Symposium theme: Ecosystem-sensitive approaches to fishing – mitigating
the negative impacts of fishing
Sea Scallop Harvest Using Flow Control
Participants:
- Clifford Goudey, CFER, MIT Sea Grant College Program
- Michael Pol, Massachusetts Division of Marine Fisheries
- Olivia Free. Massachusetts Fishermen's Partnership
- Paul Tasha, Commercial Diver
- Captain Louis Williams, F/V Pretty Girl
Conventional dredges used for the harvest of the Atlantic sea scallop (Placopecten
magellanicus) have remained essentially unchanged for decades in spite of
calls for reducing their impact on the seabed. In addition, their principles
of operation result in low efficiency and frequent physical damage to the
catch.
An alternative approach to scallop harvest has been tested that relies on
the exploitation of hydrodynamic flow to elevate the target shellfish and
reduce the need for intimate contact between the gear and the seabed. The
concept was devised based on in-situ observations and ideas of the
participating commercial diver.
Experiments were conducted in the MIT ocean engineering tow tank to
evaluate the effectiveness of various low-aspect-ratio lifting surfaces at
lifting scallop models off the bottom in order to make them vulnerable to an
off-bottom capture means. Flat, cambered and cupped shapes, singly and in
combination, were included in the tests. The effect of various
angles-of-attack, spacing, and height off bottom were observed and recorded
on video for analysis. The utility of certain low-aspect-ratio shapes at
producing large-scale vorticity was demonstrated.
The most promising arrangement was then incorporated into a small wheeled
prototype dredge for preliminary sea trials aboard a commercial fishing
vessel where video was used to observe the response of scallops and other
benthic organisms to the passage. The results of these trials will be
reported in addition to progress to date on incorporating the approach into
the design of offshore scalloping gear.
The Northeast Consortium provided funding for this pilot project. Industry
collaborators include the Massachusetts Fishermen's Partnership, diver Paul
Tasha, and Captain Louis Williams.
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