Groups of sea lampreys (Petromyzon marinus) of 10–90 g initial weight were held at temperatures of 1–20 °C for 30 days and allowed to feed ad lib. on white suckers (Catostomus commersoni). Increases in water temperature and in lamprey size caused the rate of host mortality to increase in agreement with observations that mortality in the Great Lakes is seasonal. Instantaneous growth rates were maximal at 20 °C for lampreys of 10–30 g, the optimal temperature for growth shifting to 15 °C for larger lampreys of 30–90 g. Growth rates were intermediate at 10 °C and lowest at 4 °C for lampreys of all size. Accordingly, host mortality increased with temperature over the 4–20 °C range. At all experimental temperatures, increases in lamprey weight were accompanied by an exponential decline in instantaneous growth rates, a phenomenon also observed for teleosts. Laboratory growth rates at temperatures of 5–15 °C were comparable to rates observed for lampreys in Lake Huron between April and November and agree with the observation that lampreys feed in deeper waters between April and June before moving to warmer, shallower waters during the summer when growth rate increases. Key words: sea lamprey, white sucker, host, temperature, growth, Great Lakes, mortality
THE INFLUENCE OF WATER TEMPERATURE AND FLOW ON YEAR CLASS STRENGTH OF TWAITE SHAD (ALOSA FALLAX FALLAX) FROM THE RIVER SEVERN, ENGLAND.
