Swimming Performance of Estuarine and Inland Largemouth Bass at Varying Salinities

Organisms that live in coastal estuaries often experience significant seasonal and annual fluctuations in salinity that they must either endure or move to avoid. Largemouth Bass Micropterus salmoides is a freshwater fish that lives in coastal estuaries and does not migrate/move to avoid seasonal salinity increases. Additionally, estuarine Largemouth Bass exhibit growth rates, condition factors, and life history strategies that differ from their inland counterparts. These differences suggest the potential for physiological adaptations to tolerate and even thrive in estuarine environments. We compared swimming performance (quantified as critical swimming speed, Ucrit) of Largemouth Bass (280–404 mm total length) from an Alabama estuarine population versus an inland population at 0, 4, 8, and 12 ppt salinities to test for physiological performance-based adaptation to tolerate elevated salinities. Ucrit values did not differ between inland and estuarine Largemouth Bass nor were there any salinity effects. Although inland and estuarine Largemouth Bass may possess different physiological mechanisms for tolerating salinity, those mechanisms did not affect swimming performance.