Abstract:

Remotely operated vehicle (ROV) footage was used to obtain density (fish per 100m2) estimates of damselfish observed on natural and artificial reef sites located in the northern Gulf of Mexico from 2018-05-14 to 2019-11-21 aboard charter fishing vessels. The non-native regal demoiselle was first sighted on artificial reefs in August 2018. Dataset includes estimated densities of regals along with a suite of other damselfish to document their expansion onto northern Gulf of Mexico reef sites.

Suggested Citation:

Tarnecki, Joseph. 2021. Damselfish species density estimates obtained from remotely operated vehicle (ROV) footage from natural and artificial reef sites in the northern Gulf of Mexico from 2018-05-14 to 2019-11-21. Distributed by: GRIIDC, Harte Research Institute, Texas A&M University–Corpus Christi. doi:10.7266/DKBV9PGP

Purpose:

To document regal demoiselle (Neopomacentrus cyanomos) expansion in the northern Gulf of Mexico.

Data Parameters and Units:

Date sampled (date of the ROV survey mm/dd/yyyy), Latitude and Longitude (decimal degrees), Reef type (natural or artificial), Depth (m), Relief (vertical relief of reef; m), Complexity (estimated as amount of crevices, holes, number of rocks, formation of the reef structure; low or high), Area Surveyed (ROV estimated coverage m2), and Damselfish Density by species name (fish per 100m2)

Methods:

ROV video sampling was conducted using a point-count methodology for small-scale AR habitats or a transect methodology at NR sites. Using the point-count methodology, the ROV was positioned 1 m above the seafloor and approximately 5.5 m from the reef structure. A 360° spin was performed and then the ROV was flown to the opposite side of the reef and another 360° spin was performed. Then, the ROV was flown 1 m above the reef and 10 m above the reef where additional 360° spins were performed. The ROV was then flown down to the reef module to identify small or cryptic species residing within and on the reef structure. Density (fish per 100 m2) was computed by summing the total number of fish observed for each species within the survey spins plus any additional fish observed on or in the reef structure and then dividing by the total area surveyed (176.7 m-2). Fish density is reported as individuals per 100 m2. At NR sites, the ROV was positioned 1-2 m above the seafloor, depending on visibility, and flown on 4 orthogonal 25-m transects away from a center point that was demarcated by a 7-kg clump weight attached to the tether. Fish observed during the four transects were identified to the lowest taxonomic level possible and enumerated. Area surveyed was computed by multiplying transect width (m), estimated as the product of the height off bottom (1 or 2 m) and the tangent of half the camera field of view (GoPro Hero5 = 122.6°/2), by the sum of all four transect lengths (100 m). Individual species counts were summed among transects and divided by the total area surveyed to estimate fish density.

Instruments:

GoPro Hero5 camera; remotely operated vehicle (ROV)

Individual Files: