Published 2026-06-12 · data 2018 · relative marine biomass units
Fish biomass is a sliver of ocean life
We think of the sea as fish. By mass, tiny plankton and invertebrates dominate — fish are a visible minority.
We imagine the ocean as fish. By mass, it mostly isn't. In 2018, invertebrates made up 42% of marine animal biomass and microbes & plankton 38%; fish — from anchovies to sharks — were just 15%, and marine mammals 5%. The life we notice, catch and eat is a sliver of the ocean's living mass.
1 cell = 1 relative marine biomass units (0.1% of marine animal biomass (illustrative)) · 1,000 cells
Context
The shares come from Bar-On et al.'s 2018 global biomass census, as charted by Our World in Data, rounded to an illustrative 1,000-unit scale of relative marine biomass. They measure living mass, not abundance — which is how microbes, plankton and invertebrates together outweigh fish more than five to one.
That 15% slice carries outsized human pressure. The world produces around 200 million tonnes of fish and seafood a year, and fish farms now supply more of it than wild catch — one reason output from wild fisheries has plateaued.
Seafood's importance runs ahead of its biomass share: it provides under 10% of global protein intake and about one-sixth of animal protein, and is the majority source of animal protein in countries such as Cambodia, Bangladesh and the Maldives.
Bar-On et al. / OWID marine biomass shares, rounded to illustrative 1,000 units.
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Credit this grid as Inagrid — https://inagrid.com/e/2026-06-12-ocean-biomass