A Climatology of Black Bay

Abstract

<p>Black Bay is a major hatchery for lake herring (Coregonus artedii, Leseur) on the North shore of Lake Superior. Selgeby (1978) observed and documented the rapid spring dispersal of herring larvae. This preliminary study has been directed towards the identification of some of the mechanisms of this dispersal. It is based on data obtained from two specifically set current meter stations and a bathythermograph survey conducted in the spring of 1978, as well as data from existing meteorologic and stream flow records. A spectral analysis of the current meter record was done to determine the main energy components of the flow. Evidence indicates that transports in the Bay are driven by several mechanisms which are common to coastal estuaries, including a psuedo-tide, river inflow, and circulation due to longitudinal density (thermal) gradients, as well as surface winds. It is proposed that the passage of the thermal bar through the Bay may also be a significant influence on the dispersal of the herring larvae. The distinct seasonal character of the climatology is evident, though more data is needed to properly document it. Reasons for the attractiveness of the Bay to the herring as a hatchery are suggested, as is one vulnerability of the system to contamination by surface run-off.</p>