Here is another blog post we got from John this afternoon...
Well not home actually but to Cape May, New Jersey for a
few hours. We are steaming in, at
just above an idle, from Spencer Canyon where we fished yesterday
afternoon. Chris wants to reach
the Cape May harbor entrance at first light. One engine is running too hot and
we are meeting a mechanic at the dock.
Chris hopes the problem is with an engine fuel injector, a quick fix and
turnaround.
Yesterday afternoon we started sampling our new plan on a
cold spot on the butterfish
habitat model about 13 nautical miles west of the shelf break near the
canyon. The clouds in the
satellite data didn’t give us a lot of pixels to work with, but they did give
us enough. We also have the previous days’ predictions and the 2010 model
hindcast movie. All three show
this area light up, the movie shows the dynamics, and the fishermen confirmed
the pattern before we left the dock.
Our cold spot produced no butterfish. I gave Chris the option of sampling his station before or
after the station in the hot pixels from the model. He decided to go next.
We headed due east about 9 nautical miles toward the
shelf break, but turned to run south along the 50 fathom line. Chris looked back and forth from his
hydroacoustics to the water, which was calm in the light breeze. The water
began to get streaky, the kind of thing you see when you are sitting on the
convergence between two water masses defined by temperature or salt and the
current is flowing in slightly different directions causing the water to
shear. It’s the kind of thing
Josh, as a physical oceanographer, understands much better than I do. I wish he were onboard here too.
Patches of telltale butterfish “dust” began to appear
just above the bottom on the monitor of Chris’s 200 kHz acoustic machine. “I don’t know what this will produce,
but we’ll try here.” It was show
time for him in this smackdown and he looked a little nervous to me. We spun around and set the net. As we towed along the 50 fathom isobath
we talked about his observations of the movements of fish and squid in relation
to the continental shelf break, slope, and canyon walls and the movements of
water masses along them over the course of the winter. Our 20 minutes was up. It was time to
haul back. The bag was so heavy,
Josh Wallace, one of three “supercrew” deckhands on the “Karen Elizabeth‚” had
to wrap the “whip‚” the wire off the center crane, around the net bag before it
reached deck level so it could be lifted aboard. Then Denny Stamand, supercrew
number two, tripped the net into the 8 x 8 x 3 foot deck “box” which filled to
the brim with a very clean catch of butterfish. They shined like silver
dollars‚ 2035 pounds of silver dollars to be exact. As Denny and Josh got the totes and baskets together to
begin to sort the catch from the conveyor belt table, Mike Broniewski,
supercrew three, secured the steel doors that fly like wings underwater and
keep the net spread. “It’s a few,” Chris shrugged and then swung the boat
around toward the south and the start of his next tow that is set by our
sampling protocol to be 90 degrees to the first tow and thus “downslope.”
As we steamed to the site he talked about really big “catastrophic”
tows of butterfish down off Oregon Inlet during the fall - “how the fish settle
down so tight and thick to the bottom in the late afternoon you can’t see them
on the 200 kHz machines.” From his description it sounds exactly like those
shape shifting flocks of tens of thousands of birds that curl like smoke in the
autumn sky until one bird decides to roost and the rest follow all at once. In
10 minutes 20,000 lbs of butterfish can fill the nets so full the fishermen couldn’t
get them on deck even if they wanted too.
It can take well over an hour to dump the nets and recover. That can kill the squid fishing for the
day. Chris’s second haul produced
an equally clean catch that included 2386 pounds of “silver dollars.”
Now it was the model’s turn to define habitat, by using
satellites on land and radars on the shore, bottom depth and a few other
things. We picked a random pixel
in the hotzone 11 nautical miles to south and slightly to the east in 55
fathoms of water. It was close
enough to the shelf break that that our second cross isobaths haul took us down
the bank. Each haul produced 4
lbs. This was pretty embarrassing
and no contest in that “smackdown.”
But should it be embarrassing?
Both Chris’s and the model tows were pretty close together in
space. Our model is pointing us in
the right direction, giving us a broad scale view of the dynamics of the
environment from the fish perspective, given surface ocean features we can
measure using radars on land and satellites in space, and a broad scale
seasonal snapshot of butterfish abundance on the continental shelf measured
from Hatteras to the Gulf of Maine by a single ship. But within these broad scale dynamic features, there are
finer scale dynamic gradients, the fish and fishermen are using as cues that
are too fine for us characterize from space and a single coarse scale
characterization of the continental shelf ecosystem. Habitat is dynamic, defined by suites of particular
environmental features and processes that vary at different scales of space and
time and thus nest in time and space to define ocean habitats.
1 comment:
This is a grreat post
Post a Comment