Yellowtail and Seasons
The flavor of fish meat undergoes variations throughout the year as a result of fluctuations in water temperature, environmental conditions, and the fish’s life cycle. In Japan, the optimal season for a specific fish is referred to as “Shun,” and each fish has its own unique “Shun” period. People enjoy different fish of the “Shun” every season.
Yellowtail is a type of fish that is typically associated with its peak season, known as “Shun,” occurring during the winter. When yellowtail reaches maturity, it is referred to as “Buri,” and during the wintertime, the fatty yellowtail specifically goes by the name “Kan-Buri,” which literally translates to “Buri” from the cold temperature.
Composition of Yellowtail Meat
The protein content in yellowtail meat remains relatively consistent at around 20–25% throughout the year, regardless of the age of the fish (whether young or adult). However, the fat content fluctuates between 1% and 30%, which is influenced by factors such as the season, age of the fish, and individual variations.
In general, adult yellowtails tend to possess higher levels of fat content compared to young ones, and farmed yellowtails tend to have higher lipid content than wild yellowtails. In adult yellowtails, the fat levels increase from October to March, irrespective of whether they are farmed or wild-caught. However, for young yellowtails, the season of higher fat content begins a few months earlier than their mature counterparts.
In several fish species, it has been observed that during the period of egg deposition, muscle storage lipids are utilized as the gonads develop. However, this explanation does not account for the seasonal variation in fat levels observed in young yellowtails, as they do not possess the capacity for egg deposition.
The variation in fat levels in yellowtail meat throughout the year can be attributed to the seasonality of water temperature and feeding patterns. When water temperature is high, the basal metabolic rate of yellowtail increases, and conversely, it decreases when the temperature is low. However, analyzing water temperature and feeding data reveals that while water temperature reaches its peak around August, the rate of feed intake remains relatively stable until September-October for young fish and October-November for adult fish. This suggests that yellowtails accumulate lipids in their muscles by consuming a high amount of feed during the period when their metabolic rate decreases after the summer season. During winter, as feed intake decreases, the low temperature, which is associated with the reduced metabolic rate, allows yellowtails to maintain high fat levels.
Free Amino Acids in Yellowtail
The table below presents the levels of various amino acids found in young and adult yellowtails, specifically Hamachi (approximately 1kg) and Mejiro (5–7kg). Both young and mature yellowtails exhibit elevated levels of histidine, whereas the content of glutamic acid, a key umami amino acid, is relatively limited. No significant seasonal patterns are observed in the contents of free amino acids in yellowtails.
Where and When to Eat Yellowtails
Matured yellowtail, referred to as “Buri” in Japan, migrates from Hokkaido in the north and moves southward along the Japan Sea side of Honshu island, passing through the Hokuriku region, Kinki region, and eventually reaching the Kyushu region, where they lay eggs in spring. During the winter months, as the water temperature decreases, yellowtail instinctively migrates southward in search of warmer waters.
Himi in Toyama Prefecture, located in the Hokuriku region, is considered the prime destination for “Kan-Buri,” the fatty yellowtail. This region stands out as an exceptional location because the yellowtails migrating from the north encounter the Noto Peninsula, which lies just west of Toyama. As a result, the coastal area of Toyama becomes an ideal spot for catching wild, fatty yellowtails.
In Himi, the peak season for yellowtails typically commences in late November and extends until January. The specific timing depends on the water temperature of the region, which affects the migration of the fish. Local authorities closely monitor the quality and quantity of the catches and announce the official start of the season each year when the fish meet the required standards. Throughout the peak season, the authority issues certificates for yellowtails caught in the region as a mark of their quality and authenticity.
