Destructive fishing practices
Destructive fishing practices encompass a range of techniques that harvest fish and other marine organisms while causing extensive, often irreversible damage to ecosystems, habitats, and non-target species, yielding short-term catches at the expense of long-term sustainability.[1] These methods, including blast fishing with explosives to stun or kill fish schools, cyanide or poison application to capture live reef species for aquariums, and bottom trawling that drags heavy nets across seafloors, disrupt benthic communities, fragment coral structures, and generate high bycatch rates exceeding sustainable levels.[2][3] Such practices prevail in regions with limited regulatory enforcement, notably Southeast Asia and parts of Africa, where they accelerate habitat degradation—evidenced by empirical observations of reduced coral cover and sediment disturbance persisting for years—and contribute to fishery collapses by impairing reproductive capacities of targeted stocks.[2][4] Ecologically, bottom trawling alone has been documented to alter seafloor biodiversity comparably to clear-cutting forests, with direct removal of structural habitats and indirect effects like increased turbidity hindering recovery.[3] Economically, while providing immediate livelihoods in impoverished coastal communities, these approaches undermine future yields, as causal analyses link them to depleted stocks and heightened conflict over remaining resources, often exacerbating poverty cycles rather than alleviating them.[5] Global responses include international bans under frameworks like the FAO Code of Conduct for Responsible Fisheries and marine protected areas, though enforcement challenges persist due to illegal operations and the economic incentives of high-volume, low-skill harvesting.[1]Definition and Scope
Criteria for Classification as Destructive
Destructive fishing practices are classified based on their capacity to inflict irrecoverable habitat degradation or significant adverse environmental effects that extend beyond mere biomass extraction, such as through the destruction of critical benthic structures or coral formations essential for marine biodiversity.[6] A 2024 expert consensus, derived from workshops involving marine scientists and policymakers, defines these practices as those causing irreversible damage to habitats, excessive bycatch mortality undermining food webs, or disruptions to ecosystem services like nutrient cycling and species recruitment, often rendering affected areas unproductive for decades.[6] [7] This criterion emphasizes causal mechanisms, such as shockwaves from explosives pulverizing reef matrices—evidenced in Philippine sites where blast fishing reduced coral cover by up to 90% within months—or chemical toxins persisting in sediments, as documented in Indonesian cyanide operations affecting non-target invertebrates for years.[4] Classification further hinges on the method's inherent uncontrollability and disproportionate ecological harm relative to yield, distinguishing it from regulated overexploitation.[8] The FAO Code of Conduct for Responsible Fisheries explicitly prohibits techniques like dynamiting or poisoning that produce indiscriminate shock or toxicity effects, leading to collateral mortality rates exceeding 70% in some cases, as opposed to selective gears with bycatch under 10%. Peer-reviewed analyses highlight habitat alteration as a core metric: bottom-contact gears scoring high if they resuspend sediments or remove biogenic structures at rates impeding recovery, with empirical data from global trawling surveys showing seafloor biodiversity losses persisting 5–20 years post-disturbance.[9] Excessive bycatch is quantified where discards or incidental kills disrupt trophic balances, such as in drive-net methods entangling juveniles and predators alike, reducing recruitment by 50% in targeted stocks per modeling studies.[4] Regulatory frameworks, including UNEP and FAO guidelines, incorporate thresholds for "significant adverse impact," often calibrated via before-after-control-impact studies measuring metrics like species richness decline or biomass recovery time exceeding natural regeneration cycles of 10–50 years for sensitive ecosystems.[7] While the term "destructive fishing" has been critiqued for vagueness in pre-2020 literature—frequently conflating intensity with method type—recent refinements prioritize evidence-based causality, excluding practices mitigated by spatial closures or gear modifications that maintain ecosystem integrity.[9] [8] Thus, classification requires verifiable data on permanence of damage, often verified through remote sensing or diver transects confirming structural loss beyond sustainable harvest levels.[6]Differentiation from Overfishing and Sustainable Methods
Destructive fishing practices differ from overfishing in that they entail methods causing direct, often irreversible habitat degradation and broad ecological disruption, independent of harvest volume relative to stock replenishment rates. Overfishing, by contrast, refers to extracting fish biomass at rates surpassing natural reproduction, resulting in population declines but not necessarily habitat destruction if non-damaging gear is used. For instance, the Food and Agriculture Organization (FAO) identifies destructive techniques like dynamite or poison use as harmful due to their physical or chemical impacts on reefs and benthic environments, whereas overfishing metrics focus on metrics like maximum sustainable yield exceedance, as tracked in global assessments where 35.4% of assessed stocks were overfished in 2017.[10] [11] This distinction arises from causal mechanisms: destructive practices deploy explosives that shatter coral structures—reducing reef complexity by up to 50% in affected areas—or drag heavy nets that scour seabeds, eradicating epifaunal communities and altering sediment dynamics, effects persisting for decades. Overfishing, even when severe, preserves habitat integrity if line or trap methods are employed, allowing potential recovery through reduced effort alone, as evidenced by rebuilt stocks like U.S. Atlantic sea scallops following quota enforcement without gear reform. Destructive methods, however, compound depletion by impairing recruitment and biodiversity, with bycatch mortality often exceeding 90% in cyanide fisheries, amplifying ecosystem-wide cascading failures.[6] [12] [13] Sustainable fishing methods further diverge by integrating low-impact gear with regulatory frameworks to avoid both stock collapse and environmental harm, emphasizing selectivity and ecosystem-based management. Techniques such as pole-and-line or handline fishing target species with minimal bycatch—often under 5%—and negligible habitat contact, enabling stocks to hover at or above biomass levels supporting maximum sustainable yield, as per FAO guidelines. In regions like the Maldives, where such methods predominate, tuna stocks remain stable without the chronic degradation seen in trawled or blasted zones, underscoring how sustainability hinges on gear design that preserves functional habitats for prey, predators, and juveniles alike.[14] [11] [13]Historical Development
