A salt on your senses: influences of rearing environment on salinity preference and sensing in lake trout Salvelinus namaycush

Within Salmonidae, spawning and rearing in brackish water is rare; however, brackish-water resident lake trout (Salvelinus namaycush) have recently been documented in the Arctic. Additionally, early rearing in brackish-water environments increased the fish's ability to ionoregulate in elevated salinities. Here, we examined the impact of a freshwater (FWR, 0 ppt) or brackish-water (BWR, 5 ppt) rearing environment on salinity preference in lake trout using a dynamic choice experiment. We observed significant differences in salinity preference between our treatments suggesting the importance of early environment in shaping salinity preference. Contrary to our predictions, FWR lake trout selected higher salinity (17.3 ppt) compared to BWR fish (4.8 ppt). Four of the seven FWR fish had preferred salinities near 30 ppt, which is considered physiologically challenging and potentially lethal for lake trout based on direct transfer experiments. Thus, heightened FWR salinity preference might not be a true preference but rather due to a reduced ability to sense differences in salinity, and a result of chance as mean preferred salinity was near half that of the upper and lower thresholds, and variance was larger. Selection of lower salinity by BWR fish suggests that the ability to sense and select different salinities is present in lake trout as a species and appears to be linked to difference in early rearing at elevated salinities.

Automated summary

Within Salmonidae, spawning and rearing in brackish water is rare. Early rearing in brackish-water environments increased the fish's ability to ionoregulate in elevated salinities. A study examined the impact of a freshwater or brackish-water rearing environment on salinity preference in lake trout using a dynamic choice experiment. Contrary to predictions, lake trout reared in freshwater selected higher salinity compared to those reared in brackish water.