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{{Short description|Water column of the open ocean}}
{{Redirect-multi|2|Pelagic|Open sea|the writer|Vasa Pelagić|the marketplace|OpenSea|ocean not controlled by any sovereign territory, also called the "high seas"|International waters}}
{{Use dmy dates|date=August 2020}}
[[File:Pelagiczone.svg|thumb|{{center|Layers of the pelagic zone (scaled)}}]]
{{ocean habitat topics}}

The '''pelagic zone''' consists of the [[water column]] of the '''open ocean''' and can be further divided into regions by [[Depth (coordinate)|depth]]. The word ''pelagic'' is derived {{etymology|grc|''{{wikt-lang|grc|πέλαγος}}'' ({{grc-transl|πέλαγος}})|open sea}}.<ref>{{OEtymD|pelagic  |access-date=2020-02-17}}</ref> The pelagic zone can be thought of as an imaginary [[cylinder]] or water column between the [[photic zone|surface of the sea]] and the [[seabed|bottom]].

Conditions in the water column change with depth: pressure increases; temperature and light decrease; salinity, oxygen, micronutrients (such as iron, magnesium and calcium) all change. In a manner analogous to [[Atmosphere of Earth#Stratification|stratification in the Earth's atmosphere]], the water column can be divided vertically into up to five different layers (illustrated in the diagram), with the number of layers depending on the depth of the water.

[[Marine life]] is affected by [[bathymetry]] (underwater topography) such as the seafloor, shoreline, or a submarine [[seamount]], as well as by proximity to the boundary between the ocean and the atmosphere at the ocean surface, which brings light for photosynthesis, predation from above, and wind stirring up waves and setting currents in motion. The pelagic zone refers to the open, free waters away from the shore, where marine life can swim freely in any direction unhindered by [[topography|topographical]] constraints.

The [[oceanic zone]] is the deep open ocean beyond the [[continental shelf]], which contrasts with the inshore waters near the [[coast]], such as in [[estuary|estuaries]] or on the continental shelf. Waters in the oceanic zone plunge to the depths of the [[abyssal zone|abyssopelagic]] and further to the [[hadal zone|hadopelagic]]. Coastal waters are generally the relatively shallow epipelagic. Altogether, the pelagic zone occupies {{convert|1.33|e9km3|e6cumi|abbr=unit}}, with a mean depth of {{cvt|3.68|km|mi}} and maximum depth of {{cvt|11|km|mi}}.<ref>{{cite journal |last1=Costello |first1=Mark John |last2=Cheung |first2=Alan |last3=De Hauwere |first3=Nathalie |year=2010 |title=Surface Area and the Seabed Area, Volume, Depth, Slope, and Topographic Variation for the World's Seas, Oceans, and Countries |journal=Environmental Science & Technology |doi=10.1021/es1012752 |pmid=21033734 |bibcode=2010EnST...44.8821C |volume=44 |issue=23 |pages=8821–8}}</ref><ref>{{cite journal |last1=Charette |first1=Matthew |last2=Smith |first2=Walter |year=2010 |title=The Volume of Earth's Ocean |journal=Oceanography  |hdl=1912/3862 |doi=10.5670/oceanog.2010.51 |volume=23 |issue=2 |pages=112–4|doi-access=free |bibcode=2010Ocgpy..23b.112C |hdl-access=free }}</ref><ref>[http://www.ouramazingplanet.com/oceans-depth-and-volume-revealed-0206/# Ocean's Depth and Volume Revealed] {{Webarchive|url=https://web.archive.org/web/20110823051211/http://www.ouramazingplanet.com/oceans-depth-and-volume-revealed-0206/ |date=23 August 2011 }} ''OurAmazingPlanet'', 19 May 2010.</ref> Pelagic life decreases as depth increases.

The pelagic zone also contrasts with the [[benthic zone|benthic]] and [[demersal zone|demersal]] zones at the bottom of the sea. The benthic zone is the ecological region at the very bottom, including the sediment surface and some subsurface layers. Marine organisms such as [[clam]]s and [[crab]]s living in this zone are called [[benthos]]. Just above the benthic zone is the demersal zone. [[Demersal fish]] can be divided into [[demersal fish#Benthic fish|benthic fish]], which are denser than water and rest on the bottom, and [[demersal fish#Benthopelagic fish|benthopelagic fish]], which swim just above the bottom. Demersal fish are also known as [[bottom feeder]]s and [[groundfish]].