Early Origins and Traditional Practices
The use of natural plant-based poisons to stun or kill fish represents one of the earliest documented destructive fishing practices, employed by indigenous cultures worldwide for millennia. In temperate regions across the Americas, Europe, Asia, and Africa, communities extracted toxins from plants such as Derris species (rotenone-bearing roots) or Tephrosia to create fish-killing barrages in streams and shallow waters, a method that indiscriminately affected non-target species and disrupted local aquatic ecosystems.[15] These techniques, while effective for small-scale subsistence, often led to localized depletion and water contamination persisting beyond immediate harvest periods.[16] In Europe, precursors to modern bottom trawling emerged in the 14th century, with beam trawls—nets dragged along the seafloor using wooden beams—first recorded in England around 1350. This method, initially deployed by small coastal vessels in the English Channel and North Sea, physically disrupted benthic habitats by scraping sediments and uprooting marine vegetation, prompting contemporary complaints from fixed-gear fishers about habitat degradation and interference with juvenile fish recruitment.[17] Historical accounts from the period highlight its classification as overly aggressive, capable of capturing undersized fish and damaging spawning grounds, foreshadowing later ecological concerns.[18] Traditional drive-in netting variants, such as early forms of muro-ami practiced in Southeast Asian and Pacific Island communities, involved herding fish toward shorelines using noise, divers, or weighted nets, often damaging coral structures through physical contact and entrapment of bycatch. These methods, rooted in pre-colonial customs, prioritized short-term yields over habitat preservation, contributing to gradual reef erosion in high-use areas.[19] Unlike sustainable hook-and-line or trap-based traditions, such practices reflected a causal trade-off where immediate caloric needs outweighed long-term stock viability, as evidenced by archaeological indicators of intensified reef exploitation in Polynesian sites dating to 1000–1500 CE.[20]Modern Expansion and Key Milestones
The industrialization of fishing fleets following World War II marked a pivotal expansion of destructive practices, as diesel engines, synthetic nets, and sonar enabled larger-scale bottom trawling operations that penetrated deeper waters and previously untouched seabeds.[21] Bottom trawling's reach into deep-sea habitats accelerated in the second half of the 20th century, driven by technological advances like stronger winches and echo sounders amid declining yields from coastal fisheries.[22] By the late 20th century, this method dominated high-impact catches, with over 99% of global bottom trawling occurring within national exclusive economic zones, often exacerbating habitat disruption in vulnerable ecosystems.[23] Blast fishing originated during World War II, with European influences introducing explosive use to stun fish; in the Philippines, it gained traction among local fishermen in the 1940s, who paid municipal fees for permits before nationwide bans took effect around 1970, though enforcement remained inconsistent.[24] This practice proliferated in coral reef-dependent regions of Southeast Asia and the Indo-Pacific by the mid-20th century, fueled by poverty and easy access to commercial dynamite, leading to widespread reef fragmentation despite illegality in most jurisdictions.[25] Cyanide fishing emerged in the Philippines during the 1950s to capture live ornamental species for the burgeoning aquarium trade, expanding in the 1960s with over a million kilograms of sodium cyanide deployed on reefs by the late 20th century.[26] By the 1970s, the technique shifted to live reef food fisheries, spreading to Indonesia, Malaysia, and Pacific islands, where it targeted high-value species like groupers, causing acute coral mortality and fishery collapses in affected areas.[27] These milestones reflect a pattern where short-term economic pressures and technological accessibility outpaced regulatory responses, amplifying ecological damage across tropical fisheries.[28]Specific Methods
Blast Fishing
Blast fishing, also known as dynamite or bomb fishing, involves the use of explosives such as dynamite, homemade bombs from ammonium nitrate fertilizers, or other detonable materials to generate underwater shockwaves that stun or kill fish within a radius, causing them to float to the surface for easy collection.[29][30] The method typically entails fishers throwing or placing the explosive near reefs or shoals, where the blast's pressure wave ruptures fish swim bladders and internal organs, indiscriminately affecting target species, juveniles, and non-target marine life including invertebrates and corals.[31][32] This practice yields short-term high catches—often several hundred kilograms per blast—but depletes local stocks rapidly due to its inefficiency in selective harvesting.[29] Prevalent in tropical coral reef regions, blast fishing is concentrated in Southeast Asia, including Indonesia, the Philippines, and Malaysia, as well as East Africa such as Tanzania's coastal waters, where it threatens small-scale fisheries and food security.[29][31] In Indonesia's Spermonde Archipelago, for instance, up to 75% of reefs have been damaged, creating dead zones and reducing biodiversity hotspots to rubble fields.