EFFECTS OF LARVAL DENSITY AND SALINITY ON THE DEVELOPMENT OF PERCH LARVAE (PERCA-FLUVIATILIS L)

We performed two experiments, one to test whether survival and initial swim bladder inflation of perch Perca fluviatilis are affected by pop ulation density (4 or 16 larvae l-1) or salinity (0 parts per thousand , 0.6 parts per thousand and 1.2 parts per thousand), and the second t o test the salinity tolerance of larvae. In experiment 1, survival was higher at low larval densities and at salinities of 0.6 parts per tho usand and 1.2 parts per thousand rather than in fresh water. Initial s wim bladder inflation was not affected by salinity or density. Average survival of fry 24 days after hatching varied from 29.6% to 86.3%, bu t only an average of 19.2% of the hatched larvae had grown into viable fish with an inflated swim bladder. In experiment 2, survival varied from 19% to 49%, but was not significantly affected by salinities of u p to 4.8 parts per thousand. At a salinity of 9.6 parts per thousand, only 2 out of 344 larvae survived.