American shrimp are stressors in Dutch ditches

What we should worry about are the latter two in particular. The striped and the red are the perfect invasive exotics: they are almost indestructible, they eat everything, they spread at breakneck speed and are resistant to diseases that eliminate their native competition. The males of the red American go a step further: they even come out of the ditch at the end of the summer. Those are the saucy ones you can find on the bike path or in the playground in August, threatening with scissors in the air.

The first American crustaceans arrived in Europe probably more than a century ago. There is none in the Netherlands patient zero designate. The spotted bird entered by itself through the Meuse, having been imported elsewhere in Europe as a fishing lure. “We strongly suspect that the other species were imported for culinary reasons,” says Ivo Roessink, a researcher at Wageningen Environmental Research. “It is said that somewhere in the 1980s in the Hague region there was a restorer who dumped his surplus of American red prawns into the canal. But this is obviously impossible to control ”.

Roessink conducts research on environmental stress. This also includes the impact of invasive exotics on the ecosystem. He has been dealing with crayfish since 2009. The biggest ecological problem is that they are all carriers of the lobster plague. An aquatic fungus that Americans are resistant to, but to which native European crayfish die within a few days. As a result, the European crayfish was decimated in the Netherlands. There is only one population left, somewhere near Arnhem. “Our shrimp has already had difficulties due to the canalization of the waterways and the increasing pollution of the water. Then there was the lobster plague. And high competitive pressure: these European crustaceans have adapted to the cold climate of Northern Europe: they grow slower and reproduce more slowly. These invasive species are smaller, faster and produce many more offspring. “

This endangers the entire ecosystem, because they eat everything: aquatic plants, fish eggs, rare amphibians. And they dig a lot more than European lobsters.

So such an ecosystem ends up in a vicious circle: “Fewer aquatic plants means more cloudy water. Also, digging increases the amount of sediment in the water column. As a result, less light passes through the water and the few remaining aquatic plants will do even less well. The number of small aquatic creatures is decreasing, fish are less able to spawn. The risk is to end up with a bare tank of green algae soup and some robust animals such as bream and carp and some mosquito larvae ”. And more and more of those invasive lobsters, because they themselves aren’t bothered by it. “They are like tanks. When the aquatic plants are done, they start using the organic material on the bottom. When it’s gone, they eat each other. They are really the last to come out. “

Digging those holes not only causes damage to the ecosystem, but in the worst case it leads to bank failure. Less visible is the indirect economic damage caused by the disappearance of aquatic plant structures. “But it is becoming more and more evident now that various water boards are saying that water choking also leads to more blue-green algae, so cows can no longer drink from ditches and recreation areas need to be closed,” says Roessink. , which Crayfish researches under the Knowledge Platform, explains how scientists, water managers and inland fishermen can tackle this problem together. “A quick fix is ​​no longer possible, because these creatures have been able to go about their business undisturbed for thirty years.”

There are some native predators, such as grebes, herons, gulls, pikes and sea bass, which are told that these invasive crustaceans are high in protein and well supplied. But this will not change the fortunes. Roessink: “It is rare in nature for a predator to extinguish a prey. It almost always works the other way around ”. There is only one large predator for which this applies: humans. So actively fishing and eating is the obvious solution to the shrimp problem. But then we have to catch all the shrimp, not just the big ones.

Regardless of whether fishing is theoretically the most effective method of fighting the shrimp plague, it is a totally absurd situation that the supermarket here is filled with exactly the same American red shrimp tails, but grown and completely imported from China, while here I am literally out of the ditch. Then it makes no sense not to eat them. The condition is therefore that we make fishing and landing all crayfish, including small-sized ones, profitable for inland fishermen. Luckily there is also a perfect and super tasty application for the little ones.

Crayfish are small creatures, so we eat them mainly for tail meat – claws are rarely worth breaking. Shrimp, like their saltwater cousins, are pleasantly sweet and the texture of the flesh – if not cooked for too long – is nice and supple when chewed. This is because the protein composition and structure of all lobsters are essentially the same, says Gert Flik, ​​a former professor of animal physiology at Radboud University.

However, most of the flavor is in the parts we usually throw away. The abdomen (the part chefs call the tail) is actually a large mass of swimming muscles that move the fin-shaped plates on the underside, allowing the lobster to swim backward relatively quickly if danger threatens. . What we call “head” in shrimp and lobster is actually the cephalothorax (a kind of head and body in one). There are the digestive, respiratory and circulatory, nervous and reproductive systems. The most important culinary organ is the hepatopancreas, the middle intestine. In cooking it is often called the liver, but it is actually an organ that functions simultaneously as the liver and pancreas. This is where digestive enzymes are produced and acts as a repository for energy-rich fats. This makes it one of the fattest and therefore tastiest parts of most crustaceans. That’s why the real sweet tooth always suck the “cups” of shrimp.

The armor itself, which consists of proteins and minerals, also contains the taste. Particularly in the epithelium, the “skin layer” just below the hard exoskeleton – which contains the tissue responsible for calcification of the armature – potentially contains many flavors, says Flik. He has conducted research on calcium absorption in European lobster. The biggest difference in taste between a freshwater and a sea shrimp lies in this: calcium. River water contains ten times less calcium than seawater. Logically, a shrimp’s exoskeleton contains less calcium, Flik explains. Calcium is so scarce and valuable to shrimp that they remove it from their shells before moulting and temporarily store it in stomach stones (gastroliths). They then use it in the formation of the new larger armor, according to Flik.

The trick is – for all crustaceans – use a lot of fat when frying the armor before adding water.

They therefore lack that salty and “chalk” flavor. But you can just as easily make a delicious shrimp soup. And that’s exactly what you can use very small ones for. The trick is – for all crustaceans – to use a lot of fat when frying the shells before adding the water. During heating, tissues disintegrate and proteins denature. This releases flavors and pigments, which is why a lobster turns red when cooked. Both pigments and aromas like to dissolve in oil. So a lot of fat at the beginning ensures better flavor extraction. Eventually you want to see those little red “fat eyes” that float when the broth is reduced, which contains the pigments and flavorings, so you can use color as a signal substance for taste. The aqueous phase of the soup also contains the taste, obviously other aromas dissolve in water. But without those fatty flavors, the soup’s taste is simply flatter and duller.

For an optimal taste experience, we must also make sure that we find all the aromas in every bite, and not just in the first few spoons. We do this by putting the hand blender with a few knobs of cold butter in the soup or sauce just before serving. In the kitchen this is called ‘assembly’. This is used to emulsify the sauce or soup: the hand blender breaks down the fat globules and distributes them evenly into very small fragments on the aqueous phase, so that it looks like a homogeneous mass. Now you can enjoy the full potential of dissolved flavors from both fat and water with every bite.