[33] Globally, it affects dozens of countries, with Reef Check surveys indicating persistent blasting despite bans, driven by artisanal fishers seeking immediate economic returns amid poverty and limited gear for sustainable methods.[29][34] The ecological toll includes immediate fragmentation of coral structures, where blasts pulverize reef frameworks into unstable rubble, hindering regrowth and favoring algal overgrowth that further erodes habitat complexity.[35][36] Studies in Bunaken National Park, Indonesia, show prolonged instability in blasted areas, with coral recovery impeded for decades and fish populations declining due to lost shelter and breeding grounds.[35] Economically, Indonesia faces projected losses exceeding US$570 million over 20 years from reduced fisheries productivity.[37] Blast fishing is illegal under national laws in affected nations, including universal prohibitions on explosives in fisheries, yet enforcement remains inadequate due to corruption, resource shortages, and outdated regulations, perpetuating its use in impoverished communities where alternatives like hook-and-line fishing yield lower short-term gains.[4][34][31]Bottom Trawling
Bottom trawling employs large, cone-shaped nets dragged along the seabed by one or two vessels to capture demersal fish and shellfish living near or on the ocean floor.[38] The net's mouth is kept open horizontally by hydrodynamically designed otter boards or vertically by weighted ground gear, with the latter often featuring heavy chains or rollers that maintain contact with the substrate.[39] Common variants include otter trawls, which use doors to spread the net, and beam trawls, relying on a rigid metal beam attached to shoes that skid across the bottom.[40] This method physically disrupts seafloor sediments through compression, displacement, and resuspension, akin to repeated plowing of soil, which damages benthic habitats including seagrasses, corals, and burrows of infaunal organisms.[41] [42] Studies indicate that trawling gear can penetrate sediments up to 10-20 cm deep, reducing habitat complexity and eliminating slow-growing epifaunal species like sponges and anemones.[43] In sensitive ecosystems such as seamounts and deep-sea corals, it causes widespread scarring and biodiversity loss, with recovery times potentially exceeding decades for long-lived species.[44] Bycatch constitutes a major drawback, with bottom trawls accounting for approximately 46% of global discards, equating to over 4.2 million tonnes annually of unwanted catch returned to the sea, often dead or dying.[43] [45] Shrimp trawling exhibits particularly high discard ratios, sometimes exceeding 9:1 compared to more selective gears.[46] Additionally, trawling disturbs organic carbon stocks in sediments, releasing an estimated 0.52 to 1.47 billion metric tons of CO2 equivalent yearly—comparable to global aviation emissions—by resuspending buried material and impairing sequestration.[47] [48] Regulations vary globally, with bans implemented in marine protected areas hosting vulnerable habitats; for instance, Greece prohibited bottom trawling in such zones in 2020, marking Europe's first national-level restriction, while the UK extended prohibitions to 41 sites in 2025.[49] [50] The European Union mandates phasing out trawling in protected areas by 2030, though enforcement remains inconsistent, and operations persist in many unprotected waters despite demonstrated ecological costs.[39] Peer-reviewed assessments underscore that while target stock sustainability is achievable under quotas, benthic impacts and high bycatch undermine overall ecosystem health, favoring alternatives like selective gears in sensitive regions.[43] [51]Cyanide Fishing
Cyanide fishing involves divers spraying a solution of sodium cyanide into coral reef crevices to stun fish, prompting them to emerge in a disoriented state for live capture, primarily for the global aquarium trade and live reef fish markets in Asia.[52] The method relies on cyanide's rapid inhibition of cellular respiration, rendering fish temporarily immobile without immediate lethality, though concentrations typically range from 10-30 grams per liter in seawater to achieve this effect.[53] This practice emerged in the Philippines during the early 1960s, driven by demand for live food fish like groupers and snappers, and expanded to Indonesia and other Coral Triangle nations by the 1980s amid growing export markets.[28] Prevalent in Southeast Asian reefs, cyanide fishing targets over 1,800 species, with annual harvests estimated in the tens of millions of fish across the Indo-Pacific, though precise figures remain elusive due to its illicit nature.[52] In Indonesia, where it supplies live fish to Hong Kong and mainland China markets, the technique persists despite prohibitions under the 1985 Fisheries Regulation Act, which criminalizes poison use, owing to weak enforcement and economic incentives for impoverished coastal communities.[54] Similarly, the Philippines has maintained bans since the 1998 Coral Reef Conservation Act, yet cyanide detection labs established for enforcement reveal ongoing violations, with over 1 million kilograms of the chemical deployed on its reefs since the 1960s.[28][55] Environmentally, cyanide disrupts coral symbiosis by inhibiting Symbiodinium photosynthesis, leading to rapid bleaching and tissue necrosis even at sublethal doses below 0.06 mg/L, with synergistic mortality when combined with ocean warming.[56][52] Studies on Philippine reefs demonstrate near-total mortality of hard and soft corals within 96 hours of exposure to collector-level concentrations, alongside non-target kills of invertebrates and juvenile fish, eroding reef structure and biodiversity hotspots.[57] Captured fish suffer acute organ damage, including liver and brain necrosis, with survival rates post-capture often below 50% due to lingering toxicity, exacerbating stock declines in vulnerable species.[52] Detection challenges stem from cyanide's quick dilution and metabolism in fish tissues, complicating forensic verification and undermining bans, as pulse spraying leaves minimal residue after 24-48 hours.[53] Efforts like cyanide-testing protocols by agencies such as NOAA highlight persistent trade flows, with illegally sourced fish infiltrating U.S. and European aquariums undetected in up to 70% of cases from high-risk origins.[58] Despite international calls for traceability, enforcement gaps tied to corruption and poverty sustain the practice, yielding short-term gains of $0.50-5 per fish but long-term reef degradation valued at billions in ecosystem services.[59][60]Muro-Ami and Drive-In Netting
