Morphospecies and taxonomic sufficiency of benthic megafauna in scientific bottom trawl surveys

Abstract

Scientific fisheries surveys routinely identify a large diversity of commercial and non-commercial benthic megainvertebrates that could provide useful information for Marine Strategy Framework Directive (MSFD) descriptors. Species is obviously the basic taxonomic level to which most ecological studies and theories refer. Identification at this level of organization is indeed always preferred over any other taxonomic level. Nevertheless, aggregation of species to higher taxonomic levels may be unavoidable sometimes, since errors of identification are known or suspected to occur in many surveys. Using analyses of taxonomic sufficiency (identification of organisms at various taxonomic resolutions) and groups of morphospecies (taxa identified easily by non-experts on the basis of evident morphological traits), this study aims to quantify the loss of ecological information incurred by partial identification of benthic megafauna in bottom trawl surveys in order to put such data to good use. The analyses were conducted on five scientific surveys representing a large range of geographical areas (from 150 km 2 to 150 000 km 2) and environmental conditions. Results show that genus, family and, particularly, morphospecies are good surrogates for species identification in community analyses. We suggest that bottom trawl surveys can provide reliable megafauna data that may usefully complete those obtained by grab surveys. The use of morphospecies could lead to new strategies, combining different datasets to provide indicators for MSFD descriptors (e.g. D6). Highlights ► This study quantifies the ecological loss of misidentifying benthic megafauna. ► It suggests that the morphospecies is a good surrogate to species identification. ► Bottom-trawl surveys provide reliable data to inform MSFD benthic descriptors.

Regional Variability of Megabenthic Community Structure across the Canadian Arctic

“…Scaling at the genus level was done since identifications were patchy at the species level among stations (Brind'Amour et al, 2014). We chose to remove species found at only one station to allow better detection of the underlying community similarities (Clarke and Warwick, 2001).…”

Spatial properties of sessile benthic organisms and the design of repeat visual survey transects

“…This approach is commonly taken in studies that use benthic imagery (e.g. James, Marzloff, Barrett, Friedman, & Johnson, ; Schlacher et al, ; Williams, Althaus, Barker, Kloser, & Keith, ), and has proven useful for characterizing benthic communities and detecting change (Brind'Amour et al, ). Hereafter, these morphospecies will be referred to as ‘species’.…”

“…They are assumed to represent species but were not officially taxonomically identified, as no physical samples were taken. This approach is commonly taken in studies that use benthic (Brind'Amour et al, 2014). Hereafter, these morphospecies will be referred to as 'species' .…”

Patterns of benthic mega-invertebrate habitat associations in the Pacific Northwest continental shelf waters

“…On other temperate continental shelves like the Bay of Biscay or the English Channel, mixed mud-rock habitat is described and is further divided into different categories, depending on the size and abundance of the unconsolidated rocks involved, with different assemblages (Brind'Amour et al 2014). Within this study, the differences between mixed mud-rock at BA versus the other two sites similarly may be related to the difference of the size and abundance of the unconsolidated rocks.…”

“…Given these findings, 'mixed mud-rock' should be mapped as a distinct habitat characterized by low densities of a diversity of taxa, particularly sponges, gorgonians, anemones, and burrowing echinoderms. Since Brind'Amour et al (2014) have shown that this habitat can be divided in several categories, future studies should be designed to obtain thorough coverage of transition areas between consolidated rock and mud habitats to discern whether the different sizes of the interstitial rocks in the transition zone support distinct mega-invertebrate assemblages.…”