Heyman, W.D.

Kobara, S.

Aquatic Commons

 INTRODUCTION 
Many commercially important fishes, including grou-
pers and snappers, aggregate at the same few common 
spawning sites throughout their own spawning seasons. 
These aggregations generally form at sites with specific 
reef geomorphologies.  Though the type of reef area may 
vary by geographic location, in many cases these sites are 
located on the outer edges of reefs (Koenig et al. 2000, 
Heyman and Requena 2002, Claro and Lindeman 2003), 
where favorable conditions encourage egg survival and 
larval dispersal (Johannes 1978, Colin 1992).  Several ag-
gregations have been observed on these reef promontories 
(Munro et al. 1973, Johannes 1978, Colin et al. 1987, Hey-
man and Requena 2002).  
Caribbean-wide Geospatial Analysis of the Location of Transient Reef  Fish  Spawning  
Aggregation sites using remote sensing 
 
SHINICHI KOBARA AND WILLIAM D. HEYMAN 
Geography Department, Eller O&M Building, Texas A&M University, College Station, TX  77843-3147 
 
ABSTRACT 
Most large Caribbean reef fish species form transient spawning aggregations at specific times and locations. Though 
reef fish spawning aggregation sites from many areas have been described and mapped, there has been no comprehensive 
geospatial analysis of the similarities and differences among them. The aim of this study was to analyze the locations of all 
known transient reef fish spawning aggregation sites in relation to 1. shelf edges and 2. reef bending points using remote 
sensing and field-collected position data.  Our analysis includes both published and previously unpublished data from the 
Bahamas, Belize, the Cayman Islands, Cuba, Mexico, Puerto Rico, Honduras, the Turks and Caicos Islands, and the Virgin 
Islands. Satellite-derived images of coral reef environments can receive the bottom reflectance in the depths up to 30 meters 
in clear water. The locations of many spawning aggregation sites are visible in these images, while some are deeper. To test 
our assumption that location of shelf edges could be fairly delineated using satellite images, we compared the positions of 
shelf edges from field-collected data, to shelf edges derived from satellite images. This study forms part of an ongoing pro-
ject focusing on the geomorphologic, geospatial, and oceanographic aspects of transient reef fish spawning aggregation 
sites.  
 
KEYWORDS: transient spawning aggregation, shelf edge, geospatial analysis, remote sensing 
 
Análisis Geoespacial en la Región Caribeña de Localidades Transitorias de Agregaciones de  
Desove de Peces de Arrecife usando Teledetección. 
 
La mayoría de especies de peces del caribe se agregan para desovar a horas y lugares específicos.  A pesar de que los 
sitios de agregación para desove de estos peces han sido descritas y mapeadas, un análisis geoespacial extenso de las simili-
tudes y diferencias entre ellos hace falta. La finalidad de este estudio fue la de analizar las localidades de todas las agrega-
ciones de desove de especies de peces de arrecife transitorias  en relación a 1. límite de plataforma y 2. puntos de flexión del 
arrecife, usando teledetección y data de posición recolectada en campo. El análisis incluye data publicada, como  también, 
data no publicada previamente de los siguientes países: Bahamas, Belice, Islas Caimán, Cuba, Méjico, Puerto Rico, Hondu-
ras, las Islas Turku y Caicos, y las Islas Vírgenes. Imágenes derivadas satelitalmente de entornos de arrecifes de coral pue-
den recibir el fondo reflectante hasta la profundidad aproximada de 30 mts. en aguas claras, y la localidad de varias áreas de 
agregaciones de desove son visibles en estas imágenes, mientras que algunas son más profundas. Para probar nuestra 
asumpción de que los bordes de las plataforma podrían ser equivocadamente delineados usando imágenes satelitales, se 
comparó la data colectada en campo, de las posiciones de las localidades actuales de los bordes de las platafomas, con la 
data derivada de imágenes satelitales. Luego se evaluó la localidad de cada agregación de desove  en relación con la de bor-
des de plataforma, como también la de los puntos de flexión del arrecife. Este es un proyecto en desarrollo que se enfoca los 
aspectos geoespaciales, geomorfológicos y oceanográficos de los lugares de agregación de desove de los peces de arrecife 
transitorios. 
 
