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In the southeastern Pacific jack mackerel (Trachurus murphyi) is a heavily exploited pelagic species. Its presence in Chilean waters in autumn and winter is assumed to be mainly due to an inshore feeding migration. Predator-prey relationships are known to depend on the spatial and temporal scale of observation but can also be strongly affected by factors such as diel vertical migration. The objective of this work is to study the horizontal and vertical distribution spatial organisation and occupation of jack mackerel its prey and the spatial relationships. The hypothesis is examined according to which jack mackerel predation can lead to the local depletion of prey biomass. For this purpose use is made of data from three acoustic surveys from central Chile.

The development at the Admiralty Engineering Laboratory of a laboratory coolant test rig for the evaluation of corrosion inhibitors for water and antifreeze diesel engine coolants is described. Factors affecting the corrosion of cooling systems are first outlined then the components test specimens and test procedure of the rig are outlined. Objects of the testing included collaborative testing with other rig operators comparing various corrosion inhibitor formulations including proprietary formulations investigating leak-detecting additives to antifreeze solutions and investigating the corrosion of Kanigen phosphorus nickel alloy by phosphate inhibited antifreeze. Engine opearting experience shows that inhibitor depletion rates were mainly dependent on engine running time. NaMBT depletion rates are discussed. Points to consider when selecting inhibitors are outlined and the use of a deionizing unit in the cooling system eliminating the use of inhibitors is mentioned.

The morphological developmental and behavioural differences in the olfactory system of red sea bream from wild and cultured stocks are described A four-month market survey reveals that over 90% of Red Sea bream reared in captivity possess a deformed single nasal opening. It is shown that fish reared in captivity have no problems feeding on a pelleted diet but that their wild counterparts do not accept non-living food even under a long period of starvation. Differences in the olfactory system of wild and cultured fish are discussed especially with reference to the olfactory system and fish behaviour.

Choice of sampling method and survey period can have an important impact on the perception of the structure and dynamics of an ecological community. Usually sampling methods are standardized when several countries survey the same resources. However the Celtic Sea groundfish assemblage has been surveyed with different gears by France in autumn and by the UK in spring and autumn. Although the time-series are fairly short this situation offers the rare opportunity to study gear and season effects. An attempt is made to estimate the sampling bias associated with different survey designs by comparing the emergent pictures of the groundfish assemblage. A look is taken at materials and methods addressing surveys abundance estimates and community attributes. Results are considered covering global differences in abundance estimates differences in abundance estimates by species and community effects. Lastly there is discussion.

In fish farming feed waste results in increased production costs to the industry and has negative environmental impacts. A computerised system called FFM (fish feeding monitor) is presented. This was developed to monitor assess and optimise the fish feeding process. It consists of digital scanning sonar and current meter. The system can detect and monitor quantity and direction of wasted food pellets and also predict the trajectory of pellets through the water column. Feedback information is provided to the feeding operator together with guidance on how to redirect or modify the feeding process in order to minimise feed waste. The system performed well and successfully enumerated individual pellets under the aquaculture cages. The presence of high concentrations of non-farmed fish outside the cages resulted in the degradation of the ability to successfully detect and count waste pellets. Refinement of techniques and detection and filtering algorithms is necessary to consistently detect waste pellets in the presence of unwanted fish echos.

Int symp held 27 August - 2 September 1974 Papers are Discussion of title as above The Mediterranean Regional problems with sea outfall disposal of sewage on the coasts of the United States Some problems in Hong Kong Some problems in the Baltic Bacterial indicators of sewage pollution Human enteric viruses and bacteriophages of sewage pollution The development of criteria for recreational waters Evaluation of shellfish quality by indicators of tros sewage pollution Epidemiological aspects of microbial standards for bathing beaches The case for microbial standards for bathing beaches The case against microbial standards for bathing beaches Heavy metals in the marine environment Persistent organic residues Effects of nutrient enrichment from sewage from the sea The significance of surface pollution in coastal waters Effluent quality of chlorinated sewage discharged from sea outfalls The case for treatment The case against treatment In situ methods for determination of microbial disappearance in sea water

In this paper there is discussion of the character of the Hudson River's discharge into the coastal ocean based on observations and modeling efforts during the Lagrangian Transport and Transformation Experiment (LaTTE). The main aim of LaTTE was to elucidate the transport and transformation of dissolved and suspended material as it exits New York Harbor onto the continental shelf of the Middle Atlantic Bight so it was imperative to characterize freshwater transport pathways. After some introductory information a look is taken at LaTTE field observations. This is followed by consideration of numerical modeling of the plume.

