Laboratory growth of larval lampreys (Lampetra (Entosphenus) tridentata Richardson) at different food concentrations and animal densities

Lampreys are important research animals. This study investigates some of the Parameters important for culturing the Suspension feeding larvae: food concentration, temperature and crowding. Large larvae ( Lampetra ( Entosphenus ) tridentata Richardson) were used, weigh‐ing from l·5 to 3·0 g (wet). Two food types were employed: suspended yeast cells ( Saccharo‐myces cerevisiae , 0–20 mg1 – (dry), or, in a few tests, a fine particulate fish food, Liquifry® (Interpet LTD, 0–13 mg l ‐1 ). At both 14 and 4°C, yeast could sustain weight increases comparable to those in nature: >6% month ‐1 for up to 6 months, the duration of the study. In a single lest, a vitamin Supplement failed to improve growth on yeast. Growth‐was fastest at 14°C (+41% month ‐1 , max. weight increase), although also substantial at 4°C (+11% month ‐1 , max). Growth could not be sustained at 20°C, due perhaps to difficulty in removing products of food decay from the aquaria. Food level being constant, growth rate varied inversely with animal density. It is suggested that larval lampreys release a growth‐inhibiting substance into the sand which they inhabit. Overall, the best growth was obtained at 14° C, with <0·05g of animal (wet weight) – aquarium water and average daily yeast concentrations between 4 and 13 mg –. Liquifry was associated with lowered growth rates when present continually above 4 mg (dry weight) – (14° C), although growth did occur at lower concentrations.