PALABRAS CLAVE: agregaciones de desove, transitorio, borde de plataforma, análisis geoespacial, teledetección 
Reef promontories in the Caribbean are not the only 
suitable location for spawning aggregations.  Aguilar-
Perera (1996) commented that an aggregation site off Ma-
hahual, Mexico was located at the forereef, with the shelf 
edge 500 m seaward. Colin (1992) noted spawning sites in 
both reef flats and along shelf edges in Bahamas. The type 
of reef area used by spawning aggregations in the greater 
Caribbean seems to vary but the geographical variability 
and geomorphology of spawning aggregation sites have not 
been studied well.  
The goal of this study is to identify the locations of 
transient reef fish spawning aggregations in relation to reef 
geomorphologies in the greater Caribbean.  Shelf edge 
lines were delineated using remote sensing and field-
Page 398  59th Gulf and Caribbean Fisheries Institute  
 
collected position data in order to analyze the position of 
aggregation sites in relation to shelf edges and reef bending 
points.  
 Remote-sensing is a useful tool for monitoring and 
assessing coral reef environments. Satellites can success-
fully capture images of bottom reflectance of coral reef 
environments in depths up to 30 m in clear water.  As a 
result, the locations of many spawning aggregation sites in 
the Caribbean are visible in these images.  
 
METHODS 
The Society for Conservation of Reef Fish Aggrega-
tions (SCRFA) provides a global database of reef fish 
spawning aggregations based on published documents 
(http://www.scrfa.org). This database provided geospatial 
information for The Bahamas, Belize, the Cayman Islands, 
Cuba, Mexico, Puerto Rico, Honduras, the Turks and Cai-
cos Islands, and the Virgin Islands. The original references 
used for the database were carefully reviewed to derive the 
relationship between species and the geomorphology of 
their preferred spawning habitat at each documented loca-
tion. 
Shelf edges were delineated through a digital image 
processing of satellite images. Multi-spectral Landsat im-
agery data with 30 m spatial resolution were downloaded 
from the Millennium Coral Reef Mapping project archives 
(http://oceancolor.gsfc.nasa.gov/cgi/landsat.pl).  All images 
were classified using RSI ENVI software into three catego-
ries: land, shallow water area, and deep water area through 
the ISODATA unsupervised classification process. This 
classification method groups pixels into distinct clusters 
based on similar spectral reflectance.  Water absorbs infra-
red and red bands at the surface layer, making it relatively 
simple to distinguish between land and sea.  The difference 
between shallow and deep water areas is based on visible 
bands: how much light is reflected from the water column 
and the bottom. In deep water, light can penetrate deeper 
than 30 m, but may not reflect back up towards the sky. As 
part of the post-classification process, similar features were 
clumped and all grid data were converted into a polygon 
vector file. The classified image was edited for clouds and 
the shelf edge lines were derived from this vector file using 
ArcGIS. 
The locations of 14 spawning aggregation sites in Be-
lize were collected by field sampling using a hand-held 
GPS. Bathymetric data were collected using a Lowrance 
LCX-17M echosounder at two sites in Belize. All points 
data representing latitude, longitude and depth were im-
ported into ArcGIS and used for creating a triangulated 
irregular network (TIN) based bathymetry (Heyman et al. 
2007). Slope of the reef was calculated from the bathymet-
ric data. The slope and depth data were then overlaid onto 
image channels, from which the maximum discernible 
depth was determined to be 25 to 30 m, depending on loca-
tion. 
 
