4 results
2 - The oxygen constraint
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- By Andrew Bakun, University of Miami, USA
- Edited by Villy Christensen, University of British Columbia, Vancouver, Jay Maclean
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- Book:
- Ecosystem Approaches to Fisheries
- Published online:
- 05 June 2012
- Print publication:
- 03 March 2011, pp 11-23
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Summary
In trying to understand processes and mechanisms regulating ocean ecosystems, we humans, being terrestrial mammals, naturally rely on intuitions and common sense notions formed by our terrestrial experiences as well as on our inherent terrestrial-mammalian evolved capacities and inclinations. As a result, many aspects of life that may be unique to organisms evolved and operating within marine situations may tend to elude our intellectual grasp and even our notice.
In the early 1980s, I worked with Daniel Pauly and other colleagues on developing an international collaborative “Ocean Science and Living Resources” (OSLR) program (Bakun et al., 1982). This experience presented me with, among other things, an exposure to Pauly's developing theory on the special role of oxygen in the marine situation (Pauly, 1979, 1981, 1984, 2010). The interest was on individual-organism-scale biological issues, such as growth rate and maturation timing. Not being a biologist, but rather an oceanographer habitually focused on regional population-scale issues, I found the notions intriguing while not yet beginning to apprehend their significance to the particular questions that were consuming my own attention.
But, the “seeds” were planted in my mind. Daniel's early insights on the size-related oxygen issues faced by fishes in the ocean led me over the years to the notions outlined here, and are an example of how my own joy in the “ocean quest” has been enriched by his influence.
15 - Synthesis and perspective
- Edited by Dave Checkley, Scripps Institution of Oceanography, University of California, San Diego, Jürgen Alheit, Yoshioki Oozeki, Claude Roy
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- Book:
- Climate Change and Small Pelagic Fish
- Published online:
- 08 January 2010
- Print publication:
- 20 August 2009, pp 344-351
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Summary
Summary
The Small Pelagic Fish and Climate Change (SPACC) program was created to facilitate research on the dynamics of populations of small pelagic fish, including anchovy and sardine. These populations exhibit large variations in size, extent, and production on the scale of decades. At times, anchovy and sardine alternate in abundance. Collectively, small pelagic fish often occupy a central role in the food web they occur in, often described as a wasp-waist ecosystem. Humans are an integral part of those ecosystems. Variability of populations of small pelagic fish is believed to be due primarily to variations in climate and fishing, but the mechanisms of these relations remain unknown in most cases. It is also uncertain whether these ecosystems alternate between states, e.g. regimes, and whether inherent variability may limit our ability to predict their future states. The fisheries for populations of small pelagic fish are increasingly global in nature. While the global catch of small pelagic fish constitutes approximately one quarter of the world fish catch and has been relatively constant during the past several decades, the catch of individual taxa and stocks varies much more. The management of these fisheries will be challenged by increasing demand for human consumption and mariculture in light of their finite and variable production, importance within the ecosystem, and unprecedented climate change, and will depend on both science and governance. We recommend continued, global research on climate change effects on small pelagic fish, and its periodic assessment for use by decision makers.
1 - History of international co-operation in research
- Edited by Dave Checkley, Scripps Institution of Oceanography, University of California, San Diego, Jürgen Alheit, Yoshioki Oozeki, Claude Roy
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- Book:
- Climate Change and Small Pelagic Fish
- Published online:
- 08 January 2010
- Print publication:
- 20 August 2009, pp 1-5
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Summary
Over the last 25 years, since about 1980, international co-operation in research on small pelagic schooling fish with pelagic eggs, such as anchovy, sardine, sprat, and sardinella focused, first on processes determining recruitment variability and, then, since the mid 1990s, on the impact of climate variability on ecosystems dominated by small pelagics. Recruitment research was carried out to a large extent under the umbrella of the Sardine–Anchovy– Recruitment Program (SARP) within the Ocean Science in Relation to Living Resources Program (OSLR) run jointly by IOC and FAO and the Climate and Eastern Ocean Systems project (CEOS) conducted by a variety of research institutions.
Lack of scientific understanding of the mechanisms regulating recruitment was widely recognized in the 1980s (and still is) as the key unsolved scientific problem currently hindering effective management of small pelagic fish populations. Their collapses such as the Californian sardine or the Peruvian anchovy have had enormous negative economic and social effects on fishing nations which might have been avoided had there been the opportunity to predict recruitment. Consequently, several international and national initiatives were started in the 1980s to understand the relationship between environmental processes and fish recruitment. At this point, Reuben Lasker's “stable ocean hypothesis” (Lasker, 1975, 1978) had suddenly caught the attention of the fisheries scientific community, and provided a major conceptual basis for motivating and planning the early activity. Simultaneously, two new technologies, the “Daily Egg Production Method” (DEPM) (Lasker, 1985) and a technique for daily age and growth estimates based on measuring and counting daily marks laid down on larval fish otoliths (Methot, 1983), were under development in Lasker's laboratory.
13 - Research challenges in the twenty-first century
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- By Andrew Bakun
- Edited by Dave Checkley, Scripps Institution of Oceanography, University of California, San Diego, Jürgen Alheit, Yoshioki Oozeki, Claude Roy
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- Book:
- Climate Change and Small Pelagic Fish
- Published online:
- 08 January 2010
- Print publication:
- 20 August 2009, pp 300-311
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Summary
A selection of scientific issues is presented as being likely keys to (1) effectively managing the future of small pelagic fisheries under the combined stresses of climate change and ever-increasing demand for fishery products, and (2) understanding the role that small pelagic fishes may play in maintaining the health, integrity and resilience of the large marine ecosystems in which they function. The concept of a wasp-waist ecosystem is presented, according to which a highly variable small pelagic fish component, largely responding to its own internal dynamics, may significantly drive the operation of its entire ecosystem. On the basis of this conceptual framework, a number of vital unresolved issues are briefly elaborated. Several types of nonlinear feedback mechanisms, capable of leading to abrupt instabilities and durable regime shifts, are presented together with the concept of breakout thresholds that may trigger a shift from a favorable phase of feedback operation that supports resilience to an adverse phase leading to abrupt system changes. Proposed mechanisms underlying distributional dynamics are appraised; a suggested connotation is that changes in distributional aspects of key populations may be timely harbingers of unwelcome regime shifts. Several alternative interpretations of apparent density dependent growth are offered, each presenting rather different implications with respect to sustainability. The mechanisms behind apparent niche replacements and species alternations are pondered. It is suggested that SPACC-type research be extended to similar small pelagic species and issues in other more tropical and/or more oceanic ecosystems.