Protecting Ocean Ecosystems

Destructive Trawling and the Myth of “Farming the Sea”

Trawlers trail massive plumes of sediment in the Gulf of Mexico. Photo credit: SkyTruth

In the wake of significant but highly warranted cuts to catch limits for cod, the New England Fishery Management Council spent the last day of their most recent meeting in January discussing the development of a suite of habitat protection measures known as the Omnibus Habitat Amendment. Despite the obvious need for new habitat protections to help restore Atlantic cod populations, the Council had already taken action to potentially open over 5000 square miles of previously protected areas to destructive bottom trawling. By doing so, the Council has continued to demonstrate a lack of regard for the immeasurable documented benefits of habitat protection to the health and productivity of our fisheries.

Even more concerning were the misperceptions of the effects of bottom trawling on display at the January meeting—even by members of the Council itself. Laura Ramsden, a relatively new member of the Council and an owner of the Boston-based seafood distributor Foley Fish Company, suggested that the scientists tasked with evaluating habitat protection priorities might be missing the benefits of bottom trawling. She asked the members of the Closed Area Technical Team: “As you’re evaluating the different areas, are you also taking a look at potential damage of closing them in terms of invasive species and the potential risk of not ‘tilling the soil’, if you will?”

The inexplicable myth that bottom trawling might “farm the seabed” is all too common, but it has no foundation in scientific reality. There are few serious studies that suggest that trawling may increase any kind of food production, and they are very limited in scope. A single study suggests that plaice in the North Sea may benefit from the reduced competition and increased production of some invertebrate species on which they prey. But the trawling is very limited—1 or 2 trawl passes a year—and the study does not examine the effects on other species of tearing apart complex bottom structures, removing higher trophic level predators, and reducing natural competition and biodiversity. A second, empirical study found that higher levels of trawling reduced productivity of even small invertebrates and that variability in productivity was far more closely linked to climate change than bottom trawling.

There is similarly scant scientific evidence for Ms. Ramsden’s assertion that trawling has any beneficial role in limiting the spread of invasive species. On the contrary, multiple studies suggest that human disturbance makes habitat more vulnerable to the spread of invasive species.

Meanwhile, the scientific consensus on the destruction caused by bottom trawling is nearly unanimous. It’s hardly surprising that dragging massive trawls along the seafloor destroys habitat—scallop dredges can weigh up to a metric ton (2205 lbs), and furrows up to 20 centimeters (8 inches) deep are common in trawled areas. A recent study in European waters even showed bottom trawling was changing the bathymetry of the seafloor on a massive scale.

Numerous scientific studies have shown that trawling  lowers overall productivity and can completely change the composition of local fish populations. Trawling tears apart biological structures like kelp forests and sponges and flattens out the seafloor structures that protect juvenile fish, leading to increased predation and reduced recruitment. It reduces biodiversity and species richness, which have been repeatedly shown to build resilience to invasive species. And areas with complex bottom structure, like the rocky ridges and horse mussel beds of current protected area Cashes Ledge, are the most vulnerable. In some areas trawling can stir up so much sediment—which then settles to smother eggs, larvae and other ocean creatures—that it leaves a trailing plume visible from outer space.

Protecting valuable habitat areas from trawling provides more spawning adults and juvenile fish, harbors older females with higher rates of reproductive success, and protects complex habitat like kelp forests. The current protected areas have proven themselves beneficial to struggling fish populations—they have helped scallop populations recover, and some species, like haddock, are larger and more abundant inside these closed areas. Fishermen target the edge of the protected areas because they know that more and larger fish can be found there.

Opening protected areas to bottom trawling threatens to instantaneously reverse these benefits. The best scientific evidence is that bottom trawling does not “till the soil”, but that opening protected areas will destroy vital habitat and keep cod populations from recovering. NOAA and the Council should heed the scientific record and make the right decision—to keep bottom trawling out of the groundfish closed areas.



8 Responses to Destructive Trawling and the Myth of “Farming the Sea”

  • Laura Ramsden says:

    As mentioned above, I am a newcomer to the council and I am guilty as charged of asking questions of the closed area access team to insure we are making the best decisions with respect to both the fish, the fishermen and the habitat. I do not claim extensive scientific background, nor do my questions intend to reflect any thought that I have all the answers. Rather I was looking at the current state of some stocks even with decades of closures and raising questions about the effectiveness of this management tool . Given the huge stakes for the fish and the fishermen, I would hope all interested parties would be asking many questions to best remedy the situation. Finally, one correction, our company is not a distributor, we are a processor and have been for 106 years. I do not want to become a distributor of styrofoam boxes of imported seafood. I want to work to ensure there are fish from United States waters for consumers to enjoy for generations to come. If the closed area tech team says that closing areas is the best way to achieve this, then I am on board. But let’s have a healthy dialogue with many questions to insure we are getting it right this time.

