Day One – Field Work
March 11, 2020 – Owen Nichols, Director, Marine Fisheries Research; Co-Principal Investigator

The Center for Coastal Studies (CCS), accompanied by Wellfleet Shellfish Department staff, conducted a side-scan sonar survey in Wellfleet Harbor on October 30, 2019 and identified the targets of interest, indicated on the chart below by red dots.

In early March, Wellfleet harvester Dave Seitler fabricated a set of grapples specially designed for retrieval of the most likely targets – oyster bags and racks made from steel reinforcing bar (rebar). Dave came up with two designs, a single heavy grapple and a T frame equipped with three smaller grapples (below).

Dave looked at the targets from the October survey and determined that the targets in the inner harbor south of the pier were most likely mooring blocks (below).

Today, I joined Dave and his crewman Keith on board Dave’s fishing vessel (F/V) CCB11 for a day of gear recovery using the specialized grapples.

I used a GPS to record all grappling tracks – grapples were towed in a circular pattern in areas where targets were identified by sonar. Locations of recovered gear were recorded and can now be plotted over the dredge tracks and targets marked during sonar surveys.

The individual grapple rigs were too light to tow without additional weight, so eventually both grapples were attached to the tow line together along with some additional weight (below).

We had the most success along the western side of the navigation channel, offshore of many of the aquaculture grants. Some of the sonar targets at the southern edge of the channel were most likely mooring blocks as well. Remnants of a few cages, a leadline from an old clam net, several oyster bags, and three large rebar racks were recovered, along with some non-fishing/aquaculture-related miscellaneous debris.

Dave and Keith were pleasantly surprised to note that there wasn’t too much lost gear, and almost all of it could be attributed to the damaging effects of heavy sea ice of a previous winter rather than negligence or abandonment. The heavy grapple tended to snag the cage fragments and rebar racks (some with bags still attached; below left), while the smaller grapples caught loose oyster bags (below right).

The team made two trips in to drop recovered gear off (below) at the dumpster provided by the Wellfleet Shellfish Department through the NFWF Fishing for Energy Program. Overall, this was a successful effort that demonstrated the effectiveness of the sonar imagery and Dave’s grapple designs to target aquaculture gear, and the value of collaboration.

There are concerns about a global pandemic arising from COVID-19, and protocol changes may affect recoveries moving forward.

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This project funded in part by the National Fish and Wildlife Foundation’s Fishing for Energy program.

 

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