The effect of autotrawl systems on the performance of a survey trawl

Three aspects of a survey bottom trawl performance—1) trawl geometry (i.e., net spread, door spread, and headrope height); 2) footrope distance off-bottom; and 3) bridle distance off-bottom—were compared among hauls by using either of two autotrawl systems (equal tension and net symmetry) and hauls conducted with towing cables of equal length and locked winches. The effects of environmental conditions, vessel heave, crabbing (i.e., the difference between vessel heading and actual vessel course over ground), and bottom current on trawl performance with three trawling modes were investigated. Means and standard deviations of trawl geometry measures were not significantly different between autotrawl and locked-winch systems. Bottom trawls performed better with either autotrawl system as compared to trawling with locked winches by reducing the variance and increasing the symmetry of the footrope contact with the bottom. The equal tension autotrawl system was most effective in counteracting effects of environmental conditions on footrope bottom contact. Footrope bottom contact was most inf luenced by environmental conditions during tows with locked winches. Both of the autotrawl systems also reduced the variance and increased the symmetry of bridle bottom contact. Autotrawl systems proved to be effective in decreasing the effects of environmental factors on some aspects of trawl performance and, as a result, have the potential to reduce among-haul variance in catchability of survey trawls. Therefore, by incorporating an autotrawl system into standard survey procedures, precision of survey estimates of relative abundance

Integration of crustacean aquaculture with coastal rice farming in Vietnam

Some examples are given of integration of crustacean aquaculture into coastal rice farming in Vietnam. Freshwater prawn (Macrobrachium rosenbergii ) and marine shrimp culture integrated with coastal rice farming and crab (Scylla serrata ) culture in backyard ponds and ricefields are described.

Restricted Access vs. Open Access Methods of Management: Toward More Effective Regulation of Fishing Effort

This paper gives an overview of the economic rationale for limited entry as a method of fishery management and discusses general advantages and disadvantages of license limitation and catch rights as the two primary methods of restricting access to marine fisheries. Traditional open-access methods of regulation (e.g., gear restrictions, size limits, trip limits, quotas, and closures) can be temporarily effective in protecting fish populations, but they generally fail to provide lasting biological or economic benefits to fishermen because they do not restrict access to the fishery. The general result of regulation with unrestricted access to a fishery is additional and more costly and complex regulations as competition increases for dwindling fishery resources. Regulation that restricts access to a fishery in conjunction with selected traditional methods of regulation would encourage efficient resource usage and minimize the need for future regulatory adjustments, provided that enforcement and monitoring costs are not too great. In theory, catch rights are superior to license limitation as a means of restricting access to a fishery.

1987 ecosystem view of management research in the Myakka River: review of Phase I and Phase II reports

This memorandum has four parts. The first is a review and partial synthesis of Phase 1 and Phase 2 Reports by Dr. Ernest Estevez of the Mote Marine Laboratory to the Board of County Commissioners of Sarasota County, Florida. The review and synthesis emphasizes identification of the most important aspects of the structure of the Myakka system in terms of forcing functions, biological components, and major energy flows. In this context, the dominant primary producers, dominant fish species and food habits, and major environmental variables were of articular interest. A major focus of the review and synthesis was on the river zonations provided in the report and based on salinity and various biological indicators. The second part of this memorandum is a review of a draft report by Mote Marine Laboratory on evaluation of potential water quality impacts on the Myakka River from proposed activities in the watershed. This Memorandum's third part is a review of resource-management related ecosystem models in the context of possible future models of the Myakka River Ecosystem. The final part of this memorandum is proposed future work as an extension of the initial reports.

Near and distant connection of atmospheric systems to ocean temperature change in the coastal California Current region

In studying hydrosphere, atmosphere, and biosphere interactions, it is useful to focus on specific subsystem processes and energy exchanges (forcing). Since subsystem scales range over ten orders of magnitude, it may be difficult to focus research on scales that will yield useful results in terms of establishing causal and predictive connections between more easily and less easily observed subsystems. In an effort to find pertinent scales, we have begun empirical investigations into relationships between atmospheric, oceanic, and biological systems having spatial scales exceeding 10^3 kilometers and temporal scales of six months or more.

The four seam trawl nets operated off Cochin: an analysis of the design aspects: the integration of the various parts of trawl

A study has been made of 22 different designs of four seam trawls operated at Cochin for shrimp trawling. Formulae for the relations between the different parts of the nets have been derived.

Prospects of integration of aquaculture with animal husbandry and land crop culture in Tripura State

Tripura is a densely populated small state with meagre water resources. 47.51% of the population is constituted by socio-economically backward, illiterate, orthodox, tribal and scheduled castes. Some of them are nomad and a majority of the rest of the population is refugees from Bangladesh, but almost 100% is fish eater. Settlement of tribes in villages, provision of nutritious food and employment therefore calls for proper utilization of every resource they have. The State is poor in water resources but recently has created 21,636.23 ha of new water area. Tripura is rich in pig population, besides poultry birds. Paddy is the main crop cultivated in arable lands. An integration of livestock raising and land based agriculture with pisciculture practices around mini barrages will help in solving the problems to a great extent. The paper is an attempt to outline the prospects of integration of aquaculture with animal husbandry and land based crop culture in Tripura State.

Reliability and need for standardisation of electrical systems in small wooden fishing vessels

The working condition and atmosphere in a wooden fishing vessel are generally most injurious to the electrical systems. Therefore great care has to be taken in designing electrical systems for small c1afts. This paper deals with the difficult operating conditions and standardisation of electrical systems as applicable to small fishing vessels.

Monitoring and evaluation of management effectiveness for adaptive management of MPAs in Indonesia's BOBLME area

Subcomponent 3.2 Marine Protected Areas in the conservation of regional fish stocks "Provision of Services Relating to the Assessment and Planning of Effective Management of two MPAs in Sumatra Coast, Indonesia". Assessments of management effectiveness of two Marine Protected Areas (MPAs) in Pulau Pieh National Park and Sabang District, Sumatra, were conducted through two separate workshops. Recommendations were made and future needs identified.