Reef and Fishery Assessment of Navassa Island National Wildlife Refuge
On April 23, 2009 scientists from the NOAA's Southeast Fisheries Science
This work is funded by the NOAA Coral Reef Conservation Program.
Wednesday, May 6, 2009
red-footed booby - 285 (a.m. count)
brown booby – 45
white-tailed tropicbird - 8
magnificent frigatebird - 12
cave swallow - 6
snowy egret - 2
peregrine falcon - 3
gray kingbird - 1
great blue heron - 1
cattle egret - 1
broad-winged hawk - 3
The booby species partition habitat. The red-footed boobies nest and roost in the shrubby trees along the slope and top of the island, while the brown boobies roost along the craggy rock face and cliffs at the lower edge of the island. The red-footed boobies appear to be more numerous, at least in April. And they have many color morphs, from mostly white with black wings to overall brown. They leave the island just after sunrise in search of food offshore, and they return just before dusk. They have to run the gauntlet to get back to roost, as the frigatebirds circle and hover, ready to poach a meal from the returning boobies. The brown boobies fly under the radar, so to speak, low to the water which makes it more challenging for the frigatebirds. The red-footed boobies fly high and have frequent in-flight acrobatic tussles with frigatebirds.
The falcons flew over the ship Friday afternoon and circled overhead for hours. We never did see them return to land. A lone gray kingbird landed on the ship and the CO took some nice close up photos. The cattle egret landed on the crane boom, and the CO photographed him too. The two snowy egrets flew past together, winging along the island shoreline but not landing.
There were no birds along the north side of the island when we pulled anchor Monday evening at 6:00 pm, very severe landscape with few live shrubs. We did see 3 goats, though, along the top of the steep slope on the north side.
Tuesday, May 5, 2009
However, I was able to cover nearly 2 miles of coastline and count approximately 1000 colonies of Elkhorn coral! Each yellow dot on the map is a waypoint marking the location of a single colony. They appeared to be healthy and thriving as I remembered from our last visit 2 1/2 years ago when I counted approximately 900 colonies in this same stretch of coastline. It is very difficult to count colonies so finding 100 more on this visit does not necessarily mean there is more coral. Elkhorn coral colonies can split into smaller sections as it dies back so that one large colony may appear to be 2 or 3 smaller colonies on a subsequent survey which can really confuse things for us coral counting types! Regardless, this survey shows that there has not been a major loss in elkhorn coral aalong the west side of Navassa in the past 2 1/2 years.
Monday, May 4, 2009
Yesterday, on our last afternoon at Navassa, I spent one dive revisiting a site along the west wall base where we marked permanent 1m2 plots in 2002. I knew that there had been a lot of change in this reef from hurricanes and coral disease in 2004 and probably from coral bleaching in 2006. I was somewhat shocked when I actually got the pictures back last night and compared them with the earlier versions of themselves. I am showing just one example here to give you the idea. This 1m2 area of reef had been home to a decent sprig of staghorn coral, as well as nine juvenile coral colonies of various species in November 2002 (left image). Today, (right image) a single live coral colony is visible in the quadrat (though it appears to have grown a bit). This colony is outlined in both photos to help convince you that it is the same area. Otherwise, it is pretty unrecognizable, with a brown leafy-looking seaweed covering most of the area. This alga, Lobophora variegata, may be somewhat seasonal, but it covers the majority of Navassa reef surfaces at the moment. It will take some time to analyze all the benthic cover data from the transects and photo-quadrats we took at the sites of the fish surveys, but my impression is that more live coral cover remains on the deep patch reefs along the shelf, than in the nearshore habitats around the wall base where these permanent quadrats are located.
Sunday, May 3, 2009
Saturday, May 2, 2009
Since we needed counts on the north side, we decided to send 3 small boats with fish counters. After launching at 0800, the Foster pulled anchor and rounded the point so we could be in radio contact. As loose items began hitting the floor, I looked out the window and saw waves breaking, realizing that conditions were marginal. The ship began pitching and rolling, queasiness set in, and afternoon plans changed immediately. Back to the west side for sure! Watching the small boats bounce around and NF5 asking for an alternate site away from the shore, made me realize my name would be a cussword for awhile. Maybe locking the door to my cabin would be appropriate!
Friday, May 1, 2009
Interestingly, a few of the lionfish's cousins are native and commonly found on the coral reefs of the Caribbean, Florida, Bahamas and Bermudas such as the spotted scorpion fish (Scorpaena plumieri). While scorpion fish are native of the region, the red lionfish was introduced to Florida in the early 1990s. During the last ten years the species has expanded slowly south across the region. Sightings have been documented from Bermuda, North Carolina, west coast of Florida, Bahamas, Puerto Rico and Labadee in the north coast of Haiti. Two days ago we documented the first three individuals in Navassa Island.
