Dr. Craig Kasper, HCC Aquaculture Program Zooplankton Culture Dr. Craig Kasper, HCC Aquaculture Program

Last Time: What’s a LUX?? A unit of illumination equal to the direct illumination on a surface that is everywhere one meter from a uniform point source of one candle intensity or equal to one lumen per square meter called also meter-candle a unit of illumination, equivalent to 0.0929 foot-candle and equal to the illumination produced by luminous flux of one lumen falling perpendicularly on a surface one meter square. Symbol: lx

Introduction Zooplankton is required as a first food for many cultured fish; for others it contributes to faster growth and higher survival. Since larval fish don’t take up much space, 0.1-3 acre ponds will do nicely, if you are outdoors. Indoor fry culture can be done in 250-1000 gallon tanks in a recirculation system. Tiny fry eat tiny prey, but are preyed upon by many creatures bigger than they are. Stock the right size fry and feed the right size zooplankton! Yes, some zooplankton would try to eat your fry.

First Feeding on Zooplankton Most fish fry eat three main types of zooplankton—rotifers, copepods and cladocerans. For the tiniest fish fry, HSB or WB, small rotifers may be the only zooplankton small enough to eat. If fry are too large, then they rotifers may not provide enough nutrition. Copepod nauplii, which arejust-hatched copepods, are important first foods for larval fish, too.

Rotifers

Rotifers Rotifer (0.04 -2.5 mm long). Sim. to microalgae. “Wheel organ” a ring of cilia that “rotates” around the mouth Appear early, hatch from “resting eggs” in the pond reproduced rapidly (2-8 days post hatch). Asexual reproduction: need good conditions Sexual reproduction: poor pond conditions (“resting” eggs produced)

Rotifers Hexarthra, note the egg attached to this female Floscularia, tube building rotifer, attaches to plant stems.

Rotifer Setup Sterilized water (whether salt or fresh) pH and temperature should = starter culture. Temperature is 20 - 30° C pH 8.0 Start with at least 10-20 rotifers/ml (minimizes crashing) 1-2 feedings per day; continuous preferable.

Counting… Counts determine health* *Healthy cultures of rotifers contain egg bearing females and very few males. An increase in the number of male rotifers, easily identifiable by their smaller size, is an indicator of a stressed culture (bad H20 quality). female rotifer w/eggs Sedgwick-Rafter Cells with Grid

Hatching Rotifers SW “L” Type - Brachionus plicatilis 200-360μ “S” Type - Brachionus rotundiformis 150-220μ “SS” Type - Brachionus rotundiformis 70-160 μ FW Brachionus rubens, Brachionus calciflorus Temperature: 30°C pH: 7.2-9 Feed: Nannochloropsis (algae) Feeding Rate: 15 ml of Nanno/10 million "L" type/day  Feeding Times/Day: Continuous, or every 3 hours 

Artemia nauplii “I must apply myself!!!”

Copepod Artemia nauplii Next copepods to appear from resting eggs. Artemia molt up to 12 times before reaching adult stages (provides an increasing food size for larval fish.) Adults may reach 3 mm length

Hatching Requirements Good water. Clean clean equipment, tubing hatching contianer, etc. pH: 8.5 Illumination: constant bright light Temperature: 24-28° Aeration: needed to keep Artemia cysts circulating. Salinity: recommended to be approximately 24-28ppt. Density of cysts should not exceed 10 grams / liter. Incubation Time: usually hatch out takes approximately 24 hours.

Cladocerans (Water Fleas) Cladocerans: third major group Larger fry and even adults eat them. Cladocerans 2 to 3mm long are commonly found in culture ponds several weeks after the ponds are filled. Hatch from resting eggs. Cladocerans compete with rotifers and calanoid copepods for phytoplankton.

Daphnia magna Very large! eggs

Life History D. magna live approx. 40 days at 25°C and about 56 days at 20°C. Life History: (1) egg (2) juvenile (3) adolescent (4) adult (Pennak, 1978)

Culture Parameters Salinity - 99% of Cladocerans are freshwater Oxygen - Tolerant of low oxygen. A slow aeration is needed. Aggressive bubbles kill them (Bio-foam filters work great!) pH - 7.2 - 8.5. Hardness: D. magna tends to prefer harder water (170 mg carbonate hardness) and D. pulex a little less hard (90 mg carbonate hardness). Temperature: Daphnia magna 18-22°C (64-72°F) D. pulex > 10°C. Moina 5-31°C (41-88° F); opt. 24-31°C (75-88°F). Food: Green water, yeasts, bacteria Other facts: <0.5 ppm P stimulates reproduction, but concentrations higher than 1.0 are lethal to the young.