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 populations 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.