11.1　Judging Whole Fish

A fish starts to go bad in the places with the most blood and bacteria. These are the gills, the guts, and the slime on the skin. Changes also show early in the eyes, where loss of moisture is easy to see. So when you practice judging fish quality (mekiki), look at the gills, belly, and eyes first. Do not decide on one sign alone. Judge by putting several signs together.

A fresh fish has clear eyes, bright red gills, a firm belly, and clear slime. However, a fish that has touched ice directly can have cloudy white eyes even when it is fresh. This is called ice burn. That is why you do not judge by the eyes alone.

Why You Check These Places

• Eyes　The proteins in the membrane on the surface of the eye change, and the eyeball loses water. So the eye becomes cloudy and sunken. It may also become bloodshot.
• Gills　They hold a lot of blood and have a large surface area. Hemoglobin, the red pigment of blood, oxidizes and turns brown, and bacteria grow here first.
• Skin　While the fish is alive, the slime is a film that protects its body. After death, it becomes a breeding ground for bacteria.
• Belly　Spoilage starts in the guts. Digestive enzymes and gut bacteria dissolve the belly wall, and the belly splits open. This is called belly bursting.
• Vent　In a fresh fish, the vent is tight. When gut bacteria grow and the gut wall breaks down, the vent opens, the contents leak out, and the color around it changes.
• Smell and springiness　A fishy smell and an ammonia smell come from substances made by bacteria (Chapter 10). A pressed mark remains because the proteins that frame the flesh have broken down and the cells have collapsed.
• Rigor　A fish in rigor, or just after rigor has passed, is a sign of freshness. But fish killed by nojime (fish left to die in the net or on ice) and fish kept in a warm place come out of rigor quickly. So you cannot judge time by rigor alone.

11.2　Judging Saku and Fillets

A saku is a block of flesh cut for sashimi or nigiri. When you cannot see the whole fish, as with saku or fillets, judge by the cut surface.

The first sign is drip, the liquid that comes out of the flesh. A small amount of clear drip is no problem. A large amount of cloudy red drip means the fish has been kept a long time or was thawed badly. The second sign is color. Choose white-fleshed fish with a clear look, and red-fleshed fish from bright red to deep red. Yellowed fat means the fat has oxidized. Brown on red flesh means the iron in the red pigment of the flesh has oxidized (Chapter 14). The third sign is the dark meat (chiai), the darker part that runs through the middle of the flesh. It changes from bright red to dark red and then black. If its edges are blurred, the fish is old. Fourth, check that the cut surface is glossy and not split between the muscle layers.

What to Look For in Each Kind of Fish

A lot of cloudy red drip can also mean the fish has been frozen and thawed more than once. A cut surface that is dry and split between the muscle layers means the fish was forced through filleting during rigor, or its cells were broken during thawing. A milky white color in white-fleshed fish means it is partway through aging or deterioration.

Tuna

At the market, tuna is judged by the cross-section of the tail. Choose fish whose flesh looks clear, with fine, even lines of fat and bright dark meat. A cut surface that is cloudy white and crumbly is yake (burnt flesh) (11.5). Darkening is browning (metmyoglobin formation) (Chapter 14).

White-fleshed fish: sea bream, olive flounder (hirame), and Japanese sea bass (suzuki)

All the basic checks apply. In addition, look at the color of the skin (11.3). Also check for the hole left by ikejime (killing the fish instantly and bleeding it) and the bleeding cuts (Chapter 10).

Blue-backed fish: horse mackerel, mackerel, sardines, and Pacific saury

The tautness and firmness of the belly matter most. The enzymes in their guts are strong, so they dissolve from the belly. Never use a fish with a burst belly. Also check how clear the eyes are, how vivid the stripes of mackerel and the silver of horse mackerel are, and the color of the gills. Because of the risk of histamine, do not use them raw if you have even a little doubt (Chapter 3).

Squid

In a live squid, the color dots in the skin, called chromatophores, move, and the brown spots look dark. Over time, the color dots set in an open state and turn brown, and then the squid turns cloudy white. Choose squid with clear flesh, clear eyes, and springy flesh.

Shellfish

For bivalves, choose ones whose shells are closed, or close when touched. A shellfish that stays open and does not react is dead. For sea snails, choose ones whose lid is shut tight and whose body pulls back when touched. Judge shucked shellfish by their clear look, gloss, and smell of the sea.

