Let more big fish sink: Fisheries prevent blue carbon sequestration—half in unprofitable areas

Mariani, Gaël; Cheung, William W. L.; Lyet, Arnaud; Sala, Enric; Mayorga, Juan; Velez, Laure; Gaines, Steven D.; Déjean, Tony; Troussellier, Marc; Mouillot, David

doi:10.1126/sciadv.abb4848

Cited by 101 publications

(96 citation statements)

References 48 publications

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“…If we further assume that most of these fishes are extracted from the shelf regions, and that the total air‐sea flux of carbon on the shelves is approximately ~ 0.25 Pg C yr −1 (Cai et al 2006; Laruelle et al 2010), then such an extraction represents over 8% of the total air‐sea carbon flux on the global continental shelf. A global analysis based on historical catches and fuel consumption examined the role of ocean fisheries in atmospheric CO 2 emissions, and concluded that these activities have released a minimum of 0.73 Gt CO 2 into the atmospheric since 1950 (Mariani et al 2020). However, for context, other sources of animal protein contribute significantly more CO 2 emission equivalents (livestock = 7.1 Gt CO 2 ‐equivalent yr −1 ) than global fisheries (Gerber et al 2013).…”

Section: Fish‐based Contributions To Carbon Fluxmentioning

confidence: 99%

“…Furthermore, because fishes provide other benefits to humans (nutrition, biodiversity, cultural, recreational, commercial), management decisions are currently made without understanding the trade‐offs and interdependencies between these uses, their impacts and fish‐based carbon flux (Martin et al 2016; Legge et al 2020). A recent global analysis concluded that overexploitation of fish stocks could reduce the contribution of marine fishes, particularly in carcass deadfall, to blue carbon sequestration over time (Mariani et al 2020). The economic value of carbon storage reduced by fisheries in the eastern tropical Pacific was estimated as $12.9 billion yr −1 (Martin et al 2016), while the cost of predicted declines in the biological carbon pump in the North Atlantic by 2100 due to increasing carbon emissions was estimated at between $170 and $3000 billion in mitigation costs, and $23 and $401 billion in adaptation costs (Barange et al 2017).…”

Section: Actionable Recommendationsmentioning

confidence: 99%

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Toward a better understanding of fish‐based contribution to ocean carbon flux

Saba

Burd

Dunne

et al. 2021

Limnology & Oceanography

134

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Fishes are the dominant vertebrates in the ocean, yet we know little of their contribution to carbon export flux at regional to global scales. We synthesize the existing information on fish-based carbon flux in coastal and pelagic waters, identify gaps and challenges in measuring this flux and approaches to address them, and recommend research priorities. Based on our synthesis of passive (fecal pellet sinking) and active (migratory) flux of fishes, we estimated that fishes contribute an average (AE standard deviation) of about 16.1% (AE 13%) to total carbon flux out of the euphotic zone. Using the mean value of model-generated global carbon flux estimates, this equates to an annual flux of 1.5 AE 1.2 Pg C yr −1 . High variability in estimations of the fish-based contribution to total carbon flux among previous field studies and reported here highlight significant methodological variations and observational gaps in our present knowledge. Community-adopted methodological standards, improved and more frequent measurements of biomass and passive and active fluxes of fishes, and stronger linkages between observations and models will decrease uncertainty, increase our confidence in the estimation of fish-based carbon flux, and enable identification of controlling factors to account for spatial and temporal variability. Better constraints on this key component of the biological pump will provide a baseline for understanding how ongoing climate change and harvest will affect the role fishes play in carbon flux. * Estimated from DVM fish standing stock in and out of 500 m, an assumed daily ration of 10% body weight, 50% assimilation efficiency, and 5% fecal carbon content. † Uncorrected for capture efficiency. ‡ Estimated from midwater fish standing stock and daily consumption rate assuming an egestion rate of 20% food intake. §Values reported here include only data where anchovy fecal pellets were present in sediment traps (in 12 out of 20 free-drifting sediment trap sampling deployments in fall of 1977 and fall of 1978). ¶ Assumes 14% capture efficiency. ** Maximum respiratory carbon flux as day-time net catches have not been corrected for capture efficiency. † † Value estimated as the geometric mean from the ranges reported in the study. ‡ ‡ Assumes 50% capture efficiency. § § Assumes 14% capture efficiency for Matsuda-Oozeki-Hu trawls and an additional 6% capture efficiency for Isaacs-Kidd midwater trawls. ¶ ¶ Calculated from Davison et al. 2013 (table 9), comparing Vertical Migrant (VM) export and Fish-Mediated Export (FME; vertical migrant + nonmigrant export) to passive POC flux measured from sediment traps at 150 m). ***Estimated from assuming total fish export flux is equivalent to 100% (fecal) plus 180% (excretory) plus 50% (mortality) of the fish standing stock (11.9-66 mg C m −2).**Atmospheric Arpege weather forecast model coupled with geochemical Hamburg ocean carbon cycle model. † † Ecosystem model that consists of several compartments and tracks elements, including carbon, for the biota and detrital pools....

