Thomas A Okey

University of Victoria | UVIC · School of Environmental Studies

There is broad recognition that forage fish—small, short-lived and fast growing mid-trophic level species—are primary energy pathways in many marine food webs, and that they support other valuable fish stocks and many species of marine birds and mammals. Invertebrates such as squids, shrimps, and krill are also recognized as important forage specie...

The marine life of Canada’s Pacific marine ecosystems, adjacent to the province of British Columbia, may be relatively responsive to rapid oceanographic and environmental change associated with global climate change due to uniquely evolved plasticities and resiliencies as well as particular sensitivities and vulnerabilities, given this dynamic and...

Hollowed, A. B., Barange, M., Beamish, R., Brander, K., Cochrane, K., Drinkwater, K., Foreman, M., Hare, J., Holt, J., Ito, S-I., Kim, S., King, J., Loeng, H., MacKenzie, B., Mueter, F., Okey, T., Peck, M. A., Radchenko, V., Rice, J., Schirripa, M., Yatsu, A., and Yamanaka, Y. 2013. Projected impacts of climate change on marine fish and fisheries....

There is great interest and rapid progress around the world in developing sets of indicators of marine ecosystem integrity for assessment and management. However, the complexity of coastal marine ecosystems can challenge such efforts. To address this challenge, an expert-based, hierarchical, and adaptive approach was developed with the objectives o...

Disaster research often focuses on how and why communities are affected by a discrete extreme event. We used the community capitals framework to understand how community characteristics influence their preparedness, response to, and recovery from successive or multiple disasters using the 1964 Good Friday Earthquake and the 1989 Exxon Valdez Oil Sp...

Climate change and ocean acidification are altering marine ecosystems and, from a human perspective, creating both winners and losers. Human responses to these changes are complex, but may result in reduced government investments in regulation, resource management, monitoring and enforcement. Moreover, a lack of peoples' experience of climate chang...

The effects of climate change on marine ecosystems are accelerating. Identifying and protecting areas of the ocean where conditions are most stable may provide another tool for adaptation to climate change. To date, research on potential marine climate refugia has focused on tropical systems, particularly coral reefs. We examined a northeast Pacifi...

It is increasingly recognized that demersal communities are important for the functioning of continental shelf and slope ecosystems around the world, including tropical regions. Demersal communities are most prominent in areas of high detritus production and transport, and they link benthic and pelagic biological communities. To understand the stru...

Canada’s Pacific marine ecosystems, which lie adjacent to the coast of British Columbia, are rich, extraordinarily productive, and highly textured with conditions that vary considerably on different scales of time and space. This marine and coastal environment is unique and of cultural, socio-economic, and ecological significance to the people of B...

The development of approaches to estimate the vulnerability of biological communities and ecosystems to extirpations and reductions of species is a central challenge of conservation biology. One key aim of this challenge is to develop quantitative approaches to estimate and rank interaction strengths and keystoneness of species and functional group...

Ainsworth, C. H., Samhouri, J. F., Busch, D. S., Cheung, W. W. L., Dunne, J., and Okey, T. A. 2011. Potential impacts of climate change on Northeast Pacific marine foodwebs and fisheries. – ICES Journal of Marine Science, 68: 1217–1229. Although there has been considerable research on the impacts of individual changes in water temperature, carbonat...

The latitude of the West Coast of Vancouver Island would generally indicate a low marine biodiversity, relative to that occurring at lower latitudes along coastlines around the world, but the high spatial and temporal heterogeneity of the environment and habitats, its high productivity, and the dynamic range overlap of northern and southern flora a...

A concentration of pelagic sharks was observed in an area of western Queen Charlotte Sound, British Columbia, during systematic shipboard line-transect surveys conducted (2004 to 2006) for marine mammals throughout coastal waters of British Columbia. Surveys allowed only brief observations of sharks at the surface, providing limited opportunity to...

