The thesis undertaken in the following pages originated in the author's participation in a larger study of the Atlantic region of Canada, à region which embraces the four provinces of Newfoundland, Prince Edward Island, Nova Scotia and New Brunswick. This major project is concerned with the construction of input-output tables for each of the four provinces and one for the region as a whole. It is designed to allow study of the interindustry structure of the region and its sectoral demand, first, as a function of the activity levels of the various industries, and, second, as a function of final output. [...]

The Fisheries Research Board of Canada has sponsored several expeditions in Canadian waters since 1947. A large number of specimens of euphausids and pelagic amphipods have been collected from the various expeditions. [...]

[...] Interest in the lake was stimulated by reports of Baffin Island Eskimos fishing 'giant' cod in the lake. Scientific studies were begun in 1951 when the M.V. 'Calanus' of the Fisheries Research Board of Canada was working in the Frobisher Bay area under the leadership of M.J. Dunbar. A one-day survey revealed a unique ecological situation, and subsequent investigations were made during the summer of 1952 when a two man party was landed there from the M.V. 'Calanus' for 36 days, and during the summers of 1957, 1962, and 1965 when more extensive studies were carried out by I.A. McLaren. The material for this thesis was collected during these expeditions. [...]

The mean dynamic topography (MDT) of the ocean is closely related to the mean surface circulation. The objective of this thesis is to produce estimates of the MDT for the North Atlantic using newly available data from ocean and gravity observing systems, to evaluate these new estimates and so improve our understanding of the circulation. Oceanographic estimates of the MDT are based on the mean temperature and salinity (TS) fields of the ocean. These are typically averages from sparse observations collected over many decades. The ocean is a non-stationary system so it is more appropriate to define the mean for shorter, specific periods. Whilst the Argo observing system has increased the frequency and resolution of in situ oceanographic measurements, high frequency (eddy) variability remains. A new technique is described for removing this variability using satellite altimeter measurements of the sea surface height. A new TS mean is produced, relating to the period from 2000 to 2007, and this is used to map a new oceanographic estimate of the MDT using an ocean circulation model. New geodetic estimates of the MDT are produced using geoid models that incorporate gravity measurements from the ongoing GRACE and GOCE satellite missions. These are compared with the new oceanographic estimate and validated against independent observations such as drifter speeds. The geodetic method produces realistic estimates of the mean surface circulation, thereby realizing the long time dream of oceanographers to observe the ocean circulation from space. The new oceanographic estimates are not as accurate, but the new TS mean contributes to improvements in the performance of ocean models, a necessary step in understanding and predicting the oceans. Coastal tide gauges can provide an accurate estimate of the alongshore tilt of the coastal MDT and this has been used to evaluate the above estimates. Temporal variability of the tilt along the coast of the South Atlantic Bight is used, with statistical methods and an ocean circulation model, to identify the processes contributing to the tilt. A new opportunity to use tide gauges as part of an observing system for the ocean circulation is discussed.

Commercial harvest of fish stocks and their appropriate management requires an understanding of their population dynamics and of their ability to sustain exploitation. Here, some ecological and evolutionary consequences of excessive exploitation are examined. In Chapter 2 I evaluate the knowledge base and status of commercially exploited marine populations that undergo formal stock assessment. Despite a bias towards industrialised countries and stocks of commercial importance, I show the pervasiveness of overexploitation and, by using reference points of stock status, identify important regional differences in the effectiveness of fisheries management. In Chapter 3 I develop a data format suitable for ecological analyses to best disseminate the valuable information contained in scientific trawl surveys. This data format is suitable for inclusion into the public Ocean Biogeographic Information System (OBIS) and provides detailed observations that are suitable to the reconstruction of important fisheries-independent stock indices. In Chapter 4 I examine the spatiotemporal dynamics of groundfish populations. A positive abundance-occupancy relationship was estimated for the majority of groundfish populations examined suggesting that this well-described terrestrial pattern is also pervasive in the marine environment. Spatial hysteresis was exhibited by numerous populations, indicating that the spatial distribution of individuals failed to recover despite recoveries in abundance. In Chapter 5 I estimate the demographic consequences of changes in growth and maturation characteristics. The ability of a population to sustain harvest, and its ability to recover from previous depletions can be overestimated because of trends towards earlier maturation and slower growth. In Chapter 6 I conclude the thesis by discussing the implications of my research to fisheries science and management. I argue that trends in the spatial distribution and the overall productivity of populations must be accounted for when determining sustainable fishing levels and when predicting recovery trajectories under various catch abatement scenarios. While successful management measures have been implemented in a number of marine ecosystems, this thesis highlights the importance of improving our capacity to understand the dynamics of exploited populations and to fully use the wealth of available monitoring and assessment data.

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