Factors Affecting Productivity

1. Factors Affecting Productivity • Variables related to the productivity of the system: • Fish-associated factors • Water-associated factors • Pond-associated factors • Nutrition-associated factors • Management-associated factors

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

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

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

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

6. 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 –

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

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

9. 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

10. 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

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

12. 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.      

13. 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.

14. 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.

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

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

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

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

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

20. 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.

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

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

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

24. 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.

25. 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.

26. 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.