Japan is an island nation, therefore seafood has been essential to the Japanese diet since ancient times. Although meat and diary products are as common as fish today, fish is still the main source of protein for the Japanese. Fish can be prepared grilled, boiled, and steamed, or eaten raw as sashimi (thin slices of raw fish) and sushi. There are quite a few expressions and proverbs including fish in Japanese. I wonder if this is because fish are so closely related to Japanese culture.
Tai (Sea bream)
Since "tai" rhymes with the word "medetai (auspicious)," it is regarded as a good luck fish in Japan. Also the Japanese consider red (aka) as an auspicious color, therefore it is often served at weddings and other happy occasions as well as another auspicious dish, sekihan (red rice). On festive occasions, the preferred method for cooking tai is to boil it and serve it whole (okashira-tsuki). It is said that eating tai in its full and perfect shape is to be blessed with good fortune. The eyes of tai are especially rich in vitamin B1. Tai is also considered as the king of fish because of the their beautiful shape and color. Tai is only available in Japan, and the fish that most people associate with tai is porgy or red snapper. Porgy is closely related to sea bream, while red snapper is only similar in taste.
"Kusatte mo tai (腐っても鯛, Even a rotten tai is worthwhile)" is a saying to indicate that a great person retains some of their worth no matter how his/her status or situation changes. This expression shows the high regard the Japanese have for tai. "Ebi de tai o tsuru (海老で鯛を釣る, Catch a sea bream with a shrimp)" means, "To get a big profit for a small effort or price." It is sometimes abbreviated as "Ebi-tai". It is similar to the English expressions "To throw a sprat to catch a mackerel" or "To give a pea for a bean."
Unagi is a delicacy in Japan. A traditional eel dish is called kabayaki (grilled eel), and is usually served over a bed of rice. People often sprinkle sansho (a powdered aromatic Japanese pepper) over it. Although eel is rather costly, it has been very popular and people enjoy eating it very much.
In the traditional lunar calendar, the 18 days before the beginning of each season is called "doyo". The first day of doyo in midsummer and midwinter is called "ushi no hi." It is the day of the ox, as in the 12 signs of the Japanese zodiac. In the old days, the zodiac cycle was also used to tell time and directions. It is customary to eat eel on the day of the ox in summer (doyo no ushi no hi, sometime in late July). This is because eel is nutritious and rich in vitamin A, and provides strength and vitality to fight against the extremely hot and humid summer of Japan.
"Unagi no nedoko (鰻の寝床, an eel's bed)" indicates a long, narrow house or place. "Neko no hitai (猫の額, a cat's forehead)" is another expression that describes a tiny space. "Unaginobori （鰻登り）" means, something that rises rapidly or skyrockets. This expression came from the image of an eel that rises straight up in the water.
Koi is a symbol of the strength, courage and patience. According to Chinese legend, a carp which courageously climbed up waterfalls was turned into a dragon. "Koi no takinobori (鯉の滝登り, Koi's waterfall climbing)" means, "to succeed vigorously in life." On Children's Day (May 5th), families with boys fly koinobori (carp streamers) outside, and wish for boys to grow strong and brave like carp. "Manaita no ue no koi (まな板の上の鯉, A carp on the cutting board)" refers to the situation that is doomed, or to be left to one's fate.
"Saba o yomu （鯖を読む）" literally means, "to read the mackerel." Since mackerel are a common fish of relatively low value, and also rot quickly, when fishermen offer them for sale they often inflate their estimate of the number of fish. This is why this expression has come to mean, "to manipulate the figures for one's advantage" or "to offer false numbers intentionally."