Appeldoorn, R.S.

Pagan, F.A.

English

Aquatic Commons

 Proceedings of the 63rd Gulf and Caribbean Fisheries Institute     November 1 - 5, 2010   San Juan, Puerto Rico 
Use of Small ROV Systems to Survey Mesophotic Ecosystems 
 
FRANCISCO E. PAGAN* and RICHARD S. APPELDOORN 
Department of Marine Sciences, University of Puerto Rico, Mayagüez,  
Puerto Rico 00680-9000. *franciscoe.pagan@upr.edu.  
 
ABSTRACT 
Mesophotic coral ecosystems (MCEs) are challenging to assess due to both depth and geomorphology, but their characteriza-
tion is important for the assessment of fisheries resources habitat health and threatened species.  Surveys based on rebreather and 
mixed-gas diving are costly and limited in bottom time. Patchy distributions and depth variations further complicate MCE 
assessments.  We report on use of small Remotely Operated Vehicles (ROVs) to characterize habitats and resources to depths of 130 
m, primarily off La Parguera and Ponce, Puerto Rico.  The ROV is equipped with parallel laser beams for size estimation, and a 
sampling claw, and it can be deployed off of small boats using a portable generator. Preparation times for ROV dives are shorter 
than other methods. All video images are recorded on digital tape using a camcorder, which provides a permanent record and allows 
for subsequent analyses by experts in various taxonomic or scientific disciplines.  These surveys allow for baseline observations of 
fish communities and benthic cover, habitat use (including nursery areas) and behavior.  Results to date include (1) the documenta-
tion of new areas of MCE development, (2) the abundance and distribution of threatened species, (3) the deep occurrence of 
commercially shallow species, (4) documenting the depth and spatial extent of spawning aggregations, (5) the apparent deep refugia 
for overfished shallow species, (6) the occurrence of deeper commercially important species, (5) the impacts of sedimentation on 
MCEs, and the colonization of MCEs by invasive lionfish. ROVs are excellent companions to any mesophotic research diving 
program. 
 
KEYWORDS:  ROV, mesophotic coral ecosystems 
 
 
Uso de Pequeños ROV’s para Evaluar Ecosistemas Mesofóticos 
 
Los ecosistemas Mesofóticos son difíciles de evaluar debido a su profundidad y geomorfología, sin embargo su caracterización 
es importante para la evaluación del estado de los hábitats utilizados por los recursos pesqueros. Evaluaciones basadas en 
respiradores de profundidad con mezcla de gases son costosas y limitadas en el tiempo de estudio. Distribuciones de tipo parcho y 
cambios en las profundidades complican aún más el estudio de los MCE’s. En este trabajo se presenta el uso de pequeños vehículos 
remotos (ROVs) como alternativa para la caracterización de los hábitats y recursos de La Parguera y Ponce (Puerto Rico) a 
profundidades de hasta 130m. La unidad utilizada está equipada con un láser  de medición y un brazo de muestreo; el mismo puede 
ser utilizado desde pequeñas embarcaciones con el uso de un generador de energía. Los tiempos de preparación son menores que los 
de otros métodos y las imágenes de video son grabados en una cámara digital que permite el almacenamiento de la información de 
forma permanente y su distribución a los expertos de identificación taxonómica. Estas evaluaciones sirven de observaciones base de 
las comunidades bénticas y de peces, uso de los hábitats (incluyendo áreas de desarrollo de juveniles) y el comportamiento de los 
organismos. Los resultados obtenidos al día de hoy incluyen (1) la identificación de nuevas áreas de desarrollo de MCEs (2) la 
abundancia y distribución de especies en peligro (3) la observación de especies de aguas poco profunda en áreas mesofóticas (4) 
descripción de la profundidad y distribución espacial de agreaciones reproductivas (5) una protección aparente de las especies poco 
profundas en estas áreas (6) la observación de especies de interés comercial (7) los impactos de la sedimentación en los MCEs y la 
invasión de los mismos por el pez león. Los ROVs son excelentes accesorios para toda investigación de las áreas mesofóticas. 
 
