Mapping and Characterizing Seagrass Areas Important to Manatees in Puerto

The population of manatees in Puerto Rico is the only group of Antillean
manatees (Trichechus manatus manatus) managed and protected by the United
States. The Manatee Recovery Plan for the Puerto Rico Population of West
Indian Manatees includes requirements to identify and manage habitats and
develop criteria and biological information important to its recovery. To this
end, the Sirenia Project initiated telemetry studies of manatees in Puerto Rico
at the U.S. Naval Station Roosevelt Roads (RRNS) in 1992. Concurrently, the
Project began gathering information on habitats critical to manatee in eastern
Puerto Rico. Computer aided mapping based on the interpretation of aerial
photographs and field groundtruthing was used in the current project to define
these habitats and map their distribution in the area of high manatee use.
Benthic habitats along approximately 32 miles (52 kilometers of RRNS shoreline
were mapped. Field assessment and characterization of important seagrass
habitats was conducted as a means of identifying seagrass and macroalgae
communities, especially in areas with known manatee feeding sites.

The purpose of this dataset is to identify and manage manatee habitats and to
develop biological information important to the manatees' recovery.

Data was obtained during ground truthing in October, 1994 and June, 1995. One
hundred and twenty-five sites, many representing questions raised during
preliminary habitat delineations were visited, along with sites with
characteristic signatures useful for broader interpretations. Transects were
made over several areas with rapidly changing benthic communities and confusing
signatures. Data recorded at each site included depth (range 0.5-7.1 m),
classification, dominant community, subdominant community, and pertinent
comments. the locations of all groundtruth sites were plotted onto one Arc Cad
layer of mapping information.

Groundtruthing was used to field verify and correct the initial delineations
made. Improvements were made to the draft classification scheme based on field
observations. Sites of questionable draft delineations were located on the
water and confirmed or corrected. Known manatee use of the area for resting or
feeding was noted. These sites were accurately located on the overlay for
inclusion on the maps.

Site location (latitude and longitude) was determined with a Garmin 45 GPS and
water depth (tape), temperature (hand-held mercury thermometer), and salinity
(hand-held temperature compensated refractometer) recorded. In addition,
salinity measurements were made at select nearshore locations to assess the
influence of drainage creeks and ditches on nearshore water salinity.
Underwater video photography and 35 mm photography were used to document
observations.

A review of vertical images of waters of RRNS was taken on December 17, 1993,
for the United States Navy, along with other collateral information, was used
to develop a benthic habitat classification system useful for mapping benthic
communities in the area. The system developed for this project was similar to
that developed for Geographic Information System (GIS) mapping of benthic
communities in the Florida Keys National Marine Sanctuary. Clear acetate
overlays were placed over the 9" x 9" aerial prints and the polygon method of
delineation used to outline habitats on the overlays.

Computer aided design methods (PC Arc Cad) were used to create a shoreline base
map from navigational charts for this region of Puerto Rico. Habitat polygons
extending as far from shore as allowed by the resolution of the images were
digitized onto the base map. A minimum mapping unit of 0.5 acres was applied
based on the scale and quality of the images. Once finalized, maps were
printed in both color and black-line.

The information for this metadata was partially taken from the document Mapping
and Characterizing Seagrass Areas Important to Manatees in Puerto Rico -
Benthic Communities Mapping and Assessment. Prepared for the U.S. Department of
Interior, National Biological Service, Sirenia Project. Prepared by Curtis
Kruer, Senior Biologist, Caribbean Fisheries Consultants, Inc.