Alexandra Kler Lago
Field Support and Partnerships Manager, MERMAID
To support our global community with scientifically robust and standardized data, we are updating fish data in MERMAID - aligning species names with the latest accepted taxonomy from the World Register of Marine Species (WoRMS), and refining key traits used in biomass calculations, summaries, and validations from FishBase.
Aligning species names with global taxonomy
Scientific names change over time with scientific advances in taxonomy. Some fish species currently in MERMAID are no longer accepted under their existing names. We have currently identified 27 species that require updating.
These species names will be automatically updated to their accepted WoRMS equivalents. Your raw observations (transect details, counts, sizes) remain unchanged and biomass calculations will automatically update to the new species values.
You can view and download the full list of updated fish species at the end of this blog post.
Improving fish trait data
Alongside taxonomy alignment, we are updating several fish traits to improve accuracy and consistency between MERMAID and accepted global standards in FishBase and other authoritative data sources.
Biomass coefficients
We have updated length–weight conversion factors to align with FishBase Bayesian estimates. Biomass values may change slightly, while observed data remains the same. All biomass calculations are now based on the most up-to-date information available in FishBase.
We retain historical snapshots of these coefficients, so previous biomass calculations can still be reproduced. See the following Analysis Hub article for an example:
https://datamermaid.org/analyses/fish-biomass-conversion-coefficients
Trophic group
Updates to trophic group assignments will affect biomass totals by trophic group, but only for species included in the update.
These changes are minimal and apply only where no trophic group was previously assigned
To assign new trophic groups, we used expert classifications from Parravicini et al. (2020).
Geographic regions, and maximum length
Updates to species regions and maximum lengths improve validation accuracy:
Geographical regions expanded based on the most current GBIF observations, matched to marine realms.
Maximum lengths updated using most-up-to-date length data in FishBase.
Users should receive fewer false warnings during validation.
Other reference data
We are also updating group size, functional group, vulnerability, and trophic level.
These changes primarily affect users who rely on these traits for custom analyses.
Group size is assigned based on GASPAR tropical reef fish trait data and functional groups based on MacNeil et al. (2015) "Recovery potential of the world's coral reef fishes". Vulnerability and trophic levels are updated to match the most current data in FishBase.
A seamless update to your data
This update is automatic and designed to preserve your workflow:
All observations and survey structure remain unchanged
Existing fish belt data will reflect updated species names
No action is required
As always, all information on fish species accepted in MERMAID and associated traits can be downloaded by clicking ‘Reference’ in the top bar on MERMAID Collect (app.datamermaid.org). Read more about accessing taxonomic reference information here.
Supporting consistent data collection
To maintain consistency moving forward:
Only accepted species names will appear in MERMAID Collect
Outdated names will no longer be available for new observations
Keep a record of your data
If you would like to retain previous species names and biomass estimates, we recommend exporting your fish belt data before May 04, 2026 via:
MERMAID Collect (from Export data in Submitted page)
MERMAID Explore (from Export data in Filters panel)
Or the mermaidr R package
Supporting global reef monitoring
By aligning fish data with global standards, this update:
Keeps your data scientifically current
Improves comparability across projects and regions
Strengthens confidence in analyses and reporting
These improvements help ensure MERMAID continues to support trusted, large-scale coral reef monitoring efforts.
If you have any questions or need support, reach out to us at contact@datamermaid.org. We’re here to help.