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Section: Fish‐based Contributions To Carbon Fluxmentioning

confidence: 99%

Section: Actionable Recommendationsmentioning

confidence: 99%

Toward a better understanding of fish‐based contribution to ocean carbon flux

Saba

Burd

Dunne

et al. 2021

Limnology & Oceanography

134

View full text Add to dashboard Cite

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“…Although not a focus of this review, the removal of vertebrate species by benthic and pelagic fisheries could influence the mass of OC stored in seabed sediments (Pershing et al 2010, Atwood et al 2015, Mariani et al 2020). The emerging field of “fish carbon” describes the contribution of vertebrate fauna to OC storage and sequestration within seabed sediments from defecation, pelagic mixing, bioturbation, trophic interactions and deadfall (Trueman et al 2014, Turner 2015, Saba et al 2021).…”

Section: Links Between Seabed Sediment Oc and Mobile Demersal Fishingmentioning

confidence: 99%

“…Although the magnitudes of effect are poorly resolved, the reduction in population size and average body size of marine vertebrates that results from over-harvest, is expected to reduce the amount of carbon exported to the seabed (Fig. 1f) (Pershing et al 2010, Trueman et al 2014, Atwood et al 2015, Mariani et al 2020). For example, since 1950, the combined catch of Tuna, Mackerel, Shark and Billfish is estimated to have prevented approximately 21.8 Mt of OC being stored in seabed sediments (Mariani et al 2020).…”

Section: Links Between Seabed Sediment Oc and Mobile Demersal Fishingmentioning

confidence: 99%

“…1f) (Pershing et al 2010, Trueman et al 2014, Atwood et al 2015, Mariani et al 2020). For example, since 1950, the combined catch of Tuna, Mackerel, Shark and Billfish is estimated to have prevented approximately 21.8 Mt of OC being stored in seabed sediments (Mariani et al 2020). The removal of predatory vertebrates will also cause trophic cascades, potentially leading to alterations in benthic faunal communities, triggering the feedback mechanisms on OC discussed above (Atwood et al 2015).…”

Section: Links Between Seabed Sediment Oc and Mobile Demersal Fishingmentioning

confidence: 99%

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The potential for mobile demersal fishing to reduce carbon storage and sequestration in seabed sediments

Epstein

Hawkins

Norris

et al. 2021

Preprint

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Subtidal marine sediments are one of the planet’s primary carbon stores and strongly influence the oceanic sink for atmospheric CO2. By far the most pervasive human activity occurring on the seabed is bottom trawling and dredging for fish and shellfish. A global first-order estimate suggested mobile demersal fishing activities may cause 160-400 Mt of organic carbon (OC) to be remineralised annually from seabed sediment carbon stores. There are, however, many uncertainties in this calculation. Here, we discuss the potential drivers of change in seabed OC stores due to mobile demersal fishing activities and conduct a systematic review, synthesising studies where this interaction has been directly investigated. Mobile demersal fishing would be expected to reduce OC in seabed stores, albeit with site-specific variability. Reductions would occur due to lower production of flora and fauna, the loss of fine flocculent material, increased sediment resuspension, mixing and transport, and increased oxygen exposure. This would be offset to some extent by reduced faunal bioturbation and respiration, increased off-shelf transport and increases in primary production from the resuspension of nutrients. Studies which directly investigated the impact of demersal fishing on OC stocks had mixed results. A finding of no significant effect was reported in 51% of 59 experimental contrasts; 41% reported lower OC due to fishing activities, with 8% reporting higher OC. In relation to remineralisation rates within the seabed, 14 experimental contrasts reported that demersal fishing activities decreased remineralisation, with four reporting higher remineralisation rates. The direction of effects was related to sediment type, impact duration, study design and local hydrography. More evidence is urgently needed to accurately quantify the impact of anthropogenic physical disturbance on seabed carbon in different environmental settings, and incorporate full evidence-based carbon considerations into global seabed management.

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Optimizing fisheries for blue carbon management: Why size matters

Falciani

Grigoratou

Pershing

2022

Limnology & Oceanography

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Fish contribute to the export of carbon out of the euphotic zone. They ingest organic carbon fixed by phytoplankton, store it in their tissues for their lifetime, and contribute to long-term sequestration by producing sinking fecal pellets, respiring at depth, or via their own sinking carcasses. While the flux of carbon through fish is small relative to the export flux by plankton, humans have a direct influence on fish communities and thus on the magnitude of carbon storage and flux. We use a size spectrum model to examine the combined effect of fishing and trophic dynamics on the total carbon stored as biomass of a simulated community of fish. By sampling 10,500 possible fishing strategies that randomize fishing mortality and size-selectivity, we consider optimal strategies that balance several UN Sustainable Development Goals addressing (1) food security, (2) climate action, and (3) marine conservation. The model shows that fishery management strategies that preferentially conserve large species increase overall carbon stored in the fish community. This study presents a perspective for considering carbon storage and sequestration in fisheries management alongside alternative objectives such as food production and biodiversity conservation. Our study focused on the state (total carbon in the living community). Incorporating rate processes like fecal pellet flux, vertical migration, and natural mortality would build toward a more holistic carbon approach to fisheries management.

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Let more big fish sink: Fisheries prevent blue carbon sequestration—half in unprofitable areas

Cited by 101 publications

References 48 publications

Toward a better understanding of fish‐based contribution to ocean carbon flux

Toward a better understanding of fish‐based contribution to ocean carbon flux

The potential for mobile demersal fishing to reduce carbon storage and sequestration in seabed sediments

Optimizing fisheries for blue carbon management: Why size matters

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