What Fish Do Trawlers Catch?

Key Takeaways:

Trawlers use large nets called trawls to catch fish and shellfish species that live on or near the seafloor, like cod, sole, and rockfish.
They also catch large amounts of midwater fish species such as pollock, anchovies, herring, and mackerel.
The specific catch depends on the type of trawl net used, fishing location, and target species.
Bottom trawls catch groundfish while midwater trawls catch pelagic fish in the upper water column.
Trawlers play a major role in the global commercial fishing industry but can also damage habitats and produce bycatch.

Introduction

Commercial fishing vessels known as trawlers are responsible for catching a significant portion of the world's fish supply using a method called trawling. But what specific types of fish do these large-scale fishing boats catch and bring to market? This comprehensive article will examine the key fish species targeted and caught by trawlers around the world.

Understanding the target catch of trawlers is important for characterizing the impacts and sustainability of commercial trawl fisheries. Trawlers employ large nets called trawls to catch fish, but their catch can vary based on the specific type of trawling method used and geographic fishing location. By evaluating the diversity of fish caught by these vessels, we can better understand the role of trawlers in the global seafood industry and the implications for fish populations.

This article will provide an extensive overview of the major fish and shellfish species caught by trawlers. It will analyze the key differences between bottom trawling and midwater trawling methods and the types of catch associated with each. The article will also discuss how factors like trawl net design, fishing practices, and regional regulations influence what species are ultimately caught. Whether you are a seafood supplier, fisheries manager, or conscious consumer, this comprehensive guide will illuminate precisely what fish end up in trawlers' nets.

Typical Fish Species Caught by Trawlers

Bottom Trawlers Target Groundfish

Bottom trawling is a fishing technique where nets are dragged along the seafloor to capture fish living near the bottom. Bottom trawlers specifically target groundfish species that dwell on or near the ocean bottom. Some of the major types of groundfish caught by bottom trawlers include:

Cod – Atlantic cod is one of the most iconic and heavily fished groundfish species. Bottom trawls account for the majority of Atlantic cod catches. Pacific cod is also caught by trawlers in the northern Pacific ocean.
Sole – Common sole and lemon sole are caught by bottom trawlers in the Atlantic ocean. Petrale sole, Dover sole, and rex sole are among the commercially important sole species caught by trawlers in the Pacific.
Flounder – Summer flounder, winter flounder, yellowtail flounder are targeted by trawlers on the U.S. east coast and Gulf of Mexico. Olive flounder, starry flounder, and arrowtooth flounder are caught by trawlers in the Pacific.
Haddock – Another iconic groundfish species, haddock is a popular trawl fishery in the North Atlantic ocean. They are caught by trawlers throughout their range from Norway to New England.
Pollock– Alaska pollock is a major fishery for bottom trawlers in the northern Pacific ocean. Atlantic pollock are also caught by trawlers in a smaller fishery.
Rockfish – The rockfish family includes over 100 species caught by trawlers worldwide. Widow rockfish, yelloweye rockfish, canary rockfish, and chilipepper rockfish are frequently caught in Pacific trawl fisheries.
Skates – Skates like longnose skates, winter skates, and barndoor skates are common incidental catches in bottom trawl fisheries targeting groundfish.
Plaice – European plaice, one of the most economically important flatfish, are heavily targeted by bottom trawlers in the North Sea. Alaska plaice is also caught by Pacific trawlers.

In addition to fish, bottom trawlers often catch certain invertebrate species like shrimp, crabs, squid, scallops, and clams that live on or near the seafloor. However, fish make up the bulk of bottom trawl catches worldwide.

