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Reference library · Living world · Aquatic observation

Marine & freshwater life

Water changes both the evidence and the reference set. Salinity, depth, substrate, flow, tide, water body and collection method can be as informative as morphology, while colour and body shape may change quickly out of water. These resources cover fishes and non-finfish life, accepted marine names, algae and occurrence context. They work best when the observation retains the habitat and method that produced it.

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LIMITS
What this method can and cannot settle

Distinctive adult fishes and large invertebrates can sometimes be identified from good in-water photographs, but many larvae, plankton, algae and cryptic species require counts, microscopy, internal anatomy or molecular evidence. Distribution records and image galleries narrow a candidate list; they do not verify it. If a required fin ray, appendage, valve character, reproductive structure or sequence is absent, stop at the rank the visible evidence supports.

Before you reach for an atlas

Record the characters first.

Matching a photograph against a memory is how misidentifications happen. Working through these in order gives you a description that someone else can check — and that stays useful even if the determination later changes.

  1. Water and habitat

    Record marine, estuarine or freshwater setting, water body, depth, substrate, flow, tide and temperature where known.

    State whether the organism was attached, swimming, stranded, cultured, collected by net or found in a sample. Collection method strongly shapes what can be inferred.

  2. Scale and living appearance

    Photograph the organism in water with scale before colour, posture or soft parts change.

    Retain full-body lateral and dorsal views where safe, then close diagnostic structures. Record estimated versus measured length and the measurement convention used.

  3. Counts and structures

    Record fins, rays, spines, appendages, segments, shells, valves or reproductive structures required by the key.

    A beautiful side photograph may still omit the decisive count. State when a structure is hidden or could not be observed without collecting or dissection.

  4. Life stage and association

    Record egg, larva, juvenile, adult or colony and any host or substrate association.

    Larvae and juveniles often use different keys from adults. Host specificity can be useful, but the host identification must itself be supported.

These are the observations. Standards covers the vocabularies that carry them into a record — including Darwin Core for biological occurrences, REMBI and OME for imaging, and ABCD-EFG for geological material — while each observation profile records its own method-specific context. Prepare a contribution covers what to keep alongside the files themselves.

Resources

Grouped by the question you are asking.

A resource can appear under more than one heading. Each entry states who maintains it, what it is best for, and where it stops being reliable.

Describe what you observed

Character guides and controlled terminology, so your description means the same thing to the next reader.

FishBase

FishBase Consortium and Quantitative Aquatics

A global finfish database with names, morphology, photographs, distributions, ecology, references and a substantial set of regional keys.

Best for
Comparing finfish morphology, checking meristic characters and following a regional key or species account.
Limits
Finfishes rather than all aquatic life. Data depth and interactive-key coverage vary, and photographs do not replace counts or examination in difficult groups.
Coverage
Global marine and freshwater finfishes.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

Fishes of Australia

Museums Victoria for OzFishNet and Australian museum partners

Authoritative Australian fish accounts, images, distributions, a picture-based family finder and an interactive freshwater-fish key.

Best for
Identifying Australian marine or freshwater fishes and checking the candidate against museum-supported range and diagnostic information.
Limits
Geographically restricted to Australia, and key depth differs among groups. Some identifications still require counts or specialist examination.
Coverage
Australian marine and freshwater fishes.
Reuse
CC BY 3.0 Australia unless a page or image states otherwise.
Identification key Open Research pass ·

Compare against reference evidence

Atlases, catalogues and reference collections for comparing an unknown with documented material or measurements.

FishBase

FishBase Consortium and Quantitative Aquatics

A global finfish database with names, morphology, photographs, distributions, ecology, references and a substantial set of regional keys.

Best for
Comparing finfish morphology, checking meristic characters and following a regional key or species account.
Limits
Finfishes rather than all aquatic life. Data depth and interactive-key coverage vary, and photographs do not replace counts or examination in difficult groups.
Coverage
Global marine and freshwater finfishes.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

Fishes of Australia

Museums Victoria for OzFishNet and Australian museum partners

Authoritative Australian fish accounts, images, distributions, a picture-based family finder and an interactive freshwater-fish key.

