Exvessel Price Determination in the Alaska King Crab Fishery: A Formula Price Contract under Uncertainty?

Commercial fisheries industry structure often suggests exvessel price formation occurs in the context of a competitive harvesting sector and an oligopsonistic processing sector. However, industry conduct leading to a determination of exvessel price can be notably at odds with this inference. This paper presents empirical evidence that the conduct of at least one such fishery, the Alaska king crab industry, may emulate bilateral monopoly. Exvessel price determination is consistent with an implicit formula price contract in which fishers behave as monopolists through bargaining associations, while processors behave as countervailing monopsonists, even in the absence of explicit collusion. Both sectors appear to behave in a manner consistent with joint expected profit maximization, with profit shares apportioned via the implicit formula price contract. This price formation process simplifies empirical analysis of the bilateral monopoly conduct by avoiding complicated game theoretic/bargaining models.     

Shading facilitates sessile invertebrate dominance in the rocky subtidal Gulf of Maine

Dramatic shifts in community composition occur between vertical and horizontal rocky surfaces in subtidal environments worldwide, yet the forces mediating this transition are poorly understood. Vertical rock walls are often covered by lush, diverse communities of sessile suspension-feeding invertebrates, while adjacent horizontal substrates are dominated by algae, or corals in the tropics. Multiple factors, including light, sedimentation, water flow, and predation have been proposed to explain this pattern, but experimental tests of these hypotheses are lacking. We manipulated light level and predation to test whether variation in these mechanisms could be responsible for the shift in composition of sessile communities between vertical and horizontal surfaces in the rocky subtidal Gulf of Maine. Shaded horizontally oriented granite plots were dominated by invertebrates (e.g., ascidians, barnacles, bryozoans) after 25 months. Unshaded plots were dominated by macroalgae, which was virtually absent in shaded plots. Exclusion of grazers with cages had no effect on percent cover of invertebrates or algae. Preferential settlement of invertebrate larvae to shaded plots, due to larval behaviors such as negative phototaxis, did not seem to play a role. Shading likely affects post-settlement mortality of invertebrates by alleviating competition for space with algae, although greater abundance of micropredators in algal-dominated communities could also be important. Communities on shaded plots lacked many taxa present on natural wall communities, likely due to greater disturbance on horizontal substrates and/or lack of sufficient time for colonization of these taxa. These results suggest that light plays a key role in controlling the structure, composition, and function of shallow subtidal communities.     

Invasion dynamics of the European shore crab,<Emphasis Type="Italic"> Carcinus maenas</Emphasis>, in Australia

In Australia and most other invaded locations, rates of range expansion by the European shore crab, Carcinus maenas, are typically only a few kilometres per year, despite a planktonic duration upwards of 50 days and off-shore larval development. This relatively static distribution is punctuated by rare episodes of long-distance and large-scale spread, some of which appear to be related to unusual oceanographic conditions and some of which are likely to be human assisted. These observations suggest, first, that long planktonic duration and off-shore development in a marine invertebrate does not preclude very localised recruitment, and, second, that this recruitment norm may be punctuated by brief episodes of wide scale mixing of propagules. Punctuated dispersal has previously been suggested to account for large-scale biogeographic patterns of distribution and speciation, but may also have implications for the processes that stabilise structured spatial metapopulations.     

Uptake and effects of the cypermethrin-containing sea lice treatment Excis in the marine mussel,Mytilus edulis