Background/Question/Methods Climate change is creating a warmer and more acidic world ocean. The impacts of changes in these physical variables on individual species are complex, but not completely unknown. Warmer waters will alter species’ bioenergetic rates and biogeographic ranges, while more acidic waters will modify their growth, survival, a...

The vision for the Barkley Sound Knowledge Symposium, “To assemble and share existing knowledge about Barkley Sound ecosystems, human uses, and values in a living and open knowledge-base for the support of sustainability planning initiatives,” expresses the general goal of the Symposium, but there are specific elements within that goal that should...

This document is a brief outline of research approaches and strategies for addressing the ecosystem science components of the marine planning activities of West Coast Aquatic (formerly the West Coast Vancouver Island Aquatic Management Board). It includes a listing and discussion of approaches, tools, and the utility of advisory teams or peer revie...

Indicators are useful for measuring and monitoring status of a complex system because they are easy to measure and they represent the health of the system of interest. Simple measurements of urine or blood, for example, can indicate the overall health of a person without explicitly understanding the complexities of how the individual’s physiology w...

Initiatives are emerging to develop integrated management plans for salmon species in Barkley and Clayoquot Sounds. For example, a background document on what is known about Clayoquot Chinook salmon has been drafted (Okey in prep) as an attempt to begin understanding the causes of the recent declines of Clayoquot Chinook in spite of the relatively...

Climate change is altering the rate and distribution of primary production in the world's oceans. Primary production is critical to maintaining biodiversity and supporting fishery catches, but predicting the response of populations to primary production change is complicated by predation and competition interactions. We simulated the effects of cha...

Illegal foreign fishing for sharks in Northern Australia has increased substantially over the last two decades. This has likely resulted in declines of shark species abundance, with potentially far-reaching impacts on the ecosystem. This, in turn, could also have indirectly affected the legal prawn, shark, and other fisheries in the region through...

At least two different approaches have been used to quantitatively assess the importance of species in communities. One approach is to derive relatively simple, structural importance indices from network analysis. This assumes that well-connected species are more important. Another approach is to derive functional importance indices using dynamical...

This chapter describes ecology of the Galapagos rocky reef system and the important role of biogeographic position on biodiversity, the El Niño cycle, and the history of resource extraction on the current state of the ecosystem. The chapter presents a model of the energetic pathways in the ecosystem and its predictions for fisheries yields and the...

When the biomass and area occupied by a stock decline together, catch rates can remain high (hyperstability) and management with effort controls may be ineffectual. Banana prawn (Penaeus merguiensis) catches declined from 2000 until 2005 in the Albatross Bay area in the Gulf of Carpentaria (GOC), Australia. Data from commercial logbooks were used t...

There is a growing interest in approaches that can be used to rank the relative ecological importance of species such as those that quantify dimensions of functional importance (e.g., interaction strength and ‘keystoneness’) and structural importance (e.g., weighted topological importance). It is rarely feasible to employ direct empirical studies (...

As professionals who have devoted our careers to understanding the interdependent nature of oceanic ecosystems, as well as man’s participation in those ecosystems, we believe that we are in a unique position to evaluate and describe the effects that the Exxon Valdez Oil Spill (“EVOS”) has had on the North Alaskan ecosystem surrounding Prince Willia...

A variety of changes are occurring in the ecosystems of the North Pacific Ocean and Bering Sea, but information about the mechanisms of change has been relatively limited, due in part to the region's remoteness and subarctic conditions. Any number of ecosystem components or indicators could be used to exemplify this dilemma, but here we point to th...

Commercial fishing activities, primarily bottom trawling, have severely damaged vulnerable sea-floor communities such as undersea coral gardens and the summits of seamounts. Recreational fishing can also affect ecosystems adversely. The United States Ocean Commission (2004) recommended that fisheries be managed to protect marine ecosystems and thei...

Australia's marine life is highly diverse and endemic. Here we describe projections of climate change in Australian waters and examine from the literature likely impacts of these changes on Australian marine biodiversity. For the Australian region, climate model simulations project oceanic warming, an increase in ocean stratification and decrease i...

