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* female rotifer w/eggs Sedgwick-Rafter Cells with Grid *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 H 2 0 quality).

Hatching Rotifers

• SW “L” Type -

Brachionus plicatilis

200-360 μ “S” Type -

Brachionus rotundiformis

150-220 μ “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 D. pulex

> 10 °C. 18-22 °C (64-72°F)

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.