Temperature, density and ammonia effects on growth and fecundity of the ramshorn snail (Helisoma anceps)

Abstract

Ramshorn snail (Helisoma anceps) is a freshwater gastropod found all over North America and is also an essential component to the larval and juvenile culture of endangered Delta Smelt (Hypomesus transpacificus) at the UC Davis Fish Conservation and Culture Lab (FCCL). H. anceps has been proven effective in cleaning the excess algae while not harming the larvae. A challenge at the FCCL has been having a reliable source of these snails, since previously it has been dependent upon nature and never guaranteed there would be enough to meet the needs of the FCCL. Experiments were conducted to assess the effects of temperature, food types, rearing density and total ammonia nitrogen (TAN) concentrations. Procedures recommended to increase snail fecundity for the FCCL are to rear spawning parent snails and the resultant eggs at a high temperature (16–20°C) and with a low TAN concentration (0–5 mg/L). Newly hatched snails need to be cultured at a low density (about one snail/20 cm2). After the snails grow to an acceptable size (1.3 cm diameter), they could be set aside and cultured in an environment with less optimal water quality parameters such as a high TAN level (as high as 20 mg/L) and low temperature (12°C) for quantity control prior to use.