Skip to main content

Logo for N.C. Cooperative Extension N.C. Cooperative Extension Homepage

Weighing Trout by Water Displacement

en Español

El inglés es el idioma de control de esta página. En la medida en que haya algún conflicto entre la traducción al inglés y la traducción, el inglés prevalece.

Al hacer clic en el enlace de traducción se activa un servicio de traducción gratuito para convertir la página al español. Al igual que con cualquier traducción por Internet, la conversión no es sensible al contexto y puede que no traduzca el texto en su significado original. NC State Extension no garantiza la exactitud del texto traducido. Por favor, tenga en cuenta que algunas aplicaciones y/o servicios pueden no funcionar como se espera cuando se traducen.

English is the controlling language of this page. To the extent there is any conflict between the English text and the translation, English controls.

Clicking on the translation link activates a free translation service to convert the page to Spanish. As with any Internet translation, the conversion is not context-sensitive and may not translate the text to its original meaning. NC State Extension does not guarantee the accuracy of the translated text. Please note that some applications and/or services may not function as expected when translated.

Collapse ▲

Weighing fish by displacement has been widely used by trout producers, processors, and live haulers in western North Carolina. The displacement weight method, although widely used, is somewhat misunderstood. This is an attempt to clarify some of the uncertainties related to displacement loading.

Displacement loading uses the fact that 1.02 pounds of trout displace 1.0 pound of water, regardless of fish size. Usually a transportation tank is filled with water to a specific mark on the inside of the tank. The fish are loaded until the water reaches a second mark.

The procedure for displacement loading is as follows:
Step 1 – fill the tank to a specific “empty” point with water and make a permanent mark

Step 2 – add water to the tank to a “full” level and make a second permanent mark

Step 3 – remove the water from the tank, weighing the water as it is removed and lowering the water level in the tank from the “full” level to the “empty” mark Step 4 – multiply the total weight of water removed by 1.02 to determine the pounds of trout

Example:
=> weight of the water between the “full” mark and the “empty” mark = 448 pounds
=> 448 pounds of water x 1.02 = 457 pounds of trout

Tanks used to transport a standard weight are usually calibrated. Water is filled to the same mark each time. Fish are added to a second mark to load the specified pounds. Generally 2-2.5 pounds of trout per gallon can be safely transported if sufficient aeration/oxygenation is provided. The volume of the tank (gallons) is determined from the “empty” mark.