Muro-ami, also known as a drive-in net technique, employs an encircling net deployed on coral reefs to capture schools of reef-associated fish, with divers using weighted scare lines, rocks, or pounding devices to herd fish toward the net.[61][62] This method originated in Okinawa, Japan, in the early 1900s and spread to Southeast Asia, particularly the Philippines in the 1930s via Japanese fishermen.[61][63] Operations typically involve a fleet of boats positioning a net approximately 37 meters long and 10 meters deep, while lines of divers—historically including children—advance from deeper water, creating noise and disturbance to panic fish into the enclosure.[64] The technique targets elusive reef species like snappers and groupers, yielding high catch volumes but at the cost of direct physical disruption to reef habitats.[61] The destructiveness arises primarily from mechanical impacts: divers' trampling, scare lines weighted with metal or stones that smash corals, and net dragging over benthic structures, which fracture branching and tabular corals essential for fish shelter and reproduction.[61][62] In the Philippines, where muro-ami proliferated on extensive reefs, repeated applications have led to widespread degradation, with legacy effects including reduced coral cover and altered reef topography persisting even after cessation.[65] Empirical studies in Indonesian waters, such as Karimunjawa National Park, document that pre-ban muro-ami operations correlated with suppressed biomass of herbivorous fish, which rely on intact corals for grazing algae; following the 2011 prohibition, herbivore biomass rose significantly, indicating reversal of fishing-induced trophic shifts.[66][67] Drive-in netting variants, encompassing muro-ami and similar barrier-assisted herding, amplify damage when applied to spawning aggregations, as nets intercept concentrated fish while scare tactics pulverize reef spurs and grooves.[68] In Southeast Asian contexts, these practices have depleted juvenile fish stocks by capturing breeders en masse, exacerbating recruitment failure in overexploited reefs.[69] Regulatory responses include outright bans under the Philippines' 1998 Fisheries Code, which classifies muro-ami as destructive, though enforcement remains inconsistent due to artisanal scales and poverty-driven persistence.[65] Comparable prohibitions in Indonesia since 2011 have shown measurable reef recovery, with increased structural complexity and fish diversity, underscoring the causal link between method cessation and habitat restoration.[66][67]Other Techniques Including Ghost Fishing
Ghost fishing occurs when abandoned, lost, or discarded fishing gear continues to entrap and kill aquatic organisms independently of human operation. This phenomenon arises primarily from nets, traps, pots, and lines that remain functional after detachment from vessels due to storms, snags, or intentional discard. Derelict gear entangles fish, crustaceans, seabirds, and marine mammals, leading to suffocation, starvation, or predation, while also damaging habitats through persistent dragging or smothering of benthic organisms.[70][71] Quantitative assessments indicate substantial ecological toll: an estimated 500,000 to 1 million metric tons of such gear enter oceans annually, comprising up to 10% of total marine litter. Nets and traps exhibit prolonged "soak times" correlating with catch rates, where a single derelict net can kill over 500 fish before degrading. Globally, ghost gear threatens more than 700 marine species, contributing to 35% of seabird population declines, 27% of fish stock reductions, and 20% of invertebrate losses in affected areas. Economic repercussions include competition with active fisheries, as derelict traps capture target species like crabs and lobsters, reducing yields by up to 20-25% in regions such as the U.S. Northeast.[72][73][74] Among gear-specific variants, lost pots and traps—common in crustacean fisheries—exacerbate ghost fishing by forming "trap chains" that attract and retain prey indefinitely until biofouling diminishes efficacy, often after months or years. Studies link higher loss rates to rough seafloors or poor gear maintenance, with peer-reviewed analyses confirming causal impacts on provisioning ecosystem services like sustained fisheries yields. Unlike active methods, ghost fishing persists covertly, evading direct regulation and amplifying cumulative mortality beyond initial deployments.[71][75] Other ancillary techniques include unregulated use of drift gillnets or set nets in sensitive habitats, where frequent abandonment due to illegal operations mirrors ghost effects by indiscriminately ensnaring non-target species and corals. These practices, though less explosive than blast or cyanide methods, erode reef structures through prolonged entanglement, with documented cases in Southeast Asian waters showing persistent biodiversity suppression. Mitigation hinges on biodegradable materials and tracking technologies, yet enforcement gaps in developing fisheries sustain prevalence.[75][71]Environmental and Ecological Impacts
Direct Habitat Destruction
