Rotifers (Brachionus plicatus)
As delta smelt larvae begin to feed, rotifers are the first live prey offered to them. This species of micro-zooplankton engages in slow and predictable movements that allow for their easy capture.
Rotifers are parthenogenetic, capable of transitioning between both sexual and asexual phases of reproduction. Aquaculture systems have been designed to encourage the asexual phase, given that it yields exponential rates of production. Rotifers are reared in 300L tanks maintained at a temperature of 21-23°C and a salinity of 15ppt. These precise conditions are essential for preventing the rotifer’s transition to sexual phase, which yields a much slower rate of production. The FCCL uses a continuous culture method, where peristaltic pumps provide a constant supply of algae to rotifers.
Brine Shrimp (Artemia franciscana)
Brine shrimp nauplii are the most utilized live prey by the FCCL. When exposed to unpredictable environments, they produce resting cysts that can be cultured on demand and stored for long durations of time.
Artemia cysts are incubated for 20-24 hours at a density of 1-2g/L in a salinity of 30ppt and temperature of 30°C. Once hydrated the cysts hatch on their own without any form of inducing. Each morning the newly hatched Artemia are harvested while taking special care to remove cyst shells from the live prey to be fed throughout the day. They are held in a container with an air diffuser and fed to larval and juvenile delta smelt five times a day.
Ramshorn Snail (Helisoma anceps)
The FCCL previously relied on collection of snails via manual capture from a field at the facility. However, this method posed several drawbacks; long collection hours, limited availability in the winter and early spring, and the risk of introducing parasites into fish culturing systems. As a result, a methodology for culturing the Ramshorn Snail was developed.
The FCCL rears spawning parent snails and resulting eggs at high temperature (16-20°C) and a low total ammonia concentration (0-5mg/L). These water quality conditions provide high survival and egg production. Newly produced eggs are transferred to tanks where they are cultured in a density that promotes optimal growth. Once snails have grown to a particular size, they are cultured in an environment with a less optimal water quality conditions before use.
Hung TC, Stevenson T, Sandford M, Gheremariam T (2018) Temperature, density and ammonia effects on growth and fecundity of the ramshorn snail (Helisoma anceps), Aquaculture Research 49(2), 1072–1079
The FCCL’s efforts to culture mysids began in 2016 and aquaculture methods are still in the early stages of development. Prior to these efforts, the FCCL has successfully bred several thousand mysids from a population of commercially bought mysids. In 2016, we succeeded in producing our first mysid offspring derived from a wild-caught founder population. We are currently testing the best methods for culturing F1 mysids.