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Marine Database Aims to Catalog Ocean Life by Size
By [Invented Reporter] | WASHINGTON – 2025/06/22 12:20:42
A new database is compiling the body sizes of marine organisms to better understand ocean life.The Marine Organism Body Size database (MOBS) aims to catalog all marine life by size, focusing on linear measurements like length.
Craig McClain initiated MOBS as a personal project during a 2022 sabbatical, building upon years of informal data collection. He consolidated existing data into a unified database with a standardized format.
Craig McClain holding a giant isopod (Bathynomus giganteus), one of the deep sea’s most iconic crustaceans
Credit:
Craig mcclain
According to mcclain, taxonomic inconsistencies previously hindered such efforts. He explained, “One of the things that had prevented me from doing this before was the taxonomy issue. Say you wanted to get the body size for all [species] of octopuses. That was not something that was very well known unless some taxonomist happened to publish [that data]. And that data was likely not up-to-date as new species are [constantly] being described.”
The World Register of Marine Species (WoRMS), established within the last decade, addresses this by cataloging all marine life and assigning numerical codes to validated species.McClain linked MOBS to these codes, ensuring easy updates as WoRMS adds new species. His team also gathered data from museum collections.
MOBS emphasizes body length over mass.”Almost every taxonomic description of a new species has some sort of linear measurement,” said McClain. “For most organisms, it’s a length, maybe a width, and if you’re really lucky you might get a height. It’s very rare for anything to be weighed unless it’s an objective of the study. So that data simply doesn’t exist.”
While mammal density is generally consistent, “If you compare the density of a sea slug, a nudibranch, versus a jellyfish, even though they have the same masses, their carbon contents are much different,” McClain noted.”And a one-meter worm that’s a cylinder and a one-meter sea urchin that’s a sphere are fundamentally different weights and different kinds of organisms.” Volume conversion is one solution to account for shape. Becuase length-to-weight ratios vary across marine animal groups, McClain intends to develop a separate length-to-weight conversion database.
“Almost every taxonomic description of a new species has some sort of linear measurement,”
