Abstract  Knowledge on the biology and physiology of pike, Esox lucius L., populations inhabiting saline environments is scarce. An experimental setup was used to examine egg development and fry behaviour and growth under varying salinity levels in a brackish-water pike population from the western Baltic Sea. Eggs and fry developed at 8.5 psu, which is higher than hitherto reported for other populations. Fry exhibited stress behaviour and reduced growth when subjected to salinities above 13 psu. This indicates that early life stages of E. lucius tolerate ambient salinity conditions equivalent to the natural environment in its nursery area in the Stege Nor lagoon. The population should therefore not be dependent on access to freshwater environments during spawning. However, the results also suggest that the population’s natural environment is on the margin of its physiological capacity. The results have significance for management of brackish-water E. lucius populations, e.g. in relation to stocking strategies.