The IUCN Red List of Threatened Species guides analyses to assess the status of all species globally.

Assessment criteria

It is the definitive tool to inform international dialogue and global agreements everywhere. IUCN Red List assessments categorise each species according to defined thresholds under a set of five criteria:

(A) change in population size
(B) geographic ranges
(C) small population size and decline
(D) very small populations and
(E) quantitative analysis / modelling change.

Species are categorised according to their worst status under any one of these criteria. IUCN Red List assessments are subject to peer review and are considered primary papers once published.


Proportion of seahorse species known to be globally threatened


Proportion of seahorse species that are too little studied to be assessed

A White’s seahorse (Hippocampus whitei) – one of two Endangered seahorse species. Photo by Gaetano Gargiulo / Guylian Seahorses of the World

Most recent global assessments

The last global assessment of seahorses, conducted in 2016 by Project Seahorse with the IUCN SSC Seahorse, Pipefish and Seadragon Specialist Group, established that at least one-third of the 42 species then recognised were threatened.

  • Two species are Endangered, both because of habitat degradation: Hippocampus capensis is found in just three South African estuaries and Hippocampus whitei is a coastal species endemic to eastern Australia, living in seagrasses, macroalgae and corals.
  • 12 species are Vulnerable, primarily in East and Southeast Asia and primarily threatened by fishing pressure, while one is Near Threatened.
  • 17 seahorse species are Data Deficient, so poorly understood that we couldn’t assess their status; many of these are likely to be threatened.
  • 10 seahorse species are Least Concern because (i) reductions in population size are not severe enough to meet thresholds under criterion A despite the presence of known threats, or (ii) no threats are known to affect the species.


IUCN Red List assessments should be redone at least every ten years, so we need to reassess seahorse species soon, including some that are heavily traded. Such work takes rather a lot of resources so our priority is three groups of species:

(i) those that have not yet been evaluated;
(ii) those that were previously deemed threatened; and/or
(ii) those that have new data.

The biggest challenge is to determine the conservation status of the 17 Data Deficient species; we lack population data, threat analysis and conservation responses for these species. Please do share your information to help out.

We also need to do the first assessments for the four seahorse species that have been discovered since 2016, of which three are pygmy seahorses.