S

1) survival rate ( number of fish alive after a specified time interval, divided by the initial number, usually on a yearly basis (Ricker, 1975)

2) abbreviation for siemens, a measure of conductivity, q.v

3) Silurian, a geological period within the Palaeozoic ca. 441-113 million years ago. Most of the major groups of fishes are thought to have originated in the Early Silurian

second