Direct habitat destruction from destructive fishing practices entails the physical demolition or alteration of marine substrates, including seabeds and coral reefs, via mechanical contact or explosive forces, thereby reducing structural complexity and suitability for resident biota. Bottom trawling constitutes the foremost contributor, as nets and doors scrape, plow, and compact seafloor sediments while uprooting epifaunal organisms such as sponges, corals, and bryozoans.[51] This process flattens heterogeneous benthic landscapes into homogenized plains, diminishing habitat for invertebrates and demersal fish.[42] Empirical assessments reveal immediate reductions in epifaunal density and increased damage in trawled zones compared to undisturbed references, with chronic effects including lowered biomass and shifts toward opportunistic species.[76] Blast fishing inflicts acute structural devastation on coral reefs through underwater detonations that propagate shock waves, fracturing calcium carbonate skeletons and dislodging colonies. Resultant rubble fields destabilize substrates, hindering coral recruitment and larval attachment, which perpetuates barren conditions for decades absent intervention.[35] In Southeast Asian contexts, such as Indonesia, blast-induced rubble impedes natural recovery trajectories, mirroring chronic stressors in severity and demanding active rehabilitation to restore cover.[77] Muro-ami techniques exacerbate reef damage by deploying weighted lines or stones to herd fish toward encircling nets, repeatedly smashing corals and eroding live cover. This pounding directly ablates reef frameworks, compounding fragmentation in vulnerable shallow habitats.[78] Across affected regions, these methods collectively erode the architectural integrity essential for biodiversity, with recovery contingent on cessation and habitat resilience factors like sediment stability and water quality.[43]Biodiversity Loss and Bycatch Effects
Destructive fishing practices contribute to biodiversity loss through the indiscriminate mortality of non-target species and the degradation of critical habitats such as coral reefs and benthic ecosystems, which support high levels of marine species diversity. Bycatch in these methods often includes juveniles, rare or endemic species, and ecologically key organisms like predators and herbivores, disrupting food webs and reducing overall ecosystem resilience. Empirical studies document that such practices can lead to declines in species richness exceeding 30-50% in heavily impacted areas, with recovery hindered by persistent structural damage.[79][29] In blast fishing, detonations indiscriminately kill fish and invertebrates within a radius of up to 20 meters, resulting in bycatch rates that encompass a wide array of reef species beyond the targeted reef fish. This method pulverizes coral structures into unstable rubble, which inhibits recolonization by sessile organisms and algae-grazing species, leading to documented reductions in coral-associated biodiversity; for instance, affected reefs exhibit persistent instability even decades post-blast, with fish species diversity dropping by approximately 40-60% compared to undamaged sites.[29][80][78] Bottom trawling generates substantial bycatch, accounting for about 46% of global discards, including non-target fish, sharks, seabirds, and benthic invertebrates, with discard rates in shrimp trawls reaching 60-80%. The gear's contact with the seabed crushes habitat-forming species like sponges and corals, reducing benthic biodiversity by up to 50% in trawled zones and altering community composition toward opportunistic, low-diversity assemblages. Long-term data from North Sea surveys show trawling intensity correlating with 20-30% lower species richness in infaunal communities.[43][81][51] Cyanide fishing, prevalent in the live reef fish trade, stuns target species but lethally affects bycatch through toxicity, killing up to 75% of captured reef fish via post-capture stress and damaging non-target corals and invertebrates over areas of 1 square meter per fish operation. This results in elevated mortality of symbiotic reef organisms, contributing to localized species losses; peer-reviewed analyses estimate that cyanide exposure inhibits coral photosynthesis and exacerbates bleaching, indirectly reducing fish diversity dependent on healthy reefs by 20-40% in chronic use areas.[53][82][83] Muro-ami and drive-in netting involve corralling fish over reefs, causing physical damage from beaters and nets that entangle bycatch such as juvenile fish and sessile invertebrates, with negative impacts on at least seven reef fish families documented in Philippine studies. These methods reduce structural complexity of reefs, leading to cascading declines in herbivore and predator populations, and biodiversity metrics show 25-35% lower fish guild diversity in muro-ami zones compared to protected areas.[84][78][66]| Practice | Estimated Bycatch/Discard Rate | Biodiversity Impact Example |
|---|---|---|
| Blast Fishing | Indiscriminate kill radius: 10-20m | 40-60% drop in reef fish species diversity[29] |
| Bottom Trawling | 46% of global discards; 60-80% in shrimp | Up to 50% benthic species loss[43][51] |
| Cyanide Fishing | 75% post-capture mortality | 20-40% reef-dependent diversity decline[53] |
| Muro-Ami | High entanglement of juveniles | 25-35% lower guild diversity[84] |
Long-Term Effects on Fish Stocks and Recovery Data
Destructive fishing practices such as blast fishing and bottom trawling contribute to long-term depletion of fish stocks by destroying essential habitats like coral reefs and benthic communities, which reduces juvenile fish recruitment and alters food webs.[29][79] In blast-fished areas, coral rubble remains unstable for decades due to constant shifting of fragments, preventing coral recolonization and sustaining low fish biomass levels, as observed in Indonesian reefs where damaged sites showed persistent structural instability even 20–30 years post-blasting.[80][35] Bottom trawling exacerbates depletion by repeatedly disturbing seafloor sediments, leading to a decline in invertebrate prey species that support demersal fish populations, with global analyses indicating that trawled areas exhibit reduced overall fish productivity over multi-year scales compared to untrawled controls.[43][11] Cyanide fishing, while primarily targeting live reef fish for the aquarium trade, indirectly depletes stocks through high post-capture mortality—up to 75% of captured organisms die within 48 hours from stress and poisoning—and collateral damage to reef habitats, compounding recruitment failures in affected areas.[85] Empirical data from overfished regions link these practices to broader stock collapses, with the Food and Agriculture Organization estimating that one-third of global fish stocks are overexploited, partly due to habitat-degrading methods that hinder natural replenishment.[11][86] Recovery data following bans on destructive practices demonstrate variable but often substantial rebounds in fish stocks, contingent on enforcement duration and habitat resilience. In the Gulf of Castellammare, Italy, a four-year bottom trawling ban implemented in 1988 led to an eightfold increase in total fish biomass upon reopening, with targeted species showing gains from 1.2- to 10-fold.[87] Similarly, tropical benthic communities in trawled Philippine waters exhibited significant biodiversity recovery after a trawl ban, including higher abundances of fish-associated invertebrates, indicating ecosystem-level restoration that bolstered fish populations.[88] Blast-fished reefs, however, recover more slowly; studies in Indonesia's Bunaken National Park reveal that even after decades of protection, rubble-dominated areas support far lower fish densities than intact reefs, underscoring the causal role of persistent habitat instability in prolonged depletion.[35]| Practice | Example Location | Recovery Intervention | Observed Fish Stock Outcome | Timeframe | Source |