PALABRAS CLAVE:  ROV, hábitat, ecosistemas de arrecifes mesofóticos 
 
 
Utilisation de Petits Systèmes de ROV d'Examiner des Écosystèmes de Mesophotic 
 
MOTS CLÉS:  ROV, l’habitat, écosystèmes de mosophotic 
INTRODUCTION 
Mesophotic coral ecosystems (MCEs), located along 
insular and continental slopes from 50 m and 130 m, are 
challenging to assess due to both depth and their steep and 
irregular geomorphology, but their characterization is 
important for the evaluation of fisheries resources, habitat 
health and threatened species.  Located beyond the normal 
range of air diving, surveys of these systems based on 
rebreather and mixed-gas diving are costly and limited in 
bottom time.  Patchy distributions and depth variations 
further complicate MCE assessments.  Under these 
conditions, the ability to conduct long and frequent 
quantitative or qualitative transects both horizontally and 
vertically are needed to wholly survey an area. Remotely 
Operated Vehicles (ROVs) offer a potential solution to this 
problem.   We have conducted ROV surveys extensively to 
depths of 130 m, off La Parguera and Ponce along Puerto 
Rico’s south coast.  In that work, our objectives were to 
assist in the characterization of the community composition 
and structure, including how these are limited by biological 
and geomorphological factors, the assessment of connectiv-
ity between deep and shallow reefs and the evaluation of 
the vulnerability of deep reefs to anthropogenic stress.  In 
this paper, we show how ROV surveys can be conducted, 
even from small boats, to assess MCE habitat and re-
sources. 
Page 544  63rd Gulf and Caribbean Fisheries Institute  
 
METHODS 
We used a SeaBotix LBV 200 ROV (Figure 1), which 
is a small (53 cm length), light weight (11 kg) portable 
system capable of working to depths of 200 m.  Our system 
had a standard 520-line video camera and was further 
equipped with parallel laser beams (5cm spacing) for size 
estimation and a manipulator arm equipped with sampling 
claw.   The cable connects to a control unit consisting of a 
video monitor and a separate joy-stick box that controls all 
functions of the ROV.  For a permanent record of each 
dive, and for subsequent analyses and species identification 
by taxonomic experts, video signals were exported to a 
digital video camera where the images were stored on to 
digital video tape.   
obtaining size information (Figure 4), and locating and 
characterizing spawning aggregations (Figure 5).   
Figure 1.  Seabotix 200 LBV remotely operated vehicle 
used for study of mesophotic coral ecosystems.  ROV is 
shown hovering over the shelf break. 
Our primary vessel was a 27 ft (8.3 m) Boston Whaler 
with a small cabin, with the ROV system powered by a 
sine-wave capable portable generator.  On larger vessels 
we used the ship’s electrical power supply through a UPS 
with a sine-wave filter.  In both cases the unit was 
deployed and recovered by hand.  Preparation times were 
between 10 and 20 minutes.  Typically, dives were 40 to 
90 minutes in duration. 
 
OBSERVATIONS 
We have used the ROV for a variety of purposes, 
including exploratory surveys, characterizations and 
collections.  These efforts have focused both on benthic 
organisms, especially corals, and fishes.  For the latter, the 
ROV is particularly useful for characterizing the large fish 
fauna, including commercially valuable species, over 
broad depth ranges not easily surveyed by divers.  Noted 
new observations were the occurrence of invasive lionfish 
in MCEs (Figure 2), the definition of critical nursery 
habitat for deep species (Figure 3) and the increased 
abundance of large predators at depth (Figures 4 and 5).  
Larger fish can be readily approached, which facilitates 
Figure 2.  Lionfish recorded at 61 m off Mona Island.  A 
second individual is hidden behind the sponge at left of 
center (black and white image of a color video capture). 
Figure 3.  A large school of juvenile blackfin snapper resid-
ing along a ledge in an otherwise barren landscape at 64 m 
off Buck Island National Monument, St. Croix, USVI (black 
and white image of a color video capture). 
Figure 4.  Measuring a black grouper at 84 m.  Arrows 
point to the two parallel laser beams set 5 cm apart (black 
and white image of a color video capture). 
   Pagan, F.E. and R.S. Appeldoorne  GCFI:63   (2011) Page 545 
 
