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Ocean variability and population diversity - a match made in heaven (closing remarks)Robert. C. Francis There are two objectives to this short paper. First I will summarize my view of the most salient conclusions reached in the afternoon panel discussions. And second I will summarize my own views on the significant management implications that arise from consideration of what we know about the effects of ocean conditions on salmon populations. Actually it turns out that both of these objectives converge around two words and a figure. The two words are variability and diversity. And the figure is from Bisbal and McConnaha (1998 ? Figure 1) and shows how salmon have evolved diverse population structures in order to deal with, among other things, variable and uncertain ocean conditions. And clearly salmon population diversity is directly related to the availability of healthy, complex and connected freshwater and estuarine habitat. More about this later. It is clear that ocean conditions have a significant impact on the overall production of all species of Pacific salmon, and that climate and ocean variability act at a number of time and space scales (e.g. seasonal, annual decadal time scales and global, regional and local space scales) to affect salmon production dynamics. Emmett and Schiewe (eds.) (1997) provide a good recent summary of what we think we know in this area. In fact it is becoming quite clear that interdecadal climate has forced major shifts in the basic structure of coastal marine ecosystems. The most studied and notorious of these incidents occurred with the 1977 NE Pacific climate regime shift (e.g. see Miller et al. 1994; Mantua et al. 1997; Francis et al. 1998). Recent studies have shown that interdecadal changes in atmospheric circulation affect the structure of the upper ocean (Miller et al. 1998) and, in turn, the timing (Mackas et al. 1998) and magnitude (Brodeur et al. 1996; Roemmich and McGowan 1995) of the oceanic biological production process. This, in turn, can affect major reorganizations of the coastal marine ecosystems (Anderson and Piatt pers commun.) which have such a significant impact on salmon production. Unfortunately, the scales we understand least about (seasonal and annual time scales; local space scales) are the ones that appear to be most important to salmon management, at least as it is presently practiced. And so it is very difficult if not impossible to "engineer" salmon management to match anticipated ocean conditions. And so, what can we do? I think that Bottom (1995) really hits the nail on the head when he urges that we adopt an ecosystem view towards salmon management. Thus rather than try to circumvent essentially unpredictable natural variations through the use of technology, or ignore it through the use of deterministic predictive models, we should "embrace environmental variation as an essential organizing property of living systems." The purpose of conservation, and I would add fishery management, is not to "improve" nature by eliminating variability; it is to protect the interrelationships that allow populations and communities to sustain themselves in a changing world. We only need to look as far as salmon populations themselves to see how this is done. For millenia, salmon have had to deal with the kinds of changes recently thrown at them by the ocean. And they have done this by evolving a diversity of life history strategies such as mixed year classes, extended smolt migration periods, lengthy adult spawning migrations and other strategies to hedge their bets against the uncertain freshwater, estuarine and ocean environments they are confronted with. And thus within metapopulations (e.g. Columbia River coho salmon), a diversity of genetically hard-wired behaviors provide the key buffers to the climate-driven uncertainties that must be confronted on a year to year and decade to decade basis. In this context, management should focus on maintaining the diverse metapopulation "parts" of the whole. In this view, resilience is directly related to diversity, and diversity is directly related to the availability of healthy and complex freshwater and estuarine habitat. And to say that an ecosystem is "healthy" is to say that the overall system maintains sufficient complexity and flexibility to protect its self-organizing qualities (Norton 1992; Francis 1997). It must have the capacity to respond to change. In this context, "management must have as its central goal the protection of the system's creativity" (Norton 1992). Once again in the words of Bottom (1995) - what I call the Bottom Line - "the emphasis on ecosystems reflects a growing awareness that we cannot maintain even our most carefully managed resources apart from the biophysical context that created them." And so I want to reemphasize my main point here: in order to preserve the capacity of Pacific salmon to respond to variable ocean conditions, we must preserve and restore intact and connected freshwater and estuarine habitat. Once this point is firmly institutionalized, the salmon will do the rest. It seems to me that there are four things that can be done by managers to insure that this ecosystem worldview to salmon management is incorporated. 