Types of fishing methods
Although there are many methods of catching fish, they fall into three main groups:
1. Catching fish singly or in schools by use of nets or spears
2. Trapping fish in stationary gear, such as fish traps or set nets
3. Attracting fish to get caught on hooks by use of bait, artificial lures or other means such as light
Before you go fishing you must decide what is the best method to use. There are many factors to consider - especially if you are a commercial fisher. Factors include:
- where you are fishing
- what species you are fishing for
- the weather and sea conditions
- the cost of the boat, gear and fuel
- the market requirements
While there are many types of nets, all rely on the fish getting snared or caught in the net's mesh. Nets are typically long, narrow and flat, weighted at the bottom edge and supported at the top edge by floats.
The most common form of netting for recreational fishers is "set" netting. It is also used by commercial fishers to catch fish like flounder and butterfish.
The most commonly used lining methods are hand-lines and long-lines. Hand-lines are mainly used by recreational fishers, though they are sometimes used for commercial species, such as southern bluefin tuna.
Long-lines consist of a main line running parallel to the bottom, with baited short lines (snoods) attached at intervals. The line is anchored at each end and held at the surface by floats. Long-lines are used to catch high-quality, high-value fish such as snapper.
In trolling, baited hooks or lures are towed behind a boat and fish are pulled aboard when caught. This method is designed to target fast moving surface swimming fish such as tuna, marlin and kingfish.
Trawling is the most important commercial fishing method in New Zealand, especially for deepsea species. Trawling is used to catch a range of species, for example, orange roughy, hoki, ling, hake and squid. Recreational fishers are not permitted to use trawl nets.
Trawling involves one or two fishing vessels towing a large net. Most New Zealand trawlers are single, rather than pair trawlers. Nets are usually towed for two or three hours at a speed of three or four knots.
Nets of both bottom and mid-water trawling are held open by two "doors", which act as paravanes, or underwater kites.
Danish seining is used to encircle, herd and finally trap the fish. A net bag, similar in shape to a trawl bag is operated by a long, weighted rope fixed to each end. The two ropes are used to encircle the fish and also to haul the net in. They are usually operated on the bottom and are used to catch snapper and John dory.
Purse seining is used to catch surface dwelling species such as tuna, mackerels, kahawai and trevally. Aerial spotter planes are usually used to locate the intended catch. The purse seine net is laid in a circle around the school . The net is then "pursed", drawing the bottom closed and entrapping the fish. Purse seining cannot be used by recreational fishers.
Beach seining/drag netting
Beach seining or drag netting is normally carried out using a length of net and an additional length of warp (rope). The net and warp are laid out from, and back to, the shore and retrieved by hauling on to the shore. The net used is similar to that used for set-netting. Mullet, flatfish, snapper, trevally and crabs are caught this way.
Dredging is used to gather scallops and oysters. To gather scallops, the fishing vessel tows a rigid steel-framed dredge along the sea floor. With oysters, a heavier ring mesh is usually used.
Jigging is a method of catching squid by continuously lowering and retrieving lines from the fishing vessel. Fishing is generally done at night when squid are attracted by powerful lights on the vessel. Jigging is used in preference to trawling when high quality squid is required.
Rock lobsters and blue cod are caught in pots, usually made of a steel frame, covered with wire mesh. The pot is baited with fish and dropped from the boat on the end of a rope long enough to reach the bottom. The position of the pot is marked with floats so the pot can be easily recovered.
Some commercial and recreational fishers dive for paua, scallops and rock lobsters. Paua may only be taken by divers using snorkels, not scuba gear.
Today there is more than just luck involved in finding a good fishing spot, especially in commercial fishing. Electronic navigation equipment and sophisticated fish-finding equipment can place the fisher within a few metres of the best fishing areas.
On the bridge of a modern deepwater trawler there is millions of dollars worth of electronic equipment, including a colour echo sounder, a colour net recorder, a radar set and a satellite navigation system.
Colour echo sounder
The colour echo sounder/fish finder is used to find fish and display the depth and contours of the ocean floor. The information is shown on a colour screen.
It works through a pulse sent out by a transducer in the hull of the vessel. It strikes the seabed and is reflected back upwards where it is received by the same transducer. Fish also reflect the pulse - it is the air in their swim bladders which makes them visible to the echo sounder. Orange roughy, however, have oil in their swim bladders, and so don't show up very well.
This trace from an echo sounder shows possible schools of fish (darker areas).
Colour net recorder
This works along side the colour echo sounder. The screen gives specialised information on the net and the fish moving into it, using data from a small echo sounder attached to the net itself. Modern colour net recorders can also measure the width of the net, its fullness and even the temperature at the net mouth. Experienced skippers can tell not only how much fish, but also what kind of fish, they are catching.
High tech electronic gear such as this helps commercial fishers operate more efficiently.
Radar (radio detection and ranging)
Radar is used to detect objects on the surface up to 30 to 40 km away. Radar works in a similar way to sonar (used in the echo sounder ), except it works in air rather than water. Objects the radar identifies show up as "blips" on the screen.
Satellite navigation system
Skippers also use a satellite navigation system to determine the position of the vessel. A small screen displays the vessel's position - latitude and longitude - to within a few metres. Accurate measurements can only be made when satellites are above the observer's horizon. At other times the system uses "dead reckoning", based on the ship's course and speed.
Satellites are also increasingly being used at sea to obtain information about weather, sea surface temperature, wave height, wind patterns and the location of fish and other vessels.