Fish Hatchery Management - fisheries & aquaculture

HAI'CHERY OPERATIONS 67regulated by metabolism. If the carrying capacity of a unit is known for aparticular size and species of fish at any water temperature, then the carryingcapacity for another size of the same species held at other water temperatureswill be the weight of fish thaf would consume the same amountof feed.FLOW INDEXThe feeding guide developed by Buterbaugh and Willoughby demonstratesa straight line relationship between the length of fish in inches and percentbody weight to feed (Figu.e 2tj). At a Hatchery Constant of 10, 100 poundsof 2-inch fish will receive the same quantity of food (5 pounds) as 200pounds of 4-inch fish, olt00pounds of 8-inch fish. (The Hatchery Constantis explained on page 245.)Haskell states, "if the carrying capacity of a trough or pond is known forany particular size of fish at a particular temperature, then the safe carryingcapacity for other sizes and temperatures is that quantity of fish whichwill require the same weight of feed daily." By Haskell's premise, if 100pounds of 2-inch fish is the maximum load that can be held in a rearingtank, then 200 pounds of 4-inch fish, 300 pounds of 6-inch, or 400 poundsof 8-inch fish also would be maximum loadsThe followingformula was derived for a Flow Index, where fish size ininches was used instead of weight of food fed to calculate the safe carryingcapacity for various sizes of trout.F : Flow IndexF:I,y+(Lxt)W : Known permissible weight of fishZ : Length of fish in inches1 : Water inflow, gallons per minuteTo determine the Flow Index (,F), establish the permissible weight offish in pounds (W) at a given water inflow (f) for a given size fish (Z).The Flow Index (F) reflects the relationship of pounds of fish per gallonsper minute water flow to fish size.As an example, 900 pounds of 4-inch trout can be safely held in a racewaysupplied with 150 gallons per minute water. What is the Flow Index?F:900+(+xt50)F : 1.5How do you establish the initial permissible or maximum weight of fishwhen calculating the Flow Index? A Flow Index can be estimated by