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Fishing Techniques
Tuna Fishing Techniques
Tunas are mid-water or surface-water species, and mostly
live in shoal. Some characteristics make only certain fishing
techniques possible. When the fish come in group, the number
of species caught at the same time is limited. The methods
of large scale tuna fishing have been developed constantly
due to the production cost factor. More and more fishery sectors
are putting very high investment in developing methods and
equipment in tuna catching areas. However, the concept of
responsible fisheries arose in early 1990s and brought about
a code of conduct for responsible fisheries agreed upon by
the international community in 1995. The tuna fisheries in
deep seas and coastal waters all over the world are now taken
into account. The developments aim at more responsible tuna
fishing practices for the sustainability of the tuna resource.
Tuna fish are highly migratory fish. This means catch opportunity
may last a short period of time like seasonal fisheries. An
effective catching method is using fish aggregating device
which may help in increasing catch opportunities, for both
large and small industries.
Many tuna fishing methods are developed and used in various
parts of the world. The selection of a specific fishing method
results from numerous factors such as how tunas group, fishing
areas,water depth, amount of investment and social conditions.
In most of the industrial operations, tunas are caught by
seining, drift netting, trapping, pole and lining, long lining
or trolling.
The fishing gear can cause hazards to sea mammals and birds
as well as to the safety of navigation. Therefore, FAO agreed
that the marking of fishing gear needs to be included in the
Collision Regulations. Solutions are presented as follows:
• Documents such as a licence of tuna catching.
• Recognize the fishing right regarding species and sizes
of tuna
• Use appropriate fishing gear to minimize waste, discards
and catch of non-target species/sizes
• Contribute to energy saving
• Reduce conflicts with vessels or fishermen using other
fishing gear
The equipment selection depends on tuna species and size.
With reference to the concept of fishing gear introduced above:
minimizing waste, discards and catch of non- target species,
the tuna fishery needs to consider the fishing gear the most
important issue.
Selectivity of the tuna fishing gear can be described below:
| Techniques |
Gear-related |
Non-technical |
|
Tuna purse seine |
• Seine design depth to accurately target,
erase of slipping of gear to reduce discards
• Mesh size |
• Water depth
• Fishing area
• Time/Season
• Vessel capacity
• Manpower skills |
|
Tuna driftnet/driftnetting |
• Mesh size and material
• Hanging ratio
• Gear Design
• Use of scaring devices |
• Choice of fishing area
• Time and season
• Distance from surface |
| Tuna lines/
Longlinning |
• Bait
type and size
• Hook size, type and spacing
• Bait used
• Setting Method |
• Choice
of fishing area
• Time/season
• Water Depth
• Temperature
• Manpower skill |
| Traps for
tuna/Trapping |
• Mesh
size and design
• Trap Design
• Leader net size
• Scaring devices |
• Location
of Gear
• Choice of time and season |
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Source : Tuna Conference 1997
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