Influence of hydraulics on the dowsntream migratory route of Atlantic salmon (Salmo salar)

The interaction between hydrodynamics and the upstream migration of fish has been investigated in several studies over the past few years, but there has been a relative lack of investigation into the effects of hydraulics on the downstream migration of fish. In Norway, mortality associated with downstream migration is strongly related to hydropower production. However, there is a poor understanding of how fish choose their migratory routes, which limits the development of measures to mitigate the impact of anthropogenic structures on fish migration. The current study aimed to analyze the effect of hydraulics on the choice of downstream migration route of Atlantic salmon smolts (Salmo salar) in the proximity of an intake to a hydropower plant in Norway. We combined computational fluid dynamic modeling with 3-Dimensional acoustic telemetry positioning of a group of tagged smolts to investigate the interaction between fish and the flow dynamics, and to determine the influence of this interaction on fish migratory routes. A Hidden Markov Model was used to predict migratory routes based on the relations found between the hydraulic variables and fish behaviour. Results showed relationships between fish migratory routes and the different components of flow velocity. The knowledge acquired in this study is expected to inform opportunities and decision making in aquatic resources management and engineering design to increase fish survival past hydropower intakes and other anthropogenic structures

Considering clustering measures: third ties, means, and triplets

Measures that estimate the clustering coefficients of ego and overall social networks are important to social network studies. Existing measures differ in how they define and estimate triplet clustering with implications for how network theoretic properties are reflected. In this paper, we propose a novel definition of triplet clustering for weighted and undirected social networks that explicitly considers the relative strength of the tie connecting the two alters of the ego in the triplet. We argue that our proposed definition better reflects theorized effects of the important third tie in the social network literature. We also develop new methods for estimating triplet, local and global clustering. Three different types of mathematical means, i.e. arithmetic, geometric, and quadratic, are used to reflect alternative theoretical assumptions concerning the marginal effect of tie substitution

Strategic action in network industries: an empirical analysis of the European mobile phone industry

This paper investigates the strategic moves of European mobile phone operators during the early development of the industry. Drawing on the literature on competitive dynamics and markets externalities, we study the strategic actions taken by mediators, i.e., firms based on a mediating technology such as phone operators (Organizations in Action, McGraw-Hill, New York, 1967; Strat. Manage. J. 19(5) (1998) 413). As expected, market penetration, concentration, and time evolution drive the likelihood of inter-firm cooperation and the types of strategic action taken by firms in this network industry. The results confirm the unique characteristics of the value network configuration with regard to how mediators create value, the primary activities that they perform, and the combination of competitive and cooperative conduct in this type of industry

Transaction organizations and transaction cost analysis: A theoretical investigation of the domain-expansion decisions of firms employing a mediating technology

We use the theory of network externalities in applying transaction cost economics (TCE) to inter-mediator transactions. We propose network specificity as an additional form of asset specificity associated with such transactions. Specifically, we identify and analyze two integration decisions that are distinctive to mediators and that both depend on network specificity: the network integration of nodes and the vertical integration of complement exchange activities. We derive some implications of this for managerial practice, public policy and further research.Transaction cost analysis Mediation industries Network externalities

Strategic action in network industries: an empirical analysis of the European mobile phone industry

This paper investigates the strategic moves of European mobile phone operators during the early development of the industry. Drawing on the literature on competitive dynamics and markets externalities, we study the strategic actions taken by mediators, i.e., firms based on a mediating technology such as phone operators (Organizations in Action, McGraw-Hill, New York, 1967; Strat. Manage. J. 19(5) (1998) 413). As expected, market penetration, concentration, and time evolution drive the likelihood of inter-firm cooperation and the types of strategic action taken by firms in this network industry. The results confirm the unique characteristics of the value network configuration with regard to how mediators create value, the primary activities that they perform, and the combination of competitive and cooperative conduct in this type of industry.Network industries Competitive dynamics Value-creation analysis

Competition with local network externalities

Local network externalities are present when the utility of buying from a firm not only depends on the number of other customers (global network externalities), but also on their identity and / or characteristics. We explore the consequences of local network externalities within a framework where two firms compete offering differentiated products. We first show that local network externalities, in contrast to global network externalities, don't necessarily sharpen competition. Then we show that the equilibrium allocation is inefficient, in the sense that the allocation of consumers on firms does not maximize social surplus. Finally we show that local network externalities create a difference between the marginal and the average consumer, which gives rise to inefficiently high usage prices and too high level of compatibility between the networks