1. How Can You Tell Fresh Fish by Its Eyes, Gills, and Belly?
The Chiba Prefecture page lists several features of fresh fish [1]. The eyes should be lively, clear, and a color close to blue. They should also look plump and shiny. The gills should be a bright red color. The surface of the body should have good color and luster, with scales that shine and stand up firmly. When you press the belly with a finger, it should have elasticity. The vent (the small opening near the tail) should be closed, with nothing coming out. The meat should also be firm and elastic. The key point is that you must look at the eyes, gills, surface, belly, and meat texture together, not just one spot. However, this is just a list. Reading it does not mean you can instantly judge fish. How does this ability grow?
Safety Note: Even if the eyes look clear, if the belly is soft, it is hard to make a final judgment.
2. What Is "Mekiki," the Market Expert's Eye for Judging Fish?
The ability to judge fish is called "mekiki" (expert eye). At the Toyosu Market in Tokyo, the market association explains that the job of a wholesale intermediary (nakaoroshi) is to prepare the best products at the best prices for customers [2]. Customers range from large restaurant chains to small sushi shops, each with different needs and preferences. To do this, they need more than just a high-level eye for fish. They also need to know fair prices and understand their customers' tastes. So, "mekiki" is the ability to consider the fish's condition, the price, and the customer's order together [2]. Note that this describes wholesale intermediaries at Toyosu Market, not necessarily every local fishmonger. A person from a seafood company at the Tokushima City market said that observing fish carefully is important and "every day is study" [3]. How do these fish get from the market to the shop?
3. Which Hands Does Fish Pass Through Before Reaching the Shop?
According to the Tokushima City Central Wholesale Market, fish are first shipped from producers to wholesale companies. They are sold to intermediaries (nakaoroshi) or trading participants through "auctions" (seri) or "negotiated deals" (aitai torihiki) [3]. After that, intermediaries sell them to supermarkets and restaurants. The Tokyo Metropolitan Central Wholesale Market Ordinance defines the terms. An intermediary (nakaoroshi) sorts or prepares goods received from wholesalers and sells them. A retail buyer (kaidashinin) is a retailer who buys from intermediaries and sells outside the market [4]. A local fishmonger might buy from an intermediary as a "buyer" or join the auction as a "trading participant," according to Tokushima City documents [3]. Market work is known for early hours. At a seafood company interviewed at the market, many workers start at 4:00 AM and finish at 12:30 PM. Some who collect goods at night and prepare for the next day's auction work from 7:00 or 8:00 PM until 5:00 AM the next morning. About 50 to 100 types of fish gather there each day (example from early August) [3]. These are the interviewed seafood company's hours, not necessarily the local fishmonger's shop hours. How are prices set?
4. How Does a Fish Auction Decide Who Wins a Lot?
A seafood company worker at the Tokushima market explained the auction. To win a lot of fish in an auction, you must offer the highest price for that fish. Therefore, it is important to "read the market" (predict what others will bid), which requires experience [3]. The phrase "maware, maware" is sometimes used at auction sites. It means buying the next lot at the same price as the previous one. However, this explanation is specific to this market; terms may vary by market or fish type [3]. So far, we have seen two types of "eyes": the eye for seeing the fish and the eye for reading prices. But the story of the seeing eye is not over. Freshness can change based on how the fish is handled before it reaches the market.
5. How Does "Ikejime" Killing Affect How Fast a Fish Loses Freshness?
"Ikejime" is a general term for processing live fish by killing them quickly to control quality changes after death. In Fukui Prefecture, the certification for "Wakasa-guji Kiwami" requires bleeding the fish and destroying the spinal cord (nerve-jime) on the boat [5]. The Fukui Prefectural Fisheries Experiment Station compared ikejime fish with fish that died without processing ("no-jime"). Right after landing, ATP (a substance) remained in the meat of ikejime fish, but many no-jime fish had no ATP left. The K-value (a measure of freshness decline) rose at 0.12% per hour for ikejime fish and 0.22% per hour for no-jime fish during the first 48 hours of storage. The live-killed method was significantly slower [5]. If you simply multiply these numbers by 48 hours, the rise is about 6% and 11%. This is just a rough estimate to understand the size of the difference, as changes are not always constant. After 48 hours, both rose at about 0.23–0.24% per hour, and the difference disappeared. So, it is not about lasting "forever," but a difference in the first two days. Rigor mortis (stiffening) was also lower in ikejime fish on the day of landing [5]. This result is for tilefish (amadai). It is unclear if the same applies to other fish. What rules are needed to open a fish shop?
6. What License Is Needed to Sell Fresh Fish at a Shop?
Under the Food Sanitation Act, selling fresh seafood (including frozen) from a shop requires a license from the head of the public health center. The Funabashi City guide notes that selling live seafood and selling pre-packaged fresh seafood are excluded from this category [6]. "Auction sales" of seafood are a different licensed category. National briefing materials (posted by Aomori Prefecture) state that auctions, bidding, and negotiated deals are regulated, and wholesalers are not included in this specific category [7]. License categories can change with legal amendments. Check current categories with the Ministry of Health, Labour and Welfare or your local municipality. The fishmonger's job stands on the ability to choose fish by eye, market mechanisms, freshness methods, and safety rules.
Safety Note: Connecting these points, a fishmonger's work relies on the power to choose fish by eye, buying methods in the market, freshness differences from processing, and licenses for selling safely.
7. How Can You Compare Fish Eyes and Gills at a Shop?
If you see fish at a shop, compare their eyes and gills. Think about which is closer to the Chiba guide's description: clear eyes close to blue and bright red gills [1]. Do not touch the fish; just look. To avoid disturbing others, it may help to tell the staff first. You might find that words like "clear" and "plump" are quite difficult to judge. When that happens, remember the market worker's words: "every day is study" [3]. The primary sources are Chiba Prefecture's "How to Judge Fish Freshness" and Tokushima City Central Wholesale Market's "Things You Want to Ask at the Market." The ikejime numbers are from the Fukui Prefectural Fisheries Experiment Station's FY2021 report, where you can see specific numbers showing how processing affects freshness decline [5]. The next question is whether the same difference appears in fish other than tilefish. Looking for reports by researchers is one way to proceed.