Depth Selection and In Situ Validation for Offshore Mussel Aquaculture in Northeast United States Federal Waters

Darien Danielle Mizuta,Gary H Wikfors

doi:10.3390/jmse7090293

Abstract

As mariculture progresses offshore in the US Exclusive Economic Zone, technical and ecological challenges need to be overcome, such as the choice of suitable sites that favor the production of target species. The offshore culture of blue mussels, Mytilus edulis, is performed with submerged longlines and mussels need to withstand more motion than on coastal sites. Temperature affects the ability of the byssus to adhere to farming rope, while chlorophyll concentration provides an estimation of food availability. Together, these are important factors in predicting the suitability of offshore mussel farms. To identify suitable depth of submersion for mussel ropes in New England federal waters, historical oceanographic data of temperature and chlorophyll a from 2005 to 2012 were used. The results suggest that mussel ropes were submerged during summer to a minimum depth of 15 m in northern and a 20-m depth in southern areas of New England where temperature is at a species-optimum and phytoplankton biomass is abundant. For the site offshore Massachusetts, in situ biodeposition measurements validated predicted depth, confirming satisfactory mussel performance. Promising local areas have shallow thermoclines, such as offshore Long Island, Cape Ann and New Hampshire. Recommended depths can be adjusted to future temperature increases associated with climate change.

Highlights

The United States has recently become the largest national importer of seafood in the world, overtaking Japan, because of the nation’s limited domestic production [1]
In the frequency distribution histogram, most of the blue mussel spawnings fell between 8 ◦C and 16 ◦C, with fewer events happening at temperature extremes
As our assumption was that spawning in warmer months should be avoided, the grow-out should be performed in colder waters; extreme temperatures limiting physiological activity, as aforementioned, should be avoided

Summary

Introduction

The United States has recently become the largest national importer of seafood in the world, overtaking Japan, because of the nation’s limited domestic production [1]. Offshore aquaculture in the US is generally defined as occurring in federally managed waters of the Exclusive Economic Zone (EEZ), extending between 3 to 200 nautical miles from the shore [2,3] and is recognized to provide a way to derive added value from US EEZ in the Northeast US Shelf [4]. It enables the optimization of marine space, as in increased sustainable use and minimization of coastal conflicts of use, while contributing to national food security and relieving pressure on wild fish stocks [5,6].

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