Examining the utility of a decision-support tool to develop spatial management options for the protection of vulnerable marine ecosystems on the high seas around New Zealand

Highlights

• A decision-support tool was assessed for identifying spatial conservation priorities.

• Spatial conservation prioritisation is sensitive to varying the input data.

• Balancing the protection of VMEs and use of high value fishing areas is possible.

• Cost to fishing was low given amount of VME habitat that could be protected.

• Use of a decision-support tool can improve current spatial management measures.

Abstract

The South Pacific Regional Fisheries Management Organisation (SPRFMO) Convention includes specific provisions to protect vulnerable marine ecosystems (VMEs). The SPRFMO Commission has determined that the interim measures put in place to protect VMEs should be replaced by an improved system of fishable and closed areas. We used the conservation planning tool Zonation to examine the utility of a decision-support tool to develop spatial management options that balance the protection of VMEs with utilisation of high value areas for fishing. Input data included: habitat suitability maps for VME indicator taxa, and uncertainties associated with these model predictions, for an area of the high seas around New Zealand; naturalness condition, represented by two proxy variables using New Zealand trawl effort data; and value to the New Zealand fishery using trawl catch data for two gear types and three time-periods. Running scenario analyses with these data allowed for an understanding of the effect of varying the input data on the spatial prioritisation of areas for VME conservation. The analyses also allowed for the cost to fishing to be determined, in terms of the amount of the trawl catch footprint (normalised to the catch) lost if high priority areas for VME indicator taxa are protected. In most scenarios, the cost to fishing was low given the relatively high proportion of suitable habitat for VME indicator taxa that could be protected. The main outcome of the present study is a demonstration of the practical utility of using available data, including modelled data, and the Zonation decision-support tool to develop future options for the spatial management of the SPRFMO area. Suggestions are also made for improvements in input data for future analyses.

Introduction

Many commercial fisheries that operate on the ‘high seas’ (areas beyond national jurisdiction) target fish species that live near the seafloor. Bottom-trawl fishing gear can cause impact to benthic habitat and organisms in the deep sea (see review by Clark et al., 2016). Some types of benthic habitat and organisms are particularly susceptible to the adverse effects of fishing (e.g., deep-water corals, Williams et al., 2010), and are known as ‘vulnerable marine ecosystems’ (VMEs).

In 2006 the United Nations General Assembly (UNGA) adopted a resolution which called upon parties to identify VMEs and avoid significant adverse impacts on VMEs (Resolution 61/105, UNGA 2006). Further UNGA resolutions emphasised the urgency for action and invited the Food and Agriculture Organisation of the United Nations (FAO) to develop guidance on the application of criteria for identifying VMEs (Resolution 66/68, UNGA 2009). In 2009 the FAO published such guidelines (FAO, 2009), and species or taxonomic groups that can be used as indicators of a VME were subsequently identified by regional fisheries management organisations/agreements (RFMO/As) (e.g., Parker et al., 2009; Parker and Bowden, 2010).

The Convention and Final Act of the International Consultations for the South Pacific Regional Fisheries Management Organisation (SPRFMO) was finalised in November 2009, establishing SPRFMO as the international fisheries management organisation with the mandate and responsibility to manage all non-highly migratory marine resources within the high-seas areas of the South Pacific Ocean (www.sprfmo.int). SPRFMO became a ratified fisheries organisation in 2012. The first SPRFMO Commission meeting in January 2013 discussed the “interim measures” of the Convention which had been designed to address UNGA resolutions, and had been applied by various countries to their national fleets fishing in the SPRFMO area. The interim measures included a ‘move-on rule’ obliging vessels encountering a potential VME to move a set distance away to avoid further impact (the rule's conditions are country-specific). The efficacy of move-on rules as a measure to prevent impacts on VMEs has been questioned because there is a risk that such measures will result in the spread of the impacts of trawling, and encounter thresholds do not consider catch efficiencies (Auster et al., 2011).

Over the past few years there has, therefore, been increasing emphasis on the importance of implementing adequate and representative spatial closures to protect areas known or likely to support VMEs (de Juan and Lleonart, 2010; Clark and Dunn, 2012; Ardron et al., 2014; Wright et al., 2015). In 2009, a spatial management regime with closed and open areas based on the historical trawl footprint was implemented for New Zealand vessels in the SPRFMO Convention Area (Penney et al., 2009). However, the effectiveness of these closed areas has been questioned by the cost-benefit analysis of Penney and Guinotte (2013). The SPRFMO Commission meeting in 2013 determined that the interim measures should be replaced by an improved system of fishable and closed areas. These closures would effectively represent a spatial management plan, whereby conservation and management measures are implemented that will result in sustainable fisheries and benthic protection.

Fisheries and ecosystems management on the high seas is complicated by data availability and accessibility constraints. There are relatively few data records available on the distribution and abundance of VME indicator taxa in the SPRFMO Convention Area to use for the objective planning of spatial measures to protect VMEs. However, relatively limited biological records can be combined with environmental data in statistical models to predict where VMEs are likely to occur (see review by Vierod et al., 2014). By overlaying models of the likely distribution of VME indicator taxa with the spatial distribution of fishing interest (e.g., catch data) it is possible to identify areas that can be closed to protect VMEs, and areas (ideally away from VMEs) where fishing can continue (Ardron et al., 2014). Software tools have been developed to facilitate this aspect of spatial management planning, and have been used globally to identify areas for conservation in both terrestrial and marine environments (Moilanen et al., 2009a). These decision-support tools use various computational methods to select representative sets of priority areas to conserve biodiversity over extensive geographic areas, whilst minimising the cost to existing users (e.g., Klein et al., 2008; Mazor et al., 2014; Lester et al., 2018).

Marine spatial planning for fishery management and biodiversity conservation is a complex process, particularly for the high seas, that involves multiple layers of information and strives to incorporate the viewpoints of all key stakeholders (Ardron et al., 2008). The aim of the present study was to demonstrate the functionality and evaluate the utility of a decision-support tool for informing future spatial management in the SPRFMO Convention Area.