Understanding Otter Trawls: Design, Function, and Sustainable Fishing Practices

Otter trawls are a primary method used in commercial fishing to catch bottom-dwelling fish such as cod, haddock, and flounder. These large, cone-shaped nets are towed behind fishing boats, skimming along or just above the seabed. The design of the otter trawl is specialized to maximize efficiency while targeting specific fish species.

The mouth of the net is designed to stay open while it is being towed. This is achieved by attaching floats to the top of the net and weights to the bottom. These components create a vertical opening, ensuring the net remains open as it moves through the water. Horizontally, the net is kept open by “doors,” which are large rectangular wooden frames attached to the towing lines on either side of the net’s mouth. These doors spread the net wide, increasing the area it can cover and allowing for a more effective capture of fish.

The far end of the otter trawl, known as the "cod end," is constructed with a mesh size that is small enough to retain fish of edible size while allowing smaller, juvenile fish to escape. This design is critical for promoting sustainable fishing practices, as it helps prevent overfishing of young fish that have not yet reached maturity.

After a period of towing, the net is hauled back to the boat. The cod end is then secured with a strap and lifted out of the water. A specialized mechanism allows the bottom end of the net to open, releasing the fish onto the deck. This efficient process minimizes handling time, reducing stress on the catch and ensuring the freshness of the fish for market.

Recent advances in trawl design and technology have focused on improving selectivity and reducing bycatch, further supporting sustainable fishing efforts. Additionally, ongoing research aims to minimize the environmental impact of trawling on seafloor habitats, balancing the demands of commercial fishing with the need for conservation.
Understanding Otter Trawls: Design, Function, and Sustainable Fishing Practices

Longline Fishing for Halibut

Longline fishing is a widely used technique to catch halibut, and sometimes cod and haddock, due to its efficiency and effectiveness. The method involves a heavy central line, known as the mainline, to which short lines or "gangings" are attached at right angles every few feet. Each ganging terminates in a barbed hook, which is baited to attract the fish.

To deploy the longline, an anchored line with a float and flag is fixed to each end of the mainline. The anchor ensures the gear stays on the ocean floor, while the flag, floating above the surface, marks the gear's position. The process begins by throwing the float and anchor overboard, followed by the mainline with its baited hooks, allowing it to sink to the seabed. The second float and anchor are then deployed, completing the setup.

The longline is left in place for several hours, allowing time for halibut, cod, and haddock to take the bait. After this period, the retrieval process starts by hauling in the float and anchor at one end. The mainline is then pulled into the boat, either manually or with the help of a rotating block or cylinder, especially for larger halibut.

As fish are pulled up, they are either flung onto the deck or removed from the hooks by hand, sometimes using a "gaff" – a large, unbarbed hook with a short handle. The line, now devoid of fish, is coiled into tubs for easy re-baiting and redeployment.

Longline fishing can cover extensive distances, often over a mile, making it highly productive. Recent advancements in gear technology and sustainable fishing practices have further enhanced the efficiency of longline fishing. The use of circle hooks, which reduce bycatch, and the implementation of GPS tracking for gear positioning have been significant improvements.

Moreover, regulations and quotas have been established to ensure the sustainability of halibut populations. Fishermen are required to report catches and adhere to strict guidelines to prevent overfishing. This balance between efficiency and conservation is crucial for maintaining healthy fish stocks and the long-term viability of the fishing industry.

In conclusion, longline fishing remains a vital method for catching halibut, cod, and haddock, combining traditional techniques with modern innovations to maximize efficiency and sustainability.
Longline Fishing for Halibut

Fishing of mackerel

Mackerel are small members of the tuna family, and are great fish on a fly rod. Because most mackerel have small mouths and teeth, they prefer smaller baitfish, which makes them the perfect fly rod fish.

Mackerel may be taken in pound traps or with gill nets, but by far the greatest quantities are taken with purse seines.

The principle of purse seining is to surround fish shoals by large net that can be closed so that the fish cannot escape. When the net is hauled back, the fish will become concentrated in a bag ready for brailing or pumping onboard.

If the boat is to remand out of port after the fish caught they are held in ice in the round, uneviscerated state.
Fishing of mackerel

Frozen tuna aboard the boat

Most tuna fish fishing boats make trips lasting for several months and for this reason, the fish are usually frozen aboard the boat.

The freezing process depends on the type of tuna. For bluefin tuna as an example, fisherman first cut the tail and gills, then gut bled and freeze it t -65 C for 35horus before placing them in to the fish hold at -60 C.

Normally in freezing, the whole fish are cooled in large well with refrigerated sweater circulated through it at 28 F (-2.2 C). Once the fish are cook led, the refrigerated seawater is pumped out of the well, and it is replaced with refrigerated bone at 10 F (-12.2 C) or lower.

When the fish are frozen, the brine is pump out of the well, and the fish are kept frozen in the dry well by circulating mechanically refrigerated air.

In one system brine is sprayed on refrigerated pipe coils located in the hold of the vessels until a coating of ice one foot thick or more is frozen. The compartment is then filled with fish and is flooded with brine. Accumulated ice provides refrigeration capacity needed to chill the brine and freeze the fish.

They remain there until the boat arrives at port.
Frozen tuna aboard the boat

Fishing tuna

At one time, fishing for tuna was carried out exclusively with pole lines. The pole lines are the traditional method and a cotton line with a barbless small fish-shaped hook attached to it is used.

Live bait is carried in a big tank on deck and these small fish are thrown overboard to attract schools of tuna when on the fishing grounds. Once tuna begin to strike, the crew starts fishing with poles and lines using a feather lure that contains a barbless hook.