Shrimp

Choose shrimp with clear-looking shells and heads firmly attached to the body. Blackening that starts from the head is blackspot (melanosis) caused by enzymes. It is not spoilage itself, but it is a sign that time has passed.

11.3　Wild and Farmed Fish

Farmed fish grow in a holding pen (live tank), an enclosure built in the sea. They do not swim much, and they eat fatty feed every day. So fat builds up all over their bodies, whatever the season, and the flesh looks whitish. Wild fish keep swimming in search of food. Their fat builds up mainly on the belly side in the period before spawning, and it is lost after spawning.

Farming has an advantage. You can buy fish of the same size and the same fat content all year round, on fixed days, at fixed prices. Farmed fish are often shipped after ikejime or shinkei-jime (destroying the spinal cord), and they are often in better condition than wild fish killed by nojime. Also, farmed fish raised on formulated feed, made by pressing fish meal and other ingredients together, do not eat krill or small fish. Krill are small shrimp-like creatures, and both krill and small fish carry Anisakis. So the risk of parasites is extremely low (Chapter 3). However, this does not apply to fish raised in the sea from wild-caught fry, or to fish raised on raw feed.

Catching wild young fish and fattening them in pens is called ranching. It is different from closed-cycle aquaculture, which raises fish from eggs. In both cases, the fish are kept on fatty feed, so fat spreads all through their bodies, whatever the season. Rich fat is attractive, but it can become heavy over several pieces. So handle these fish differently from wild fish, for example by slicing them thinner.

It is not true that "wild is better and farmed is worse." A well-managed farmed fish is often better as neta (topping) than a wild fish that has grown thin after spawning. What matters, wild or farmed, is to match the fat of that fish. Change the thickness of the slices and how you pair the topping with the shari (sushi rice).

Quality and Appearance of Fat

The feed for farmed fish is mainly fish meal and fish oil. Their fat is not only more plentiful. It is also said to melt at a slightly lower temperature, reflecting the fat in the feed. It has the strength of spreading richly in the mouth, but as you keep eating, it can feel "heavy." Fat also gets into the muscle, so even red-fleshed fish can look pinkish. Wild Japanese amberjack (buri, yellowtail) is red on the back and white only on the belly. Farmed amberjack is white all over, as if marbled. The fat of wild fish reflects its food, such as small fish and shrimp, and has aroma and acidity.

Farmed red sea bream (madai) are exposed to sunlight in shallow pens, so their body color darkens. Their tail fins are worn round by rubbing against the net, and many have no divider between their nostrils. Wild red sea bream live in deep water, so they are a vivid cherry-blossom pink with small blue spots scattered on the back and pointed tail fin tips. In recent years, fish farming has improved. For example, shade nets keep the color, and citrus or herbs mixed into the feed change the smell of the fish.

Pre-Harvest Fasting, and an Exception for Freezing

Farmed fish are taken off feed for several days before shipping. This is called pre-harvest fasting, and it reduces the contents of the gut. The EU exempts farmed fish that meet certain conditions from the requirement to freeze fish before it is eaten raw, because the risk of parasites is low (Chapters 1 and 3). Wild or farmed, chefs adjust to the amount and quality of fat. They change the thickness of the slices, the strength of the vinegar in the shari, the condiments, and whether to sear the fish (Chapters 14 and 23).

More About Ranching

In ranching, besides young fish, adult fish that have grown thin after spawning or for other reasons may also be caught. They are then fed and fattened for several months to several years. Typical examples are Pacific bluefin tuna (in the Mediterranean, Mexico, and the waters around Japan) and Japanese amberjack raised from wild fry called mojako. Ranched tuna are given a lot of fatty feed such as sardines and mackerel. So fat spreads through the whole body, even into parts that would not yield toro (fatty tuna) in a wild fish. The fat melts richly in the mouth. But because the layers of fat are thick, eating too much feels heavy, and the acidity and aroma of the lean red meat are often weak. Sushi restaurants work around this in several ways. They pair it with wild lean meat, slice it thinner, serve it with shari seasoned with stronger vinegar, or use aburi (searing with a flame) to melt off fat.