This project set out with two main purposes: firstly, to develop, built and apply a model that allows us to estimate the direct effects of trawling on benthic biota under various scenarios of prawn fisheries management, and secondly to examine how to extend such model to include the follow-on effects of trawling on the wider ecosystem. To meet the...

No Yes

Trade-offs between the benefits and the costs of marine resource extraction become increasingly conspicuous as ecological limits are approached. Unfortunately, the historical lack of trade-off accounting has led to unexpectedly adverse effects. An integrative policy-search procedure in the modeling software Ecopath with Ecosim was used to shape fis...

Some of the adverse effects of the Exxon Valdez oil spill have persisted for 15 years in Prince William Sound (PWS), Alaska. The main challenge in detecting these effects is distinguishing lasting population impacts from background environmental fluctuations and ecological transients. Nevertheless, the consistent assumption is that the overall biol...

Keystone species play a central role in shaping at least some marine communities in the sense that system-wide phase shifts can be mediated by the presence, absence, or the relative abundance of these key interactors. Identifying keystones is considered crucial for understanding the resilience of ecosystems to exogenous forces because non-linear, o...

A balanced trophic model of a Galápagos rocky reef system was constructed using Ecopath and Ecosim. The Ecopath approach allowed characterization of food web structure through integration of disparate ecosystem information derived from many years of study of Galápagos shallow-water rocky reefs. Ecosim and Ecospace routines enabled us to explore var...

A balanced trophic model of a Galápagos rocky reef system was constructed using Ecopath and Ecosim. The Ecopath approach allowed characterization of food web structure through integration of disparate ecosystem information derived from many years of study of Galápagos shallow-water rocky reefs. Ecosim and Ecospace routines enabled us to explore var...

Phytoplankton blooms are increasingly conspicuous along the world's coastlines, and the toxic effects of these blooms have become a major concern. Nutrient enrichment often causes phytoplankton blooms, which decrease water transparency, but little is known about the effects of such light regime changes on whole communities of the continental shelf....

Accumulations of sunken drift macrophytes are known to stimulate high secondary production in submarine canyon heads, but the details of macroinvertebrate colonization of these subsidies are poorly known. I conducted a series of algal and macrofanual sampling programs and manipulative algal-placement experiments in different Monterey Canyon head su...

The failure of modern fisheries management is blamed on myriad socio-economic and technical problems, but the most fundamental reason for failure might be the overwhelming dominance of extractive interests in participatory decision-making venues. In the United States, commercial fishing interests made up 49% of appointed voting members of the eight...

A better understanding of the whole Prince William Sound (PWS) food web and its dynamics was achieved by constructing a balanced trophic model using the Ecopath approach. The PWS model was a cohesive synthesis of the overall biotic community with a focus on energy flow structure, and response to perturbations, both natural and anthropogenic. Forty-...

Detailed knowledge of the status and productivity of stocks has been the primary focus of fisheries management in order to maximize resource extraction. Ironically, maximum extraction is usually constrained only by the most optimistic stock scenarios from detailed single species models. This has led to degradation of marine ecosystems because natur...

Just as real-world food webs contain complex interactions among species, so too must scientists and others interact to describe food webs in realis- tic ways. The most useful ecosystem models are constructed through collaboration among a wide range of experts. Collaboration among Prince William Sound (PWS), Alaska, researchers resulted in a mass-ba...

A large area of axis sediment (>500 m2) may be annually removed from the head of Monterey Submarine Canyon with the first onshore storm of the fall/winter storm season. In this scenario, flushing events are followed by accumulation of sediment and organic debris—especially macro-algae—in the shallow axis. Net accumulation of this fill material incr...

Seasonal sediment flushing, earthquakes, and sunken drift algae influence the abundance and distribution of benthic macrofauna in Monterey Canyon's head. Each contributes to the canyon's overall disturbance regime. Large scale (> 100 m2) sediment flushing may occur in the axis with the first fall storm. A year of monthly sampling revealed fluctuati...

Thesis (Ph.D.)--University of British Columbia, 2004. Includes bibliographical references.