In our characterization of benthic organisms we were 
able to count, identify and measure individual coral 
colonies (Figure 6).  Photographs extracted from video 
images taken perpendicular to the surface can be used for 
gross calculations of percent cover, using the parallel laser 
beams to scale the size of the image and thus control height 
of the photo off the bottom.  The manipulator arm was 
useful for collecting only small specimens, including 
rhodoliths (Figure 7) and samples of small weakly-attached 
benthic invertebrates for identification and genetic 
analysis.   Frequently seen during our surveys have been 
species of concern, such as sharks and, to a lesser degree 
turtles (Figure 8).   
Surveys off of Ponce, on Puerto Rico’s south coast 
showed that, although deep, these areas can be threaten 
with high sedimentation (Figure 9), preventing MCE 
development or smothering existing benthic communities. 
New substrate from the late 1990’s (deep outfall pipe; 
boulder backfill) showed no coral colonization in meso-
photic depths, but antipatharians were abundant. 
DISCUSSION 
 
As a consequence of our work with this ROV, we were 
able to document new areas of MCE development, the 
abundance and distribution of threatened species, and the 
deep occurrence of commercially valuable deep and 
shallow species.  This latter work was critical in recogniz-
Figure 5.  Assessing the extent and abundance of yellowfin 
groupers (in circles) at an aggregation site, which extends 
from 30 to 50 m (black and white image of a color video 
capture). 
Figure 6.  Characterization of mesophotic coral ecosys-
tems, showing a colony of Agarica undata at 93 m.  Colony 
is approximately  25 cm across the horizontal based on the 
parallel laser beams = two light spots in the center of the 
image (black and white image of a color video capture). 
Figure 7.  Using the manipulator arm to sample rhodoliths 
at 92 m (black and white image of a color video capture). 
Figure 8.  Male hawksbill turtle observed feeding at 65 m 
(black and white image of a color video capture). 
Figure 9.  Insular slope at 70 m off of Ponce, Puerto Rico 
showing the area to be completely sediment covered and 
devoid of any benthic community (black and white image 
of a color video capture). 
Page 546  63rd Gulf and Caribbean Fisheries Institute  
 
ing MCEs as apparent deep refugia for overfished shallow 
species and the connectivity between shallow and meso-
photic areas, with the dependence of some components of 
the MCE fish community on shallow nursery areas.  In 
contrast, coral communities below 50 m were comprised 
primarily of species restricted to deeper waters, and those 
shallow species that did occur (e.g., Montastraea caverno-
sa) were small and widely scattered, questioning both their 
maturation/fecundity and ability to have eggs fertilized.  
This suggests that coral at these depths have little connec-
tivity to shallow water coral ecosystems and cannot be 
looked upon as a source of recruits to recolonize shallow 
reefs. 
Our observations suggest that the use of small ROVs 
can greatly enhance the assessment of mesophotic habitats 
and resources.  However, there are limitations, not the least 
of which is cost; our unit when new was close to $50,000 
US (we also had an acoustic tracking unit installed).  The 
low video resolution makes identification of smaller or 
more cryptic individuals difficult, although a high 
definition camera can be added (but at a large increase in 
price).  Much of our work has been in conjunction with the 
use of mixed-gas rebreather diving, with ROV surveys 
being used to locate sites for detailed field work and 
extending the range of observations.  This is particularly 
useful in depths below 70 m, where we have limited diver-
based surveys due to exponential increases in the time 
needed for outgassing when ascending.  Small ROVs have 
limited collection capabilities; the arm can only be used to 
collect one item, and cannot lift heavy objects or break off 
specimens that are solidly attached, including, on occasion, 
those sea whips and wire corals that foul the propellers.  
Lastly, ROVs cannot be launched in high wind or wave 
conditions, which still would allow diver activities, due the 
inability of the ship to hold position. 
 
 


Use of Small ROV Systems to Survey Mesophotic Ecosystems

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Use of Small ROV Systems to Survey Mesophotic Ecosystems

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