Impact Of “Ghost Fishing“ Via Derelict Fishing Gear

BACKGROUNDWhat is ghost fishing?Ghost fishing refers to lost or abandonedfishing gear, also called derelict fishing gear(DFG), that continues to capture fish andother marine animals after the gear is nolonger under the control of a fisherman(Smolowitz, Corps, and Center, 1978). Themost common types of DFG to ghost fish aregillnets and crab pots/traps, but other typesof fishing gear, like longlines and trawls,can also ghost fish if they become DFG.Although the original intent of each is tocapture a particular “target” species, whetherfor commercial or recreational use, derelictfishing gear can continue to fish for targetas well as non-target species (called ghostcatch) after it is lost, broken, or discarded.For example, a crab trap may break loosefrom its buoy in bad weather and continueto trap crabs, which may then act asbait themselves and attract other fish orspecies not originally intended for capture.Ghost fishing specifically implies that theorganisms caught in the DFG die as a resultof starvation, predation, or cannibalism(Smolowitz et al., 1978). This means that justbecause an organism enters a piece of DFG,also known internationally as abandoned,lost or otherwise discarded fishing gear(ALDFG), the gear is not necessarily ghostfishing unless mortality occurs. The timeover which DFG can continue to ghost fishcan vary according to the specific gear type,but can range from days to years. Over thecourse of its lifespan, a piece of DFG maykill large numbers of commercially valuableor threatened species (Laist, 1987). Thisghost fishing phenomenon is a part of theglobal marine debris issue that impactsmarine organisms and the environment.Ghost fishing can impose a variety ofharmful impacts, including: the abilityto kill target and non-target organisms,including endangered and protected species;causing damage to underwater habitats, likecoral reefs and benthic fauna; economiclosses from target species mortalities andreplacement costs; and contributing tomarine pollution.2There are many ways that fishing gear canbecome derelict, and more than one of thefollowing can be contributing factors:1. Environmental: storms, wave actionor currents, sedimentation, ice cover,deep-water conditions2. Gear conflict: entanglement with othervessels or bottom topography such asreefs or rocky bottoms3. Gear condition: breaks loose/cut loose(intent can be accidental or deliberate)due to old age/overuse;4. Inappropriate disposal at seaincomplete reporting of how much gear isactually lost and the difficulty in monitoringor retrieving DFG. Factors that contributeto the likelihood of DFG ghost fishing arethe rates at which gear is lost, the catchingefficiency of each specific gear type, andthe species that are present in the area thatmay then be susceptible to ghost fishing(Brown and Macfadyen, 2007). Also notwell-understood are the catch rates (howmany organisms are caught) and mortalityrates (how many organisms die) of speciescaught in DFG.Early research into ghost fishing beganin the 1970s (High, 1976; Pecci, 1978),shortly after the 1973 prohibition ofabandonment or dumping of fishing gearby the International Maritime OrganizationConvention for the Prevention of thePollution from Ships. Also during this time,construction of fishing gear transitionedfrom natural, biodegradable materials suchas cotton and wood to plastic monofilamentand vinyl-coated steel. Although thesematerials last longer, which is advantageousfor the fishermen, they do not readilydegrade and therefore prolong the potentialfor ghost fishing to occur, and they increasethe total amount of marine debris overall asDFG.Despite previous research that increased ourunderstanding of DFG and ghost fishing,detailed information on DFG based onthe above factors is still relatively scarce,as few detailed studies have been done.Some areas have been intensively studied(e.g., Northwestern Hawaiian Islands),while others have little to no data available.There are numerous logistical difficultiesin executing ghost fishing research studies,and consistent units of measure have notbeen used across studies, complicatingcomparison of results. Differences ininternational, national, and regionalregulations and compliance are alsoproblematic, in that catch limits, gear usage,gear type, sink times, and even attituderegarding proper gear use and disposalcan vary widely geographically. Taken inthe context of these differences around