What Is in the Box When Live Shrimp Are Shipped Without Water?
The shrimp in question is the kuruma prawn (Japanese name kuruma-ebi; scientific name Penaeus japonicus, also written Marsupenaeus japonicus). It is a large shrimp, farmed in warm bays in Japan and sold as an expensive treat. A national association of seawater fish farmers says this shrimp is so hardy that it can be moved with sawdust alone, with no water [1].
A research institute in Okinawa, a chain of islands in southern Japan, describes the usual way. Farmed shrimp are first calmed in chilled seawater. Then they go into a cardboard box together with an absorbent sheet or sawdust. At the market, workers open part of a box and check the shrimp, and the number of dead ones found at that moment has a strong effect on the price [2]. So every shrimp that dies on the road costs the seller money, which is why people have studied this carefully.
Why not use water? Water is heavy and the shrimp take up little of it. In the box, the shrimp are the cargo and almost nothing else is. The harder question is the one in the title: how can an animal that lives in the sea manage in a box with no water?
Can a Shrimp Breathe Out of Water?
A shrimp breathes with gills, not lungs. The gills sit inside the shell around the chest, where they stay protected. A wholesale seafood company in Yokohama explains the idea this way: the gills take oxygen from the water that touches them, so if the gills stay damp the shrimp can keep breathing, and if they dry out the shrimp dies. The company adds that the chest area should be well moistened before the shrimp are packed [3]. (This is a trade blog from 2016, not a scientific paper, so treat it as a clear explanation rather than a measurement.)
Staying out of water is still a strain. Researchers at Xiamen University in China, studying kuruma prawns, note in their paper that air exposure is a common stress for crustaceans during waterless transport. Their experiments looked at heart rate, lactate (a substance that builds up when muscles work without enough oxygen), and the activity of stress and cell-death genes. Many of these changed as time in the air went on [4]. Only the abstract of that paper could be read for this article.
So the shrimp can cope without water for a while, but it is being pushed. The next question is how the box makes that easier.
What Does the Sawdust Do, and Why Does the Cold Matter?
The Yokohama company says sawdust holds moisture very well, so it keeps water around the gills. It also says the shrimp are buried and cannot move much, so they use little oxygen [3].
Temperature is the other half. The same company says shrimp become quiet at about 8 to 15°C (46 to 59°F), and that below 5°C (41°F) or above 30°C (86°F) they may die [3]. In the 1988 experiment described in the next section, the researchers set their rooms to 15°C (59°F), chosen to match the temperature then used for live shrimp transport [5]. The Okinawa institute tells shippers to chill seawater to 12°C (54°F) to calm the shrimp before packing [2].
One way to picture this: shrimp are cold-blooded, so a cooler body runs more slowly, a bit like an animal in hibernation. That is a simple picture, not a result from these reports. What the reports do show is that you can overdo it. Okinawa's guidance warns that adding a 75-gram cold pack inside the 1-kilogram box that holds the shrimp led to deaths from too much cooling. If extra cooling is needed, the pack should go in the outer box instead [2]. The target is a temperature that keeps shrimp still, not the coldest one possible.
How Long Can Live Shrimp Last in Sawdust?
In 1988, four researchers at the Kumamoto Prefectural Fisheries Experimental Station in southwest Japan measured this. They took kuruma prawns 11 to 14 centimeters long (about 4.5 to 5.5 inches) and weighing 20 to 30 grams (about 1 ounce), rested them in a tank for about five hours, and packed 15 into each of six sealed 2.7-liter containers with sawdust. The containers sat in a 15°C room, and every 12 hours the team opened one and examined the shrimp [5].
The share of shrimp still alive was 100 percent at 12 hours, 86.7 percent at 24 hours, 68.8 percent at 36 hours, 6.7 percent at 48 hours and 0 percent at 60 hours [5]. All were alive at 12 hours, about 87 percent at 24 hours, and only about 7 percent at 48. In other words, the box works well for a day and then fails fast.
The team also looked inside the muscles. ATP, a molecule muscles use as fuel, fell from 636 to 16 micromoles per 100 grams between the start and hour 48, while lactate rose from 574 to 1,930 by hour 36. The authors read this as shrimp getting more tired over time until they die. They suggested that the proportion of ATP among all the ATP-related compounds in the muscle could serve as a measure of how lively a shrimp is, because it tracked survival [5].
There was good news too. Shrimp that had spent 24 hours in sawdust and were put back in 15°C seawater got that ATP proportion back above 90 percent within one hour [5]. So at that point, some of the measured changes could still be reversed.
One caution: this was a lab test in small sealed containers, not a real shipping box on a real journey, so the numbers show a pattern rather than a promise.
Why Is Summer Shipping Harder, and What Helps?
The Okinawa institute says live kuruma prawns sell for about 40 percent more in summer (June to August), when fewer arrive from Okinawa, the main producing area of farmed kuruma prawns. Summer is hot there, which makes raising and shipping market-size shrimp difficult [2]. The 1988 paper also gave a reason for studying the problem: shrimp lose liveliness in a shorter time in summer than in winter [5].
So Okinawa tried keeping the inside of the box cool. Over 11 test shipments between 2016 and 2019, the team used cold packs, foam insulation boards and an insulating aluminum sheet. In ten outer boxes where the temperature stayed mostly at or below about 20°C (68°F), the shrimp death rate averaged 7 percent. In five boxes where it did not, the average was 22 percent. The better boxes also sold for more per kilogram [2]. The sample is small, and the groups were separated by whether the cooling mostly worked, so it is best read as strong evidence that a cooler box helps, not an exact recipe.
Do Crabs Travel Without Water Too, and Is It Always Sawdust?
Crabs show that sawdust is only one answer. The Hyogo Prefectural technology center describes a way to move live red snow crabs from Kasumi port on the Sea of Japan with no water for up to 24 hours. Sawdust is not part of it. Instead, a crab is sandwiched between sealed bags of ice inside a foam box, with its claws and legs tied with rubber bands. The aim is to bring the temperature near 0 to 1°C (32 to 34°F), which the center says is the temperature where the crabs live [6].
The center also says to choose lively crabs: ones that stand on their own in water and grip strongly when touched near the mouth [6].
Put the two cases side by side. Kuruma prawns travel at about 12 to 15°C in damp sawdust. Red snow crabs, from a much colder deep sea, travel at about 0 to 1°C beside ice. Both trips are cold and waterless, but each uses the temperature that suits that animal.
What Can You Look Into Yourself, and What Is Still Unknown?
The two prefecture reports are short and free to read online. Try comparing the temperature numbers in the Okinawa shrimp report [2] with those in the Hyogo crab report [6]. Each shows a graph of the temperature inside the box over a day or so.
At a store, look at the label on packs of fish or shrimp. Does it say a storage temperature? Why do you think the numbers differ between products?
Some things were not found. No source named who first packed shrimp in sawdust. And the sources did not agree on, or clearly state, what kind of wood the sawdust should come from. Those questions are still open.