This document outlines many factors that can affect productivity in aquaculture, including water temperature, dissolved oxygen levels, nutrition, and management practices. Water quality factors like temperature, dissolved oxygen, and ammonia levels impact fish metabolism and growth. Fish behavior and welfare are also influenced by their environment. Proper nutrition is key to optimizing growth. The aquaculturist must balance environmental conditions, nutrition needs, and management to maximize productivity within the limits of the system.

1. Factors Affecting Productivity
Example:
Increase of water temperature by 2oC
1.
2. The oxygen demand (metabolic rate)
increases
3.
4.
5. The oxygen-based carrying capacity of
the pond decreases

2. Factors Affecting Productivity
If pond inflow rate is increased:
1.
2. The water velocity increases
3.
4. The oxygen demand increases
•

3. Factors Affecting Productivity
Fish-Associated Factors (intrinsic factors)
Stress response:
• everyday hatchery practices –
• Decreases in circulating ascorbic acid
(vitamin C)
• Increase in plasma cortisol

4. Other fish-associated factors
Ammonia-nitrogen:
• Natural byproduct of protein metabolism.
• Ammonia (NH+) is generated –
4
• Ionized NH4
+ is non-toxic to fish –
•
Factors Affecting Productivity

5. Factors Affecting Productivity
Behavior:
•Each fish species has a unique life history and
behavior patterns reflect this.
•Must raise fish under situation that does not
inhibit normal behavior patterns
•Fish can adapt to unnatural situations –

6. Factors Affecting Productivity
Nutritional Requirements:
• Dietary requirements must be satisfied based
on species needs.
• Nutritionally adequate diets are available for
most salmonids and ictalurids.

7. Factors Affecting Productivity
Environmental Requirements:
Coldwater species
•
• Maximal growth rate –
Coolwater species
• S.E.T. is generally between 15oC and 20oC
•

8. Factors Affecting Productivity
Warmwater species
• Fish whose S.E.T. is generally > 20oC
Thermal Death Point –
• In addition to water temperature, other water
chemistry factors must be maintained within
“no-effect” limits

9. Factors Affecting Productivity
Product Definition:
• Identification of starting dates and management
processes to be implemented
•
• By working backwards, the start date, number and
size of fish can be determined and implemented as
the product definition

10. Factors Affecting Productivity
Growth Rate Potential (GRP):
• The maximum growth rate that may be achieve and
is measured as increases in length, weight or both.
•

11. Factors Affecting Productivity
• Allowable Growth Rate (AGR) is the growth rate
that the system will permit and is dependent on
many factors:
i. Water temperature
ii.
iii. Water osmolality
iv.
v. Feed quantity
vi.

12. Factors Affecting Productivity
Disease History:
•If clinical or subclinical episodes of infectious
and non-infectious disease are experienced
productivity may be affected.
•Direct measurement of such episodes and their
relationship on productivity are difficult.

13. Factors Affecting Productivity
Length:Weight Relationship: (“condition
factor” K=W(g)/L(mm)3 x 10,000)
•
• For accurate data the condition factor should
be calculated at the end of each growth
period by weighing and measuring
individual fish.

14. Factors Affecting Productivity
Cannibalism:
•
• Can be minimized by frequent grading and diligent
feeding practices.
Oxygen Uptake:
• Rate of oxygen uptake across the gill lamellar
membranes is important

15. Factors Affecting Productivity
Oxygen Demand:
•Regulated by the metabolic rate, which is
influenced by factors such as water temperature
and age of animal.
•

16. Factors Affecting Productivity
Fecal Solids:
• If allowed to accumulate, a reduction in growth rate
will occur due to:
1. Increases in Biological Oxygen Demand
(B.O.D.)
2. Sestonosis – accumulation of solids and other
detritus on the buccal aspect of the gill rakers
3. Lamellar thickening (hypertrophy or
hyperplasia) resulting from physical irritation
4.

17. Factors Affecting Productivity
Carbon Dioxide:
•Generated as respiratory by-product.
•

18. Factors Affecting Productivity
Water-Associated Factors (quality and quantity)
Dissolved Oxygen (DO)
•
• D.O. should generally be > 5mg/l for salmonids.
• Saturation levels -

19. Factors Affecting Productivity
Nitrite-Nitrogen
• Nitrite is the oxidation product of ammonia
nitrogen and is influenced by the bacteria
Nitrosomonas sp.
• The accepted tolerance level of nitrite is 0.55mg/l.
•

20. Alkalinity and Hardness
• Hard water (>250mg/l alkalinity)
• Soft water (<100mg/l alkalinity)
•
Factors Affecting Productivity

21. Factors Affecting Productivity
Contaminants
• Water must be free of municipal, industrial, and
agricultural contaminants.
• Natural heavy metals must be below 1 mg/l.
•

22. Factors Affecting Productivity
Solids
•
• Net results of suspended/settleable solids is
generally a reduction in growth rate and increased
food conversion rates.

23. Factors Affecting Productivity
Container-Associated Factors:
• Related to the hydraulic aspects of the system,
such as water velocity and water replacement
time.
• Must provide adequate available dissolved
oxygen for the fish and remove waste products
from the rearing area.

24. Factors Affecting Productivity
Nutrition-Associated Factors:
• Key factor for optimizing growth and producing a
high quality product.
•
• Aquaculturist has a high degree of control over
the nutrition based factors.

25. Factors Affecting Productivity
Management-Associated Factors:
• Adjustments to the system or growth cycle that
can be implemented by the culturist.
• Example: increase of feeding rate
1. May increase growth rate
2. Could have negative impacts on fish if not
done within the limits of the system.