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Navassa Cruise 2006 Day 2
Day 2: 4.21.06 ñ First day of operations
Mission: Habitat Characterization of Navassa Island
Today was our first full day of operations on Navassa Island. With the shakedown dive behind us, everyone was ready and confident to begin sampling. Today, we:
- did two deep water habitat surveys
- made contact with Haitian fishermen
- began conch surveys
- collected fish for ciguatera studies.
Habitat Surveys
and Amy Uhrin prepare to dive,
photo by C. Addison
Our habitat dives focused on the south side of the island. We surveyed two sites, with eight divers doing three dives per site.
Our objective is to characterize and describe habitat and fish communities in water depths 90 feet and greater, supplementing shallow water surveys done on previous research cruises by Dr. Margaret Miller, NOAA-Fisheries Southeast Fisheries Science Center, and others.
The most common habitat encountered on today’s dives was patchy reef with dense algal and hard cover coral. The photo shows an example of a benthic habitat photo which will later be analyzed to find out what organisms (such as corals, sponges, algae, etc.) were present and in what densities. Common fish recorded in fish counts today were:
- squirrelfish
- barracuda
- surgeon fish
- lobster
Queen Conch Census
by C. Addison
Today's objective was to do an initial coarse scale survey for conch aggregations around the island. Little is known about conch populations surrounding Navassa, but on other Caribbean islands, conch face heavy fishing pressure. We surveyed most of the south side of Navassa by towing a snorkeler on a manta board, a small board towed behind a boat at a slow speed.Due to conch's well camouflaged shells (often encrusted with algae) we were unable to identify them from the surface. We did see amazing rock structures, steep coral encrusted ledges, small reef fishes, and barracudas. Tomorrow we will do a fine scale conch survey using SCUBA and we hope to determine the age structure and density of resident conch populations.
Gear Impact Study
by A. Uhrin
Yesterday, scientists Amy Uhrin and Jean Weiner made their first contact with a group of Haitian fishermen With Jean translating from the fishermen's native Creole language, Amy and Jean would converse with the fishermen in their native Creole language and inquire about the location of some of their traps. These Haitian fishermen mark their traps with scavenged plastic bottles filled with foam, a simple yet effective method.
photo: fishermen's catch, by A. Uhrin |
 photo: Jean and drop camera,
by A. Uhrin |
Today, these fishermen caught
the following fish types:
- rock beauty
- squirrelfish
- cowfish
The scientists used an underwater drop-camera to survey the types of habitat being fished as well as to investigate potential habitat damage from traps and other fishing gear. Tomorrow, Amy and Jean will continue talking with the fishermen and searching for additional fishing gear.
Ciguatera Sampling
Ciguatera is an illness that is caused by consumption of seafood containing toxins that are produced by species of harmful algae (dinoflagellates in the genus Gambierdiscus). Ciguatera poisoning is the most common form of seafood poisoning affecting as many as 50,000 people yearly world wide. The toxins are transferred up the food chain from the single celled Gambierdiscus microalgae through small fishes that feed on the cells to the larger predatory fishes that feed on the small fish to humans and animals that consume the small and larger predatory fishes. The toxins produced by Gambierdiscus species are called ciguatoxins and are classified as neurotoxins because they affect the central nervous system. Some symptoms of ciguatera poisoning include nausea, vomiting, itching, blurred vision, numbness and tingling, hot and cold reversal, and cardiovascular irregularities. Severe poisoning can result in paralysis, coma, and death. Symptoms can persist for days or for as long as years with occasional recurrences.
Paula Whitfield and barracuda, by J. VanderPluym
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photo: blackfin tuna and Jenny VanderPluym, by B. Degan
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The research goals of our lab include collecting ciguatoxic fishes and new strains of Gambierdiscus cells for laboratory culture so that we can begin physiological and ecological studies to gain a better understanding of ciguatera dinoflagellates and their biology.
Fish of interest to us include:
- barracudas
- jacks
- amberjacks
- groupers
- hogfish
Fish sampling using conventional fishing gear allows the scientists aboard the Nancy Foster to be productive even in transit between dive sites. Today’s fishing was quite successful bringing in black fin tuna and two barracudas, one exceeding 3 feet in length. Both barracudas will be great contributions to the lab’s ongoing ciguatoxins study.