Why are the eyes of the golden-eyed snapper golden?

Golden-eyed snapper is a specialty of the areas around Shizuoka Prefecture, such as Sagami Bay, Suruga Bay, and the Izu Peninsula, and has long been a luxury fish that has been highly valued, especially at celebratory occasions, mainly in the Kanto region.

In recent years, catches have increased in Kyushu and Shikoku, and the distribution of frozen fish caught in New Zealand and the Indian Ocean has also increased, making this a fish that is consumed nationwide.

The golden-eyed snapper lives in the deep sea, at depths of 300-800 meters , and has "golden eyes" that allow it to efficiently find prey even in the low light conditions. This golden light is emitted by a reflective layer called the tapetum, which it uses to collect and find prey. Normally, light information is reflected by the retina and recognized, but when there is little light, the information is not reflected by the retina and cannot be recognized. However, because there is a reflective layer called the tapetum below the retina, incoming light passes through the retina, is reflected by the tapetum, and is reflected back onto the retina. This allows it to see efficiently even in low light. Incidentally, felines also have this tapetum, and it is this tapetum that reflects light that makes cats' eyes appear to glow.

Therein lies the secret to their ability to grow fat and eat lots of small fish and shrimp without any trouble at the bottom of the dark deep sea.