==Depth and layers==
{{aquatic layer topics}}
The pelagic zone is subdivided into five vertical regions. From the top down, these are:

===Epipelagic (sunlight)===
{{See also|Photic zone|Epipelagic fish}}
{{Hatnote|From the surface ([[sea level|MSL]]) down to around {{cvt|200|m|ft}}}}

The illuminated zone at the surface of the sea, and the only zone with sufficient light for photosynthesis. This zone is just above the continental shelf and has the lowest [[atmospheric pressure]] on the oceans surface, at 1 atm for every 10 meters. Nearly all [[primary production]] in the ocean occurs here, and about 90% marine life is concentrated in this zone, including: [[plankton]], [[Sargassum|floating seaweed]], [[jellyfish]], [[tuna]], [[Whale|whales]], [[Shark|sharks]], [[Dolphin|dolphins]], and many more diverse species.<ref name="Ocean Zones">{{Cite web |date=2024-09-16 |title=Ocean Zones - Let's Talk Science |url=https://letstalkscience.ca/educational-resources/backgrounders/ocean-zones |access-date=2025-09-24 |website=letstalkscience.ca |language=en}}</ref>

===Mesopelagic (twilight)===
{{See also|Mesopelagic zone|Pelagic fish#Mesopelagic fish}}
{{Hatnote|From {{cvt|200|m|ft}} down to around {{cvt|1000|m|ft}}}}

The [[thermocline]] serves as the boundary from the warmer top zone to the much colder mesopelagic zone, which is also located right under the continental shelf.<ref name="Ocean Zones" /> This zone contains a very trace amount of sunlight and has a pressure of about 20 - 100 amt.<ref name="Ocean Zones" /> A variety of creatures live in this zone, including species of [[swordfish]], [[squid]], [[Anarhichadidae|wolffish]] and some species of [[cuttlefish]]. Many organisms living here have evolved adaptations, such as [[bioluminescence]], due to the lack of sunlight.<ref name="marinebio.com2">[https://web.archive.org/web/20100410222157/http://www.marinebio.com/Oceans/open-ocean.asp The Open Ocean - MarineBio.org]</ref><ref name="Ocean Zones" /> Some mesopelagic creatures rise to the epipelagic zone at night to feed.<ref name="marinebio.com2" /> [[Heterotroph|Heterotrophic]] bacteria are among the more abundant organisms in this zone, and they primarily feed and break down falling matter from the upper zone.<ref name=Mazuecos2012>{{cite journal |last1=Mazuecos |first1=E. |last2=Arístegui |first2=J. |last3=Vázquez-Domínguez |first3=E. |last4=Ortega-Retuerta |first4=E. |last5=Gasol |first5=J.M. |last6=Reche |first6=I. |year=2012 |title=Temperature control of microbial respiration and growth efficiency in the mesopelagic zone of the South Atlantic and Indian Oceans. |journal=Deep Sea Research Part I: Oceanographic Research Papers |volume=95 |pages=131–138 |doi=10.3354/ame01583 |hdl=10261/95626 |doi-access=free |hdl-access=free}}</ref>

===Bathypelagic (midnight)===
{{See also|Bathyal zone|Pelagic fish#Bathypelagic fish}}
{{Hatnote|From {{cvt|1000|m|ft}} down to around {{cvt|4000|m|ft}}}}

The name stems {{ety|grc|[[wikt:βαθύς|βαθύς]]|deep}}. In this zone, the environment is pitch black at this depth and contains no trace of sunlight, apart from occasional [[Bioluminescence|bioluminescent]] organisms, such as [[anglerfish]].<ref name="Ocean Zones" /> The temperature and salinity of this zone is stable.<ref name="Haddock2024">{{cite journal | last1=Haddock | first1=Steven H.D. | last2=Choy | first2=C. Anela | title=Life in the Midwater: The Ecology of Deep Pelagic Animals | journal=Annual Review of Marine Science | volume=16 | issue=1 | date=2024-01-17 | issn=1941-1405 | doi=10.1146/annurev-marine-031623-095435 | doi-access=free | pages=383–416 | pmid=38231738 | bibcode=2024ARMS...16..383H }}</ref><ref>{{Cite journal |last=Sutton |first=T. T. |date=December 2013 |title=Vertical ecology of the pelagic ocean: classical patterns and new perspectives |url=https://onlinelibrary.wiley.com/doi/10.1111/jfb.12263 |journal=Journal of Fish Biology |language=en |volume=83 |issue=6 |pages=1508–1527 |doi=10.1111/jfb.12263 |pmid=24298949 |bibcode=2013JFBio..83.1508S |issn=0022-1112}}</ref>No plants live here. Most creatures survive on [[detritus]] known as "[[marine snow]]" falling from the zones above or, like the [[marine hatchetfish]], by preying on other inhabitants of this zone.

