Control of aquatic weeds and undesirable species from nursery pond

1. Submitted by,
Nazmul Ahmed Oli
Reg: 12-05-2835
Level: 3
Course code: GFB-332

2. Nursery Pond
A pond where fry & fingerlings are reared for 10 to 15 days for grow out.
Characteristics:
• 10-25 decimal
• 1-1.5m water depth
• Rectangular pond with 1:2 or 1:1.5
• Loam or clay loam soil
• Organic matter in pond bottom should be below 10-
15cm
• Pond dikes should be high enough, strong
• Enough Light and air
Fig: Nursery pond

3. Types Of Aquatic Weed:
Aquatic plants can be divided into:
(1) algae
(2) rooted water plants.
Generally rooted plants are 4 types:
Floating
Weeds: Water
hyacinth, Lily
Emerged
Weeds: Typha
Submerged
Weeds:
Hydrilla,
Marginal
Weeds:
Marsilea

4. Common Floating Plants
Spatterdock, Nuphar advenaWatershield

5. Submerged Plants:
hydrilla

6. Problems of associate with Weeds
 Mortality
 Less primary productivity
 Successful competitor.
 Predator Shelter
 Hampering netting operation
 Fish flavor problems
 Pond water odor problems
 Stunned Growth of fish
 Disturbance in oxygen

7. Weed Control: Physical Removal
Drain
Dredge
Dragging
Raking
Cutting
Skimming
Harvesting
Aeration

8. Chemical Control
Algae
• Copper Sulfate,
• Copper Complex (Cutrine)
Submerged Weeds
• Diquat (Reward),
• Fluridone (Sonar / Avast),
• 2, 4-D, (Aqua-Kleen)
• Endothal (Aquathol K)
Floating (Duckweed and Watermeal)
• Diquat,
• Fluridone
Emergent and floating Plants
• Endothal, Fluridone, 2,4-D
• Glyphosate (Rodeo)

9. Biological Control
Herbivores can control by eating the weed..Eg: Grass carp
Aquatic
weeds
Amount
weeds
(kg/dec)
No. of
grass
carp/dec
Weight of
each
fish(g)
Time (day)
Hydrilla 275 2.6 113 42
Spyrodella 24 5 474 20
Fig: Grass carp

10. Undesired Species Control
Before stocking the fry in the nursery pond predatory & weed fish must
be eradicated.
Common predatory fishes are:
Channa spp., Clarias batraches, Heteropneustes fossailis, Pangsius,
Mystus sp. Ompok spp., Wallage attu
Common weed fishes are:
Puntius sp., Oxygaster sp., Ambassis sp., Amblypharyngodon mola.
Colisa sp., Rasbora sp

11. Removal of predatory and weed fishes:
Repeated netting.
Dewatering the nursery pond.
Drying.
Use of poison.
Use of pesticides.

12. Commonly used pesticides are:
Mahua oil cake
• It kills fish at 200-250 ppm in 6-10 hours.
Tea seed cake
• 145-150g/dec at 30cm water depth
Ammonia
• Kills fish @ 20-25 ppm
Rotenone
• rotenone is 2 g/m3 for common predators and 8 g/m3 for eel.

13. Conclusion:
Nursery pond is very important for successful aquaculture. To
get good quality of fry we should carefully manage the nursery
pond. So we should always be careful & eradicate the weeds &
predator or weed fish from the nursery pond.