The red lionfish is not a native species of the West Indies region and the ecological and economical implications of its introduction are still unclear. The species is a top voracious predator, ambushing and sucking their prey like groupers and toadfish do. With very few natural predators, their diet consists of crustaceans, small fish, and even juveniles of their own species. The long pectoral fins and the striped colorations create a disruptive coloration that with their sneaky behavior is a fatal combination for their prey.
This invasive species evolved in a different natural environment and the consequences of their predatory behavior might be detrimental for the native species of the region. Limiting the spread of the red lion fish in the region is being attempted in most regions to avoid potential ecological shifts in the natural ecosystem. Yesterday, Mandy and I when for a lionfish hunt session in the afternoon, put our red protective equipment on, dove down 90 feet, found this misplaced creature underneath a fish trap, took a net, got the lionfish in the net, closed the net, snapped some shots and went up. Unfortunately, that was the end of this lionfish's life.
The hunt for the lionfish is now on. By the way, if stung by a lionfish, a common treatment is to soak the affected area in hot water. Although they spines are not deadly they might be very painful and could cause anaphylaxis reactions in susceptible individuals.
2nd photo by Abel Valdivia
Yesterday I started our Elkhorn snorkel mapping and happened on ALOT of healthy Elkhorn Coral! I will blog about that more later, but the more exciting thing is that I saw the first turtle that has been seen on this trip. It was a small Hawksbill turtle swimming along the wall. He was rather startled and I was caught off guard since I was in Elkhorn search mode, but I was able to snap a quick picture of him (Click to see it better). We should have seen more by now so hopefully this is only the first of many turtle observations. I see them pretty frequently in Florida, but no matter how often I see them I get excited! Dana
Thursday, April 30, 2009
While I was trying to get inspired to write my first Navassa blog, Dave Mac called me to go on my second trip out, which usually happens later in the day but today there was one boat that came in earlier. We got ready pretty fast and by 1250 Jack, Steve and myself together with our coxswain Trey were on our way to the dive site. We went in the water at 1307 and dove down to about 94ft to patchy hard bottom in sand habitat. Jack tied the reel and I positioned myself to start my RVC count. A few minutes into my count, while rotating and recording all species of fish observed I looked down, and to my surprise inside of a barrel sponge I saw two lionfish! Lionfish are invasive and spreading rapidly throughout the Caribbean. Both fish were predominantly black and white, characteristic of the “black” lionfish. The largest individual was 25cm (both photos) and the smallest 18cm long (fork length). When I approach them the larger fish came out displaying its beautiful patterns and ornate fins, but after a minute or so it went back into the sponge. The smaller fish stayed in the sponge the entire time. I took photos and video of both fish. Upon arrival to the ship, we found out that about 20 minutes before my observation, Margaret had also seen one smaller lionfish while diving one of the fish traps. So, today is not only hump day for our expedition, but is a historic day. Today officially marks the first time a lionfish has been observed and recorded in the RVC database, and also around Navassa Island!
Wednesday, April 29, 2009
Mike - photo wikipedia
Tomorrow we will continue with the CPUE data collection for the other four traps that have been observed around the island. And of course, we are eagerly awaiting the arrival of Haitian fishermen!
Tuesday, April 28, 2009
When I first visited Navassa in 2002, we encountered a few very small thickets of staghorn coral and scattered colonies on several of our dives to the deeper patch reefs. When we returned in 2004 we found coral disease actively spreading around the reefs of Navassa and only saw 1 colony in our many dives. In 2006 we found substantial coral bleaching and only found 2 small sprigs of this coral, one of which was diseased and dying! So this year we have once again issued an ALL POINTS BULLETIN for staghon coral sightings amongst the 12 divers in our group! So far one small colony has been seen by Jack Javech of the fish counting team. If the weather continues to be too rough to survey elkhorn coral along the wall I will join the hunt for this now rare and emperiled coral. Although it appeared to be doomed on our last visit, this is a relatively fast growing coral and I am hoping that we will find small colonies that have persisted through these tough times! --Dana
Dave Mc, Jack, Natalia (photo), Joe, Mike and Dave G.
Monday, April 27, 2009
Sunday, April 26, 2009
Before we arrive at Navassa, I need to finish rewriting my qualifying exams! I have attached the photo here so that my advisor can see how hard I am working.
Since most of the shallow area is wall, all of the corals that usually live on the shallow part of a typical reef have to find a way to live and grow sideways! In past years we have found Elkhorn coral growing and thriving in this environment. However, rather than growing up like a tree as it usually does, it encrusts the walls of Navassa forming a carpet of Elkhorn with stubby branches!
This year we hope to repeat this survey but it will depend on the weather conditions while we are there. To do this survey I have to swim very close to the rocks and big waves can make it a little dicey to say the least! --Dana
Saturday, April 25, 2009