| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1998: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Research Abstract |
The world population expansion in the 21^<st> Century will require the further sustainable development of marine fisheries industry from the view point of the global awareness of environmental conservation. The fishing technology has now the great target how to establish the new concepts for the research and development activities, not only for increasing the catch as the traditional goal, but also for improving the capture process to minimize the fishing impact to the environment and bio-diversity.
The comprehensive approach for developing the sustainable fisheries, the following research activities were completed, both with the comparative fishing and laboratory experiments.
Fishing gear selectivity : Trawl net, gill net, pot and trap are the main target of the selectivity studies for species and sizes with mesh shape and size modifications, escape vent and some other devices of BEDs/BRDs, mentioned below. The evaluation method for the selectivity performance is urgently required in ac
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oordance with the practical goals of resource management.
Conservation technology : In case of the trawl gear, the by-catch/discards issue is the most urgent target to be solved. For the coastal trawl, some trials with the BRDs of inside sorting grid or the sorting panel at the net mouth have been challenged. Concerning set-net and purse seine gears, the escape window panel with the use of herding/attracting stimuli will be the next target for excluding non-target species and sizes by separating from the target catch.
Underwater observations of the capture process : The tools such as the video, fish finder, sonar and bio-telemetry are now in popular use for understanding animal behavior at sea, for the trawl, set-net and purse seine etc. A comprehensive approach to employ several tools will be required as the next step to see all details of the capture process in quantity and quality in both time and space scales.
Fish Behavior and Physiology : Sensory physiology and muscle physiology can be good tools to understand the stimuli-response system in the capture process of the fishing gears. In relation to this approach, the heart beat rate is employed as the index of stimuli recognition towards sound, light, strobe light etc. The stress and survival of fish after escape is also a big target in response with the on-going selectivity works. This can be one of the tools to understand the fishing impact on the target species and bio-diversity in the fishing ground.
Low investment sustainable technology : The goal of the research and development activities in the field of fishing technology is to establish the environmentally friendly harvesting systems. In this point, the effect of fishing should be clearly understood in each fishing gear in corresponding fishing ground. The stress and survival of fish after escape is also the big target in response with the on-going selectivity works. This can be one of the tool to understand the effect of fishing to the target species and bio-diversity in the fishing ground. Another point is the cost efficiency in fishing technology to seek the low-investment sustainable technology in various fisheries. Some case studies in the field of fishing technology and fish behavior will be summarized here.
a) Effect of Fishing-case study in coral reef fisheries
The full understanding of the capture process can give the idea how the fishing operation affect the environment and fish resources, and then how to minimize these fishing impacts through the technological solutions. The effects of fishing have been discussed mainly for the trawl fisheries, by Craik et al (1990), or very recently from the view points of the physical impact of the towed gears in ICES Working Group on Fish Behavior and Fishing Technology (1999) and
Conservation Biology meeting (1998). The wide range of impacts should be clearly understood at first, and challenged towards the solution to minimize them. They can be classified into 3 categories as the fishing ground especially for the benthic disturbance, bio-diversity including the by-catch/discards of unwanted species, and target resources for the over-fishing and juvenile by-catch/discards. The ghost fishing, stress and survival of fish after escape or being discarded can be also included for both the target and unwanted catch species. Coral reefs are well recognized as the important buffer for global warming issues, and as the nursery area for the diversified ecosystem in the tropical zone, where the destructive fishing practices such as the explosives and toxins have been criticized and prohibited Here, the environmentally friendly fishing technology for the coral reef area should be suggested to alter the conventional destructive practices.
b) Stress and survival of fish after escape
Survival and stress of fish after escaping the gear can be the cue to establish the sustainable fishing technology, together with the technological improvement of size/species selectivity of the fishing gear. In case of the increase of the unaccounted mortality due to the selectivity function of the gear, the higher selectivity may just result into the higher mortality for escapees. Case study for the sweeping trammel net will be summarized here. The sweeping trammel net is a type of entangling gear with the sweeping procedure for encircling the sandy fishing ground targeting the Japanese whiting Sillago japonica. Though the mesh selectivity studies, the survival and stress of captured fish were investigated for identifying the escapees fate due to the gear impact during the capture process, by the following protocol ;
1) Survival experiment by observing the mortality rate with time elapsed in the keeping tank, and
2) Stress measurement by means of Plasma Cortisol level according to the time elapsed toward the death/recovery. Less
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