theworld, more data are needed across widergeographical areas to better refine theimpacts of ghost fishing that occur due toDFG.Derelict fishing gear contributes to marinedebris in general. Although it is impossibleto get an accurate global number, a roughestimate is that less than 10% of marinedebris by volume is DFG (Macfadyen,Huntington, and Cappell, 2009) and DFGis the main type of submerged marinedebris (Macfadyen et al. 2009; Nagelkerken,Wiltjer, Debrot, and Pors, 2001; Chiappone,White, Swanson, and Miller, 2002; Sheridan,Hill, Matthews, G. Appledoorn, Kojis, andMatthews, T., 2005). A United Nations(UN) Food and Agriculture Organization(FAO) and UN Environment Programme(UNEP) report states that while most gearis not deliberately discarded, the problemof abandoned, lost and discarded fishinggear is getting worse due to the increasedscale of global fishing operations and theabove mentioned introduction of highlydurable fishing gear made of long-lastingsynthetic materials (Macfadyen et al.,2009). This suggests that the likelihood ofghost fishing may be increasing, althoughit is difficult to know exact numbers due to2015 MARINE DEBRIS GHOST FISHING REPORTThis report is a summary of the currentscientific knowledge of ghost fishing, thederelict fishing gear that mainly contributeto it, the species mortalities, and theeconomic losses to certain fisheries due toghost fishing mortalities. Gaps in knowledgeare identified, and suggestions for theprevention and mitigation of DFG andpossible future research foci are presentedwithin the framework of prevention,removal, and education as focus areas andmeans of reducing ghost fishing. These threefocus areas, however, should be consideredtogether as a multi-pronged approachtoward that goal.

OcurrenceAnywhere fishing gear is deployed, thereis the potential risk for ghost fishing, andthus DFG can enter marine systems at avariety of locations worldwide. On thisglobal scale, drifter experiments haveshown five main areas where marine debristends to accumulate which are known asconvergence zones (Maximenko, Hafner,and Niiler, 2012). The ocean currents andprevailing winds concentrate water massesinto these specific regions, and marinedebris, including DFG, can likewise beconcentrated there. One such “hot spot”of DFG accumulation with documentedghost fishing in the U.S. is the NorthwesternHawaiian Islands (NWHI). This hotspot is due to a concentration of oceancurrents in an area known as the NorthPacific subtropical convergence zone. DFGaccumulated in this zone leads to the coastsand coral reefs of the islands, which hasresulted in ghost fishing (Kubota, 1994;Donohue, Boland, Sramek, and Antonelis,2001; Pichel, Veenstra, Churnside, Arabini,Friedman, Foley, Brainard, Kiefer, Ogle, andClemente-Colon, 2003; Pichel, Churnside,Veenstra, Foley, Friedman, Brainard, Nicoll,Zheng, and Clemente-Colon, 2007). TheDFG that are mostly responsible for ghostfishing in this area may originate fromvarious current drift net fisheries fromNorth Pacific Ocean fisheries, or maybe decades-old remnants of Japanese,Korean, and Taiwanese fleets lost priorto high-seas drift net bans in the early1990s (Donohue et al., 2001; NationalMarine Fisheries Service, 2007; Bolandand Donohue, 2003). Since 1996, NOAA’sNational Marine Fisheries Service,NOAA’s National Ocean Service, andother state and federal organizations haveremoved hundreds of tons of derelict netsfrom the NWHI’s coral reefs in an effortto restore fragile habitats and reduce theimpact on the local marine fauna (PacificIslands Fisheries Science Center, 2012).DFG released in the North Pacific Oceanrepresents only one area, albeit a very largearea, where DFG accumulates and posesproblems via ghost fishing. Other oceanbasins, such as the South Pacific Oceanand the North Atlantic Ocean basins,also contain DFG, although these zoneshave not received as much attention inthe literature as the North Pacific Ocean.Additionally, as mentioned earlier, DFG canbecome a problem anywhere that fishinggear is deployed, including along coastlines.There are numerous other coastal regionsand resources, like the Chesapeake Bay(Havens, Bilkovic, Stanhope, and Angstadt,2011; Havens, Bilkovic, Stanhope, Angstadt,and Hershner, 2008), the Puget Sound(Pichel, et al., 2003; Good, June, Etnier, andBroadhurst, 2009; and Maselko, Bishop,and Murphy, 2013), and the Gulf of Mexico(Guillory, McMillen-Jackson, Hartman,Perry, Floyd, Wagner, and Graham, 2001),where both floating (e.g., gill nets, longlines) and fixed (e.g., crab traps/pots) fishinggear are lost and subsequently ghost fishfor years. In these areas, the NOAA MDPhas supported efforts to survey where DFGhas been deposited in order to get a bettersense as to where DFG occurs due to fishingactivity in these areas. However, more workneeds to be done to get a better sense of theoverall extent of where DFG accumulates,both in the water column and on the seafloor.Figure 1. A map of the Eastern and Western Garbage patches. These regions have higher debris concentrations because of ocean circulation patterns.(Photo Credit: NOAA Marine Debris Program)3