===Abyssopelagic (abyssal zone)===
{{Main|Abyssal zone}}
{{Hatnote|From around {{cvt|4000|m|ft}} down to above the [[ocean floor]]}}

The name is derived {{ety|grc|[[wikt:ἄβυσσος|ἄβυσσος]]|bottomless}}.  The [[Seabed|ocean floor]] is next to this zone, and it forms volcanos, mountains, and vents from the movement of the [[Plate tectonics|tectonic plates]].<ref name="Ocean Zones" /> Among the very few creatures living in the cold temperatures, high pressures and complete darkness there are several species of squid; [[Echinoderm|echinoderms]] including the [[basket star]], swimming cucumber, and the [[Scotoplanes|sea pig]]; and marine arthropods including the [[sea spider]]. Many species at these depths are transparent and eyeless.<ref name="marinebio.com2" />

===Hadopelagic (hadal zone)===
{{Main|Hadal zone}}

The name is derived from the realm of [[Hades]], the [[Greek underworld]].  This is the deepest part of the ocean at more than {{cvt|6000|m|ft}} . Such depths are generally located in [[Ocean trench|trenches]].This zone contains 13 short narrow troughs and 33 trenches. The deepest trenches stretch to 10,924 m deep, while average trenches are usually 5 - 10 kilometers deep. This zone can have an atmospheric pressure of 1,100 atm.<ref name="Ocean Zones" /> In this zone, there is an increase in temperature from [[Adiabatic process|adiabatic heating]].<ref name="Wolff1959">{{cite journal | last=Wolff | first=Torben | title=The hadal community, an introduction | journal=Deep Sea Research (1953) | volume=6 | date=1959 | doi=10.1016/0146-6313(59)90063-2 | pages=95–124 | bibcode=1959DSR.....6...95W | url=https://linkinghub.elsevier.com/retrieve/pii/0146631359900632 | access-date=2025-10-13}}</ref> Very few creatures live in this zone. Some of the recorded species are [[Coelenterata|coelenterate]], [[Polychaete|polychaetas]], [[Amphipoda|amphipods]], [[Echinoderm|echinoderms]], and [[Mollusca|mollusks]].<ref name="Wolff1959" />

==Pelagic ecosystem==
The pelagic ecosystem is based on [[phytoplankton]]. Phytoplankton manufacture their own food using a process of [[photosynthesis]]. Because they need sunlight, they inhabit the upper, sunlit epipelagic zone, which includes the coastal or [[neritic zone]]. Biodiversity diminishes markedly in the deeper zones below the epipelagic zone as dissolved oxygen diminishes, water pressure increases, temperatures become colder, food sources become scarce, and light diminishes and finally disappears.<ref>Walker P and Wood E (2005) [https://books.google.com/books?id=O0GpAZsmrVAC&q=intitle:The+intitle:Open+intitle:Ocean ''The Open Ocean''] (volume in a series called ''Life in the sea''), Infobase Publishing, {{ISBN|978-0-8160-5705-4}}.</ref>

===Pelagic invertebrates===
Some examples of pelagic invertebrates include [[krill]], [[copepod]]s, [[jellyfish]], [[Decapodiformes|decapod]] [[larvae]], [[hyperiid]] [[amphipod]]s, [[rotifer]]s and [[cladocera]]ns.

