FISH CONNECTS WORLDS

How to Compare Fish Records When Sources Disagree

You have found two descriptions of what appears to be the same fish, but they give different names, measurements or distributions. The next step is not to choose the more polished page or average the numbers. First find out whether the sources are answering the same question about the same animal. A careful comparison often reveals that an apparent contradiction comes from a difference in identity, scope, date or terminology.

Overview

This guide offers a practical note-taking method for that comparison. It is intended for readers following links through Fish Atlas, rather than specialists making a formal taxonomic decision. You can use it with two sources or several. The result may be a supported answer, a narrower question, or an explicit uncertainty. All three are more useful than combining incompatible statements into a confident summary.

Write Down the Claim You Are Checking

Start with one sentence. “These sources give different lengths” is less useful than “One source labels this value as a maximum, while the other does not explain its value.” The more precisely you state the disagreement, the easier it becomes to find the relevant part of each source. Avoid comparing whole pages as if every sentence had the same purpose or level of detail.

Create a small record for each source: its title, address, date if supplied, the relevant statement, and the species name it uses. Distinguish your own paraphrase from an exact quotation. Keep quotations brief and preserve the surrounding context in your notes. If the source is unavailable or a detail cannot be found again, mark that limitation before relying on the claim in a public correction or article.

Confirm the Identity Before Comparing Details

Check the full scientific name in both records. Then investigate any difference in spelling, accepted name or synonym through the references supplied by the source. A shared common name is not enough to establish that the pages concern the same species. Likewise, a page about a genus or family may be providing background that should not be applied to every species within that group.

Record your conclusion separately from the original names. You might establish that both sources refer to the same species, or you might find that the identity remains uncertain. If you cannot resolve it, stop short of merging the facts. This is particularly important when following a label from a shop, an image search result or an old publication, where the amount of identifying information can vary considerably.

Match the Scope of the Evidence

Ask what each record covers. One may summarize a species across its range while another describes observations at a single location. One may report a field observation while another gives guidance for captive animals. These are different scopes. A local observation can add useful detail without establishing that the same conditions apply everywhere, and a broad summary may omit exceptions described in a narrower study.

Make the scope part of your rewritten statement. Instead of saying that a behavior always occurs, explain the setting in which the source reports it. Instead of silently replacing a broad distribution with one observed locality, keep the locality as a separate observation. The purpose is not to make every sentence longer, but to preserve the information that determines where and when the claim can reasonably be used.

Check Units, Definitions and Dates

For measurements, copy the units and the field definition alongside the number. Do not compare values until you know whether they represent the same kind of measurement. If a source distinguishes a maximum from a usual value, retain that distinction. When the method is missing, say so. A precise-looking number without an explanation may be less useful for your question than a broader but well-described observation.

Dates also need labels. The date you visited a website is not necessarily the date of the research, the observation or the assessment it describes. Write those dates separately when they are available. A recently updated page can cite older work; an older paper can still be the source of a specific observation. Recency alone does not determine which statement is correct, but it helps explain what evidence was available.

Follow a Reference to the Relevant Passage

A list of references is useful only if you can connect it to the claim under discussion. Follow the closest citation and look for the passage, table or record that supports the statement. If a summary cites another summary, keep track of that chain. Several pages repeating the same source do not provide several independent observations, even when their wording differs.

Use a simple confidence note: directly supported, partly supported, or unresolved. Explain why you chose it. For example, a source may establish the identity but not the measurement you are checking. Avoid converting an institution's reputation into blanket support for every sentence on another website. The test is whether the particular reference supports the particular claim within the scope you intend to use.

Build a Comparison That Another Reader Can Follow

Before writing your conclusion, arrange your notes in matching fields: identity, claim, scope, method, date and source. Empty cells are useful because they show where information is missing. Do not fill them with assumptions simply to make the comparison look complete. If one source answers a different question, explain the difference instead of forcing it into a vote for one side of the disagreement.

Your conclusion should say what you established and what remains open. A good correction can be modest: a missing unit, an outdated name that needs explanation, or a statement that should be limited to the study's location. Include the Fish Atlas page address, the specific wording and the supporting reference when reporting it. This gives the editor a reproducible path from the reported issue to the evidence needed to assess it.