Oceanic Sharks Clean at Coastal Seamount

Interactions between pelagic thresher sharks (Alopias pelagicus) and cleaner wrasse were investigated at a seamount in the Philippines. Cleaning associations between sharks and teleosts are poorly understood, but the observable interactions seen at this site may explain why these mainly oceanic sharks regularly venture into shallow coastal waters where they are vulnerable to disturbance from human activity. From 1,230 hours of observations recorded by remote video camera between July 2005 and December 2009, 97 cleaner-thresher shark events were analyzed, 19 of which were interrupted. Observations of pelagic thresher sharks interacting with cleaners at the seamount were recorded at all times of day but their frequency declined gradually from morning until evening. Cleaners showed preferences for foraging on specific areas of a thresher shark's body. For all events combined, cleaners were observed to conduct 2,757 inspections, of which 33.9% took place on the shark's pelvis, 23.3% on the pectoral fins, 22.3% on the caudal fin, 8.6% on the body, 8.3% on the head, 2.1% on the dorsal fin, and 1.5% on the gills respectively. Cleaners did not preferentially inspect thresher sharks by time of day or by shark sex, but there was a direct correlation between the amount of time a thresher shark spent at a cleaning station and the number of inspections it received. Thresher shark clients modified their behavior by “circular-stance-swimming,” presumably to facilitate cleaner inspections. The cleaner-thresher shark association reflected some of the known behavioral trends in the cleaner-reef teleost system since cleaners appeared to forage selectively on shark clients. Evidence is mounting that in addition to acting as social refuges and foraging grounds for large visiting marine predators, seamounts may also support pelagic ecology by functioning as cleaning stations for oceanic sharks and rays

Negotiation as a cooperative game

Game theory provides us with a set of important methodologies for the study of group decisions as well as negotiation processes. Cooperative game theory is a subfield of game theory that focuses on interactions in which involved parties have the power to make binding agreements. Many group decision and negotiation processes (such as legal arbitrations) fall into this category, and as such, they have been central in the development of cooperative game theory. Particularly, an area of cooperative game theory, called bargaining theory, focuses on bilateral negotiations as well as negotiation processes where coalition formation is not a central concern. The object of study in bargaining theory is a (bargaining) rule, which provides a solution to each bargaining problem (or in other words, negotiation). Studies on bargaining theory employ the axiomatic method to evaluate bargaining rules. This chapter reviews and summarizes several such studies. After a discussion of the bargaining model, we present the important bargaining rules in the literature (including the Nash bargaining rule), as well as the central axioms that characterize them. Next, we discuss strategic issues related to cooperative bargaining, such as the Nash program, implementation of bargaining rules, and games of manipulating bargaining rules. We conclude with a discussion of the recent literature on ordinal bargaining rules