Today tuna are mainly caught with purse seines which, due to the size of the fish, are made with heavy twine.

Catching tuna with purse seines is the most efficient method currently available. The catches of tunas by purse seines have increased rapidly since the early 1980s and large part of this increase has been due to increased used of fish –aggregating devices.

Some tuna may still be taken with pole lines and some with troll lines. In the Pacific, about 70 percent of the catch of principle market tuna is taken by purse seiners, 10 percent by pole and line and 8 percent by long-lines. In the Indian Ocean, these values are 45, 15 and 20 percent.
Fishing tuna

The Resources

The Resources
Around five sixths of the surface of our planet is covered with water. This vast area represents a giant volume in which around 20,000 species live and multiply.

Since antiquity fishing and seafood consumption has played an important role in coastal regions.

In contrast to other maritime deep water resources seafood undergoes a continuous biological renewal and recycling. Only human interference by overfishing pollution of the environment can put an end to this eternal biological circle.

Under the pressure of big demand many valuable species of marine fish and invertebrates are now being produced under controlled conditions in aquaculture.

Fish are highly efficient in converting food into animal proteins. For every 1.5 kg of feed they gain 1 kg of body weight. This equal poultry converting feed protein into body protein.

Generally this conversation rate is higher than in slaughter animals.

The labor productivity is high since a well managed catfish farm can yield about 5 ton of fish per man year of labor from 1 acre of earthen ponds.

This compares favorably with industrial beef farming.

The steady increase of industrial fish farming shows in some countries great potentials. Catfish, carp, trout, tuna and salmon are harvested in aquacultures. Fish species with fer bones, white meat and a mild flavor are attractive to the consumer.

It may be assured that industrial fish farming will gain further prioress and development though organized research including genetic engineering.
The Resources

Fly Fishing

Fly Fishing
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The Rod
In fly fishing a fly fisherman's tackle will comprise of a rod, reel, line, leader and a variety of artificial flies to tempt that illusive fish. The purpose of this tackle is to gently yet accurately place the artificial fly or lure on the water with minimum disturbance. To achieve this result, fly fishing tackle utilizes a uniquely manufacture tapered line with an engineered light weight rod. Traditionally trout fishing and salmon fishing fly rods were manufactured out of bamboo cane with the hexagonal split cane rod being the mostly widely used from 1900 to the 1950's. From 1950 onwards the glass fiber rod started to dominate due to the lower manufacturing costs. In the late 1970's carbon fiber was invented and the weight of fly rod's plummeted, this made line weight a critical factor in the performance of the rod.

Throughout the world the trout fly rods vary quite a bit although they will usually comprise of two or three sections which can be dismantled and stored safely in a rod tube. Trout and Salmon Fly rods are said to have a tip action or a through action. Tip Action - This refers to the tip of the fly fishing rod being worked to about halfway through its length with the lower end closest to the reel doing minimal work.

Through Action - In contrast to the tip action fly fishing rod, the through action fly fishing rod will work through its entire length. The best way to find out which fly fishing rod suits you best is to go to your local retailers or trout fishing retail event where you can try the different fly fishing rods with line and leaders to determine which best suits your style of casting. The type of trout fishing water together with the species of fish being sought impacts on the required length of a rod. For example, a fisherman trying to tempt a wily Salmon will usually use a rod of between 12 and 14 feet. A lake fisherman looking for a crafty trout will usually use a rod of some 9 feet in length. The same angler if fishing a small stream could use a rod as small as 6 feet in length. Obviously the length of a rod impacts greatly on the weight of the rod. Long length Salmon rods will tend to be close to 1 lb in weight while the smaller stream rods may only way a couple of ounces. The average weight of a lake rod will be in the region of 4-5 ounces or perhaps as low as 1 ¾ ounces for the higher end of the market rods.

When using a Salmon fishing rod they are fished with both hands and the longer length allows for much greater control of the line. If you were attempt to use this kind of rod on a lake after a couple of hours you would begin to feel tired therefore, lake rods are generally much lighter allowing for longer fishing sessions.

Shorter rods are usually used on small streams for trout fishing where the cover of foliage restricts the cast somewhat. In addition to this, over shorter distances a small rod is a great deal more accurate. In summary then, choosing the correct fly rod is essential and what suits one person does not suit another's style. A fast action rod is harder for someone just starting out in fly fishing to use as the time between the forward cast and the back cast is much shorter. The longer salmon fishing rods weigh much more than the trout fly fishing rods. There are of course variations in the types of rods and the best way to find out which suits your style is to try casting.

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Long Lines Fishing

Long Lines Fishing
Long Lines are used to catch halibut and in some instance, cod and haddock. The long line has a comparatively heavy central line to which short lines or “gangings” are attached right angles to the main line and at distances of every few feet.

A barb hook, which is baited, is fasted to the end of each ganging. An anchored line carrying a float and flag is fixed to each end of the central line, the anchor holding the gear on the bottom and the flag, which rests above the water surface, serving to indicate them position of the gear. In setting the long line, the float and anchor at one end are thrown overboard, and the central line, with gangings and baited hooks, is run and allowed to sink to the bottom. The anchor and float at the other end of the line are then thrown overboard.

After the set has been allowed to lie for a period of several hours, the float and anchor at one end are taken in, and the line is pulled into the boat with (for halibut) or without the aid of a rotating block or cylinder. As the fish reach the boat they are flung onto the deck, or removed from the hook by hand with or without the aid of a “gaff” (or large unbarbed hook with a short handle). As the line, with fish remove, is brought into the boat, it is coiled into tubs so that the hooks can be baited without difficulty. Long lines may be set over a distance of one mile or more.
Long Lines Fishing