Robert C. Francis

A Pacific Interdecadal Climate Oscillation with Impacts on Salmon Production

Evidence gleaned from the instrumental record of climate data identifies a robust, recurring pattern of ocean–atmosphere climate variability centered over the midlatitude North Pacific basin. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal timescales. There is evidence of reversals in the prevailing polarity of the oscillation occurring around 1925, 1947, and 1977; the last two reversals correspond to dramatic shifts in salmon production regimes in the North Pacific Ocean. This climate pattern also affects coastal sea and continental surface air temperatures, as well as streamflow in major west coast river systems, from Alaska to California.

Inverse Production Regimes: Alaska and West Coast Pacific Salmon

Abstract A principal component analysis reveals that Pacific salmon catches in Alaska have varied inversely with catches from the U.S. West Coast during the past 70 years. If variations in catch reflect variations in salmon production, then results of our analysis suggest that the spatial and temporal characteristics of this “inverse” catch/production pattern are related to climate forcing associated with the Pacific Decadal Oscillation, a recurring pattern of pan-Pacific atmosphere-ocean variability. Temporally, both the physical and biological variability are best characterized as alternating 20-to 30-year-long regimes punctuated by abrupt reversals. From 1977 to the early 1990s, ocean conditions have generally favored Alaska stocks and disfavored West Coast stocks. Unfavorable ocean conditions are likely confounding recent management efforts focused on increasing West Coast Pacific salmon production. Recovery of at-risk (threatened and endangered) stocks may await the next reversal of the Pacific Decad...

Ten Commandments for Ecosystem-Based Fisheries Scientists

Abstract In an effort to accelerate the ongoing paradigm shift in fisheries science from the traditional single-species mindset toward more ecosystem-based approaches, we offer the following “commandments” as action items for bridging the gap between general principles and specifie methodologies. 1. Keep a perspective that is holistic, risk-averse, and adaptive. 2. Question key assumptions, no matter how basic. 3. Maintain old-growth age structure in fish populations. 4. Characterize and maintain the natural spatial structure of fish stocks. 5. Characterize and maintain viable fish habitats. 6. Characterize and maintain ecosystem resilience. 7. Identify and maintain critical food web connections. 8. Account for ecosystem change through time. 9. Account for evolutionary change caused by fishing. 10. Implement an approach that is integrated, interdisciplinary, and inclusive. Although the shift in worldview embodied in these commandments can occur immediately without additional funding, full implementation o...

BOUNDARIES OF OPEN MARINE ECOSYSTEMS: AN APPLICATION TO THE PRIBILOF ARCHIPELAGO, SOUTHEAST BERING SEA

We applied ecosystem energetics and foraging theory to characterize the spatial extent of the Pribilof Archipelago ecosystem, located in the southeast Bering Sea. From an energetic perspective, an ecosystem is an area within which the predatory demand is in balance with the prey production. From a foraging perspective, an ecosystem boundary should at least include the foraging range of the species that live within it for a portion of their life cycle. The Pribilof Islands are densely populated by species that adopt a central place foraging strategy. Foraging theory predicts that the area traveled by central place foragers (CPF) should extend far enough so that their predatory demands are in balance with prey production. Thus, the spatial extent of an ecosystem, as defined by energetics and the foraging range of constituent species, will require a similar energy balance, and independent assessments should yield similar results. In this study, we compared the area of maximum energy balance, estimated with a food web model during the decade 1990- 2000, with estimates of the foraging range of northern fur seals (the farthest traveling CPF in the Pribilof Islands community) obtained from the literature. From the food web sim- ulations, we estimated that a circle of 100 nautical miles (NM), or 185.2 km, radius encloses the area of highest energy balance and lowest biomass import and that it represents a switch from a piscivorous-dominated (smaller areas) to a zooplanktivorous-dominated (larger ar- eas) community. The distance from the breeding site to locations recorded at sea for lactating female fur seals, during the years 1995-1996, ranged from 5.0 to 172.2 NM (9.3-318.9 km), with a median of 97 NM (179.6 km). Thus, ;50% of the locations recorded for lactating fur seals occurred beyond the area of energy balance estimated by the model, indicating that additional factors can motivate their foraging extent. We propose that en- ergetic constraints set the minimum extent of the Pribilof ecosystem, while the foraging distance of fur seals may indicate the maximum extent. In discussing these results, we highlight the limitations of current definitions of the spatial extent in ecosystems, when related to open oceanic environments, and discuss viable alternatives to characterize bound- aries of aquatic systems that are not physically separated from adjacent areas. We believe that these arguments, though controversial, are very timely given the increased emphasis currently placed on the management and protection of entire marine ecosystems.