RESULTS AND DISCUSSION 
There are 131 out of 134 spawning aggregation re-
cords in the database reported to aggregate at or near the 
shelf edges (www.scrfa.org, accessed 15 May 2006).  In 
Belize, all known spawning aggregation sites were located 
at shelf edges.  These results were used to validate the re-
mote-sensing-based shelf edge lines.  
The 12 Belizean spawning aggregation sites within 
Turneffe Islands Atoll (4 sites), Lighthouse Reef Atoll (5), 
Glover’s Reef Atoll (2) and Gladden Spit (1) were overlaid 
onto the derived shelf edge lines’ layers. These point data 
of aggregation sites went across the remote-sensing based 
shelf edge lines (Figure 1).   
Eleven out of 12 spawning aggregation sites were on 
or near (50 ± 51 m) remote-sensing-based shelf edge lines.  
One exception was the site at Caye Bokel, southern 
Turneffe Atoll. The spawning aggregation site was 400 m 
off the remote-sensing based shelf break line. This is be-
cause this area had a lot of sediment, increasing turbidity 
and decreasing light penetration depth. As a result, light 
could not reflect off the bottom and the site was misclassi-
fied as deep water and thus it required more manual con-
textual editing to reassign a group of misclassified pixels to 
an adequate category. 
According to bathymetric data for the Halfmoon Caye 
and Gladden Spit sites, the shelf drop-off, where the slope 
increased dramatically (30 – 80 degrees) was found within 
a 100 m of both the spawning aggregation sites and the 
derived shelf edge lines. The depths of the spawning aggre-
Figure 1. Shelf edge lines derived from remotely-sensed 
image for the southern Lighthouse Reef atoll. Fish marks 
indicate spawning aggregation sites.  
   Kobara, S and Hayman, W GCFI:59  (2007)            Page 399 
 
gation in both sites were between 25 – 30 m. These also 
indicate that the remote-sensing based lines suitably fit the 
shelf edges. 
Remote-sensing based shelf edges and bathymetric 
map information are helpful to identify geomorphologic 
features of spawning aggregation sites, including water 
depth, distance from the shelf edges, and the shape of the 
shelf.  This methodology can be applied to the other region 
to understand the difference or similarities among spawn-
ing aggregation sites. 
 
LITERATURE CITED 
Aguilar-Perera, A., and W. Aguilar-Davila. 1996. A 
spawning aggregation of Nassau grouper Epinephelus 
striatus (Pisces: Serranidae) in the Mexican Caribbean. 
Environmental Biology of Fishes 45 (4):351-361. 
Claro, R., and K. C. Lindeman. 2003. Spawning aggrega-
tion sites of snapper and grouper species (Lutjanidae 
and Serranidae) on the insular shelf of Cuba. Gulf and 
Caribbean Research 14 (2):91-106. 
Colin, P. L. 1992. Reproduction of the Nassau grouper, 
Epinephelus striatus (Pisces: Serranidae) and its rela-
tionship to environmental conditions. Environmental 
Biology of Fishes 34 (4):357-377. 
Colin, P. L., D. Y. Shapiro, and D. Weiler. 1987. Aspects 
of the reproduction of two groupers, Epinephelus gut-
tatus and E. striatus in the west indies. Bulletin of Ma-
rine Science 40 (2):220-230. 
Heyman, W. D., J.-L. Ecochard, and F. B. Biasi. 2007. 
Low-cost bathymetric mapping for tropical marine 
conservation - a focus on reef fish spawning aggrega-
tion sites. Marine Geodesy 30 (1):37-50. 
Heyman, W. D., and N. Requena. 2002. Status of Multi-
Species Spawning Aggregations in Belize. Punta 
Gorda, Belize: The Nature Conservancy. 
Johannes, R. E. 1978. Reproductive strategies of coastal 
marine fishes in the tropics. Environmental Biology of 
Fishes 3 (1):65-84. 
Koenig, C. C., F. C. Coleman, C. B. Grimes, G. R. Fitz-
hugh, K. M. Scanlon, C. T. Gledhill, and M. Grance. 
2000. Protection of Fish Spawning Habitat for the con-
servation of warm-temperate reef-fish fisheries of 
shelf-edge reefs of Florida. Bulletin of Marine Science 
66 (3):593-616. 
Munro, J. L., V. C. Gaut, R. Thompson, and P. H. Reeson. 
1973. Spawning Seasons of Caribbean Reef Fishes. 
Journal of Fish Biology 5 (1):69-84. 
 
Page 400  59th Gulf and Caribbean Fisheries Institute  
 


Caribbean-wide geospatial analysis of the location of transient reef fish spawning aggregation sites using remote sensing

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Caribbean-wide geospatial analysis of the location of transient reef fish spawning aggregation sites using remote sensing

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