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DAY 9 – MAY 5
VIEQUES’ MILITARY PAST
Isla Vieques (seven miles southeast of mainland Puerto Rico) was formerly used by the United States Navy for naval gunfire support and air-to-ground ordnance training since the early 1940's. Beginning in 2001, the Navy turned over land on the western end of Isla Vieques to the Municipality of Vieques, the United States Department of the Interior (DOI), and the Puerto Rico Conservation Trust. On May 1, 2003, the Navy ceased all military operations on the island and transferred its property on the eastern side of the island to the US Fish and Wildlife Service and the land was designated as a wildlife refuge.
The Navy is currently investigating areas it previously occupied to determine the extent of any potential contamination. NOAA’s Office of Response and Restoration (ORR) is assisting the Navy with the assessment of contamination, identification of risks to the environment, and development of cost-effective strategies for assessment, cleanup, and restoration of natural resources. For more information about ORR’s work in Vieques check out http://www.response.restoration.noaa.gov.
FISHERIES AROUND VIEQUES
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Fisheries around Puerto Rico have been overexploited. Due to the past presence of the United States Navy, the extent of overexploitation is not as severe around Isla Vieques making it a promising location for establishment of a Marine Protected Area (MPA) designed to sustain fisheries in the area. One of the aims of our cruise is to compare fish communities at different locations around Isla Vieques to allow us to identify the best locations for establishment of an MPA. The study will help understand the connection between different fish species and habitat, and identify what habitats are of most value for fisheries around Vieques. In addition to helping to prioritize conservation efforts these data will also assist in the cleanup and restoration efforts.
Many of the commercially important reef fish species of the region have
a life cycle that involves a cross shelf migration. Adults are found offshore
on deep reefs where they form aggregations and spawn. Their floating eggs
hatch to a larval stage over the shelf and after a month or so of growth
and development in the water column these larvae settle to the bottom. These
early juveniles tend to move inshore to shallow water where they find shelter
in a variety of habitats. As these juveniles grow they tend to move back
offshore where they join the adult stock spawn and the cycle turns. This
graph displays mean grunt lengths from a variety of habitats across the island
shelf. These data indicate that the largest grunts occupy reefs and that
adult grunts are found on offshore reefs.
Smaller juvenile grunts are found in seagrass and an intermediate size in mangrove
habitat.
The size of fish populations and their production may be greater in some areas than others due to differences in the amount and types of habitat available and how these habitats are arranged relative to one another across the shelf. One of the factors that will influence the productivity of an area is the amount of nursery habitat available for juvenile fishes as this will influence their abundance, survival and growth rates. Probably the most important types of nursery habitats are seagrass and macroalgae beds.
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Because of their small size and timid nature, juvenile fishes are poorly sampled in vegetated habitats by visual and sonar surveys. As a result we estimate juvenile fish densities in seagrass and macroalgae beds with a push-net. Two divers push the net over the bottom for a distance of around 100 ft (30 meters). The net is two meters wide so that the catch provides a density estimate for the 60 square meters over which it sweeps. Target species are juvenile tropical fishes, including snappers, grunts, parrot fishes, goat fishes, some wrasse species, and groupers that hide and feed in seagrass and macro-algae meadows that have developed in the shallow areas of the island’s shelf. These Essential Fish Habitats should be included within a Marine Protected Area designed to sustain fisheries.