Sharks don't like chicken

As part of the JBL research expeditions and the cooperation with the shark conservation organisation SharkProject, we’ve come across a lot of shark encounters which are also relevant for us as aquarists:

The diver wags the dead, bloody chicken wildly at a depth of 20 metres. The sharks circle him with complete disinterest. After more than ten minutes, a reef shark takes pity and grabs the chicken - only to spit it out again immediately afterwards. Now it's my turn: I open a barrel with dead fish remains. While I'm still opening it, the sharks get nervous and bite into the barrel. The smell of fish blood makes them nervous and makes them search for the supposedly injured fish. A shark gets hold of a piece of fish and in its nervousness, accidentally swims against my camera.

The experiment off the coast of Florida shows that sharks can smell blood in extreme dilution, but only react to certain types of blood. Human blood does not excite sharks, as they are not familiar with it and humans do not form part of their cuisine. On the JBL expedition to the Red Sea we were able to see this for ourselves live: A deliberate cut in the finger was not noticed at all by the oceanic whitetip sharks present, which were about three metres tall.

There are hardly any fish species in the world that regard mammals as prey: Only tiger sharks and bull sharks are interested in absolutely anything that looks or smells like food. They bite into it and then decide whether it is edible or not. The great white shark eats only a very small percentage of warm-blooded animals like seals. Its main food is fish. The large bonytongues, also called arowanas, snatch up any unwary animals they can reach on the shore. Even piranhas only turn to warm-blooded meat when no other food is available. We’ve been in the water with piranhas in many different places and all our fingers or toes are still intact. The indigenous people usually lose their digits fishing for piranhas when they release the snapping fish from the hook and the wiggling piranhas in the boat latch on to their feet.

Feeding discus with cattle heart is just as natural. The flat body shape of discus has evolved and adapted to their predatory hunting method, so that when they raid cattle, they can better fit between their ribs to "rip out” their heart. But why do aquarists feed cattle heart at all? There is no clear answer to this question, because scientists have been able to prove beyond doubt that fish have issues with warm-blooded meat. It cannot be digested properly and is to a large extent excreted again, which leads to heavy water pollution. In its natural habitat the discus is an opportunist: in the rainy season, when the trees are metres under water, they even eat fruit, whereas in the dry season they search for shrimps and other food at the river bottom.

So what is really important for the nutrition of our aquarium fish? Unfortunately, the food fish like doesn’t necessarily have the right composition for them. A Tropheus (cichlid) from Lake Tanganyika loves to eat red blood worms - and dies of it after a short time. Children would also prefer sweets to vegetables.

Scientists can determine quite precisely for each feeding type which protein/fat ratio is the right one. And right is really important, because it means: healthy, perfect colours, offspring and a long life. People know that too, even if they choose not to stick to their own healthy diet.

The following figures clearly illustrate how varied the requirements of the fish are: The diet of a predatory cichlid, which feeds mainly on fish, has a protein-fat ratio of 11:1. In other words, a lot of protein and hardly any fat. Many of our aquarium fish feed on insect larvae, but unlike fish, they have a protein-fat ratio of 4:1. Even marine aquarists who think they are doing their fish some good with frequent feeding of opossum shrimps (mysis) need to think again, because shrimp contain almost only protein (P:F=13:1). No fish feed only on opossum shrimps and they will certainly not live long on such a high-protein diet. Neons and most other small tetras are plankton eaters that are always on the verge of starvation due to food scarcity in their natural habitat. With a pure plankton food like PlanktonPur , the fish feel like they are in paradise and show even more beautiful colours than in the wild!

In the JBL research department these facts, together with observations and the results of JBL research expeditions, are taken into account in the development and composition of the food. You can see the result on every food tin by taking a look at the protein and fat content: on JBL NovoBel , for example, it says 43 % protein and 8.3 % fat. If we divide 43 by 8.3 we get the protein-fat ratio, in this case 5.2 and thus the optimal range for omnivorous freshwater fish.

Besides the right composition, variety is THE key to keeping your fish happy and healthy. Try feeding different types of food in the morning, at lunchtime and in the evening: concentrate JBL Krill for breakfast, a five-course menu for lunch ( JBL NovoBel contains 5 different types of flakes) and light plant food for dinner. Your fish will hopefully thank you with numerous offspring!

And don't forget: sharks prefer to eat fish rather than humans!

The next JBL research expedition will take you to the unspoilt South Seas in French Polynesia in 2023. Details and registration form can be found on the JBL homepage: Spedizione esplorativa Pacifico del Sud

© 09.01.2022
Heiko Blessin
Heiko Blessin
Dipl.-Biologe

Tauchen, Fotografie, Aquaristik, Haie, Motorrad

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