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Andrew Blitman likes to draw and write about philosophy, poetry, and science. The author of two books, he will graduate from the University of Miami in May 2014 with a Masters of Professional Science degree in Marine Affairs. If you have any questions, feel free to e-mail him at thewrittenblit@gmail.com.

Bygone Bycatch: The Overfishing of Billfish

Bycatch Collage

Bycatch Collage

Introduction to Overfishing

The sea is a harsh mistress. For millennia, she has tantalized our kind with the promise of infinite bounty. However, we are just starting to realize the limits of infinity. Despite her immense size, her immeasurable depth, and her unfathomable biodiversity, Amphitrite is not limitless. The oceans have boundaries. However, advances in technology have allowed us to transcend those boundaries and reap the seas’ resources without restraint.

Today, most of the oceans’ living resources are controlled by people. Many are commercially overfished, or harvested to such a degree that entire ecosystems are affected. A meaty chunk of that catch is unintentional. It is also discarded. While measurements vary between fisheries, the latest reports suggest that around eight percent of the global catch—between 6.8 and 27 million tons of fish—is thrown away annually (“Bycatch”). From its international surveys the World Wildlife Foundation estimated discards greater than 38.5 million tons, equal to approximately 40 percent of the total marine catch (Davies et. al 2009). Incidental capture, or bycatch, is the second-greatest threat to the oceans after overfishing (“Threats to Oceans”) and is one of the reasons why more than three-quarters of the oceans are fished beyond capacity (FAO 2000). Billfish, marine mammals, and sharks are common examples of non-target bycatch species.

Long the mascots of recreational fishing, billfish are increasingly becoming poster children for the bycatch crisis. They, like other large fish, are victims of circumstance. All twelve species of billfishes—the nine marlin, the two sailfish, and the lone swordfish—face extinction from incidental and intentional overfishing (“Billfish in Popular Culture”).

Behind Overfishing

Overfishing is the greatest threat facing the oceans today (Norse and Crowder 2005). Around the world, fisheries are reeling because people are taking more fish out of the ocean than can be replaced by those remaining (“Unsustainable Fishing”). As a result, 53% of the world’s fisheries are fully exploited, and 32% are overexploited, depleted, or recovering from depletion (FAO 2010). Furthermore, most of the top ten marine fisheries, which account for about 30% of all capture fisheries production, are fully exploited or overexploited (FAO 2010).

There are two kinds of overfishing. One is biological overfishing, which occurs when fishing mortality has reached a level where stock biomass has negative marginal growth (“Abbreviations”). Biological overfishing is divided into three subcategories of scale. First is growth overfishing, which occurs when fish are harvested at an average size that is smaller than the size that would produce the maximum number of offspring (“Abbreviations”). The second recognized type is recruitment overfishing, which occurs when the population of sexually mature adults (or spawning biomass) is depleted to a level where it no longer has the reproductive capacity to replenish itself. In other words, there are not enough adults to produce young (“Abbreviations”). The third and most dangerous kind of biological overfishing is ecosystem overfishing, when the balance of the ecosystem shifts as its components are removed through overfishing (“Abbreviations”).

Overfishing Collage

Overfishing Collage

Economic overfishing, on the other hand, occurs when fish are removed from the fishery so quickly that the fishery becomes unprofitable (“Abbreviations”). A more dynamic definition of economic overfishing involves a discount rate, or the rate at which a fishery depreciates in value over time (Wikipedia.org).

Regardless of type, overfishing can drastically alter fisheries and the ecosystems they depend on. Due to overfishing, populations of both targeted and non-targeted species can collapse. Those populations, in turn, experience diminished reproductive potential as selective pressures force individuals to reproduce earlier (Norse and Crowder 2005). As a result, the average size of overfished species decreases over time (Norse and Crowder 2005). For hermaphroditic fish, the male-to-female ratio skews. In the case of groupers (which morph from females to males when they reach a certain size), the sex ratio for overfished species can be skewed 30:1 (“Gag Grouper”). As a consequence, their population can become sperm-limited and reproductive failure can occur.

This is a pattern seen in fisheries around the world. Today, as many as 90% of the ocean’s large fish have been fished out (Myers and Worm 2003). Several important commercial fish populations have declined to the point where their survival is threatened (“Unsustainable Fishing”). Unless the current situation improves, stocks of all species currently fished for food are predicted to collapse by 2048 (Worm 2006).

Behind Bycatch

Where overfishing takes place, bycatch also occurs. The process of incidental capture has a high mortality rate. Though not all fish die after they are discarded, many do. Some species, notably certain flatfish, can survive the fish capture process quite well (Berghahn et al., 1992) but this is not the norm. For example, Hill and Wassenberg (1990) found that only 1-2% of fish survived, though as much as 50% of crustaceans survived.

