characterisation of seabird captures in New Zealand fisheries
Project Code: ENV2004/04
Start Date: 1 October 2004
Completion Date: 30 March 2006
Vessel Use: Nil

Overall Objective:

1. Characterisation of seabird captures in New Zealand fisheries.

Specific Objectives:

1. To estimate and report the total numbers, and rates of captures, releases and deaths of seabirds, where possible by species, fishery and fishing method, caught in fishing operations up to the end of the fishing year 2002/03.
2. To provide an estimate of rate of seabird incidental capture, where possible by species, fishery and fishing method, for the fishing year 2003/04.
3. To examine factors related to fishing operations influencing the probability of capture of seabirds.
4. To classify fishing areas, seasons and fishing methods into different risk categories in relation to the probability of seabird incidental captures.
5. To recommend the observer coverage levels needed to estimate seabird captures within these risk categories, with highest precision in areas of highest risk. Statistical confidence (CV's) for estimates of total captures by fisheries at 10, 20 and 30% will be required.

Rationale:

General

Under the sustainability measures set out in the Fisheries Act (1996, s 15), the fishing-related mortality of marine mammals or other wildlife may be managed to avoid, remedy or mitigate any adverse effects of fishing on the related protected species. The information provided by the an examination of the factors influencing the probability of incidental catch of seabirds across New Zealand fisheries fulfils, in part, this responsibility.

The level of seabird incidental catch varies significantly between fisheries and within each fishery by season, and location (Duckworth 1995, Baird 1996, 1997, 1998). This project aims to use an improved data set to that available to Duckworth (1995), to examine range of factors that influence capture probability in both trawl and longline fisheries.

Factors such as location, season, vessel characteristics, use of bycatch reduction devices, and gear type will be examined. Note that data have been collected on an ad hoc basis, rather than using robust experimental design, and this may limit the ability of the research to determine causal factors.

Objective 1

A synopsis of the available observer data is needed to relate changes in observed seabird catch across New Zealand fisheries to changes in fishing practices, observer coverage, and other variables. This research should encompass all observer data to provide a robust analysis of data collected to date. In addition separate estimates of seabird captures by species and fishery, where possible, are needed for the fishing year 2004/05.

Objective 2

For the fishing year 2003/04, the total numbers of seabirds captured in fisheries, where possible by species, fishing method and fishery is to be reported. This research will detail the capture rates, incident rates, and total fishing effort in fisheries where seabird interactions are observed. Fishing seasons and areas may be broken into separate groupings in the analysis, as required.

Captures should include all instances where the legislative term ‘take’ can be applied to seabirds, with a distinction made in the analyses between ‘dead’ and ‘captured’ birds. Both should be reported and criteria for defining ‘dead’ birds agreed in consultation with the Ministry.

The representative-ness of observer cover as it relates to estimation of seabird capture rate and incident rate will be reported on, with an indication of the level of heterogeneity between different vessels and vessel groups within the fishery fleets. Incident and capture rates by vessel will be examined for each fishery, and compared with the mean and 75th percentile values for that fishery in each case. Where the data allow, an estimate of total captures of seabirds per fishery will be made, and for species, where possible, along with accompanying variance. For fisheries with less than 10% observer coverage, heterogeneity in the fleet will be examined, and an estimate made where vessel means are homogenous and the data show homoscedasticity. Thresholds for estimation will be discussed with the Ministry of Fisheries, and criteria developed that can be applied across all fisheries.

Seabird captures by different fisheries will be reported separately for each species comprising the main component of the seabird incidental take in fisheries (e.g. the most prevalent 20 species). This reporting shall indicate the total minimum removals from individual seabird species-populations based on observer data for the 2003/04 fishing year for the New Zealand EEZ. This should combine estimated levels of take where observer cover allow, and minimum fisheries removals where observer cover is lacking to enable estimation of catch. These two types of estimate need to be clearly identified. The sex and age groupings of individuals by species should be reported, where available.

Incidental information recorded by observers which may assist in identifying problems associated with fishing practice will be noted. This includes information on factors affecting the performance of ‘outlier vessels’ which have either high or lower than average seabird capture rates, use of mitigation techniques, etc.

Objective 3

An analysis of factors affecting the probability of seabird captures is needed, involving observer data held by Ministry of Fisheries and other agencies. Selected fisheries where high levels of observer coverage have been achieved over the past years will be targeted for this research. Trends through time in seabird incidental take will be examined in relation to the changing characteristic of the fisheries.

Objective 4

Seabird-capture rates and incident rates are known to vary significantly by area, season and vessel within fisheries. Due to this variability, it is difficult to determine where most effort is needed in mitigating the effect of fisheries mortality is needed. An analysis is required, using the current observer data set which spans more than a decade to classify the New Zealand EEZ, by fishery and region into zones of high, medium, and low risk for seabird mortality.

Objective 5

An analysis is required to examine the effects of deploying observer cover at different levels, in relation to the category of risk of incidental capture of seabirds, examined in Objective 4, above. In moving to a species-based approach to estimating seabird mortality (where possible) in New Zealand fisheries, a higher level of precision is required in observer estimates of seabird capture. Expending uniform levels of observer effort across fisheries, or arbitrarily targeting certain fisheries with high levels of coverage may allow estimation of the effect of fisheries mortality on seabird populations. Similarly, deploying observer cover only on selected fisheries at high levels, to the detriment of cover in others, may result in topical seabird incidental mortality issues going undetected. The research will examine how best to deploy observer effort in relation to the risk of seabird mortality around the New Zealand EEZ. Outputs under this objective will include recommendations on the effective placement of observers for the fishing year 2005/06, to enable, where possible, species level estimation of catch of seabirds in New Zealand fisheries.

Strategic Relevance

This research addresses the environmental principle of the 1996 Act that “…associated or dependent species should be maintained above a level that ensures their long-term viability…” and the strategy for marine environment research “…to develop and apply methods to ensure the use of fisheries resources is compatible with the requirements to avoid, remedy or mitigate any adverse effects of fishing on the marine environment, to maintain biological diversity and to protect habitat of particular significance for fisheries management”. This project forms a part of the Aquatic Environment research theme ‘…to determine the direct effects of fishing on associated or dependent species…’. This project is therefore consistent with the Aquatic Environment Research section of the Ministry of Fisheries Strategic Research Directions document.

Cost Recovery Information:

The percentage allocation for this project will be attributed to the following Fishstocks according to rule 7 schedule 3 of the Fisheries (Cost Recovery) Rules 2001:

• All ALB, BAR, BIG, BNS, HAK, HOK, JMA, LIN, ORH, RCO, SBW, SCI, SQU, SSO, STN, SWA, SWO, YFN Fishstocks

The project is estimated to cost between $50,000 — $100,000.