Midwater Trawlers Target Pelagic Fish

Unlike bottom trawlers, midwater trawlers use nets designed to capture fish species in the upper water column rather than those living near the bottom. Midwater trawling targets pelagic fish that swim in the open ocean away from the coast and seafloor. Common pelagic fish caught by midwater trawlers include:

Anchovies – These small, schooling forage fish are heavily caught by midwater trawlers off South America, Europe, Africa and the U.S. west coast. Peruvian anchoveta is the most landed fish species globally.
Herring – Atlantic herring and Pacific herring schools are targeted by midwater trawl vessels in northern hemisphere waters. They are caught for bait, food products, and their roe.
Mackerel – Chub mackerel, Atlantic mackerel, and King mackerel are extremely common midwater trawl catches. Mackerel are caught worldwide and used for a variety of products.
Jack Mackerel – This fast-growing pelagic species is primarily caught by midwater trawlers off the coasts of Chile and Peru where large fisheries exist.
Horse Mackerel – Trachurus jack mackerels like Mediterranean horse mackerel and Chilean jack mackerel are heavily exploited by midwater trawl fleets.
Sardines – European pilchard, Japanese pilchard, and other sardine species are significant midwater trawl catches used for fish meal, oil, and human consumption.
Menhaden – Atlantic and Gulf menhaden are small pelagic fish caught in large volume by midwater trawlers off the U.S east coast. They are processed into fishmeal and oil.
Pollock – Although they are bottom dwellers, Alaska pollock form large midwater aggregations that are efficiently caught by pelagic trawlers in the northern Pacific.
Hoki – This deepwater fish is one of the major species caught by midwater trawlers off New Zealand and Australia. It is commonly used for surimi seafood products.
Frigate Tunas – Auxis thazard and other small tunas are very common incidental catches of midwater trawlers throughout tropical oceans.

Other common pelagic catches include anchovies, lanternfishes, squids, smelt, sauries, and mackerels. The seafood industry heavily depends on midwater trawl catches to produce products like surimi, fish meal and fish oil.

How Trawl Type and Design Influences Catch

Trawlers employ different types of trawl nets tailored to capture their target species. Bottom trawl gear is designed to herd and scoop up bottom fish and shellfish, while midwater trawls corral pelagic schools. But even within these categories, net size, drag speed, and mesh size can affect what is ultimately caught.

Bottom Trawls

Beam trawls – Beam trawls are bottom nets held open by a fixed metal beam. They are used to target flatfish, skates, shrimp and scallops. The heavy net and beam can damage seafloor habitats.
Otter trawls – Otter trawls are the most common bottom trawls. Otter boards act like kites to keep the net open horizontally. They catch groundfish like cod, rockfish, and whiting.
Nephrops trawls – These smaller trawls target Norway lobster (Nephrops). Their fine meshes retain smaller fish like haddock and monkfish.
Scallop dredges – Dredges with toothed metal bars are dragged to rake up scallops from the seafloor, while catching fish as bycatch.

Midwater Trawls

Pelagic pair trawls – Boats drag two trawls between them to target large pelagic fish aggregations near the surface. Common for tuna.
Single midwater trawls – One large midwater trawl net is dragged from a single trawler to catch pelagic fish schools deeper in the water column.
High opening trawls – These trawls can open hundreds of feet high to target fish far below the surface. Used for jack mackerel, hoki and grenadiers.

No matter the specific gear, trawl size and tow speed affect which fish can escape and which get captured. Larger mesh sizes over 200 mm selectively catch larger adult groundfish, while small mesh sizes below 100 mm retain more juveniles and smaller pelagic fish.

Regional Variation in Trawl Catches

The species of fish caught by trawlers can vary widely between different oceans and fisheries around the world due to factors like marine biology, fishing practices, and regulations.

Northeast Atlantic Ocean

The Northeast Atlantic Ocean supports some of the world's largest trawl fisheries. Common groundfish catches here include Atlantic cod, haddock, pollock, plaice, sole, catfish, rays, and shark. Midwater trawlers frequently catch Atlantic herring, horse mackerel, mackerel, and blue whiting. There are concerns over dwindling cod and sole populations due to intense bottom trawling.

Northwest Atlantic Ocean

Major trawl fisheries off the northeast U.S and Atlantic Canada target Atlantic cod, pollock, haddock, flounders, and monkfish. Pelagic catches include Atlantic herring, mackerel, menhaden, shad, and squid. Catches have declined over the decades due to stock collapses and fishing limits.