|---|---|---|---|---|---|
| Bottom Trawling | Gulf of Castellammare, Italy | 4-year ban (1988) | 8-fold biomass increase | 4 years | [87] |
| Bottom Trawling | Tropical Philippines | Trawl ban in coastal waters | Increased benthic biodiversity supporting fish recovery | Multi-year post-ban | [88] |
| Blast Fishing | Bunaken National Park, Indonesia | Decades of protection post-peak blasting (1990s) | Persistent low fish biomass due to unstable rubble | 20–30+ years | [35] |
Socio-Economic Factors
Drivers Rooted in Poverty and Local Economies
In regions such as Southeast Asia and East Africa, coastal communities exhibit acute poverty, with 20-30% of the approximately 270 million people in coastal areas of developing countries living below poverty lines, often heavily reliant on reef-associated fisheries for subsistence and income.[91] This economic dependence fosters destructive practices like blast and cyanide fishing, as impoverished artisanal fishers, lacking capital for sustainable gear or alternative livelihoods, opt for methods yielding immediate, high-volume catches to address daily food and cash needs amid declining stocks from overexploitation.[92] [34] In the Philippines, for example, over one million small-scale fishers depend on reefs providing up to 50% of animal protein and supporting 70% of fish harvests on certain islands, pressuring households toward dynamite fishing when sustainable yields falter.[92] Local economies structured around small-scale, labor-intensive fishing amplify these incentives, as population pressures and limited diversification—such as into tourism or mariculture—constrain options in areas with high unemployment and low education levels.[93] In Tanzania, where 10,000-15,000 full-time marine fishers rely on reefs and 37% of the population lives below $1 per day, poverty intersects with resource scarcity to make explosives appealing for youth facing unsustainable effort in legal methods.[92] [94] Similarly, in Indonesian villages, declining catches and absence of viable non-fishing employment drive adoption of blast techniques, despite bans, as short-term economic gains outweigh perceived long-term risks in cash-strapped households.[95] Empirical analyses, however, reveal mixed causality, with a 2021 global review of blast fishing finding limited direct evidence that poverty alone drives prevalence, emphasizing instead enabling factors like explosive availability and enforcement gaps that exploit economic vulnerabilities rather than originate from them.[29] In such contexts, poverty functions more as an amplifier in local economies, where institutional failures and market demands for high-value species (e.g., live reef fish) intersect with survival imperatives, perpetuating destructive cycles without addressing root livelihood deficits.[29] [92]Role of Global Markets and Demand
Global demand for high-value seafood drives the persistence of destructive fishing practices, as fishers in resource-poor regions prioritize methods that enable rapid, large-scale captures to meet export quotas and capitalize on premium prices. The global fisheries trade, valued at approximately USD 171 billion in exports as of 2024, underscores this dynamic, with crustaceans such as shrimp accounting for 22% of traded volume and commanding significant economic incentives for intensive harvesting.[96][97] Affluent markets in Asia, Europe, and North America fuel this pressure, where rising consumption of luxury items like live reef fish and processed shrimp incentivizes techniques that bypass sustainable limits, often at the expense of long-term stock viability.[11] The live reef food fish trade exemplifies market-driven adoption of cyanide fishing, primarily supplying upscale restaurants in Hong Kong and China, where demand for fresh, high-end species like groupers has escalated with economic growth. This illicit method, involving sodium cyanide to stun fish for live transport, yields prices several times higher than for dead catches, motivating fishers across the Indo-Pacific to target coral reefs despite habitat damage and illegality in most source countries.[98] Annual harvests via cyanide are estimated to involve tens of millions of fish, correlating directly with trade expansion that prioritizes immediate supply over ecological sustainability.[28][99] Bottom trawling for shrimp similarly responds to surging international demand, with the global shrimp market projected to exceed USD 69 billion by 2028, driven by exports to Western consumers seeking affordable protein.[100] In exporting nations like those in Southeast Asia, trawling's efficiency in bulk extraction aligns with competitive pricing pressures, resulting in seabed disruption and bycatch rates as high as 46% of discards in shrimp fisheries, yet persists due to the method's alignment with high-volume trade requirements.[43][101] These practices reflect a causal chain where distant consumer preferences subsidize environmental costs borne by source ecosystems, underscoring the need for supply-chain traceability to mitigate incentives.[102]Challenges in Enforcement and Governance
