Towards a fully automated underwater census for fish assemblages in the Mediterranean Sea

Assessing underwater biodiversity is labour-intensive and costly, but is crucial for measuring the extent of the decline in local fish stock. In most cases, Underwater Visual Census (UVC) is the preferred method, however this can be costly in terms of human effort and is limited by meteorological and logistical factors. Advances in technology allows the utilisation of more autonomous video recording methods (i.e. Remote Operated Vehicles (ROV)) which addresses these limitations. This study used a transect-wise UVC coupled with diver operated videos (DOV). For the video analysis, a comprehensive fully automated pipeline was developed to extract frames from DOV and perform colour correction. This pipeline integrates a YOLO-based model to detect 20 Mediterranean fish species and validate the presence or absence of each species within individual transects. This study was conducted to evaluate the feasibility of using video-based methods for UVC with minimal human-input. The result of automa..., 1. Study area and data collection
The training dataset (DATAT ) was gathered in eight different locations in the Mediterranean Sea along the French Riviera, following the same UVC protocol on each site (Harmelin-Vivien et al., 1985). The depth ranged from 1-37m and was carried out during the whole year in 2022 (cold and warm season) to cover the full range of conditions and possibilities of fish occurrences.
The experimental dataset (DATAE) was recorded in October 2023 in and around two protected areas, one no-take zone (Cap Roux) and one Natura2000 site (Corniche Varoise), which both have elevated biodiversity. The specific coordinates and meta data can be found in the supplementary material (Table S1). A total of 64 videos, each corresponding to a transect, from 14 sites (8 on seagrass meadows and 6 on rocky substrates) were evaluated and compared. Each site consists of 3 to 6 transects, depending on the availability of video recordings and UVC data from the divers.
The videos were ob..., , # Data from: Towards a fully automated underwater census for fish assemblages in the Mediterranean Sea

[https://doi.org/10.5061/dryad.f7m0cfz6f](https://doi.org/10.5061/dryad.f7m0cfz6f)

## Description of the data and file structure

### 1. Study area and data collection

The training dataset (DATA_T) was gathered in eight different locations in the Mediterranean Sea along the French Riviera, following the same UVC protocol on each site. The depth ranged from 1-37m and was carried out during the whole year in 2022 (cold and warm season) to cover the full range of conditions and possibilities of fish occurrences.

The experimental dataset (DATA_E) was recorded in October 2023 in and around two protected areas, one no-take zone (Cap Roux) and one Natura2000 site (Corniche Varoise), which both have elevated biodiversity. A total of 64 videos, each corresponding to a transect, from 14 sites (8 on seagrass meadows and 6 on rocky substrates) were evaluated and compared. Each site consists of...