Research Document 2017/077

Coast of Bays seawater vertical and horizontal structure (2009-13): Hydrographic structure, spatial variability and seasonality based on the Program for Aquaculture Regulatory Research (PARR) 2009-13 oceanographic surveys

By Donnet, S., Cross, S., Goulet, P., and Ratsimandresy, A.W.

Abstract

Upon a recent rapid increase of the finfish aquaculture industry in the Coast of Bays, an area of the South Coast of Newfoundland (9 fold production growth from 2003 to 2013), Fisheries and Oceans Canada (DFO) carried out a research project to better understand the physical oceanography of the area. This report is the second of a series aiming to provide an oceanographic knowledge baseline of the Coast of Bays (i.e., data and analyses) to help manage and ensure the sustainable growth of the aquaculture industry. This report presents the analysis of 790 water profiles of temperature, salinity and dissolved oxygen concentration sampled at 276 stations over the course of a 5-year oceanographic program (2009-13). The profiles were analyzed using along-channel vertical sections plots (i.e., transects), surface property maps and water masses statistics.

The results of this study highlight the hydrographic structure of three distinct geographical regions: a very stratified fjord subject to large freshwater runoff (Bay d’Espoir), a large stratified bay subject to important freshwater runoff (Belle Bay) and a peninsula producing limited amount of freshwater discharge and consisting of two open bays and one narrow inlet (Connaigre Peninsula). As a result of the geographical variation of freshwater inputs, the surface layer characteristics (temperature, salinity, dissolved oxygen and pycnocline depth) vary significantly among the bays studied. Bellow the seasonal surface layer, two main water masses were identified and are unevenly distributed across the area; due mainly to topographic features which impede or limit water exchanges (i.e., sills). Short-term (i.e., order of hours to days), seasonal and inter-annual variations are also discussed but their assessment, and understanding, is limited by the spatial and temporal resolution. Similarly, the physical processes responsible for those variations are poorly understood. Further research would be needed to address those important knowledge gaps.

Based on these geographical differences across regions and within each of the bay studied, hydrographic zones are defined and may be used, in conjunction with other relevant factors, for aquaculture management purposes.

Data used and presented in this report will be available at the Government of Canada’s Open Data website.

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