Explanation

Euryhaline organisms are those that can tolerate a wide range of salinity, such as salmon that migrate between fresh water and the sea. Catadromous fish (which migrate from fresh water to the sea to spawn, e.g., eels) are a subset of euryhaline species. Stenohaline organisms tolerate only narrow salinity ranges, osmoconformers match their internal salinity to the environment (mostly marine invertebrates), and osmoregulators actively maintain internal salt balance — none of these describes tolerance of wide salinity swings. Hence euryhaline is correct.