Large mesopelagic fishes biomass and trophic efficiency in the open ocean

Irigoien, Xabier; Klevjer, Thor A.; Røstad, Anders; Martinez, Udane; Boyra, Guillermo; Acuña, José Luis; Bode, Antonio; Echevarrı́a, Fidel; González-Gordillo, J. Ignacio; Hernández‐León, Santiago; Agustı́, Susana; Aksnes, Dag L.; Duarte, Carlos M.; Kaartvedt, Stein

doi:10.1038/ncomms4271

Cited by 617 publications

(523 citation statements)

References 61 publications

(84 reference statements)

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“…4B). This finding is consistent with other studies (11)(12)(13), suggesting the importance of moving from the broad TE ranges applied herein toward estimation of TE probability densities (61). Such probability densities could allow Bayesian approaches to more formally incorporate prior parameter estimates.…”

Section: Discussionsupporting

confidence: 90%

“…Improvements in catch reporting (6) could further reduce biases in trophodynamic estimates arising from catch reporting gaps. We also note that the catch-based analysis herein cannot address potential yield of largely unexploited but potentially substantial mesopelagic fisheries (12).…”

Section: Discussionmentioning

confidence: 99%

“…Uncertain differences in fishing effort and impacts of fishing history complicate attribution of catch differences to "bottom-up" considerations of ocean productivity or "top-down" fishing effects (7). Difficulties directly observing and estimating trophodynamic properties, including NPP (8), trophic levels (9,10), and trophic transfer efficiencies (3,(11)(12)(13), also weaken trophodynamic constraints.…”

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confidence: 99%

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Reconciling fisheries catch and ocean productivity

Stock

John

Rykaczewski

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

233

255

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Photosynthesis fuels marine food webs, yet differences in fish catch across globally distributed marine ecosystems far exceed differences in net primary production (NPP). We consider the hypothesis that ecosystem-level variations in pelagic and benthic energy flows from phytoplankton to fish, trophic transfer efficiencies, and fishing effort can quantitatively reconcile this contrast in an energetically consistent manner. To test this hypothesis, we enlist global fish catch data that include previously neglected contributions from small-scale fisheries, a synthesis of global fishing effort, and plankton food web energy flux estimates from a prototype high-resolution global earth system model (ESM). After removing a small number of lightly fished ecosystems, stark interregional differences in fish catch per unit area can be explained (r = 0.79) with an energy-based model that (i) considers dynamic interregional differences in benthic and pelagic energy pathways connecting phytoplankton and fish, (ii) depresses trophic transfer efficiencies in the tropics and, less critically, (iii) associates elevated trophic transfer efficiencies with benthic-predominant systems. Model catch estimates are generally within a factor of 2 of values spanning two orders of magnitude. Climate change projections show that the same macroecological patterns explaining dramatic regional catch differences in the contemporary ocean amplify catch trends, producing changes that may exceed 50% in some regions by the end of the 21st century under high-emissions scenarios. Models failing to resolve these trophodynamic patterns may significantly underestimate regional fisheries catch trends and hinder adaptation to climate change.fisheries catch | primary production | ocean productivity | climate change | food webs N early 50 years ago, John Ryther (1) published his seminal work "Photosynthesis and Fish Production in the Sea" in which he hypothesized that differences in net primary production (NPP) alone could not explain stark differences in fish catch across disparate marine ecosystems. Drawing upon "trophic dynamic" principles governing the transfer of energy through ecosystems (2), he hypothesized that synergistic interactions between NPP differences, the length of food chains connecting phytoplankton and fish, and the efficiency of trophic transfers were required to reconcile catch differences. The trophodynamic principles drawn upon by Ryther now underpin diverse models and indicators used in ecosystem-based marine resource management (3-5), yet stubborn uncertainties in the relationship between ocean productivity and fish catch persist. Official catch reports often omit globally significant discards and small-scale artisanal and subsistence catch (6). Uncertain differences in fishing effort and impacts of fishing history complicate attribution of catch differences to "bottom-up" considerations of ocean productivity or "top-down" fishing effects (7). Difficulties directly observing and estimating trophodynamic properties, including NPP (8),...