Impacts of Ghost FishingThere are a wide variety of impacts thatghost fishing can have, including the DFGresponsible for ghost fishing being a typeof marine pollution, but three in particularstand out. Although the most obvious is themortality of organisms in DFG, damage canalso be done to the habitat in which DFGbecomes lost, and economic losses are also aconsequence of ghost fishing.a recent study estimated there areover 85,000 lobster and crab ghosttraps in the Florida Keys NationalMarine SanctuaryHabitatFisheries operate in many different typesof habitats in order to capture their targetspecies, whether it is along the coast inshallow waters, or further offshore in openocean (pelagic) areas. Coral reefs, like thosein Hawai‘i, are one type of habitat that canbe impacted by ghost fishing, not only bythe loss of organisms dying in DFG, but thephysical damage done by the gear itself. Thiscan occur when DFG such as lobster potsor bottom trawls sink or get dragged alongthe reefs by currents and storm action,which can destroy fragile corals and theirassociated inhabitants. Another habitattype that can be susceptible to impactsfrom DFG and ghost fishing is the benthos(Butterworth, Clegg, and Bass, 2012). Theseocean bottom regions, although generallyremote in location, can still be damagedsignificantly when DFG, especially trap gear,sinks to the bottom where it can smotherorganisms that live on top of and just belowthe sediments, like seagrasses, crabs, andworms.Species MortalityOne of the most significant ghost fishingimpacts of DFG is the unintended deathsof target and non-target species, whichcontribute to the overall depletion ofpopulations. DFG that begins ghost fishingposes a threat to a variety of non-target fish(Stewart, and Yochem, 1987), turtles (Carr,1987; Meager and Limpus, 2012), seabirds(Good, et al., 2009; Piatt and Nettleship,1987), whales (Volgenau, Kraus, and Lien,1995; Meager, Winter, Biddle, and Limpus,2012), and seals (Boland and Donohue,2003; Page, McKenzie, McIntosh, Baylis,Morrisey, Calvert, Haase, Berris, Dowie,Shaughnessy, and Goldsworthy, 2004). Thisis especially problematic when endangeredor protected species including marinemammals and sea turtles die as a resultof ghost fishing. Protected marine species4have already declining populations thatcan be further set back by DFG. Even innon-endangered target species, mortalitiesdue to ghost fishing can further deplete thepopulation and lessen the sustainabilityof the fishery. One way ghost fishingis perpetuated is by the trapped anddead animals in the DFG acting as bait,attracting and potentially entrapping moreorganisms. For example, fish or crustaceanscan enter a derelict lobster pot lookingfor food (which could be already trappedorganisms) or shelter and may then becometrapped themselves. To give an idea of thescale on which this could potentially occur,a recent study estimates there are over85,000 lobster and crab ghost traps in theFlorida Keys National Marine Sanctuary(Uhrin, Matthews, and Lewis, 2014). Thissuggests a definite risk for ghost fishing injust one region of the U.S. alone.EconomicIt is difficult to gauge accurate total costsassociated with ghost fishing, as this variesacross specific fisheries, and can dependon the gear type, weather, and ghost catchrates, among other factors. Questionsthat make calculating economic impactsdifficult include: At what rate is trap gear lost annually? How long exactly can trap gearcontinue to ghost fish? How effective is the trap gear at ghostfishing? How is a value placed on the lossof both commercial AND noncommercial species? What are the costs of DFG on theenvironment?For the fishers, their direct costs rangefrom the money required to replace lostgear, to increased resources (i.e., fuel, shiptime, more fishing gear, special equipment)2015 