[[Thorson's rule]] states that [[benthic]] [[marine invertebrates]] at low latitudes tend to produce large numbers of eggs developing to widely dispersing pelagic larvae, whereas at high latitudes such organisms tend to produce fewer and larger [[lecithotrophic]] (yolk-feeding) eggs and larger offspring.<ref name="Thorson">{{cite book |editor1-first=J.W. |editor1-last=Hedgpeth |last1=Thorson |first1=G |year=1957 |chapter=Bottom communities (sublittoral or shallow shelf) |title=Treatise on Marine Ecology and Palaeoecology |publisher=Geological Society of America |pages=461–534}}</ref><ref name="Mileikovsky">{{cite journal |last1=Mileikovsky |first1=S. A. |year=1971 |title=Types of larval development in marine bottom invertebrates, their distribution and ecological significance: a re-evaluation |journal=Marine Biology |doi=10.1007/BF00352809 |volume=10 |issue=3 |pages=193–213|bibcode=1971MarBi..10..193M |s2cid=84623588 }}</ref>

===Pelagic fish===
{{Main|Pelagic fish}}

Pelagic fish live in the [[water column]] of coastal, ocean, and lake waters, but not on or near the bottom of the sea or the lake. They can be contrasted with demersal fish, which do live on or near the bottom, and [[coral reef fish]].<ref name="Lal82">{{cite book |last1=Lal |first1=Brij V. |author-link1=Brij Lal (historian) |url=https://books.google.com/books?id=T5pPpJl8E5wC&pg=PA8 |title=The Pacific Islands: An Encyclopedia |last2=Fortune |first2=Kate |date=January 2000 |publisher=University of Hawaii Press |isbn=978-0-8248-2265-1 |page=8}}</ref>

Pelagic fish are often [[Fish migration|migratory]] [[forage fish]], which feed on [[plankton]], and the larger [[predatory fish]] that follow and feed on the forage fish.  Migratory fish come up to the more dense prey areas of the pelagic zones to feed, and then descend at night to avoid predators.<ref name="Eduardo2024" /> Examples of migratory forage fish are [[herring]], [[Anchovy|anchovies]], [[capelin]], and [[menhaden]]. Examples of larger pelagic fish which [[Predation|prey]] on the forage fish are [[billfish]], [[tuna]], and oceanic [[Shark|sharks]].<ref>{{Cite journal |last1=H. |first1=Engelhard, Georg |last2=A. |first2=Peck, Myron |last3=Anna |first3=Rindorf |last4=Sophie |first4=C. Smout |last5=Mikael |first5=van Deurs |last6=Kristina |first6=Raab |last7=H. |first7=Andersen, Ken |last8=Stefan |first8=Garthe |last9=A.M. |first9=Lauerburg, Rebecca |last10=Finlay |first10=Scott |last11=Thomas |first11=Brunel |last12=Geert |first12=Aarts |last13=Tobias |first13=van Kooten |last14=Mark |first14=Dickey-Collas |date=2014-01-01 |title=Forage fish, their fisheries, and their predators: who drives whom? |url=https://academic.oup.com/icesjms/article/71/1/90/643678 |journal=ICES Journal of Marine Science |language=en |volume=71 |issue=1 |doi=10.1093/ice |doi-broken-date=13 October 2025 |issn=1054-3139 |archive-url=http://web.archive.org/web/20250719145105/https://academic.oup.com/icesjms/article/71/1/90/643678 |archive-date=2025-07-19}}</ref>

===Pelagic reptiles===
''[[Yellow-bellied sea snake|Hydrophis platurus]]'', the yellow-bellied sea snake, is the only one of the 65 species of [[Hydrophiinae|marine snakes]] to spend its entire life in the pelagic zone. It bears live young at sea and is helpless on land. The species sometimes forms aggregations of thousands along slicks in surface waters. The yellow-bellied sea snake is the world's most widely distributed snake species.<ref name="Lillywhite2014">{{cite journal | last1=Lillywhite | first1=Harvey B. | last2=Sheehy | first2=Coleman M. | last3=Brischoux | first3=François | last4=Grech | first4=Alana | title=Pelagic sea snakes dehydrate at sea | journal=Proceedings of the Royal Society B: Biological Sciences | volume=281 | issue=1782 | date=2014-05-07 | issn=0962-8452 | pmid=24648228 | pmc=3973276 | doi=10.1098/rspb.2014.0119 | doi-access=free | article-number=20140119 | bibcode=2014RSPSB.28140119L }}</ref>