Some animals that interact with the gear escape, but may nevertheless die, contributing to the overall mortality caused by fishing. Such mortality is sometimes referred to as “unaccounted mortality” (ICES 1997) because it is rarely considered in the assessment and evaluation of fish stocks. Hence the overall direct by-catch impact of fishing will be due to the deaths of the discards and the deaths related to contact with the gear (Cook 2001).

The unaccounted mortality due to contact with the gear may be large (Cook, 1998), though few studies have quantified it. Species that are especially fragile, such as many deep-water fish, are especially at risk (Cook 2001).

Bycatch, like overfishing, can result in extinctions. In fact, bycatch has created a history of extinctions in the oceans. Many happen below the radar of the general public. Sometimes, even scientists fail to notice. Such was the case with the barndoor skate Raja laevis, almost declared extinct in the 1990s due to more than four decades of incidental capture (Casey and Myers 1998). This was also the case with the baiji or Yangtze River Dolphin (Lipotes vexillifer), which went extinct in 2007 as a result of both accidental and intentional capture (Smith et al. 2008).

Today, bycatch rates are not slowing down. In 2010, the journal Conservation Letters reported that millions of endangered sea turtles have been accidentally captured or killed over the past two decades by longline, gillnet and trawl fisheries worldwide (Viegas 2010). Bycatch is also the primary threat for 62 of the 71 extant species of toothed cetaceans in the world and is increasing (Wildwhales.org). Various forms of fishing gear such as gillnets, driftnets, traps, weirs, purse-seine nets, long-lines, trawls and others were implicated with causing entanglement that may lead to suffocation and death of whales, dolphins and porpoises (Wildwhales.org). Globally, over 300,000 small cetaceans die each year due to entanglement in fishing gear (WWF 2011).

Billfish Bycatch

A billfish is a species of large, fast-swimming open-water fish that possess a streamlined body and a long, pointed, spearlike snout (Google Dictionary). There are twelve extant species in total—nine marlin, two sailfish, and one swordfish (Fierstine 2006). For these billfish, the situation is just as bleak.

In the Pacific, blue marlins (Makaira nigricans) are an incidental catch of longline fisheries, bycatch in swordfish fisheries, and an important resource for big game recreational fishing. More than 73% of reported landings are incidental to large offshore longline fisheries, and other major fisheries are the directed recreational fisheries of the USA and other countries (Collette et al 2011). Protections efforts for blue marlin have continued to decrease in recent years, as deeper longline gear is introduced (Collette et al 2011). They face similar threats in the Atlantic. However, blue marlins are also intentionally targeted by commercial and recreational fisheries (Collette et al 2011).

Because billfish in reality are mainly a “bycatch species” (caught accidentally in fisheries for other species) getting reliable catch data can be difficult. Commercial catch data are compiled by the various Regional Fishery Management Organizations (RFMOs). However, catch data are plagued by chronic under-reporting, and fish that are discarded at sea, alive or dead, also are often not reported. Many billfish are recorded only if they are landed (“Why Take Marlin Off the Menu?”).

International billfish landings are compiled by the United Nations Food and Agriculture Organization (FAO). The following represents catches of the top five species in metric tons (mt) reported by FAO in 2004.

  1. Blue marlin: 26,765 metric tons
  2. Indo-Pacific sailfish: 25,722 metric tons

3.   Unclassified billfish: 23,658 metric tons

4.   Striped marlin: 7,380 metric tons

5.   Black marlin: 3,755 metric tons (Gentner 2007)

Overall, many more billfish are harvested in the Pacific (83,677 mt in 2004) than in the Atlantic (6,753 mt) (Gentner 2007). Most billfish bycatch in the Atlantic is from high seas longlining. With more than 100 million hooks annually, Japan is the biggest player, harvesting 10 percent of all white and 35 percent of all blue marlin (Gentner 2006). In the Pacific, longlines take 48 percent of billfish landings and purse seines 38 percent (Gentner 2007). However, both Pacific and Atlantic landings data are intentionally manipulated to avoid regulations, which results in high levels of unclassified catch and underestimates of true billfish harvest (Gentner 2007).

While Taiwan is the biggest exporter of billfish products (8,169 metric tons/year), the United States is the greatest importer (between 2001 and 2005). During that period, the US sold 166 metric tons each year, though the Food and Drug Administration (FDA) estimates imports 7 to 8 greater (Gentner 2007). Also according to FDA data, between 2003 and 2006 the U.S. imported approximately 1,260 mt of billfish annually. This figure is substantially higher than that reported by FAO and underscores the underreporting that plagues international trade data (“Why Take Marlin Off the Menu?”).

The Billfish Conservation Act

However, the plight of billfish has not gone unnoticed. On September 23, 2012, Congress presented the world’s first moratorium (or national ban) on billfish products. Ten days later, President Barack Obama signed into law the Billfish Conservation Act (BCA), the product of years of lobbying by the Billfish Foundation (TBF) and the International Game Fish Association (IGFA) (Billfish.org and IGFA.org).