Best for
Identifying Australian marine or freshwater fishes and checking the candidate against museum-supported range and diagnostic information.
Limits
Geographically restricted to Australia, and key depth differs among groups. Some identifications still require counts or specialist examination.
Coverage
Australian marine and freshwater fishes.
Reuse
CC BY 3.0 Australia unless a page or image states otherwise.
Identification key Open Research pass ·

SeaLifeBase

SeaLifeBase team, FishBase Consortium and Quantitative Aquatics partners

A global companion to FishBase for aquatic organisms other than finfishes, with species pages, images, maps, ecology and references.

Best for
Finding baseline information and comparison material for marine invertebrates and other non-finfish aquatic groups.
Limits
Coverage and depth are much less complete than the diversity it represents. It is not a consistent diagnostic key, and accepted names should be checked in the relevant specialist register.
Coverage
Global non-finfish marine and freshwater organisms, uneven by group.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

AlgaeBase

AlgaeBase team associated with the University of Galway and its international contributor network

A global reference for algal taxonomy, nomenclature, distribution, literature and selected images across marine, freshwater and terrestrial habitats.

Best for
Resolving algal names and checking synonyms and distribution after morphology or sequence evidence has produced a candidate.
Limits
A work in progress reflecting editorial taxonomic opinions. It is not an interactive key, image and verification coverage are uneven, and bulk reuse is controlled.
Coverage
Global algae, including cyanobacteria and diatoms, across marine, freshwater and terrestrial settings.
Reuse
Browser use is open; database, bulk-data and image reuse are subject to AlgaeBase and contributor licensing.
Taxonomic authority Open Research pass ·

Resolve the name or identifier

Authorities that settle an accepted biological or mineral name, astronomical designation or other stable identifier.

WoRMS

World Register of Marine Species

International specialist editorial boards, hosted by the Flanders Marine Institute and supported by LifeWatch Belgium

An expert-controlled global register of accepted marine names, synonyms, classification, sources and durable Aphia identifiers.

Best for
Verifying the accepted name and taxonomic placement of a marine organism after diagnostic evidence has produced a candidate.
Limits
Primarily nomenclatural rather than a visual key. Images, distributions and identification tools are uneven among groups, and whole-database redistribution has additional conditions.
Coverage
Global marine taxa, with specialist subregisters for many groups.
Reuse
WoRMS data are broadly available under CC BY with citation; media and some source records carry separate terms.
Taxonomic authority Open API Research pass ·

FishBase

FishBase Consortium and Quantitative Aquatics

A global finfish database with names, morphology, photographs, distributions, ecology, references and a substantial set of regional keys.

Best for
Comparing finfish morphology, checking meristic characters and following a regional key or species account.
Limits
Finfishes rather than all aquatic life. Data depth and interactive-key coverage vary, and photographs do not replace counts or examination in difficult groups.
Coverage
Global marine and freshwater finfishes.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

Fishes of Australia

Museums Victoria for OzFishNet and Australian museum partners

Authoritative Australian fish accounts, images, distributions, a picture-based family finder and an interactive freshwater-fish key.

Best for
Identifying Australian marine or freshwater fishes and checking the candidate against museum-supported range and diagnostic information.
Limits
Geographically restricted to Australia, and key depth differs among groups. Some identifications still require counts or specialist examination.
Coverage
Australian marine and freshwater fishes.
Reuse
CC BY 3.0 Australia unless a page or image states otherwise.
Identification key Open Research pass ·

SeaLifeBase

SeaLifeBase team, FishBase Consortium and Quantitative Aquatics partners

A global companion to FishBase for aquatic organisms other than finfishes, with species pages, images, maps, ecology and references.

Best for
Finding baseline information and comparison material for marine invertebrates and other non-finfish aquatic groups.
Limits
Coverage and depth are much less complete than the diversity it represents. It is not a consistent diagnostic key, and accepted names should be checked in the relevant specialist register.
Coverage
Global non-finfish marine and freshwater organisms, uneven by group.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

AlgaeBase

AlgaeBase team associated with the University of Galway and its international contributor network

A global reference for algal taxonomy, nomenclature, distribution, literature and selected images across marine, freshwater and terrestrial habitats.

Best for
Resolving algal names and checking synonyms and distribution after morphology or sequence evidence has produced a candidate.
Limits
A work in progress reflecting editorial taxonomic opinions. It is not an interactive key, image and verification coverage are uneven, and bulk reuse is controlled.
Coverage
Global algae, including cyanobacteria and diatoms, across marine, freshwater and terrestrial settings.
Reuse
Browser use is open; database, bulk-data and image reuse are subject to AlgaeBase and contributor licensing.
Taxonomic authority Open Research pass ·

Place it in context

Occurrence, stratigraphic, catalogue and archive services that situate a record in space, time and literature.