Many species of [[Sea turtle|sea turtles]] spend the first years of their lives in the pelagic zone, moving closer to shore as they reach maturity.<ref name="Lillywhite2014" />

===Pelagic birds===
{{See also|Seabird}}
Pelagic birds, also called ''oceanic birds'' or [[Seabird|seabirds]], live on open seas and oceans rather than inland or around more restricted waters such as rivers and lakes. These birds have very long wings which give them the ability to fly for long periods of time. Some pelagic birds dive deep into the water to catch prey. Pelagic birds feed on planktonic [[Crustacean|crustaceans]], [[squid]] and [[forage fish]]. Examples are the [[Atlantic puffin]], [[Macaroni penguin|macaroni penguins]], [[Sooty tern|sooty terns]], [[Razorbill|razorbills]], [[Shearwater|shearwaters]], and [[Procellariiformes]] such as the [[albatross]], [[Procellariidae]] and [[Petrel|petrels]].

[[File:Representative ocean animal life.jpg|thumb|upright=2|left| Some representative ocean animals (not drawn to scale) within their approximate depth-defined ecological habitats. [[Marine microorganisms]] also exist on the surfaces and within the tissues and organs of the diverse life inhabiting the ocean, across all ocean habitats. The animals rooted to or living on the ocean floor are not pelagic but are [[benthic]] animals.<ref name=Apprill2017>Apprill, A. (2017)"Marine animal microbiomes: toward understanding host–microbiome interactions in a changing ocean". ''Frontiers in Marine Science'', '''4''': 222. {{doi|10.3389/fmars.2017.00222|doi-access=free}}. [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>]]
[[File:Hydrophis platurus 118933110.jpg|thumb|The yellow bellied sea snake as it glides across the surface of the ocean.]]
[[File:Diomedea_exulans_in_flight_-_SE_Tasmania.jpg|right|thumb|The pelagic [[wandering albatross]] (''Diomedea exulans'') ranges over huge areas of ocean and can circle the globe.]]

{{clear}}

==Food web==
{{See also|Marine food web}}
[[File:Oceanic Food Web.jpg|thumb|upright=1.4|Pelagic [[food web]]]]

Compared to terrestrial environments, marine environments have [[biomass pyramid]]s which are inverted at the base.<ref name="Kolding2016">{{cite journal | last1=Kolding | first1=Jeppe | last2=Bundy | first2=Alida | last3=van Zwieten | first3=Paul A.M. | last4=Plank | first4=Michael J. | title=Fisheries, the inverted food pyramid | journal=ICES Journal of Marine Science | volume=73 | issue=6 | date=2016-06-01 | issn=1095-9289 | doi=10.1093/icesjms/fsv225 | doi-access=free | pages=1697–1713 | url=https://academic.oup.com/icesjms/article-pdf/73/6/1697/31230428/fsv225.pdf | access-date=2025-10-15}}</ref><ref name="Woodson2025">{{cite journal | last1=Woodson | first1=C. Brock | last2=Schramski | first2=John R. | last3=Joye | first3=Samantha B. | title=A unifying theory for top-heavy ecosystem structure in the ocean | journal=Nature Communications | volume=9 | issue=1 | date=2018-01-02 | issn=2041-1723 | pmid=29295998 | pmc=5750233 | doi=10.1038/s41467-017-02450-y | doi-access=free | url=https://www.nature.com/articles/s41467-017-02450-y.pdf | access-date=2025-10-15 | page=}}</ref> In particular, the [[Biomass (ecology)|biomass]] of consumers ([[copepod]]s, [[krill]], [[shrimp]], [[forage fish]]) is larger than the biomass of [[primary producers]]. This happens because the ocean's primary producers are tiny [[phytoplankton]] which tend to  have a fast life history (are [[r-strategists]] that grow and reproduce rapidly) so a small mass can have a fast rate of primary production.<ref name="Edwards2016">{{cite journal | last=Edwards | first=Kyle F. | title=Community trait structure in phytoplankton: seasonal dynamics from a method for sparse trait data | journal=Ecology | volume=97 | issue=12 | date=2016 | issn=0012-9658 | doi=10.1002/ecy.1581 | pages=3441–3451 | url=https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.1581 | access-date=2025-10-15}}</ref> In contrast, terrestrial primary producers, such as mature forests, often have a slow life history (are [[K-strategists]] that grow and reproduce slowly) so a much larger mass is needed to achieve the same rate of primary production.<ref name="Reich2014">{{cite journal | last=Reich | first=Peter B. | title=The world‐wide ‘fast–slow’ plant economics spectrum: a traits manifesto | journal=Journal of Ecology | volume=102 | issue=2 | date=2014 | issn=0022-0477 | doi=10.1111/1365-2745.12211 | doi-access=free | pages=275–301 | url=https://onlinelibrary.wiley.com/doi/pdfdirect/10.1111/1365-2745.12211 | access-date=2025-10-15}}</ref>

