Fish Weaned to Pelleted Diets Goal: Fast Growth Goal : Uniform Size Goal: Cost Effective Feeding Goal: Reduce Environmental Impacts Goal: Healthy Fish –Approach - Wean fish early and completely in Hatchery –Approach - Complete Compound Feeds –Approach - No Wet Fish (Trash Fish) Diets
No Defects Goal : High Product Quality –Approach - In Hatchery Provide Optimal Environmental Conditions –Approach - Provide high quality diets
0% 25% 50% 75% 100% Total hatch 6912 Temp ( o C) Developmental Anomalies (Temperature) Other Jaw Spine Normal
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% Total hatch 1520253035 Salinity (ppt) Developmental Anomalies (Salinity) Other Jaw Spine Normal
Uniform in Size –Approach - Start with uniform graded fish –Approach - Genetic Selection for Uniform High Growth. –Approach - Completely weaned to High Quality Pelleted diets. Goal: Uniform Product at Harvest
Physiologically Appropriate Goal - Excellent Growth and Survival under conditions in Offshore cages. –Perhaps lower Oxygen –Perhaps stronger currents –Approach - Species Selection Bioenergetics model under conditions likely to be found at site.
Simple Bioenergetics Model E = G + R + L –Where: –E is the total energy taken in by the fish from the diet –G is the amount of energy going into growth –R is the amount of energy used for everything that is not growh (movement, fighting diseases, reproduction, etc) –L is the losses due from Feces, Urine and energy to digest the feed (SDA)
♀ ♂ 0 1 2 3 4 5 6 051015202530 RF+U+SDA G Total 0 1 2 3 4 5 6 051015202530 Age (years) Yearly energy demand (MJ) Energy use curves for wild Blue Rockfish showing energy partitioning. Female Male Growth (G) represents a very small part of the energy budget of wild animals. Respiration (R) and Waste (F+U+SDA) represents a large portion of the energy budget Growth in farmed salmon can reach 50% of the total energy budget
Need to develop a simple bioenergetics model for species of interest in off shore aquaculture Conditions off shore are likely to be different than near shore. In Washington State it is likely that they will have: –Lower Oxygen –Higher Currents than traditional near shore aquaculture areas used by the salmon farming industry. Potentially more energy will be needed for R making less available for G. The cost/benefit to G from increased/reduced R is likely to be different among species The cost/benefit to G from increased/reduced R is likely to be different among sites.
Bioenergetics models can be developed for different conditions and species using respirametry Flow DO in CO2 in Flow DO out CO2 out By measuring the uptake of Oxygen under various conditions you can determine R and predict G
Summary What is quality? It’s –Healthy fish –Weaned to Pelleted Feeds –No defects –Uniform Size –Physiologically appropriate
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