Constructing a baseline groundfish trawl survey for an offshore windfarm development area

Objective

Large-scale offshore windfarms are proposed along the U.S. Northeast coast; the first is the Vineyard Wind lease area, which is planned for construction in 2023. During the fall of 2018, an experimental bottom trawl survey in the Vineyard Wind lease area and adjacent control area was conducted to collect preliminary estimates of fish assemblage composition, density, and size distribution.

Methods

Initially, a new open cod end design was tested, but poor visibility due to fine substrate rendered the gear inefficient. The survey was completed using the traditional closed-tow method.

Result

The estimates of density and variance enabled a power analysis, which recommended a minimum of 20 tows in the development area and 20 tows in the control area to achieve a 25% chance of detecting a shift in the density of the four most abundant species.

Conclusion

These results led to the development of a seasonal bottom trawl survey beginning in 2019 using protocols that align with other shelfwide bottom trawl surveys.