Enforcing prohibitions on destructive fishing practices, such as cyanide use and blast fishing, faces significant hurdles due to the vast expanse of marine environments and limited surveillance capabilities. Coastal states in Southeast Asia, where these methods are prevalent, often lack sufficient patrol vessels, aircraft, and personnel to monitor remote reef areas effectively, allowing small-scale operators to evade detection.[58] For instance, in Indonesia and the Philippines, bans implemented in the 1990s have proven difficult to uphold, with illegal activities persisting because enforcement relies on sporadic patrols that cover only a fraction of affected waters.[54] Detection of specific destructive techniques exacerbates enforcement challenges, particularly for cyanide fishing, where residues degrade rapidly and field testing methods remain unreliable. Workshops convened by NOAA in 2006 highlighted that without advanced, portable detection tools, authorities struggle to gather prosecutable evidence, leading to low conviction rates even when suspects are apprehended.[58] Similarly, blast fishing leaves temporary damage that dissipates, complicating attribution to individual actors amid widespread community involvement driven by immediate economic needs.[103] Corruption within fisheries governance structures further undermines enforcement efforts, enabling illegal operators to secure licenses, bribe inspectors, or receive protection from prosecution. A 2015 UNODC analysis identified corruption in licensing and oversight as a primary facilitator of illegal practices, with officials in resource-poor nations prioritizing short-term gains over long-term sustainability, resulting in distorted quota allocations and ignored violations.[104] In regions like West Africa and Southeast Asia, this has led to systemic failures, where up to 30% of catches may involve unreported destructive methods, eroding public trust in regulatory bodies.[105] International governance adds layers of complexity, as destructive practices often occur in transboundary waters or high seas, where jurisdictional overlaps hinder coordinated action. Frameworks like the FAO's Port State Measures Agreement aim to close loopholes but suffer from uneven ratification and implementation, with only 60 countries fully compliant as of 2023, allowing flagged vessels from non-signatory states to offload illicit catches.[106] Weak inter-agency cooperation and inadequate data-sharing among nations exacerbate these issues, perpetuating illegal, unreported, and unregulated (IUU) fishing that includes destructive elements, estimated to cost global economies $23-50 billion annually.[107]Regulatory Efforts and Outcomes
International Frameworks and Agreements
The Food and Agriculture Organization (FAO) of the United Nations adopted the Code of Conduct for Responsible Fisheries in 1995 as a voluntary framework promoting sustainable practices, explicitly urging states to "prohibit dynamiting, poisoning and other comparable destructive fishing practices" under Article 8.4.2. This instrument emphasizes minimizing habitat damage and bycatch through selective gear and techniques, while integrating fisheries into broader coastal management to prevent environmental degradation from methods like explosives or chemicals. Adopted following the 1992 International Conference on Responsible Fishing, the Code has influenced over 100 national policies but lacks binding enforcement, relying on state implementation.[108] The United Nations Convention on the Law of the Sea (UNCLOS), opened for signature in 1982 and entering into force in 1994 with 169 parties as of 2025, establishes general obligations to conserve marine living resources and protect the marine environment from harmful fishing technologies under Articles 61, 62, 119, and Part XII.[109] States must determine allowable catches considering ecosystem impacts, minimize bycatch and habitat damage, and cooperate on transboundary stocks, providing a legal foundation to restrict destructive methods like bottom trawling where they cause pollution or resource depletion. However, UNCLOS does not specify bans on particular practices, leaving specificity to subsequent instruments and national laws.[110] Targeted at deep-sea operations, the FAO's International Guidelines for the Management of Deep-sea Fisheries (2009) recommend governance measures to protect vulnerable marine ecosystems (VMEs) from bottom-contact gears such as trawls and dredges, including prior environmental assessments, real-time protocols for halting operations upon VME encounters, and "move-on" rules to relocate fishing efforts. Developed in response to UN General Assembly Resolution 61/105 (2006), which mandated regulation of high-seas bottom fisheries to avoid significant adverse impacts, these non-binding guidelines have informed Regional Fisheries Management Organizations (RFMOs) but show variable compliance, with ongoing unregulated trawling documented in areas beyond national jurisdiction.[111] Complementing these, the 1995 Agreement for the Implementation of the Provisions of UNCLOS relating to the Conservation and Management of Straddling Fish Stocks and Highly Migratory Fish Stocks (UNFSA), with 92 parties, requires precautionary approaches and ecosystem-based management, indirectly curbing destructive practices through compatibility of measures and impact assessments on associated biological communities.[112] The 2023 Biodiversity Beyond National Jurisdiction (BBNJ) Agreement, adopted under UNCLOS and requiring 60 ratifications for entry into force (achieving 61 by September 2025), enables area-based management tools like marine protected areas and mandatory environmental impact assessments in high seas to mitigate threats including destructive fishing.[113] Despite these frameworks, global enforcement gaps persist, as evidenced by SDG Target 14.4's unmet 2020 goal to end destructive practices, with reliance on port state measures and RFMOs for practical outcomes.[114]National and Regional Bans