Whale displacement by acoustic "pollution" has been difficult to document as noise effects can rarely be separated from other stimuli. This study presents data collected from January 1985 to December 2000 by two independent research projects on the daily presence of killer whales in both western Johnstone Strait through Blackfish Sound and the waters of the adjacent Broughton Archipelago. Throughout the 15-year period the Johnstone Strait area was not exposed to acoustic harassment devices whereas the Broughton Archipelago area was exposed to them for five years. A look is taken at materials and methods followed by results and discussion.

Int Conf held in London on 22-23 February 1989 Papers are Deepwater technology-past present and future Deepwater hydrocarbon prospectivity-a global view Development of seismic profiling remotely operated coring and shallow drilling for deepwater areas Deepwater drilling-implications for exploration and the transition to production A designer's view of extended well testing and deepwater production An operator's view of extended well testing and deepwater production-experience with Petrojarl 1 High performance composites for deepwater risers Branch barrier-a new subsea valve Experience with deepwater installations Integrated intervention and subsea production systems The future of ROV technology Poseidon multiphase pumping production systems-industrial applications Motion characteristics of deepwater FPVs and the design implications for associated subsea systems

Following investigations into drift characteristics, it was discovered that results obtained for VLCC's were not necessarily indicative of the behaviour of smaller vessels. Computer programs were developed by the National Maritime Institute (NMI) to assess drift behaviour of these ships, which required validation. Some free model experiments were carried out to investigate wave drift forces and also to determine the accuracy of results obtained. OCMIF and NMI worked together on the project to estimate the effects of wind, waves and current upon the drift track, heading and speed of such vessels under a variety of conditions. The experiments and results are presented in this publication.

The Spar is a deep draft cylindrical vessel designed to produce offshore oil fields in deep water ranging from 1000 ft to greater than 7500 ft. Two Spars are planned to be installed in the Gulf of Mexico in 1996 and 1998. One will be a production workover Spar which will be moored over a group of six predrillled wells. Additional wells will be drilled later by a semisubmersible while the Spar is on location producing. The second Spar is in the initial design stage and will support a drilling rig full production facilities and have slots for 20 wells. This will also be capable of drilling and producing simultaneously. A third drilling production and oil storage Spar which might be applicable for Brazil waters is also discussed. The main advantages of Spars include: simple low-cost construction; favourable motion characteristics combined with a tight watch circle; surface trees and steel risers that are shielded from waves and currents to a depth of 650 ft; insensitivities to deck load and water depth; easy relocation; and storage of oil in the hull below hard tanks.

Two Gulf of Mexico spars planned for installation in deep water are described. The first is a production workover spar operated by Oryx Energy in partnership with Consolidated Natural Gas on the Neptune Field. The second is a drilling and production spar operating in 3000 feet of water. A drilling production and storage spar designed for North Atlantic and Norwegian Sea operations is also described. The well systems mooring and installation methods are highlighted. The principal characteristics of the spar's motion are discussed and the results of computed extreme values are summarised for three design conditions including a 100-year storm and a loop current.

Advances in scientific drilling over the last decade have enabled progressively better recovery and greater confidence in the fidelity and coherence of recovered sections. The resulting interpretations and analyses have enhanced the high-resolution short- and long-term records of changes in the Earth system. The adaptation of riser drilling technology for scientific ocean drilling purposes on board the D/V Chikyu represents a giant step forward for the scientific ocean drilling community. In this article an attempt is made to enumerate the technological and operational means by which core recovery core preservation borehole stability geophysical measurement and borehole monitoring operations are enhanced using riser drilling.

