Avoid squeezing or forcefully holding the fish. Fish may be anesthetized with MS-222 if necessary. The fish may struggle less if a cloth is placed over its head. Holding brood fish at the hatchery Environmental factors in the brood fish holding tank such as dissolved oxygen, water temperature and absence of disturbance to the fish following hormone injections are believed to play an im-portant role for successful induced spawning. The handling stress and the physiological processes of final maturation of eggs and sperm increase the oxygen de-mand of the brood fish.
High temperature accelerates egg maturation, resulting in an even greater oxygen demand by the fish.
Elevated temperature will also increase the rate of development of disease organisms. However, if the temperature is too low, spawning will be delayed or in many cases completely inhibited. Holding tanks should be large enough to allow complete freedom of movement to the brood fish. Round tanks or tanks with rounded corners are preferable be-cause they minimize injury to the fish. Holding tanks should be covered to provide shading that will help quiet excitable species and prevent the fish from jumping to their death.