Behaviour of Cyclopoid, Harpacticoid, and Calanoid Copepods from Coastal Waters of Taiwan

Abstract. Cinematographic techniques were used to compare behaviour patterns of three cyclopoid, one harpacticoid, and two calanoid species of copepods from coastal waters of Taiwan. Behaviour was quantified in terms of allocation of time to swimming versus non-swimming behaviour, and behavioural transitions/minute. The different species of copepods exhibited different patterns of behaviour. Oithona nana and O. similis had long periods of inactivity punctuated by comparatively few transitions to intermittent leaps of motion. Oncaea venusta had a more jerky pattern of numerous small hops with frequent transitions between motion and rest. Macrosetella gracilis spent more time swimming than did the cyclopoids, but with fewer behavioural transitions than O. venusta , more like the Oithona species. Temora turbinala swam virtually continuously and transitions to non-swimming were rare. Undinula vulgaris var. taiwanicus frequently alternated between upward motion and sinking at rest, making a feeding current about a fourth of the time. There was considerable intraspecific variability between individual animals, but for reasons of experimental design, it was impossible to statistically test the significance of this variation. Differences in behaviour patterns between the different species are discussed within the context of what is known about the feeding ecology of these species from previous investigations.     

Free vibrations of a cantilever beam with a spring–mass system attached to the free end

An exact solution for the title problem is obtained using the Bernoulli–Euler theory of beam vibrations. Natural frequencies are obtained for a wide range of the intervening physical parameters. The problem is of interest in naval and ocean engineering systems since in order to avoid dangerous resonance conditions the designer must be able to predict natural frequencies of the overall mechanical system: structure–motor and its elastic mounting.     

Coherent reflection of an acoustic plane wave from a random sediment layer over an elastic sea floor

The problem of coherent reflection of an acoustic plane wave from a seabed consisting of a randomly inhomogeneous sediment layer overlying a uniform elastic sea floor is considered in this analysis. The random perturbation in the sediment layer is attributable to the sound-speed variations, resulting in volume scattering due to medium inhomogeneities. An approach based upon perturbation theory, combining with a derived Green's function for a slab bounded above and below, respectively, by a fluid and an elastic half-space, is employed to obtain an analytic solution for the coherent field in the sediment layer. A linear system is then constructed to facilitate the computation of the coherent reflection field. The results of the coherent reflection coefficient for various sediment randomness, frequency, sediment thickness, and sea floor elasticity have been numerically generated and analyzed. It is found that the higher/larger the randomness, frequency, thickness, and shear-wave speed, the lower is the coherent reflection. Physical interpretations for the characteristics of the various results are provided.     

Towards a market-oriented management model for straddling fish stocks

Management of straddling fish stocks has been noted for its political complexity. Negotiations frequently falter as each party seeks to focus upon their own individual and shorter-term goals than the collective interest of the sector. Entrenched positions are often only deepened as new entrants participate to establish their own claims to any emergent share of resource. Unsurprisingly, deadlocks are common and typically compromises are reached only after the real period of biological then economic crisis has passed. Examples to illustrate this tendency can be found in most of the world's oceans and is writ large within the current impasse over blue whiting (Micromesistius poutassou) in the North Atlantic. The development of this fishery is discussed and it is shown that despite the scope to add value to the resource base through a pattern of exploitation focussed more upon human consumption than fish meal and oil, there seems little incentive to extricate participants from the cycle of demise that has engulfed negotiations so far.