Correlations between annual catch of coastal commercial species of fish and the environmental factors of sea temperatures and St. Lawrence River discharge have led to an investigation of the relationship between the latter. Examining year-to-year variability of monthly means, effects of the St. Lawrence River discharge can be traced by correlation analysis with sea temperatures to propagate from the Gulf of St. Lawrence onto the Scotian Shelf and through the Gulf of Maine at known coastal current drift speeds. Seasonal salinity and transport data support such a flow at least to a section off Halifax on the Scotian Shelf. Within the Gulf of Maine seasonal salinities do not support continuity of flow; however, possible reasons and mechanisms for this are discussed. Other factors such as local river runoff in the Gulf of Maine, Labrador Current, and large-scale weather systems are briefly considered and discussed. It is proposed that the Gulf of St. Lawrence to the Gulf of Maine inclusive be considered as an oceanographic system and events occurring in the southern part on time scales of a month or more are not independent of more northerly events. It is not interpreted that the river discharge is the driving force of such an oceanographic system but rather influences the water properties within the source region of the flow, i.e. the Gulf of St. Lawrence. Some biological implications of the Gulf of St. Lawrence to Gulf of Maine pathway are pointed out.

Sea surface temperature (SST) variability in the shelf-slope region of the northwest Atlantic is described and then explained in terms of latent and sensible heat exchange with the atmosphere. The basic data are primarily engine-intake temperature measurements made by merchant ships over the period

Fish abundance, based upon commercial fish catches and numbers offish-feeding birds, is shown to increase southward along the Labrador Shelf from Hudson Strait. Also, yearly abundance of Labrador Atlantic cod (Gadus morhua) using virtual population analysis is shown to be closely correlated with salinity changes at Station 27 off St. John's, Newfoundland. We suggest these observations are related to physical oceanographic events originating within Hudson Strait. Analysis of available data indicates nutrient enrichment of the surface waters through physical mixing in Hudson Strait. These waters are carried by the residual circulation onto the northern Labrador Shelf. Our interpretation of the southward increase in fish abundance is that fish production develops downstream of the area of nutrient injection due to the southward flow of the Labrador Current coupled with the time required for food chain development. The yearly variation of cod is interpreted as arising from the variation of the nutrient supply, which is itself correlated with salinity. The fresh water discharge into Hudson Bay which eventually flows out through Hudson Strait and onto the Labrador Shelf appears to suppress mixing and hence years of higher discharge would tend to decrease the nutrient supply.

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