Network models for ecosystem-based fishery analysis : a review of concepts and application to the Gulf of Alaska marine food web

We apply graph theory and network analysis to the food web of the Gulf of Alaska marine ecosystem to classify its structural properties, which suggest how the ecosystem as a whole may respond to heavy fishing pressure on its components. Three conceptual models of network structure, random, small-world, and scale-free, each have different implications for system behavior and tolerance to perturbations. We constructed two food web network models using detailed quantitative information on the stomach contents of 57 predator (fish) species collected during trawl surveys of the Gulf of Alaska between 1981 and 2002. The resulting food webs displayed both small-world and scale-free network properties, suggesting that impacts on one species might spread to many through short interaction chains and that while most food web connections are not critical, a small set of fished species support critical structural connections. Ecosystem-based fishery management should therefore first focus on protecting the highly conn...

Climate Change and Marine Fisheries

Abstract Increased concentrations of greenhouse gases may significantly change global climate over the next century. Atmos- pheric temperatures are expected to increase at a rate of 4°C per hundred years, a rate that exceeds the postglacial warming by more than an order of magnitude. This paper discusses the three areas where we must immediately make significant efforts to improve our knowledge if we are to stand any chance of unraveling the complex linkages between global climate change and marine fisheries production. The three areas are the prediction of oceanographic effects of climate change, the improvement of our understanding of the structure and function of the marine food chain, and the improvement of our understanding of the important social aspects of marine fisheries. We, as fisheries scientists, must develop new methodological concepts and change our way of thinking when developing public policy in anticipation of global change.

The effect of surfactants on a packed distillation column

Abstract Z uiderweg and H armens [1] have already given strong evidence of the importance of interfacial properties in various types of distillation equipment. The work herein reported demonstrates how some of the interfacial effects can be controlled to advantage by the use of small amounts of surfactants. The efficiency of a small packed distillation column is increased by as much as 100 per cent by the addition of small amounts of such materials.

A Conceptual Model for Multispecies, Multifleet Fisheries

Marine fisheries scientists and managers are becoming more cognizant of the need to regard the exploitation of many single species stocks as part of a larger multispecies system (see, for example, Mercer 1982 and the 26 papers published therein). A problem in the analysis and management of any ecological and/or economic system is demarcating its boundary: there will always be components external to the bounded system that strongly influence its behavior and yet are dealt with in a simple manner often as a time varying input function. The approach that needs to be taken, especially with regard to managment problems, is to be pragmatic, to strike a balance between complexity and utility and to be goal oriented. If the goal is to understand the biological mechanisms that determine larval survival rates and hence recruitment levels, then comprehensive ecologically based models are required (cf. Laevastu, Favorite and Larkins 1982). If the primary goal is to assess stock and yield levels from catch and effort data, then a less biologically detailed approach is appropriate (cf. Murawski 1984, Ursin 1982).

Biological Basis For Management of Commercial Fishery Resources of the Eastern Bering Sea

Some biological considerations involved with the management of three Eastern Bering Sea fisheries are reviewed. Groundfish management is very complex due to multispecies and multifishery interactions superimposed on a highly variable fishery, The abundance of the various species is assessed through catch information and independent research trawl and acoustic surveys, and a total allowable catch is assigned for individual species and the total groundfish complex. This total catch is adjusted for various biological and socioeconomic factors, and conservative allocations are made to the various fisheries, The biological input related to the management of the walleye polllock fioshery is illustrated as an example. Management of the Bristol Bay sockeye salmon fishery is inherently less complex since it deals with a single species and fishery, one management agency and a relatively limited time frame. However, biological eomplexities involving different run timings, brood-year interaetions, eyclic dominanee, and long-term elimatic ehanges render optimal spawner level decisions based on spawner-reeuit relations of questionable value. Forecasts of run size are based on serial monitoring by a pre-season test fishery, as well as in-season cateh and escapement monitoring, and cateh is adjusted aecordingly. King crab management is based on tbe supposition that male crabs that have already mated at least once represent a surplus that may be harvested. Close monitoring of cateh and pre- and postreeruit abundance Ievels is critieal to the suceess of this strategy in such a cyelically variable fishery. Since all three fisheries undergo long-term fluetuations possibly driven by environmental eonditions, evolution toward a more dynamie management poliey is advocated.

A Simulation of the Pacific Whiting Fishery Using an Age-Structured Stochastic Recruitment Model

Abstract This paper applies a model developed by Getz and Swartzman (1981) to the Pacific Whiting (Merluccius pvoduatus) fishery off the North American Pacific continental shelf. Recruitment in this stock is lonked both to stock level and water temperature in their spawning area. This link forms the basis of a transition matrix in the model for recruitment which depends both on stock level and spawning grounds temperature. Comparison with historical data on fishery catch and stock estimates shows model output to be realistic. A number of modifications to the original Getz-Swartzman model have increased model speed, allowed a larger number of age classes, improved model stability, and eliminated errors resulting from discretization of the population in the model.