Towards a scientific community consensus on designating Vulnerable Marine Ecosystems from imagery

Abstract

Management of deep-sea fisheries in areas beyond national jurisdiction by Regional Fisheries Management Organizations/Arrangements (RFMO/As) requires identification of areas with Vulnerable Marine Ecosystems (VMEs). Currently, fisheries data, including trawl and longline bycatch data, are used by many RFMO/As to inform the identification of VMEs. However, the collection of such data creates impacts and there is a need to collect non-invasive data for VME identification and monitoring purposes. Imagery data from scientific surveys satisfies this requirement, but there currently is no established framework for identifying VMEs from images. Thus, the goal of this study was to bring together a large international team to determine current VME assessment protocols and establish preliminary global consensus guidelines for identifying VMEs from images. An initial assessment showed a lack of consistency among RFMO/A regions regarding what is considered a VME indicator taxon, and hence variability in how VMEs might be defined. In certain cases, experts agreed that a VME could be identified from a single image, most often in areas of scleractinian reefs, dense octocoral gardens, multiple VME species’ co-occurrence, and chemosynthetic ecosystems. A decision flow chart is presented that gives practical interpretation of the FAO criteria for single images. To further evaluate steps of the flow chart related to density, data were compiled to assess whether scientists perceived similar density thresholds across regions. The range of observed densities and the density values considered to be VMEs varied considerably by taxon, but in many cases, there was a statistical difference in what experts considered to be a VME compared to images not considered a VME. Further work is required to develop an areal extent index, to include a measure of confidence, and to increase our understanding of what levels of density and diversity correspond to key ecosystem functions for VME indicator taxa. Based on our results, the following recommendations are made: 1. There is a need to establish a global consensus on which taxa are VME indicators. 2. RFMO/As should consider adopting guidelines that use imagery surveys as an alternative (or complement) to using bycatch and trawl surveys for designating VMEs. 3. Imagery surveys should also be included in Impact Assessments. And 4. All industries that impact the seafloor, not just fisheries, should use imagery surveys to detect and identify VMEs.

Evaluation of the full set of habitat suitability models for vulnerable marine ecosystem indicator taxa in the South Pacific high seas

“…Though taxon‐specific, density is central to the VME concept (Baco et al., 2023), because density of habitat for species is innately linked to assemblage diversity, functionality, and structural complexity (de la Torriente et al., 2020). Where systematically collected data are available, more useful models can be developed to predict abundance of VME indicator taxa (Piechaud & Howell, 2022; Rowden et al., 2017) and also to relate to one or more of the FAO (2009) functional definitions of what constitutes a VME (e.g., Baco et al., 2023; Rowden et al., 2020) or translated into maps for VME indices (Stephenson, Bowden, et al., 2023). Outputs from abundance models, even if geographically limited, can be used to fine‐tune boundaries of spatial closures that have been based on information from presence‐only models, to provide more reliable management for specific areas or taxa.…”

“…When predicting into unsampled space, it is important to consider how well the training data used captures the environmental variables in the projected space (Elith et al, 2010), that is, how similar environmental conditions are in data-rich areas compared to data-poor areas (Bridges et al, 2023). Training dataset coverage of environmental space was estimated for presence-only models, as described by Stephenson et al (2020Stephenson et al ( , 2021 and others (Pinkerton et al, 2010;Smith et al, 2013).…”

“…Currently, no specific density thresholds define a VME, but density is key for the formation of structurally complex habitats and ecosystem functioning (Thurber et al, 2014). Recent attempts to develop consensus on what constitutes a VME, however, show this is not a simple task because some VMEs can be identified by a single image (e.g., scleractinian reefs), while a single coral colony providing habitat for other taxa in an image presents a greater challenge (Baco et al, 2023). Broadscale density information would provide additional context surrounding single images to enable informed density threshold determination across large geographic scales [e.g., following methodology suggested by Rowden et al (2020)].…”