Several countries in Southeast Asia and the Pacific have enacted national prohibitions on blast fishing, a destructive method involving explosives that damages coral reefs and fish habitats. In the Philippines, the use of dynamite or other explosives to catch fish was declared illegal under Republic Act No. 428, enacted on June 7, 1950, which prohibits the possession, sale, or distribution of fish stupefied or killed by such means.[115] This was reinforced by Presidential Decree No. 704 in 1975, banning the catching of fish with explosives, and further codified in the Philippine Fisheries Code of 1998 (Republic Act No. 8550), which imposes penalties including imprisonment and fines for explosive use in fishing.[116][117] Cyanide fishing, another destructive practice used for live reef fish capture, is similarly prohibited under the 1998 Fisheries Code, with violations punishable by up to six months imprisonment and fines.[118] In Indonesia, blast fishing has been illegal under national fisheries regulations since at least the late 20th century, though specific enactment dates for comprehensive bans are tied to broader prohibitions on destructive gear in the Ministry of Marine Affairs and Fisheries laws, with intensified enforcement efforts noted from the 1990s onward.[103] In Tanzania, dynamite fishing was first banned in 1970, with the prohibition strengthened in 2003 under the revised Fisheries Act, which mandates minimum sentences of five years for perpetrators and 12 months for possession of explosives.[119][120] Fiji has implemented national prohibitions on destructive offshore practices, including dynamite and poison fishing, as outlined in its Fisheries Act, which explicitly bans explosives, noxious substances, and SCUBA-assisted fishing to protect reefs.[121][122] Regional bans on bottom trawling, which drags heavy nets across seafloors and disrupts benthic ecosystems, have emerged in various jurisdictions. In New Zealand's Waikato region, the Regional Council approved a prohibition on destructive bottom-contact fishing methods, including bottom trawling, in October 2025, following advocacy for marine protection, though appeals may delay full implementation.[123] In the United Kingdom, the government pledged in June 2025 to ban bottom trawling in 41 marine protected areas (MPAs) covering sensitive offshore habitats, expanding protections beyond prior limited closures, while France committed to similar restrictions in select MPAs during the same period.[124][125] However, the UK later clarified no blanket ban across all MPAs, allowing the practice in approximately 90% of its 377 designated areas as of September 2025.[126] European Union member states have authority under court rulings to impose national bans on bottom trawling in MPAs to safeguard vulnerable marine ecosystems, as affirmed by the EU General Court in 2025, though no uniform EU-wide phase-out exists, and implementation varies by country.[127] In the Pacific, regional frameworks have prohibited destructive methods like bottom trawling since the 1980s in areas managed by bodies such as the Western Pacific Fishery Management Council.[128] These bans often target specific zones but face challenges from overlapping jurisdictions and international fleets.Empirical Evidence on Ban Effectiveness
Empirical studies on bans targeting destructive fishing practices, such as bottom trawling and dynamite fishing, indicate that effective enforcement can lead to measurable recoveries in benthic communities, fish abundance, and habitat health, though outcomes vary due to factors like illegal activity and environmental pressures. In regions with strong compliance, bans have demonstrated increases in macrobenthic abundance and diversity, alongside improvements in fish size structures and spillover effects to adjacent fisheries. However, persistent challenges, including incomplete enforcement and non-trawling pressures, often result in mixed or partial recoveries, underscoring the need for complementary measures like monitoring and alternative livelihoods.[88][129] A prominent case is Hong Kong's territory-wide trawl ban implemented on December 31, 2012, which prohibited motorized bottom trawling to restore overexploited coastal ecosystems. Surveys comparing pre-ban (2012) and post-ban (2015) conditions revealed significant benthic recovery: macrobenthic abundance rose from 253 to 848 individuals per site, species richness increased from 27.5 to 48.3 species per site, and functional diversity metrics, such as niche occupancy, improved from 10.45% to 18.90%. Biomass remained stable overall (65.50 g to 70.81 g per 0.5 m²), but rose at previously trawled sites from 17.39 g to 50.05 g per 0.5 m², linked to reduced sediment disturbance and higher total organic matter. Concurrently, demersal fish and crustacean abundance substantially increased, with predatory fish populations showing restored size structures and trophic dynamics. For specific taxa like stomatopods, while abundance and biomass did not significantly rise—attributed to predation, competition, ocean acidification (pH drop from 8.12 to 7.86), and residual illegal trawling—mean body sizes grew notably, e.g., 46.1% increase in weight for Harpiosquilla harpax by 2015–2016. These findings highlight rapid biotic responses within 2.5–3.5 years, though full ecosystem restoration requires addressing multifaceted stressors.[88][130][131][129][132] In the Philippines, community-enforced bans on destructive practices like dynamite fishing around Apo Island, established via a marine sanctuary in the 1980s and formalized with a 1986 prohibition on such methods, have yielded sustained fishery improvements. Fish biomass in protected no-take zones exceeded that in adjacent fished areas, with spillover effects boosting yields outside reserves; coral-associated fish trophic biomass correlated strongly with reef health recovery post-ban. Local monitoring data showed initial catch declines followed by higher overall yields from sustainable hook-and-line methods, as destructive techniques fragmented reefs and reduced long-term stocks. Compliance, driven by community buy-in and traditional knowledge revival, contrasted with national-level bans hampered by weak enforcement elsewhere, where dynamite fishing persists despite prohibitions. Empirical assessments confirm that such localized bans, when paired with education and tourism alternatives, enhance resilience without impoverishing fishers.[133][134][135]| Case Study | Key Metrics Pre- vs. Post-Ban | Duration Assessed | Limitations Noted |
|---|---|---|---|
| Hong Kong Trawl Ban (2012) | Abundance: 253 → 848 ind./site; Richness: 27.5 → 48.3 spp./site; Size increase in stomatopods (e.g., +46% weight) | 2.5–3.5 years | No abundance gain in some taxa; illegal activity, acidification |
| Apo Island Destructive Ban (1986) | Higher reserve biomass; spillover yield gains; reef health-linked trophic biomass | Decades-long | Initial catch drop; requires community enforcement |