11.4　Peak Season

Peak season (shun) is the time when a fish's fat and flavor are at their best. For many fish, peak season comes before spawning. The fish eat a lot to make eggs or milt, and they store the nutrients as fat. Once spawning begins, the nutrients go to the eggs or milt, and the flesh becomes thin and watery. Right after spawning, any fish loses flavor. Also, as the water temperature drops toward winter, fish store fat to get through the winter. Fish with "kan" (winter) in their names, such as winter buri, kan-birame (winter hirame), and kan-saba (winter mackerel), taste good. This is said to be because the fat stored before spawning and the fat stored for winter come together. In summer, on the other hand, the water is warm and the body works faster. So even if a fish eats the same amount, less of it remains as fat.

Peak season has three stages. Hashiri, at the start, is when the fish are smallish and have less fat, but have a good aroma and bite. Sakari is when the flavor is at its best and the price is also highest. Nagori, at the end, is when the fat remains but the flesh starts to loosen. Chefs look at both flavor and price to decide. They may pay a high price for fish in sakari, or buy fish in hashiri or nagori at a lower price and make up the difference with their preparation work. During spawning, the flesh loses flavor, but a different delicacy appears: shirako (milt) and mako (roe). Going outside peak season does not mean doing it without knowing. It means knowingly choosing a different value.

Peak season moves with sea temperatures. Even for the same fish, it can differ by 1 to 2 months between the north and the south. Sometimes a school finishes spawning in the south, moves north, and reaches its peak in the north. The peak seasons of the main toppings are listed in Appendix D. They are guides based on markets in the Kanto region, so check the peak seasons of the seas your own restaurant buys from.

Pacific bluefin tuna spawn from spring to summer and use up their body fat to do so. In summer, Pacific bluefin tuna has lost its fat, its flesh is firm, and its iron flavor and acidity come to the front. This is called summer bluefin. Southern bluefin tuna, from the Southern Hemisphere, have the opposite season, and they are fatty during the Japanese summer (Chapter 14).

Why Summer Tuna Tastes Sour

Pacific bluefin tuna spawn around the Nansei Islands from about April to July, and in the Sea of Japan from about July to August. They swim long distances and use up their fat. So the true flavor of the lean red meat, once covered by fat, comes to the front. That flavor is the metallic taste of the iron in myoglobin, the red pigment, and the sourness of lactic acid in the muscle. Tuna swim fast, so their muscles hold a lot of glycogen and produce a lot of lactic acid after death. In winter tuna, this sourness is hidden by the sweetness of the fat. This is thought to be why people say "summer tuna is sour." It is different from the sourness of spoilage. It suits guests who like light, lean red meat, but it disappoints guests who want toro. This is why, in summer, many restaurants use southern bluefin tuna from the Southern Hemisphere, whose season is the opposite, or tuna from the Atlantic and the Mediterranean, or ranched tuna (Chapter 14).

11.5　Fishing Methods, Origin, Distribution, and Quality

The same fish, from the same sea, on the same day, can have completely different flesh depending on how it was caught. The suffering and injuries caused by the fishing method lead directly to the loss of ATP, the energy source, and to contamination by bacteria (Chapter 10).

Remember this: pole-and-line fish fetch the highest prices, and few bottom-trawled fish are suited to sushi. Yake is especially important. Tuna and skipjack tuna have a system that keeps their body temperature higher than the surrounding seawater. If they struggle for a long time on a longline or in a purse seine, their muscle temperature goes above 30°C, and lactic acid makes the pH drop sharply. This heat and acid change the proteins, and the flesh becomes cloudy white, sour, and watery. A fish with yake will not recover, however it is aged. Line-caught fish fetch high prices not "because they were caught on a line," but "because they were killed quickly."

Origin and Distribution

Here is the basic flow for fish in Japan. At the market in the producing area, fish pass from fishers to brokers (nakagai). At the central wholesale market in the consuming area, they pass from wholesalers to intermediate wholesalers (nakaoroshi). The intermediate wholesalers then deliver them to restaurants. Intermediate wholesalers are also called nakagai. They buy fish at the market and sell it to restaurants. Prices are set by auction or by negotiated sale, in which the seller and buyer agree on a price by talking it over. Shipping direct from the source, from producers or brokers in the producing area straight to restaurants, is also growing. Its advantage is that you can specify the killing method and the shipping time.

