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 bethe 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.

RotifersRotifers

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

Floscularia, tube building rotifer, attaches to plant stems.

Hexarthra, note the egg attached to this female

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/eggsSedgwick-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.