Because of this inversion, it is the [[zooplankton]] that make up most of the marine animal [[Biomass (ecology)|biomass]]. As primary consumers, they are the crucial link between the [[primary producers]] (mainly (phytoplankton) and the rest of the marine food web ([[secondary consumer]]s).<ref>{{cite web | date = 2008 | url = https://public.ornl.gov/site/gallery/detail.cfm?id=326 | title = Carbon Cycling and Biosequestration | page = 81 | quote = Workshop report DOE/SC-108 | publisher = US Department of Energy &ndash; Department of Energy Office of Science }}</ref>

If phytoplankton dies before it is eaten, it descends from the [[euphotic zone]] down through the pelagic [[water column]] as part of the [[marine snow]], and settles into the depths of sea. In this way, phytoplankton sequester about 2 billion tons of carbon dioxide in the ocean each year, causing the ocean to become a sink of carbon dioxide holding about 90% of all sequestered carbon.<ref name="EarthTimes">{{cite web|url=http://www.earthtimes.org/scitech/role-marine-plankton-sequestration-carbon/1062/|title=The role of marine plankton in sequestration of carbon | vauthors = Campbell M |date=22 June 2011 |website=EarthTimes|access-date=22 August 2014}}</ref>

In 2010 researchers found whales carry nutrients from the depths of the ocean back up the pelagic water column to the surface using a process they called the [[whale pump]].<ref name="Roman_2010">{{cite journal | vauthors = Roman J, McCarthy JJ | title = The whale pump: marine mammals enhance primary productivity in a coastal basin | journal = PLOS ONE | volume = 5 | issue = 10 | article-number = e13255 | date = October 2010 | pmid = 20949007 | pmc = 2952594 | doi = 10.1371/journal.pone.0013255 | bibcode = 2010PLoSO...513255R | id = e13255 | doi-access = free }}</ref> Whales feed at deeper levels in the ocean where [[krill]] is found, but return regularly to the surface to breathe. There whales [[Whale faeces|defecate a liquid]] rich in nitrogen and iron. Instead of sinking, the liquid stays at the surface where [[phytoplankton]] consume it. In the Gulf of Maine the whale pump provides more nitrogen than the rivers.<ref name="ScienceDaily">{{cite web|url=https://www.sciencedaily.com/releases/2010/10/101012101255.htm|title=Whale poop pumps up ocean health| vauthors = Brown JE |date=12 Oct 2010|website=Science Daily|access-date=18 August 2014}}</ref>

{{clear}}

== Observing and sampling methods ==
Exploring and learning more about the ocean is a main factor to ocean [[resource management]], which sustainably manages how much and how fast we use the oceans resources. [[Ocean exploration]] also observes patterns in the oceans weather and climate, and the means why which they were affected. Researchers are better able to understand and see natural phenomena such as earthquakes and tsunamis and react accordingly. Scientists and researchers have developed many methods to sample the ocean [[biome]], and pelagic fish.<ref name="Lin2020">{{cite journal | last1=Lin | first1=Mingwei | last2=Yang | first2=Canjun | title=Ocean Observation Technologies: A Review | journal=Chinese Journal of Mechanical Engineering | volume=33 | issue=1 | date=2020 | issn=1000-9345 | doi=10.1186/s10033-020-00449-z | doi-access=free | article-number=32 | bibcode=2020ChJME..33...32L }}</ref><ref name="Eduardo2024">{{cite journal | last1=Eduardo | first1=Leandro Nolé | last2=Mincarone | first2=Michael Maia | last3=Sutton | first3=Tracey | last4=Bertrand | first4=Arnaud | title=Deep-Pelagic Fishes Are Anything But Similar: A Global Synthesis | journal=Ecology Letters | volume=27 | issue=9 | date=2024 | issn=1461-023X | doi=10.1111/ele.14510 | url=https://onlinelibrary.wiley.com/doi/10.1111/ele.14510 | access-date=2025-10-13 | article-number=e14510 | bibcode=2024EcolL..27E4510E }}</ref>