A moratorium is defined as a legal suspension of activity (Dictionary.com). Because the BCA is a national ban on the distribution and sale of billfish products in the United States, it eliminates the American billfish importation industry. While these cutbacks might seem like an enormous loss, in reality they affect a tiny part of the American seafood industry.

According to FDA records, the legal billfish market is very small in the United States, especially when compared to American seafood at large. The total United States economic impacts of Hawaii harvesting and the mainland importation of billfish in 2005 are 675 jobs supported nationwide, $23.5 million in income/value added nationwide, and $44 million in output nationwide (Gentner 2007). To put these estimates in perspective, the $23.5 million in value added generated nationwide represents only 0.071% of $32.9 billion; the value added generated by all seafood industry activities in the United States for 2005 (Gentner 2007).

While moratoria have proven somewhat successful for whales (“Whaling”), they have proven unsuccessful with cod (MacDonald 2009), tuna (Torres-Irineo 2011), and endangered African fauna like the rhinoceros (Lewis Smith 2008). When moratoria fail, they drive hunting and trading underground. Such is the case with the moratorium on Africa’s endangered species, something that has fueled the illegal bushmeat trade and driven the “protected” species further into oblivion (Bowen-Jones 1999).

It is likely that the Billfish Conservation Act will meet Gentner’s predictions in 2006:

“A review of the seafood demand literature suggests that the demand for most fish species is highly elastic, although no billfish specific elasticity estimates exist. This suggests that a ban on the importation of billfish would have little consumer welfare impact and whatever welfare impact that was generated would fade quickly (Gentner 2007).”

I believe that if anything were to change America’s taste for billfish, health warnings on billfish products would be key. This also matches Gentner’s assumptions:

“The literature found that consumers elasticity is affected by health warnings, as well as “green” or sustainability certifications, which suggests that an informational campaign related to the health impacts of eating an apex predator with high mercury levels or the inability to sustain the harvest of billfish, like the dolphin safe tuna campaign, may be an effective means to drive down consumer demand” (Gentner 2007).”

Additionally, elastic demand means that the economic impacts of any policy that reduces billfish importation would likely be short lived if felt in the economy at all. Because billfish are a byproduct of the tuna harvesting process, banning imports or reducing domestic demand may not reduce billfish mortality (Gentner 2007).


Lingering Problems

Although the Billfish Conservation Act does not completely resolve the problem of billfish mortality, I do believe it is a step in the right direction. If the BCA is properly enforced, the landmark piece of legislation could still bring positive change to dwindling billfish populations.

But how can it be enforced? Since 2011, the Feds have used forensic science—genetic markers—to identify billfish meat (Virginia Institute of Marine Science 2011). The genetic marker test was needed to ensure that the blue marlin sold in U.S. seafood markets were not taken from the Atlantic Ocean. The import and sale of blue marlin from the Pacific or Indian oceans was legal in the U.S. before the BCA, while the marketing of Atlantic blues can bring civil or criminal penalties, including fines, seizure of a catch, or the loss of a fishing permit (Virginia Institute of Marine Science 2011).

In order for enforcement to be effective, however, Americans need to care about their seafood. The most recent survey by Rutgers University found that Americans (at least those in Colorado, Illinois, Massachusetts, and New Jersey), care when their health is at stake (O’Dierno 2006).

In that study, seventy-four percent of those surveyed were aware of health concerns about seafood. Sixty-five percent had heard concerns about mercury in seafood. Fifteen percent mentioned contaminants in general, 7 percent identified bacterial concerns, and 6 percent food poisoning. In both Chicago and Colorado Springs, people specifically mentioned cadmium as a concern (O’Dierno 2006).

O’Dierno also found that the majority of seafood consumers cared about seafood production methods (67%) and the way seafood was harvested (72% prefer wild-caught fish). Fifty percent of those surveyed said they would pay more for seafood if it had an eco-friendly label, while 71% said that they could care less about countries of origin when purchasing their seafood (O’Dierno 2006).

Most people are also unaware that marlin have been documented to accumulate harmful levels of mercury (“Why Take Marlin Off the Menu?”). The United States Environmental Protection Agency (EPA) health guidelines for fish consumption indicate that any fish with a mercury level greater than 1.5 parts per million (ppm) should not be consumed in any amount. Marlin, especially large specimens, have been found to have mercury levels as high as 15 ppm, and a recent study reported an average mercury level of 4.08 ppm for blue marlin sampled in Australian waters (“Why Take Marlin Off the Menu?”).

As a result, I believe the best weapon against billfish mortality is the awareness campaign. It saved the whale. It helped the sea turtle. Now we can use it to protect the marlin by telling consumers “they are what they eat”. Endangered.


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