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Reconciling fisheries catch and ocean productivity

Stock

John

Rykaczewski

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

233

255

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“…21. ADCP data provide continuous, depth-resolved views of migrating sound-scattering layers, which can be integrated with in situ net data to obtain a comprehensive picture of migrating animal communities (22)(23)(24). Our technique identifies the depth of the main DVM stationary depth, at which the strongest subeuphotic sound scattering layer is centered during the daytime.…”

Section: Dvm Association With Anoxic Watersmentioning

confidence: 99%

Enhancement of anammox by the excretion of diel vertical migrators

Bianchi

Babbin

Galbraith

2014

Proc. Natl. Acad. Sci. U.S.A.

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Measurements show that anaerobic ammonium oxidation with nitrite (anammox) is a major pathway of fixed nitrogen removal in the anoxic zones of the open ocean. Anammox requires a source of ammonium, which under anoxic conditions could be supplied by the breakdown of sinking organic matter via heterotrophic denitrification. However, at many locations where anammox is measured, denitrification rates are small or undetectable. Alternative sources of ammonium have been proposed to explain this paradox, for example through dissimilatory reduction of nitrate to ammonium and transport from anoxic sediments. However, the relevance of these sources in open-ocean anoxic zones is debated. Here, we bring to attention an additional source of ammonium, namely, the daytime excretion by zooplankton and micronekton migrating from the surface to anoxic waters. We use a synthesis of acoustic data to show that, where anoxic waters occur within the water column, most migrators spend the daytime within them. Although migrators export only a small fraction of primary production from the surface, they focus excretion within a confined depth range of anoxic water where particle input is small. Using a simple biogeochemical model, we suggest that, at those depths, the source of ammonium from organisms undergoing diel vertical migrations could exceed the release from particle remineralization, enhancing in situ anammox rates. The contribution of this previously overlooked process, and the numerous uncertainties surrounding it, call for further efforts to evaluate the role of animals in oxygen minimum zone biogeochemistry.anammox | denitrification | oxygen minimum zone | diel vertical migration W ater column oxygen minimum zones (OMZs), where oxygen concentrations plummet to submicromolar levels (1), are responsible for approximately one-third of the total removal of fixed nitrogen from the oceans (2, 3). Several processes mediated by specialized prokaryotes convert fixed inorganic nitrogen (NH 4 + , NO 2 − , and NO 3 − ) to N 2 in anoxic waters. Canonical denitrification, consisting of dissimilatory NO 3 − reduction to NO 2 − (DNRN) followed by the further oxidation of organic matter with NO 2 − (the denitrification step), was long considered the dominant fixed N removal pathway in anoxic waters. Over the last decade, anammox has gained attention as a major sink of fixed N in nearly anoxic waters (O 2 < 10 mmol·m −3 ) (4, 5).Stoichiometric considerations would suggest a close coupling between denitrification and anammox (6, 7). Under anoxic conditions, the NH 4 + liberated by the remineralization of organic matter through DNRN and denitrification should accumulate in the water column because conventional (aerobic) nitrification cannot proceed. However, this accumulation is not observed in the cores of anoxic waters, where observed NH 4 + concentrations are generally much less than 1 mmol·m −3 (8). In these regions, oxidation of NH 4 + with NO 2 − by anammox is thought to be the major sink of NH 4 + (9). Given that no significant NH 4 + acc...

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“…With respect to their temporal preservation within death-assemblages, it should be noticed that mesopelagic taxa are typically represented by small and thin otoliths, prone to vanish earlier than the large and thick otoliths, pertaining to the benthic and benthopelagic species, comparable to the two components found in the molluscan study. Nevertheless, the significant otolith abundance of the former reflects their dominant biomass in the present ocean (Irigoien et al, 2014), even if wearing away rapidly. Indeed, both components in the death-assemblage represent two sets of ecological and trophic strategies related to turnover rate.…”

mentioning

confidence: 99%