The Seascapes

The Seascapes

Monday, December 12, 2011

Butterfish Smackdown: Stray dogs

Here is a blog post that John sent us from the ship this afternoon.

Chris moved from the wheel to the winch controls that face aft toward the net reel to set up the first tow at the last station we will sample to the north side of the Hudson Shelf Valley till we return from the south. As he crossed the wheelhouse he glanced at the fishery hydroacoustic screens and the arcs of green, yellow and red light against the black backround on his 38 khz machine. 'Looks like a pack of stray dogs', he said. Sure enough we hauled up a thousand pounds of spiny dogfish less than a foot long after only a 20 minute tow.

All day Sunday I tried to pull Chris back from the offshore edge of the footprint of our model. All day long he kept pushing harder to get us over the edge of the shelf and onto the dropoff. This was a real problem because we made our butterfish model using the best available data. This included not just the satellite and HF radar information but also the NOAA fisheries survey data. And the fisherman we talked too told us that the movie made of the model we built with their help looked pretty accurate.

The NOAA survey is remarkable. It has been performed twice a year since 1963 and covers the continental shelf from from Hattaras to Canada. But doesn't cover areas in the nearshore including estuaries, or habitats off the edge of the continental shelf. So our butterfish habitat model is really aimed at habitat conditions on continental shelf, not off the edge. I wrote a note to Laura, Josh and Matt apologizing for pushing the outer boundary so hard and promised to pull us back to do some midshelf stations. To truly evaluate this model we need to stay on the shelf.

But wait, what if Chris was telling me something about butterfish and their habitats I didn't know? What if really prime butterfish habitat during this time of year isn't on the shelf at all but just off the shelf break. Since this is a habitat modeling study we really need to understand the full range of environmental conditions where the animals live. And we already have the NOAA survey performed this fall to evaluate our model for the area of the shelf area. Why not change up our research plan and adapt quickly to what we have learned over the first 36 hours of this cruise. Like 'stray dogs' lets systematically spend a little time off the reservation and evaluate our model footprint too.

So here's the new plan. We are still going to sample areas where our model predicts there is potentially good and poor butterfish during the day and the night off the Chesapeake and Delaware estuaries. But in each of these survey areas we will give Chris a station during both times of day to use his practical ecological knowledge of butterfish to show us what we don't yet know.

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