A traits dataset for the BESITO index.

This dataset, including more than 1000 benthic species found in different regions of Spanish waters, offers a comprehensive and updated dataset with biological traits information, to be used in the application of the BESITO index (González-Irusta et al., 2018). The BESITO index was developed based on a reduced list (less than 100 species) frequently found in the International Bottom Trawl Survey (IBTS) of the Spanish north coast, DEMERSALES, as an index which classifies species according to their sensitivity to trawling disturbance. During the development of the indicator SoS (Serrano et al., 2022), which relies on the BESITO index to assess the impact of trawling on benthic habitats, this list was extended up to more than 200 species. Finally, in the last years, with the application of the SoS indicator to the implementation of the Marine Strategy Framework Directive (MSFD) to all waters in Spain, the list has been extended to 1049 species listed in this dataset, including species from the Gulf of Cadiz, Spanish Mediterranean Sea and the Canary Islands. The dataset includes mainly epibenthic species but also adds some infauna taxa. The list provides information up to 8 different traits (used to score the BESITO index): size, longevity, motility, attachment, benthic position, flexibility, fragility and feeding habits (see González-Irusta et al., 2018 for details). Furthermore, the list also provides the BESITO score for each species. The traits were assigned by consensus among a diverse group of experts (see authors of the dataset) from several Spanish Institute of Oceanography (IEO) laboratories across Spain, covering Atlantic (Santander, A Coruña, Cádiz and Tenerife) and Mediterranean waters (Málaga, Murcia and Balearic Islands). To assign the traits an updated version of the guidelines described in González-Irusta et al (2018) was used. These updated rules are detailed below. UPDATED RULES TO ASSESS SCORES TO THE BESITO TRAITS In the last eight years, since the publication of the BESITO index (González-Irusta et al., 2018) the criteria to assign scores to the eight traits that form part of the BESITO index has been discussed and clarified by an extended group of experts listed as authors on this dataset. As a result of these discussions, some criteria for scoring the traits have been clarified and, in certain cases (attachment and feeding habits), additional scores have been introduced or some scores removed (see Table 1). A new score (score 2) is defined for the attachment trait to account for species with sessile habits that lack any form of attachment to the sediment (e.g., bivalves). The sensitivity of species with sessile habits but no attachment was scored lower (less sensitive) than species with attachment (even if temporal) since it was considered that recovering its original position in the sediment after a physical pressure was less stressed for these species than for species with an attachment. On the other hand, they were scored higher than vagile animals for the inverse reason. Furthermore, the trait of feeding habits has been also modified, separating species sensitive to sediment resuspension from trawling (e.g., sponges, score 4) from others that, while share similar feeding strategies are more resilient to the smothering effect of trawling because have certain motile capacity to remove sediment (e.g. anemones, sea pens). Furthermore, the scores one and two for feeding habits has been merged in one unique score (score 1) which englobe all other feeding habits not covered by the score three and four. The distinction between scavengers and predators in the marine ecosystem is difficult to establish since most of them can feed on carrion if the opportunity appears, so to avoid confusion, both traits have been merged. In addition to the CSV file containing traits and BESITO scores for the 1049 species, an Excel file with the bibliography for each entry is available as supplementary material for 241 of the 1049 species. For these species, if a specific reference is not listed, it is because no primary source was found, and the trait was scored based on expert criteria (for instance using information from similar species for which we found information). OTHER CLARIFICATIONS Size: Regardless of the usual method for measuring the size of each species (e.g., carapace length, cephalothorax length, disc diameter, etc.), the size ranges in Table 1 refer to total size, including arms, spines, etc. Furthermore, trait values reflect the size observed in the expert's specific geographical area; therefore, these values may differ in some cases when applied to other areas. Flexibility: This trait applies ONLY to sessile organisms. All vagile organisms are scored with one for this trait. The flexibility angle is measured from the base to the top of the organism. Benthic position: "Burrowing" refers to all species capable of burying themselves, regardless of they can occasionally crawl (e.g., Nephrops norvegicus, Spatangus purpureus). The idea is to reflect the lower exposure to trawling when they are buried. Sea pens are a special case which deserves separate explanation. Although they spend most of their time as emergent fauna, they have developed strategies to escape physical pressures (some bury themselves, while others lie on the substrate). Therefore, the trait is assigned based on this behavior (a score of 1 if they bury themselves and a score of 3 if they lie down). This criterion will be applied if other species exhibit similar avoidance behaviors. Fragility: Scores were assigned as follows: 1 (hardshell) for species with very hard shells (e.g., requiring a hammer to break them); 2 (strong) for species with some form of protection, whether calcareous or otherwise, where the shell is not necessarily hard but does not increase species sensitivity; 3 for species lacking any special protection; and 4 for species whose shell structure renders them particularly fragile upon impact, increasing its sensitivity (e.g., Echinus melo). SCORES 1 2 3 4 Size Small (< 2 cm) Medium (2-10 cm) Medium large (10-50 cm) Large (>50 cm) Longetivity <5 5-10 11-50 >50 Motility Swimmer Crawl Burrow/Crevice/ Occasional crawl Sessile Attachment None (Vagile) None (Sessile- Occasional crawler) Temporary Permanent Benthic position Burrowing - Surface Emergent (>20 cm) Flexibility High (>45º or no sessile) - Low (10-45º) None (<10º) Fragility Hardshell Strong No protection Fragile shell Feeding habits Scavengers and/or Carnivorous - Deposit-feeder or suspension feeder not sensitive to clogging Suspension feeders sensitive to clogging and filter-feeders Table 1. Updated version of the table published in González-Irusta et al.,