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DISPATCH 7: "A Theory Explored" - 6.06.2006 | Mark Schrope
One key step in understanding the ecology and diversity of the reefs will be to survey the
fish-what species are found here, in what abundance, and what type of habitat they are most
often associated with. Tracey Sutton, a Harbor Branch
fish expert and co-chief scientist for
the cruise, has the job of overseeing this work. His efforts have included close scrutiny of
all video shot from the submersible to identify every species of fish seen-more than 20 all
told so far. At certain times, the team is running straight-line transects of specific sections
of the reef and in these cases Sutton is also counting the fish present. Using an abundance
of information from transect video, which covers a known distance and area, he is able to
calculate out an estimate of the total number of a given species found on a reef. The video
analysis is also giving him the chance to identify the types of habitat where particular species
tend to spend their time, which has led to some interesting and surprising discoveries.
Besides analyzing sub video, Sutton has also had the chance to do two dives himself, an
opportunity he says is vital to gaining anything close to a real understanding of the fish
community. "You can look at video, which is fascinating, but it's not real yet, it's still
an abstract concept," he says. "But to go down and see the fish, to be so close to them and
see their little behaviors, it's like you're not just guessing anymore. You start to see
things the way they really are."
Some definite patterns are emerging regarding where certain species are found, indicating
that they are not uniformly spread throughout the reefs. One of the most abundant fishes on
the reefs is the codling, a relative of the cod as you may have guessed. The larger codlings
are almost always seen hiding in the reef structure itself, but, surprisingly, the smaller
codlings seem to live almost exclusively out in the open over flatter rocky areas. Sutton
thinks this habit may be an unusual protective adaptation. When the codlings swim, they stay
fairly straight and just flutter the back portion of their body, something like a flag flapping
in the breeze. Swimming like this over the rock may make them look like other growths on the
rocks. As it happens, another fish common on the reefs is the scorpionfish, a fish that favors
hiding in reef holes and that very likely preys on the young codlings. Hiding in the reef, as
so many fish do, might therefore not be the best plan for the codlings. Sutton calls this all
a "crazy theory" at this point, but one worth exploring.
The most abundant large fish on the reefs are the wreckfishes, relatives of seabass and
grouper, which grow over three feet long and probably weigh on average about 60 pounds.
These fish too seem to concentrate in very specific areas, in this case at the vertical
ledges, though why is not yet clear. Previously, wreckfishes were only known around the
Azores and off North Carolina. "The presence of wreckfish here shows that there's something
different about this place," says Sutton. The team is not certain whether the fish are here
for spawning or here year round, but the answer is likely the latter as Harbor Branch
researchers have seen them on the reefs at multiple times of year. It's also almost certain
that wreckfishes play a key role in maintaining the health of the reef systems. Top predators
like the wreckfishes are known as keystone species and they tend to keep populations of other
species lower on the food web in proper check and also healthier, by preying on the weak and
sick. Hence, removing such keystone species, by fishing or some other means, can have serious
harmful impacts on an ecosystem.
Wreckfish are commercially exploited in other regions, though not yet to a significant degree
in Florida. This is a good thing. Like most living things, fish don't receive much attention until
they are already endangered, and in some cases beyond saving. "Here's a chance to get baseline data
about something we can actively protect," says Sutton.
Other interesting fish finds have been the occasional shark, including a 10-foot sand tiger shark
that rammed the sub, and endangered snowy grouper, for which the reefs likely provide essential habitat.
Perhaps Sutton's most impressive sighting though, wasn't even of fish. Monday night, as he and
pilot Don Liberatore were coming over a ridge in a very strong current, they began to see a couple
of squid coming their way. As they crossed over the ridge, they became engulfed in an absolutely
massive school of squid moving together in a tight, round ball two to three times the size of the
23-foot long
Johnson-Sea-Link.
It's impossible to say how many there were, but judging from the video its safe
to say the number had to be in the tens of thousands at least. A truly astonishing sight, and one
the likes of which even Liberatore had never seen in his decades of piloting.
So, this relatively short cruise is producing a number of answers to questions about who is here
and why, but much will have to remain unknown for now. It's a start though, and with the baseline
information gathered now the scientists will be able to monitor the reefs in coming years to allow
them to make critical recommendations to managers about how best to protect the resources here.
Based in large part on preliminary research on the reefs by Harbor Branch over the past couple of
years, these and other deepwater reefs are already under review for federal protection. In fact,
the other chief scientist, John Reed, is leaving the ship Wednesday to present the latest data on
the reefs to the South Atlantic Fisheries Management Council to aid them in their decisions about
protecting the reefs.
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