Energy Requirements/growth Daily energy requirement (kcal/unit bwt) Overall energy requirement/fish increases with size (related to increased biomass) Metabolism – Requires energy (nutritional) reproduction, maintenance and growth

Energy Requirements/growth Metabolism (cont.) Gross energy (GE) – Digestible energy (DE) – energy available for metabolism and growth DE = GE – FE (fecal energy) Metabolizeable energy (ME) – Can be affected by env. conditions – respiration energy (RE) and energy in urine/gills (UE) ME = DE – (RE + UE)

Energy Budget Gross Energy Fecal Energy Digestible Energy Metabolized Excreted (urine, gills, Body surface) Basal/heat met. increase (swimming E) Recovered (tissues, gametes)

Food Conversion Ratio (FCR) FCR = Feed fed (dry wt. basis)/weight gain amount of feed to produce one unit weight gain Fish – very efficient converters (FCR’s < 1.0) To estimate FCR for feed being used: FCR = E/(ME * 1000) E: metabolizeable kcal required for 1 unit weight gain ME: kcal per g of feed

Feeding rates Do not overfeed!! Fish fed ad libitum or on a % body wt basis Feed to satiation? Calculation of daily feed requirements: Adjust based on estimated growth (% daily gain) Should adjust as often as possible Feeding tables – based on length and temperature

Feeding rates Methods to calculated feeding rates: (can be based on length or weight increases) 1.Method#1 (assumes linear growth rate) W t = W o + F/C 2.Method#2 (assumes logarithmic growth) W t = W o e kt