MARINE DEBRIS GHOST FISHING REPORTneeded to capture decreasing target fisherypopulations. This is especially problematicin deep-sea species that grow slowly(Merrett and Haedrich, 1997; Koslow,Boehlert, Gordon, Haedrich, Lorance,and Parin, 2000). If significant numbersof these animals are lost to ghost fishing,this further strains the sustainability ofthe population. Fishers also lose revenuefrom target organisms killed due toghost fishing. Some studies estimatethat over 90% of species caught in DFGare of commercial value (Al-Masroori,Al-Oufi, McIlwain, and McLean, 2004),which can contribute to a significant lossof revenue for fishermen. The economicimpact of DFG is usually calculated eitheras the percentage of the catch that hascommercial value in the region, or as apercentage of the commercial catch of theindividual species caught. Some examplesare a 1.46% loss of the commercialmonkfish catch in northern Spain (Sancho,Puente, Bilbao, Gomez, and Arregi, 2003),a 4–5% loss of the commercial catch in theBaltic Sea (Tschernij and Larsson, 2003),and 20–30% of the Greenland halibutcatch in Norway (Humborstad, Løkkeborg,Hareide, and Furevik, 2003), all attributedto ghost fishing (Ceccarelli, 2009). Anotherstudy in Washington state found earlyghost fishing rates account for an estimated4.5% loss in the Dungeness crab fishery peryear, which equates to a harvest loss of over 744,000 (Antonelis, Huppert, Velasquez,and June, 2011).These examples show thatthe economic impacts of ghost fishingcan be substantial, but they are specific toeach fishery and area studied. And as withall the potential impacts of ghost fishingjust mentioned, impacts will vary with thespecific type of fishing gear in use.

The GearThere are a variety of fisheries, usuallycategorized by what target species they aretrying to catch specifically and by their scaleof operation. Industrial and commercialfisheries operate on a broad scale requiringlarge boats and lots of gear (e.g., the Gulf ofMexico shrimp trawl fishery). Small-scalefisheries use smaller boats and less gear,like artisanal or recreational/sport fisheries.No matter what type of fishery it is, all runthe risk of gear potentially becoming DFG.The types of DFG most often cited for ghostfishing are, in the order of prevalence andamount of available information (Shomuraand Godfrey, 1990): (a)GillnetsPots/TrapsBottom trawl netsLonglinesGillnets and pots have been the mostdocumented gear types to date regardingghost fishing, and this paper thereforeconcentrates on their loss rates, speciesmortalities, and mitigation efforts.(b)(c)(d)Figure 2. Several examples of different types of derelict fishing gear, from (a)gill nets, (b)to pots /traps, to (c)monofilament, to (d) trawl nets.Photo credits: (a) US Fish and Wildlife Service, (b, c) Northwest Straits Foundation, (d) NOAA .2015 MARINE DEBRIS GHOST FISHING REPORT5

GillnetsGillnets are so named because the fishtend to swim through the mesh and getentangled by their gills, but they can alsoswim through mesh such that their bodiesget wedged in the mesh or become snaredby fins, teeth, or other body projections.Varying the mesh size of the net targetsspecific sizes of fish, and can be veryselective for certain fisheries. There aremany types of gillnets that can becomeDFG and therefore potentially ghost fish,but they mainly fall into two groups. Someare considered active gear as they aretowed from a boat and then retrieved, aswith trammel nets. Others are consideredpassive gear, like a drift net, as they areusually set in a particular location, thenleft unattended for a period of time, called“soak time,” until retrieval. Although thespecifics of how different types of gillnetsare set vary, they are generally weighted atthe bottom and have floats at the top edgeso the net is oriented vertically in the watercolumn. Passive gear can have soak timesthat last from hours to days depending onthe fishery. This makes these passive types ofgillnets more susceptible to becoming DFGand therefore more likely to ghost fish, asthere is no person actively monitoring thenet, as there is with active gear types (Kaiser,Bullimore, Newman, Lock, and Gilbert,1996; Carr, Blott, and Caruso, 1992). Themost common ways that gillnets becomederelict are: breaking free from the floats;entanglement with the bottom surface, likereefs or rocky bottoms; and interactionor entanglement with other fishing gearpresent. This paper will primarily discussgillnets as being the passive