Thoughts on Preference and Utility in the Salmon Case Study

Pacific salmon are an extremely valuable resource on the Pacific Rim of Canada. On the Skeena River, one of six major salmon watersheds in B.C., the dollar value of the commercial catch is between ten and twenty million dollars annually. In addition, the salmon stocks provide recreational benefits for many residents of British Columbia and contribute strongly to the local recreational economy. Millions of dollars are spent annually on managing the commercial and recreational salmon fisheries; there is a current proposal by the federal government to spend several hundred million dollars enhancing the salmon stocks over the next few years. The current salmon case study has been involved in extensive modeling efforts to determine policy options for salmon management and assess these options. However, we have recently realized that despite our model's optimization techniques and the incredible elegance of our approach, we really don't know what the people of Canada want from the salmon fishery

Expected Changes in Stock Recruitment Parameters When Exploiting Mixed Stocks of Salmon

The parameters for a Ricker stock recruitment relationship can change due to a number of factors. Methods for distinguishing between habitat elimination, lowered brood success, and elimination of less productive substocks are discussed. Data for the Columbia River Fall Chinook, and Skeena River Sockeye are analyzed in light of these considerations. It is also shown that the expected changes in productivities are strongly affected by the correlation of productivities of the different substocks. The importance of the above factors are discussed in relation to proposed enhancement facilities

Stock Enhancement in Salmon & Maintenance of Historic Runs

W.E. Ricker has recently shown that the failure of present day salmon fisheries to maintain historically high yields may be due in part to the fact that different stocks, which are subjected to the same fishing pressure, have different biological productivities, and the equilibrium maximum sustained yield may cause smaller less productive stocks to reach very low levels or even go extinct. This author explores the problem in two ways: he first analytically examines the relationship between two stocks subjected to the same fishery, and then tests these conclusions against a much more complex numerical simulation model of a salmon fishery

Fish -- More Than Just Another Commodity

This brief highlights the contribution of wild capture fisheries to nutritional security in fish dependent developing countries. It is intended to stimulate debate around two broad themes: (1) when should the focus of fisheries policies be on local food security and human well-being as opposed to revenue generation, and (2) how does the current research agenda, with its emphasis on environmental and economic issues, assist or impair decision making processes

Adaptive Control of Fishing Systems

This paper discusses some formal techniques for deciding how harvesting policies should be modified in the face of uncertainty. Parameter estimation and dynamic optimization methods are combined for the Ricker stock recruitment model to show how exploitation rates should be manipulated to give more information about the model parameters. In general, harvesting rates should be lower than would be predicted by the best fitting recruitment curve unless this curve predicts that the stock is very productive. A decision procedure is developed for comparing alternative stock recruitment models; when applied to the Fraser River sockeye salmon, the procedure indicates that an experimental increase in escapements would be worthwhile. It appears that there is considerable promise for extending these methods and procedures to cases where the stock size is unknown and where fishing effort is poorly controlled

Tsallis' q index and Mori's q phase transitions at edge of chaos

We uncover the basis for the validity of the Tsallis statistics at the onset of chaos in logistic maps. The dynamics within the critical attractor is found to consist of an infinite family of Mori's $q$-phase transitions of rapidly decreasing strength, each associated to a discontinuity in Feigenbaum's trajectory scaling function $\sigma$. The value of $q$ at each transition corresponds to the same special value for the entropic index $q$, such that the resultant sets of $q$-Lyapunov coefficients are equal to the Tsallis rates of entropy evolution.Comment: Significantly enlarged version, additional figures and references. To be published in Physical Review

Transitions to improved confinement regimes induced by changes in heating in zero-dimensional models for tokamak plasmas

It is shown that rapid substantial changes in heating rate can induce transitions to improved energy confinement regimes in zero-dimensional models for tokamak plasma phenomenology. We examine for the first time the effect of step changes in heating rate in the models of E-J.Kim and P.H.Diamond, Phys.Rev.Lett. 90, 185006 (2003) and M.A.Malkov and P.H.Diamond, Phys.Plasmas 16, 012504 (2009) which nonlinearly couple the evolving temperature gradient, micro-turbulence and a mesoscale flow; and in the extension of H.Zhu, S.C.Chapman and R.O.Dendy, Phys.Plasmas 20, 042302 (2013), which couples to a second mesoscale flow component. The temperature gradient rises, as does the confinement time defined by analogy with the fusion context, while micro-turbulence is suppressed. This outcome is robust against variation of heating rise time and against introduction of an additional variable into the model. It is also demonstrated that oscillating changes in heating rate can drive the level of micro-turbulence through a period-doubling path to chaos, where the amplitude of the oscillatory component of the heating rate is the control parameter.Comment: 8 pages, 14 figure

Hamiltonian chaos in a coupled BEC -- optomechanical cavity system

We study a hybrid optomechanical system consisting of a Bose-Einstein condensate (BEC) trapped inside a single-mode optical cavity with a moving end-mirror. The intracavity light field has a dual role: it excites a momentum side-mode of the condensate, and acts as a nonlinear spring that couples the vibrating mirror to that collective density excitation. We present the dynamics in a regime where the intracavity optical field, the mirror, and the side-mode excitation all display bistable behavior. In this regime we find that the dynamics of the system exhibits Hamiltonian chaos for appropriate initial conditions.Comment: 5 figure