shade and light

~He measures the light by averaging the amount of light from above and the amount reflected from the bottom and uses this information to calibrate the degree of camouflage needed for safety.

~He measures the directional wavelengths or light source to orient himself in the world of water.

What problem or damage does excessive light cause for a koi?

~Stress from being too conspicuous in the environment creates a neuronal change since certain types of fish have inherited levels in camouflage safety both from a vertical direction and a horizontal direction. If these levels are above the safety level the GAS (General Adaptation Syndrome) is is activated which usually results in disease development and growth retardation.

~ The skin pigments in the wild fish must change to compensate for excess radiation and this change creates a stress induced weakness in the integument. This is commonly called sunburn or a sun tan and can result in scar tissue being formed.

~The growth hormone is partially controlled by the type and amount of light and sunlight

~Excessive or deficient light will decrease the amount of growth hormones available to the koi for which results in limited growth patterns for the koi.

~Growth hormone is partially controlled by the type and amount of light that is registered primarily by the Koi’s eyes. Sunlight especially affects the levels of available growth hormone and an excessive or deficient amount of light will reduce the amount of growth hormone available. This deficiency of growth hormone will be expressed in body confirmation and shapes.

What light sources are used by the Koi?

~ One problem is the color spectrum shifts that occurs throughout the day since the constituent light wavelengths (color) change from night to early morning to mid day to afternoon and finally to night. Our eyes and brain correct for this shift automatically, and this normally does not create a problem unless you’re a photographer and forget to change filter, type of film or use an artificial light source. The camera only registers the wavelength, but our eye registers the wavelength and modifies it in the brain so that red is the red we know it should be and not the wave length color. If we give the wrong kind of light and at the wrong time the koi does not develop as well or utilize its environment correctly since it is utilizing the wrong information. This applies to numerous husbandry animals such as milk production, egg laying etc. So if at all possible we should maintain the circadian rhythm in all wavelength. A point to remember is that light has three major components that are as follows 1) infrared (60% ) 2) visible light (37%) and 3)ultraviolet (3%)

The ultraviolet component is broken down into three additional categories as follows 1) UVA, 2) UVB and 3) UVC. The UVC is the most damaging and carcinogenic but luckily the ozone layer almost completely absorbs this wavelength. Even the small amount that does penetrate our atmosphere will damage a fish if there is a sudden change in exposure such as removal of shade cloth, being taken to a show without a shade, sudden clearing of the water, etc. This extra sensitivity is partially caused by koi being a bottom fish and the dangerous wavelength are normally filtered by the water and do not reach the koi in the wild.. UVB irradiance is greatest between 10:00 and 2:00 p.m. UVA intensity continues throughout the day and can exceed UVB by up to 1000-fold depending on the prior mentioned variables. In the northern hemisphere, UVB has the highest level during the summer months. Circannual variation in UVA is less seasonal.

What are the destructive changes from UVA?

~The destructive changes have long been known but only recently have the more potentially harmful effects of UVA been substantiated. UVA is a major rish factor for potentially serious damage to the epidermis and dermis. The longer UVA wavelengths penetrate deeply into the dermis, whereas UVB is absorbed primarily in the epidermis.

~There is still considerable controversy concerning the quantitative and qualitative nature of the toxic action of individual UVA wavelengths and how this can best be prevented and or treated. After being radiated the damage can be divided into acute and chronic actions. Acute effects are primarily a laser burn. The chronic responses include among others, degenerative changes to the sin, altered immune response, actinic keratosis and various forms of skin cancer.

~Since koi have been artificially bred for precise color, skin texture and tissue structure rather than natures design to resist the environment the natural defense to UVR is greatly reduced and the negative effects can be increased. This may account for some of the skin problems of koi.