Wild and farmed mussels, Mytilus edulis, coexist with salmon farms in Scottish sea lochs. A synthetic pyrethroid, cypermethrin, is licensed for use on fish farms to control sea lice infestations as a formulation called Excis. In this study, uptake of cypermethrin from Excis exposure is investigated through the use of gas chromatography with mass-spectrometry. The effects of Excis on mussels are also examined by measuring the neutral red retention time of lysosomes, aerial survival and shell closure. The isomeric ratios of cis:trans cypermethrin measured in mussels are around 80:20; a marked increase from 40:60 to which the mussels were exposed. This is most likely due to preferential metabolism of trans-isomers, as the same response is seen in vertebrates. There is a pronounced behavioural effect of shell closure, where mussels exposed to 1000 microg/l cypermethrin shut their shells within an hour of exposure. Arguments are presented for this effect being either a voluntary response on recognition of cypermethrin, or an effect arising from an involuntary action of cypermethrin on the adductor muscle. Even at 1000 microg/l cypermethrin, neutral red retention time and aerial survival are not affected. The data suggest that the responses of mussels shown here are unlikely to occur in the field, even at the concentrations of cypermethrin used in fish cages, for the treatment of sea lice.     

SEDIMENT DISPERSION IN SALMON SPAWNING STREAMS: THE INFLUENCE OF FLOODS AND SALMON REDD CONSTRUCTION1

ABSTRACT: Magnetically tagged particles were used to investigate the effects of sockeye salmon (Oncorhynchus nerka) and floods on the dispersion of coarse bed material in the Stuart‐Takla region, British Columbia, Canada. The dominant annual sediment transporting event in the channels is the snowmelt flood events, with lesser activity usually accomplished during summer floods. Annually in August, the channel bed material is reworked by the Early Stuart sockeye salmon spawning, as the fish excavate the streambed to deposit and bury their eggs. These nesting cavities are called redds. Results from 67 tracer recovery experiments over five years were highly variable, subject to the magnitude of floods and the returning population of salmon. Overall, the depositional pattern from nival flood events usually demonstrated a high degree of clast mobilization, long travel distances (up to 150 m), and mean depths of burial up to 18 cm. Summer flood events showed somewhat lower rates of mobilization, distances of travel, and depths of burial. Although the fish did not move the tracers very far, their effect on the bed was generally quite pervasive ‐ up to 100 percent of the clasts were mobilized, and the depth of burial was considerable (mean burial depths up to 14 cm). The amount of vertical mixing of sediment by salmon was often on the same order of magnitude as flood events. The significant vertical mixing of sediments by the fish has important implications for the mobility of sediment in the stream. Since any armoring layer formed during high flows throughout the year is subject to the bioturbation of salmon, this suggests that the transport threshold in the creeks remains relatively low. Salmon likely play an integral role in the sediment transport dynamics and annual sediment budget of the lower reaches of these creeks.     

Designing and managing successful endangered species recovery programs

Endangered species recovery is characterized by complexity and uncertainty in both its biological and organizational aspects. To improve performance in the organizational dimension, some models of organizations are briefly introduced with an emphasis on the organization as a system for processing information, i.e., for successfully dealing with the high uncertainty in the task environment. A strong task orientation,which rewards achievement of the primary goal, is suggested as ideal for this task, as is generative rationality, which encourages workers to observe, critique, and generate new ideas. The parallel organization—a flexible, participatory, problem-solving structure set up alongside traditional bureaucracies—is offered as a useful structure for meeting the demands of uncertainties encountered during recovery. Task forces and projects teams can be set up as parallel organizations. Improved managerial functions include coordinating roles to facilitate the flow and use of information; decision making to avoid groupthink—the defects, symptoms, and countermeasures are described; and productive, active management of the inevitable conflict. The inability of organizations to solve dilemmas, to examine their own structures and management, and to change themselves for more effective, efficient, and equitable performance is seen as the major obstacle to improved recovery programs. Some recommendations for effecting change in bureaucracies are made along with a call for case studies detailing the organizational dimensions of endangered species recovery programs.     

Non-isothermal gaseous exchange between soil and atmosphere

The theoretical and experimental basis of a non-isothermal rotary gas exchange (NRGE) between soil and atmosphere is given. A method of measurement for the NRGE intensity in porous media, including soil, is given and its validity is examined. The global NRGE of selected gases is determined. Relatively high NRGE intensities are found to exist for some gases. The heat transfer determination method is given. An electrical scheme for simulating the NRGE process is also described.