WoRMS

World Register of Marine Species

International specialist editorial boards, hosted by the Flanders Marine Institute and supported by LifeWatch Belgium

An expert-controlled global register of accepted marine names, synonyms, classification, sources and durable Aphia identifiers.

Best for
Verifying the accepted name and taxonomic placement of a marine organism after diagnostic evidence has produced a candidate.
Limits
Primarily nomenclatural rather than a visual key. Images, distributions and identification tools are uneven among groups, and whole-database redistribution has additional conditions.
Coverage
Global marine taxa, with specialist subregisters for many groups.
Reuse
WoRMS data are broadly available under CC BY with citation; media and some source records carry separate terms.
Taxonomic authority Open API Research pass ·

FishBase

FishBase Consortium and Quantitative Aquatics

A global finfish database with names, morphology, photographs, distributions, ecology, references and a substantial set of regional keys.

Best for
Comparing finfish morphology, checking meristic characters and following a regional key or species account.
Limits
Finfishes rather than all aquatic life. Data depth and interactive-key coverage vary, and photographs do not replace counts or examination in difficult groups.
Coverage
Global marine and freshwater finfishes.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

Fishes of Australia

Museums Victoria for OzFishNet and Australian museum partners

Authoritative Australian fish accounts, images, distributions, a picture-based family finder and an interactive freshwater-fish key.

Best for
Identifying Australian marine or freshwater fishes and checking the candidate against museum-supported range and diagnostic information.
Limits
Geographically restricted to Australia, and key depth differs among groups. Some identifications still require counts or specialist examination.
Coverage
Australian marine and freshwater fishes.
Reuse
CC BY 3.0 Australia unless a page or image states otherwise.
Identification key Open Research pass ·

SeaLifeBase

SeaLifeBase team, FishBase Consortium and Quantitative Aquatics partners

A global companion to FishBase for aquatic organisms other than finfishes, with species pages, images, maps, ecology and references.

Best for
Finding baseline information and comparison material for marine invertebrates and other non-finfish aquatic groups.
Limits
Coverage and depth are much less complete than the diversity it represents. It is not a consistent diagnostic key, and accepted names should be checked in the relevant specialist register.
Coverage
Global non-finfish marine and freshwater organisms, uneven by group.
Reuse
Database content is CC BY-NC 4.0; images retain separately stated rights.
Database Open Research pass ·

OBIS

Ocean Biodiversity Information System

Intergovernmental Oceanographic Commission of UNESCO through its International Oceanographic Data and Information Exchange programme and the OBIS node network

The world's largest open-access infrastructure for marine biodiversity occurrences, measurements and associated environmental data.

Best for
Checking marine geographic, depth and temporal plausibility and tracing an occurrence back to its survey, collection or monitoring dataset.
Limits
An occurrence aggregator, not an identification key. Coverage follows sampling effort, records can inherit source errors, and sensitive or culturally governed data require CARE as well as FAIR handling.
Coverage
Global marine biodiversity from a network of regional and thematic nodes.
Reuse
Datasets carry CC0, CC BY or CC BY-NC licences; verify and cite every contributing dataset used. OBIS-derived information products are CC0.
Data repository Open API Research pass ·

AlgaeBase

AlgaeBase team associated with the University of Galway and its international contributor network

A global reference for algal taxonomy, nomenclature, distribution, literature and selected images across marine, freshwater and terrestrial habitats.

Best for
Resolving algal names and checking synonyms and distribution after morphology or sequence evidence has produced a candidate.
Limits
A work in progress reflecting editorial taxonomic opinions. It is not an interactive key, image and verification coverage are uneven, and bulk reuse is controlled.
Coverage
Global algae, including cyanobacteria and diatoms, across marine, freshwater and terrestrial settings.
Reuse
Browser use is open; database, bulk-data and image reuse are subject to AlgaeBase and contributor licensing.
Taxonomic authority Open Research pass ·

Corrections

Know this field better than this page does?

The most valuable correction is not another link. It is knowing that an entry's stated limit is wrong, or that a resource practitioners rely on is missing.

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