Research method

Sources and Methodology

Every figure on this site comes from somewhere, and the point of citing sources is to make that somewhere findable. Each profile lists the material consulted for it, and the full citation registry is published below so that a reader can go directly to the institution rather than taking a compiled page at its word.

This page explains the method instead of repeating the list. It covers how sources are ranked against each other, why conservation status comes from one authority rather than several, what happens when two reputable institutions publish different numbers for the same animal, why some measurement fields are deliberately left empty, and how often the whole body of material is rechecked.

How a profile is put together

Research on a species begins with the broadest and most formally reviewed material and works inward. The global conservation assessment establishes the accepted status, the population trend and the threats. A government fisheries or wildlife agency account supplies management-grade biology and distribution for waters that agency oversees. Museum and research institution accounts then fill in anatomy, behavior, reproduction and ecological role. Specialist reference databases, which compile measurements from the primary literature, supply the numeric ranges. Narrative writing comes last, so that the prose is built to fit the evidence rather than the evidence being selected to fit an already-written story.

Measurements are recorded as they appear in the source, in the metric units the literature uses, with a minimum, a maximum and a typical adult value wherever the material supports all three. Each stored figure keeps a note describing how it was obtained, which population or sex it describes, and what limits its reliability. Conversion to feet and pounds happens for display only, so that no reader-facing figure is a conversion of a conversion. Rounding follows the certainty of the underlying measurement rather than the precision the arithmetic happens to produce.

Nothing here rests on original field research, unpublished observation or private communication. This site runs no studies, holds no specimens and has no formal relationship with any organization it cites. Citing a public source is not a partnership, a sponsorship or an endorsement, and none of the institutions referenced across these pages has reviewed this material or bears any responsibility for how it is presented. Where the published record is genuinely unsettled, the profile records the disagreement rather than resolving it, and points the reader back to the sources so the question can be examined at first hand.

The source hierarchy

Sources are grouped by what they are built to do, and each group is trusted for the kind of claim it handles best. Assessment bodies carry out structured, periodically revised evaluations of population status and threat, and they are used for conservation categories and trends. Government agencies produce management-grade biology for the waters they oversee, and they are used for distribution, stock information and regulatory context. Museums and research institutions are used for anatomy, behavior, life history and ecological role.

Specialist reference databases occupy a distinct position. They compile measurements from scattered primary literature and record where each figure came from, which makes them the right tool for length, weight, growth and depth ranges. They are not, however, treated as an authority on conservation status, since that is not what they are built to evaluate. Using each source for the question it was designed to answer avoids importing a weak claim from an otherwise excellent publication.

What each group is used for

  • Assessment bodies: conservation category, population trend, threat classification
  • Government agencies: distribution, stock status, protection and management context
  • Museums and research institutions: anatomy, behavior, reproduction, ecological role
  • Specialist databases: length, weight, depth, growth and lifespan ranges
  • Taxonomic authorities: accepted scientific names and family placement

One authority for conservation status

Conservation status on this site comes from a single global assessment authority, the IUCN Red List, for every species. The reason is comparability rather than any judgment that other bodies are less careful. Categories such as Vulnerable and Endangered are defined by specific quantitative criteria within that system, and a label from one framework does not translate cleanly into the vocabulary of another. Mixing sources would produce a catalog in which the same word carried different meanings on different pages.

National listings and trade regulations are reported separately as additional context rather than folded into the status. A species can be protected in one country's waters, listed under an international trade convention and still assessed globally as data deficient, and those are four different statements about four different things. Keeping them apart lets a reader see which protections apply where, without any of them being mistaken for the global assessment.

When sources disagree

Disagreement between reputable sources is common, particularly on maximum size, lifespan and speed. The first step is to establish what each figure actually describes, because most apparent conflicts turn out to be comparisons between different things: a total length against a fork length, a mature female against a pooled adult figure, a record specimen against a population range, a burst speed against a sustained cruising speed. Once the definitions are aligned, many disagreements disappear.

Where a genuine conflict remains, the figure reproduced independently across several institutional sources is preferred over one that traces back to a single account, however widely that account has since been repeated. Historical measurements are weighted cautiously, since early specimens were often measured after decomposition, estimated at a distance or reconstructed from partial remains. The competing figure is not deleted. It is recorded in the note attached to the measurement, with an explanation of why it is treated as less reliable.

Why some figures are missing

Empty measurement fields are deliberate. If no cited source gives a defensible figure, none is published. Nothing is estimated from a related species, inferred from body proportions or carried over from a popular account, because a plausible number with no origin is harder to correct than a visible gap and far more likely to be quoted elsewhere as fact.

Some animals are simply not well measured. Deep-water squid are known largely from damaged specimens and remotely operated vehicle footage in which scale is difficult to judge. Swimming speeds for large open-ocean fish depend on measurement methods that are themselves disputed. Lifespans for slow-growing species were revised dramatically once tissue-dating techniques replaced growth-band counts. An absent value states honestly that the question is open.

Common reasons a field stays empty

  • Too few specimens have been measured to support a range
  • Published figures rest on a measurement method the sources themselves dispute
  • Available records describe captive or stranded animals rather than wild ones
  • The only figures in circulation trace back to a single uncorroborated account
  • Sources conflict so sharply that any single number would mislead

How often sources are rechecked

The citation registry is reviewed alongside the profiles on a yearly cycle. Each entry is confirmed to be current, still published by the organization named, and still supporting the claims that reference it. Where an institution revises an account or replaces a resource, the affected profiles are reread rather than merely relinked, since a revision often changes the substance of what was cited and not just its location.

Individual sources are rechecked sooner when something prompts it. A new conservation assessment, a change to a protected listing, a widely reported study or a reader report will all pull the relevant material forward. When a recheck changes a published figure, the change is handled under the corrections policy and dated on the page it affects.

Reading the citations

The registry below lists every source the catalog draws on, with its publisher and a note describing what it is used for. Each species profile lists the subset consulted for that animal. Together those two lists are meant to make the path from a statement on this site to the institution behind it as short as possible.

Readers working on academic, professional or regulatory questions should use the original sources directly rather than citing a compiled reference, and the citations are published in enough detail to make that straightforward. Questions about which source supports a particular figure can be sent to [email protected]. Those are answered with the specific citation and, where it helps, the passage the figure was drawn from, rather than with a general pointer to an institution's home page.

Reference list

These are the bodies whose published work the 33 profiles draw on. Each profile also lists the specific subset used for its own figures.

Last updated .