2. Avoid fishing practices that are selective towards specific metapopulation components. Francis (1997) points out that in the case of Bristol Bay sockeye, nature has dealt the system at least as much variability, in both the short (annual) and long (decadal) term, as the (apparently) sustainable fishery has been able to remove at its peak. And thus with its freshwater and estuarine habitat in virtually pristine condition, the Bristol Bay sockeye ecosystem has evolved and maintained the capacity of absorbing significant levels of ocean-induced variability over multiple time scales, even in the presence of the largest single species salmon fishery on the planet. One should note that Alaska fishery managers make every effort to spread the fishery out over as broad an array of system components as possible. 3. Manage hatchery programs to avoid negative impacts on wild stocks. In particular this requires the management and control of the release of hatchery fish as well as their harvest. In general, fishery managers need to develop ecologically based performance standards and monitoring programs to insure that the risks of hatchery programs are minimal (Bottom 1995). 4. Conservation and management must be based on sound science. This seems obvious but is often ignored in the rush to satisfy short-term political agendas. As Bottom (1995) points out, "prudent ecosystem conservation is not the same as quantitative prediction. It is a deliberative process of informing both citizens and decision-makers so that they can choose wisely despite the many ecological and cultural uncertainties involved in any management choice." Holling (1993) argues that there are at least two "streams" of science. In the first stream, the machine metaphor for nature pervades. Management is oriented to smoothly changing and reversible conditions, and operates under the view that one needs to know before taking action. In the second stream, which Holling (1995) argues is more appropriate for approaching ecosystem issues, the view is that knowledge will always be incomplete. And so in order to be a science for management, uncertainty and surprise must become an integral part of a sequence of actions, one dependent on the results of how the system responded to those that have come before (Francis 1997). This, then, is a science which openly acknowledges indeterminacy, unpredictability, and the historical nature of resource issues. The scientific problems faced by taking an ecosystem view are not amenable to solutions based on knowledge of small parts of the whole, nor on assumptions of constancy or stability of fundamental relationships - ecological, economic or social. In this context the focus best suited for management policy is "actively adaptive designs that yield understanding as much as they do product." (Holling 1993). Bisbal, G.A., and McConnaha, W.E. 1998. Consideration of ocean conditions in the management of salmon. Can. J. Fish. Aquat. Sci. 55: 2178-2186. Bottom, D.L. 1995. Restoring salmon ecosystems - Myth and reality. Restoration and Management Notes 13: 162-170. Brodeur, R.D., B.W. Frost, S.R. Hare, R.C. Francis, and Ingraham, W.J. 1996. Interannual variations in zooplankton biomass in the Gulf of Alaska, and covariation with California Current zooplankton biomass. CalCOFI Rep. 37: 80-89. Emmett, R.L., and Schiewe, M.H. (eds.). 1997. Estuarine and ocean survival of Northeast Pacific salmon: Proceedings of the workshop. U.S. Dept. Commer. NOAA Tech. Memo. NMFS-NWFSC-29. Francis, R.C. 1997. Sustainable use of salmon: Its effects on biodiversity and ecosystem function, p. 626-670. In Harvesting Wild Species - Implications for Biodiversity Conservation. Edited by C.H. Freeze. Johns Hopkins Univ. Press, Baltimore, MD. Francis, R.C., S.R. Hare, A.B. Hollowed, and Wooster, W.S. 1998. Effects of interdecadal climate variability on the oceanic ecosystems of the Northeast Pacific. Fish. Oceanogr. 7: 1-21. Holling, C.S. 1993. Investing in research for sustainability. Ecol. Appl. 3: 552-555. Mantua, N.J., S.R. Hare, Y. Zhang, J.M. Wallace, and Francis, R.C. 1997. A Pacific interdecadal climate oscillation with implications on salmon production. Bull. Am. Met. Soc. 78: 1-11. Mackas, D.L., R. Goldblatt, and Lewis, A.G. 1998. Interdecadal variation in development timing of Neocalanus plumchrus populations at Ocean Station P in the Subarctic North Pacific. Can. J. Fish. Aquat. Sci. 55: 1878-1893. Miller, A.J., D.R. Cayan, T.P. Barnett, N.E. Graham, and Oberhuber, J.M. 1994. The 1976-77 climate shift in the Pacific Ocean. Oceanog. 7: 21-26. Miller, A.J., D.R. Cayan, and White, W.B. 1998. A westward-intensified decadal change in the North Pacific thermocline and gyre-scale circulation. J. Clim. 11: 3112-3127. Roemmich, D., and McGowan, J. 1995. Climate warming and the decline of zooplankton in the California Current. Science 267: 1324-1326. |
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