=== Trawling ===
[[File:Schéma de pêche - chalut pélagique (Ifremer 00581-69329).jpg|thumb|Pelagic fish being captured with a pelagic trawing net]]
{{Main|Trawling}}

This method can be used from a boat to capture organisms like deep pelagic fish. A mesh net is dragged at different depths to collect for recording the captured organisms. This method can produce large amounts of specimen. However it is costly, time consuming, and mostly used by research groups with a lot of support and funding. There are also many fish that are able to out swim the net, which limits data.<ref name="Eduardo2024" /><ref name="Haddock2024" />

=== Active Acoustics ===
{{Main|Sonar}}

This method analyzes fish that are detected or present in sound pulses that are emitted from the surface, where the pelagic fish' [[biomass]] in the reflected single is analyzed. This method of sampling cannot reach deep depths in the ocean. The pulses cover a broad area of the ocean and causes little harm or distress. The received data from this method is complicated to interpret, due to specific variations of swim bladders in fish, such as having little gas or not having a swim bladder.<ref name="Eduardo2024" /><ref name="Haddock2024" />

=== Remotely Operated Vehicles (ROV) ===
[[File:Enquête du BEA - Photo sous-marine du ROV Victor 6000 (Ifremer 00790-90242 - 50868).jpg|thumb|An ROV immersed in pelagic waters observing the pelagic world]]
{{Main|Remotely operated underwater vehicle}}

Remotely operated vehicles (ROC) are used for sampling and examining the deep pelagic sea in ways that other techniques cannot match. An ROV is an unoccupied machine equipped with lights, cameras, sensors, or arms, which allows for detailed and live observations of its surroundings and of pelagic organisms. It can conduct experiments and collect samples.<ref name="Haddock2024" /> These machine are limited in ground coverage, as well as expensive and hard to control, so few research groups use them. They can also be loud, bright, and big, causing organisms to avoid them.<ref name="Eduardo2024" />

=== Additional Methods ===
Some other sampling and observation methods are: predator gut examinations, analysis of [[environmental DNA]], organisms that get washed up on shore from [[upwelling]], analyzing [[Marine sediment core|sediments core]]s, and pelagic [[longline fishing]].<ref name="Eduardo2024" />

==References==
{{Reflist}}

==Further reading==
* Ryan, Paddy [https://web.archive.org/web/20080619124248/http://www.teara.govt.nz/EarthSeaAndSky/SeaLife/DeepSeaCreatures/en "Deep-sea creatures"] ''Te Ara – the Encyclopedia of New Zealand'', updated 21 September 2007
* [https://www.britannica.com/EBchecked/topic/449062/pelagic-zone "Pelagic-zone (oceanography)"] Encyclopædia Britannica Online. 21 March 2009.
* Grantham HS, Game ET, Lombard AT, et al. (2011) [http://dx.plos.org/10.1371/journal.pone.0016552 "Accommodating Dynamic Oceanographic Processes and Pelagic Biodiversity in Marine Conservation Planning"] ''[[PLOS One]]'' '''6'''(2): e16552. {{doi|10.1371/journal.pone.0016552|doi-access=free}}.
* {{cite book |last1=Wrobel |first1=David |last2=Mills |first2=Claudia |date=2003 |orig-date=1998 |title=Pacific Coast Pelagic Invertebrates: A Guide to the Common Gelatinous Animals |publisher=Sea Challengers and Monterey Bay Aquarium |isbn=0-930118-23-5 |url-access=registration |url=https://archive.org/details/pacificcoastpela00wrob}}

{{physical oceanography|expanded=other}}
{{aquatic ecosystem topics|expanded=none}}
{{Biomes}}
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[[Category:Aquatic biomes]]
[[Category:Fisheries science]]
[[Category:Oceanographical terminology]]
[[Category:Oceanography]]