type, but othertypes may be referenced as well.The ability for a gillnet to ghost fish dependson how open the net is as it drifts throughthe water column. Nets that “ball up”due to currents or tides tend not to be aseffective, but those that have some open netsurface remaining can continue capturingmarine organisms to varying degrees(Erzini, Monteiro, Ribeiro, Santos, Gaspar,Monteiro, and Borges, 1997). Studies usingexperimental ghost nets suggest that as thenet tangles and the open net area decreases,so does its ability to ghost fish (Kaiser et al.1996; Carr et al. 1992; Revill and Dunlin,2003). The likelihood of how well derelict6gillnets can ghost fish can also vary withwater depth. Those in shallower waterswith more dynamic tidal and currentconditions tend to ball up faster and stopfishing earlier, while gear lost or discardedin deep water with little tidal or currentactivity can continue to fish for years ratherthan months (Kaiser et al., 1996; Erzini etal., 1997).The monofilament constructionallows for the nets to be nearly invisiblein the water, thus making gillnets hardfor fish and other marine organisms tosee and avoid. The plastic monofilamentdoes not degrade and, once discarded orlost, these nets can potentially continueto ghost fish for extended periods of time;some have been recovered actively ghostfishing after 20 years (Good, June, Etnier,and Broadhurst, 2010). The shape, size,and visibility of gillnets has an importantbearing on how much gets caught (Ayaz,Acarli, Altinagac, Ozekinci, Kara, andOzen, 2006), but nets generally declinein ghost catch rate with time (Brown andMacfadyen, 2007; FANTARED). Biofouling(the attachment and growth of other livingorganisms, such as algae) makes thesenets more visible and thus easier to avoidwith time, which ultimately decreases thecatching ability of the net as well.“Some studies estimatethat over 90% ofspecies caughtin DFG are ofcommercial value,which can contributeto a significant loss ofrevenue for fishermen.”2015 MARINE DEBRIS GHOST FISHING REPORTGillnet Loss FrequencyThere is little information regarding thefrequency at which gillnets become DFGand the numbers of organisms lost due toghost fishing. Early documented work onlost gillnets and ghost fishing began withWay (1977) describing finding fish andcrabs in lost Newfoundland cod gillnets,and High (1981) demonstrating that derelictgill nets have the potential for causingmajor fish losses. The first comprehensivegroup of studies on DFG and ghost fishingconsequences were the FANTAREDstudies, done between 1995–2005 andcovering various parts of the UnitedKingdom, Norway, Sweden, Spain, France,and Portugal (Brown and Macfadyen,2007). These studies, and others (Hareide,Garnes, Rihan, Mulligan, Tyndall, Clark,Connolly, Misund, McMullen, Furevik,Humborstad, Hoydal, and Blasdale, 2005;Brown, Macfadyen, Huntington, Magnus,and Tumilty, 2005), did include some gillnetloss rate data. Rates of static fishing gear lossin the European Union (EU) were foundto be low, at 1% of all nets deployed eachyear, primarily due to high recovery ratesof fishing vessels using GPS (Brown et al.,2005). One common factor found was therelationship between water depth and gillnetloss rates. Those nets used in coastal waters 200m are not considered to be a significantproblem, while those used in deep waters 500m are most likely to be lost due toexcessive net length, increased soak timesand gear stress (Hareide et al., 2005). Deepwater fisheries in the northeast Atlanticwere a noted exception to low gear losses,as they accounted for more than 25,000 netsof the total 33,038 reported lost (Brown etal., 2005). In addition to higher loss rates,the deep-water fish species present tend tobe slow growing, long lived, and have lowreproductive rates (Merrett and Haedrich,1997; Koslow et al., 2000). These traits makesuch species highly vulnerable if ghostfishing significantly impacts populationnumbers.

Table 1. Summary of gillnet loss/abandonment/discard indicators from around the worldRegionFishery/gear typeIndicator of gear loss (data source)Data sourceNorth Sea & NE AtlanticBottom-set gill nets0.02–0.09% nets lost per boat per year

Taken in the context of these differences around the world, more data are needed across wider geographical areas to better refine the impacts of ghost fishing that occur due to DFG. This report is a summary of the current scientific knowledge of ghost fishing, the derelict fishing gear that contribute