A linear integrated beam stiffness model is discussed which incorporates the geometric stiffness effect of buoyancy-gravity loading in a consistent manner. The versatility of the method is successfully demonstrated by applying it to two distinct cases namely to an offshore guyed tower problem in which the elastic effects are primary and the buoyancy-gravity effects secondary and to an articulated column example in which the buoyancy-gravity effects are primary. For systems such as semisubmersibles and articulated columns the integrated model obviates the need to carry out a two step analysis namely rigid body motion analysis first and stress analysis subsequently as is often done. It is expected that the tangent stiffness formulation based on the proposed geometric stiffness terms will enhance nonlinear analysis of buoyant elastic systems.

The aim of this paper is to present experimental results on the dynamic compression of rigid and flexible risers obtained in towing-tank tests. Two small-scale models have been built one emulating the dynamic behaviour of a steel catenary riser (SCR) and the other corresponding to a much more flexible case. Uniform circular motion has been applied to the top of the line representing the floating system oscillation. Four different amplitudes have been considered each one of them with five different frequencies. The influence of current velocity has also been evaluated. Tension has been measured at the top. In this work the small-scale models and experimental set-up are described and some comprehensive results are presented and discussed. In a companion paper comparisons between theoretical (numerical and analytical) and experimental results are presented.

Results gained in three series of experiments using (a) bead-on-plate specimens in low-carbon steel (b) low-carbon steel specimens with several kinds of surface discontinuities and (c) specimens taken from butt welds in high-strength steels are described. The main aim of these studies is to look into the possibilities of using a system consisting of a scanning laser microscope (SLM) and a portable video microscope (PVM) for early detection of fatigue crack initiation in weldments.

The effects of chlorination treatment of ballast water are considered. The reasons for selecting this means of ballast water treatment are outlined. Sodium hypochlorite was selected as the biocide. The results prove that chlorination treatment is effective in killing organisms and bacteria in seawater. They also show that available chlorine with a concentration of 20 m/L is able to kill almost all the bacteria in the seawater. However the concentrations of available chlorine for photoplankton zooplankton and benthic invertebrate's treatment vary depending on the species and the density ranging from 5 mg/L to 100 mg/L. The exposure duration is not considered. The test design is described. Test results are presented. Conclusions are drawn and recommendations are made.

The introduction of electro-hydraulic controls on proven BOP systems has affected the operator's ability to efficiently work with a remote complex item of seabed equipment. Two newly proposed concepts are introduced: firstly the BOPAPS (BOP Active Position System); and secondly BOPITS (a BOP Intelligent Test System). The BOPAPS concept is a means of registering the real time position of the BOP functions and this relates their exact positions to the surface user. It is discussed how BOPITS could improve testing operations and reduce the time taken. In addition tests can be speedily and positively carried out with real time feedback. An important benefit of this approach is the improvement in assessing any poor test and being able to make a reliable diagnosis of the problem possibly saving the unnecessary tripping of a BOP. Also discussed is the combination of the BOPAPS and BOPITS concepts and how they can improve operations reduce risk and save time.

British Petroleum and the British National Oil Corporation's first purpose built semi-submersible emergency and support vessel Ioiair with its two pontoons supporting a platform superstructure on 6 vertical columns is described. The paramount importance of the security and integrity of both power and control systems is considered and primary generation and distribution is discussed covering the HT power system design system insullation propulsion machinery considerations high voltage transformers and cable and HT switchboard. System interactions including protection system stability fault analysis and short circuit calculations are detailed. The design of the 415 volt distribution galley and laundry earth system grouped starter boards electro-boiler and the lighting are described. Operational features e.g. security dynamic positioning fault finding aids and the formal procedure required for safe working the HT system are outlined.

The development of electrical power generation systems on offshore oil and gas installations over the last thirty years is outlined. The advantages offered by ac interconnection of platforms is examined and the technical difficulties that this might introduce are discussed. Long ac cables introduce a significant capacitance to the system lowering the natural frequency so that under some operating conditions it may coincide with a frequency which is characteristic of drive converters. Active filters may have a role to play in future interconnected systems. A comparison is made between ac and dc interconnectors. Medium voltage direct current (MVDC) transmission may be a suitable method of electrically linking offshore installations. Computer simulations are used to assess the usefulness of this new technology.