    • Sean Cosgrove (CLF) says:

      Thank you Ms. Ramsden for your response. We appreciate the clarification on your company’s work. We heartily agree that asking good questions and seeking good information are important roles for Council members and vitally important for the responsible management of our fisheries. Scientists, commercial and recreational fishermen and others recognize that protecting habitat for spawning, nursery areas and allowing females to grow to maturity is a management requirement for restoring Atlantic cod. Because the NEFMC has failed at completing the required designation of habitat protection in the Omnibus Habitat Amendment (and NOAA has failed to act) the protected areas we have in place serve as the best opportunities for recovering the cod population. Real world evidence, such as Canada’s experience with a cod fishery that collapsed in 1992 and has yet to recover, also tells us that habitat protection for cod is important. We urge you to consider the overwhelming evidence which strongly supports continued protection for these important habitat areas.

  • ierene says:

    “till the soil”?? That’s so funny I could cry

  • Frank Mirarchi says:

    The article titled “Destructive Trawling and the Myth of ‘Farming the Sea'” does a disservice to your readers. It conflates the legitimate objective of the NEFMC to reopen areas originally closed to reduce fishing mortality with the protection of sensitive habitats.

    Under Amendment 16, adopted by NMFS on May 1st, 2010, New England groundfish management was transitioned to an output based strategy.This shifted the focus of management away from reducing the fishery’s efficiency through measures such as days at sea, trip limits and large area closures to a direct accounting of catches. This model was expected to improve the efficiency, economic yield and safety of the fishery.

    Unfortunately, there has been reluctance to divest of many of these now redundant input control measures. Among these are the unnecessarily extensive area closures which you now cite as vital to resource recovery.

    In reality there should be a network of new closed areas designed not to inhibit efficiency, but rather around complex habitat which has been demonstrated to support the reproduction and growth of fish stocks. Moreover, these closures should be closed to all fishing, not just gears which you disfavor. The Council has, albeit slowly, been developing another set of area closures developed around these criteria.

    • Peter Shelley (CLF) says:

      Captain Mirarchi is one of the best commercial fishermen in New England. And he has put his time in both on the water and in fisheries management and his perspective demands respect. We can’t, however, agree with him here. Amendment 16 never promised the elimination of all the old fishing controls such as opening of the year-around closed areas, fishing gear regulations, and other input controls. It did promise and seems to have delivered increased efficiency and, we hope, lower costs and safety to a significant part of the fleet. Closed areas are critical for a number of biological reasons that are particularly compelling under the current crisis circumstances a number of important stocks face. Hard quotas do not in any way advance these same biological objectives. Whether the current areas are too extensive or not extensive enough given this crisis is a science question that is under current investigation. Conclusions concerning the results of those analyses are premature at best. As far as which gears should be allowed in these areas, that decision should also await that analysis. In any event, the notion that bottom destruction through trawling is beneficial because it is akin to tilling soil is a convenient myth that is not backed up by much empirical fact.

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  • Bob Vanasse says:

    This article ignores the credible science backing the New England Fishery Management Council’s proposals to change closed habitat areas off New England. Accounting for new management practices and updated science, the Council has concluded that the boundaries of these closed areas can be changed to the benefit of marine habitats. A comprehensive analysis on the effects of the proposed changes, examined by the Council’s Science and Statistical Committee, determined that opening parts of these areas to fishing (including trawling) would minimize the total adverse effects from fishing in this region.

    Several peer-reviewed studies published in the last decade conclude that the impact of trawling in these areas is insignificant in comparison to natural events, which often produce forces equivalent to hurricane winds on land. Additionally, recent data that were not available when these closures were first enacted in the 1990s indicate that the boundary lines of many of the closed areas are not in locations best suited for habitat protection. For that reason revisions to these boundaries are both appropriate and needed.

  • Bob Vanasse, the industry lobbyist for Saving Seafood, is offering a red herring by conflating two separate Council processes. Yes, the current closed areas are subject to revision and the Council has failed to do its job in that regard by dragging this process out for years – the “Omnibus Habitat Amendment” is in the ninth year of a five year process. He is using this failed process to also argue that the best protected habitat areas in New England should be opened to new commercial fishing before the Council completes that process because groundfish populations are at a historic low.

    Further, he claims that damage caused by bottom trawling equates the natural disturbance of strong currents on a sandy seafloor. Let me hazard an analogy, Bob: If a wind storm blows over a number of trees, is that the same impact as driving a bulldozer through an otherwise healthy forest?

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