Mediterranean Sea

More than 100 trawl fisheries operate in the Mediterranean, catching hake, mullets, picarel, Atlantic mackerel, Pandora fish, bogue fish, octopus, shrimp, squid, cuttlefish, and blue whiting. Trawling bans in sensitive habitats are aiming to improve sustainability.

Southeast Atlantic Ocean

In West Africa, shrimp are the main target of coastal trawlers, which also catch demersal fish like croakers, grunts, snappers, and groupers as bycatch. The rich fishing grounds off southern and eastern Africa yield large catches of Cape hakes, kingklip, monkfish, sole, and squid.

Northeast Pacific Ocean

Some of the world's largest fisheries are located in the northern Pacific ocean. Walleye pollock is the biggest trawl fishery here, followed by Pacific cod, sole, plaice, rockfish, sablefish, and Pacific ocean perch. Herring, salmon, and squid are key pelagic catches.

Southeast Pacific Ocean

The Humboldt Current ecosystem along South America boasts exceptional productivity that supports enormous midwater trawl fisheries targeting anchovy, Chilean jack mackerel, South American pilchard, and Peruvian hake. El Niño events dramatically influence catches year-to-year.

Southern Ocean

Antarctic krill are a vital trawl target, caught for aquaculture feed. Toothfish, icefish, lanternfish and squid are also caught here. Trawling was once unregulated near Antarctica but the Commission for the Conservation of Antarctic Marine Living Resources now manages these fisheries.

Effects of Regulations on Catches

Fishery managers employ various regulations to influence the amount and species caught by trawlers in different regions. Common measures include:

Catch limits – Limits on total allowed catches help prevent overfishing of vulnerable species. However, they can increase bycatch when fishing pressure concentrates on unrestricted stocks.
Size restrictions – Minimum size requirements allow juveniles and spawning fish to escape nets. This preserves fish recruitment and reproductive potential.
Time-area closures – Closing certain areas or seasons protects habitat and spawning fish. This reduces trawl impacts on the ecosystem.
Gear restrictions – Requirements on net mesh sizes or trawl dimensions selectively catch or exclude certain sizes of fish to support sustainability.

Well-designed regulations allow trawl fisheries to operate while ensuring adequate fish, invertebrate, and habitat conservation. However, illegal, unregulated fishing often undermines these management efforts.

Environmental Concerns With Trawling

While trawling produces substantial seafood yields, it faces criticism over habitat damage, high levels of bycatch, and unsustainable exploitation of fish stocks.

Bottom trawling can destroy seafloor habitats and ecosystem structures that support fish and invertebrate populations. The heavy gear crushes or scours sensitive environments like coral reefs and sea sponges. This ecological harm threatens the future productivity of fished populations.
Midwater trawling catches large quantities of juvenile fish and non-target species along with the target stocks. Most trapped bycatch perishes, contributing to further depletion of fish populations and marine food webs.
Intensive trawling has caused the collapse of major fisheries globally, including the Atlantic cod fishery off Canada and the pelagic Peruvian anchovy fishery. Overfishing by trawlers can decimate fish populations.

Innovations in trawl gear design and fishing regulations are attempting to mitigate these damages. More selective nets, modifications to trawl doors and footgear, closed areas, andquota limits help reduce seafloor contact, bycatch, and overexploitation by trawlers. However, balancing trawl fisheries with ocean conservation remains an ongoing challenge.

Conclusion

Trawlers make an invaluable contribution to the global seafood supply by catching huge quantities of species like cod, pollock, mackerel, anchovies, and shrimp. Yet the future sustainability and expansion of trawl fisheries depends on addressing their environmental repercussions. With improved management and innovation, these industrial fishing vessels could provide food to growing populations while maintaining the health of our oceans and fish populations. By understanding the diversity of species caught by different trawling methods, we gain key insights into designing smarter practices for utilizing these resources.

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