Abstract In this work, we examined the effects of rapid changes in salinity on the availability (mobility and swimming) of the prey rotifer Proales similis. Rotifers were transferred as follows: 5 to 15, 25 and 35 (T1); 15 to 5, 25 and 35 (T2); 25 to 5, 15 and 35 (T3) and 35 to 5, 15 and 25 ppt (T4) during 1–240 min. Results showed that in T2 and T3, the percentage of mobile rotifers in the water column recovered up to 100 after 15 min. At T1 and T4, mobility regained slower at 35 and 5 ppt respectively. All individuals transferred at 15 and 25 ppt maintained their mobility above 93 after 15 min. In general, swimming speed ranged from 0.37 to 0.65 mm s−1 and was higher at 15 ppt and lower at 35 ppt. In all salinities, swimming increased with time and recovered better in T2 and T3. These data suggest that P. similis can acclimate to a wide range of salinity gradients in the short term (1–240 min). According to the literature and our results, P. similis has a greater tolerance to sudden salinity changes than brachionid rotifers used traditionally in fish larviculture.
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