Project 1.2.1.D

Do Atlantic Salmon Close Their Life Cycle in the Bras d’Or Ecosystem of Cape Breton?

Bruce G. Hatcher

Background

The Bras d’Or estuary and its associated watershed is one of those Atlantic salmon refuges where significant runs sustain food and recreational fisheries in four river systems of the 2,400km² watershed. The 1200km² estuary comprises two large basins to 280m depth, connected by a single channel, and several smaller basins and channels, into which flow four significant salmon rivers and several salmon streams. The virtually landlocked system is linked to the Atlantic Arena through one major channel and two insignificant passages. The hypothesis that salmon close their life cycle within the Bras d’Or ecosystem has not been rejected and, if supported, will lead to substantial opportunities for research, stock enhancement, and ecosystem-based management.

Figure 1. Bras d’Or Array phase I sites.
project 1.2.D

Our approach to testing derivative hypotheses is multidisciplinary and inclusive of extensive expertise available in the region. Observations and numerical modelling of the Bras d’Or estuary reveal that these several geomorphologic restrictions result in extreme variations in hydrology and hydrodynamics, creating fine scale mosaics of salmon habitat. Ecological connectivity models provide a predictive framework on which to overlay tracks of salmon movements. This eco-contextual work, plus the manageable scales and geographically controlled transit points, make the Bras d’Or a logistically feasible and highly affordable array for optimizing receiver reliability and coupling bioambits to oceanographics.The Bras d’Or Lakes Array extends throughout the Bras d’Or estuary, including all channels connecting the estuarine waters to those of the surrounding ocean, the channels connecting the major basins of the estuary, and the mouths of the main rivers flowing into the estuary. The initial array is composed of 15 stations (Fig. 1) placed in depths of 3 to 40m. Details of the deployment geometry (spacing between receiver stations and depth of receivers) are for illustrative purpose, as changes may be required upon analysis of the range test data.

An additional 11 sites are proposed for subsequent years, depending on the results obtained during the first tagging experiments.

Figure 2. Robin Stuart (red) and Bruce Hatcher (blue) deploy current meters in Cape Breton’s deep marine channels (photo courtesy of Mark Tekamp).

project 1.2.D (2)

Modest funding is available for support of undergraduate student research in the Bras d’Or Array. Please Contact bruce_hatcher@cbu.ca for further details.

The Bras d’Or Array seeks funding partners in the academic, government, and private sectors who share an interest in expanding or commercializing research products from the array. The impending declaration of the Bras d’Or ecosystem as a UNESCO Man and the Biosphere Reserve offers timely opportunities for effective leveraging of funds.