Brands such as Seki-saba and Seki-aji, Akashi sea bream, Oma tuna, and Himi buri are not just about good waters. What gives them meaning is that an organization guarantees the fishing method, the killing method, and the control of time and temperature until shipping. Do not feel safe just because of a label saying "from such-and-such place." On the other hand, fish from a fisher who carefully kills and bleeds them are no worse than brand-name fish, even from an unknown area. At the market, fish killed by ikejime or shinkei-jime clearly sell for more than fish killed by nojime, even for the same kind and size of fish. This difference is the price paid for the energy source that remains and for longer shelf life.

11.6　The Practical Side of Buying

Your Relationship With Intermediate Wholesalers

Buying fish is about relationships with people. At first, keep going to one intermediate wholesaler and tell them specifically which fish, what size, what use, and what budget you have. "What use" means nigiri, rolls, or simmering. Intermediate wholesalers do not pass good fish to customers who go from shop to shop looking only at price. Good fish are few, and they sell them first to customers they can trust. There is one way to tell whether an intermediate wholesaler is trustworthy. When the fish is bad, do they say "Today's isn't good"? A good intermediate wholesaler will suggest a substitute if the fish you ordered is not good, and will also tell you the outlook for next week.

What to Watch at the Market, and Taking Fish Back

At the market, look not only at the fish but also at how it is handled. Is there enough ice? Are the fish sitting in meltwater? Are they drying out in the sun or in the wind from a fan? Are they stacked so that the fish underneath are crushed? Fish from a shop that handles them badly carry many bacteria, even if they look fresh, and cannot stand up to aging. Move the fish you buy into your own foam box right away. Wrap the fish in paper or bags so they do not touch ice directly, and carry them in a box with holes to let meltwater drain. Do not leave them in the car. Process them as soon as you reach the restaurant (Chapter 5).

Quantity and Price

To decide how much to buy, estimate the number of pieces you need from your reservations and your average number of guests. Then work backward from the yield. Yield is the share of usable flesh from a whole fish. As a guide, it is about 30 to 40% of the original weight for red sea bream, and about 40 to 50% for blue-backed fish. Decide in advance where leftover fish will go: cooked dishes, cured dishes, the staff meal (makanai), or aging for the next day. Then you will not cut your purchases too much out of fear of loss. Prices rise after rough seas (shike), around market holidays, at the end of the year, and before long holidays. Do not force yourself to buy expensive fish. Being able to prepare substitute toppings that play the same role keeps a restaurant stable. You will learn more in Chapters 27 and 28.

11.7　Buying Fish Outside Japan

Buying fish outside Japan is harder than in Japan. In Japan, the cold chain, which keeps fish cold without a break from catch to restaurant, is taken for granted. In many countries, this chain is broken along the way. It is not unusual for fish to sit on market tables at room temperature, for ice to run short, or for trucks to have no refrigeration. A fish that spent a long time above 10°C along the way carries many bacteria, even if it looks fresh.

Also, the label "sushi grade" has no legal definition. It is just a claim made by the seller. Do not rely on the label. Check the freezing records in writing: when the fish was frozen, at what temperature, and for how many hours. If the records are unknown, freeze the fish in your restaurant at −20°C or below for 24 hours or more before use (Chapter 12).

Freezing Standards, and the Dangers of Local Fish

Japan has standards for "fresh seafood for raw consumption" under Japan's Food Sanitation Act. They cover things such as the count of Vibrio parahaemolyticus bacteria and storage at 10°C or below. However, these are minimum hygiene standards, not quality grades for toppings. What the United States and the EU set are freezing conditions to control parasites. The U.S. FDA Food Code sets conditions such as −20°C or below in the freezer for 7 days, including the time to freeze, or freezing at −35°C or below and then holding at −35°C for 15 hours. The EU sets −20°C or below in every part of the product for 24 hours or more, or −35°C or below for 15 hours or more (Chapters 1 and 12).

Freshwater fish carry parasites that sea fish do not, such as Gnathostoma and the Chinese liver fluke. Large fish living on tropical coral reefs carry a risk of ciguatera toxin. Fish of the mackerel family and mahi-mahi are high in histidine.

Outside Japan, make active use of farmed fish. Salmon, hamachi (young or farmed Japanese amberjack), red sea bream, striped jack, sea bass, kuruma prawns, and others are available in many countries. Killing and temperature control are in place from the start, and the risk of parasites is low. Good local farmed fish is often safer and tastier than wild fish flown in from Japan.