The observer is required to correctly identify the type of gear a vessel may use and be able to comment on the characteristics and dimensions of its components. (See Glossary, Appendix A). While the vast majority of the observer's work will be with otter trawls, he will periodically be deployed on vessels using longline or seines or other gear types. The following sections will hopefully aid the observer in distinguishing the various gear types and their components. Observers are encouraged to expand their knowledge of fishing gears by reading relevant publications and by focusing their attention on particular aspects of gear behaviour during trips.
The bottom trawl (figure 28) is the gear most frequently encountered by observers. First used in the last century, these large mobile nets have since become widely used and one of the most favoured pieces of equipment.
Shaped something like a huge funnel, these nets are towed through the water at speeds generally ranging from three to five knots. These trawls were first used by vessels that would set and haul them over the side, but in the early 1950's larger vessels were developed with the capacity to shoot and haul the trawl through a stern ramp. This gear is still used by vessels ranging in size from the smallest 15 meter inshore vessels to 4000 ton monsters, working on fishing grounds all over the world.
During a tow, the trawl is generally kept open through the use of large metal plates known as doors which provide a spreading action. In bottom trawls these are generally oval shaped, unlike in mid-water trawls where rectangular doors are used. These oval doors plus the heavily protected footrope which rides on the seabed, serve as the main distinctions between bottom trawls and pelagic trawls. The footrope is often rigged with heavy steel rollers or large metal chains and will often acquire a “shiny” appearance from constant riding on the bottom. These trawls are used to catch cod, haddock, pollock, silver hake and the flounder species in Canadian waters.
The midwater, or pelagic trawl, was first employed in the early 1940's as a method to pursue both pelagic and semi-pelagic species. This gear really became prominent in Canadian waters with increased markets for redfish in the 1960's and has since become a valuable tool in catching squid.
Midwater trawls are distinguished from bottom trawls by the lack of rollers on the footrope, large meshes in the square and wings (mouth of the trawl) and rectangular doors. They can be of much greater volume than conventional bottom trawls, and often appear to be of much more fragile construction than bottom trawls. The gear functions, as the name suggests, in the middle of the water column (generally 10–20 metres off bottom) and requires careful vessel speed control to avoid damaging the gear on the seabed. The operating principle in midwater trawling is that the gear will rise with increases in speed but drop as speed is decreased. This lightweight gear is extremely responsive, and can be raised or lowered to take advantage of concentrations of fish seen on echo sounding equipment.
fig. 28 Bottom Trawl
fig. 29 Off-Bottom Chain trawl
This gear is a hybrid of midwater and bottom trawl (figure 29). Rectangular doors are used, but the gear is rigged for contact with the bottom. The trawls are designed to ride 1–3 metres off the bottom employing a series of chains or bobbins hanging from the main footrope to drag along the bottom. In off-bottom chain gear, the chains dangle freely whereas in off-bottom bobbin gear the bobbins are joined to form a “dummy footrope”. If either of these gears are encountered, extra care should be taken to record the weight and dimensions of the chains or bobbins.
These are, as the name implies, long lines that are used to suspend a series of baited hooks. Longlines may be adapted for either swordfish or tuna in the upper reaches or the middle of the water column, or demersal species such as cod or haddock on the ocean floor.
Longlines generally consist of a continuous section of rope or wire that is periodically marked using buoys or even radio markers and lights. The hooks are attached to swivels on ropes known as gangions, which in turn are attached to the longline. Longline gear can extend for over 20 nautical miles and this is often a highly automated operation.
The purse seiner is the most common type of seiner. This type of vessel employes huge sections of net that have floats along the top edge and weights along the bottom, and are set in the water in a circle using a second smaller boat known as a skiff. Once the fish are encircled, the bottom is pulled together to close the net around the fish (a series of rings on the bottom of the net make this possible). When the gear is closed, it can be pulled closer to the surface, allowing the fish to be pumped aboard the main vessel.
