science

Ikejime

Ikejime is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ikejime rather than just read about it. In short: Ikejime (活け締め) or ikijime (活き締め) is a method of killing fish that maintains the quality of its meat. The technique originated in Japan, but is now in widespread use.

Key takeaways

Ikejime belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ikejime to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ikejime from memory before moving on to harder problems.

Reference excerpt

Ikejime (活け締め) or ikijime (活き締め) is a method of killing fish that maintains the quality of its meat. The technique originated in Japan, but is now in widespread use. It involves the insertion of a spike quickly and directly into the hindbrain, usually located slightly behind and above the eye, thereby causing immediate brain death. After spiking the brain, a thin needle or piece of wire is inserted into the spinal column's neural canal to prevent any further muscle movement. When a fish is spiked correctly, the fins flare and it relaxes, immediately ceasing all motion. Destroying the brain and the spinal cord prevents any reflex action; such muscle movements would otherwise consume adenosine triphosphate (ATP) in the muscle, which would result in the production of lactic acid and ammonia, making the fish sour, soggy, and less tasteful. Further, ikejime causes the blood contained in the flesh of the fish to retract into the gut cavity, producing a better coloured and flavoured fillet, and prolonging shelf life. This method is considered to be the fastest and most humane method of killing fish. Ikejime-killed fish is sought after by restaurants as it also allows the fish to develop more umami when aged. It is very similar to the technique used on frogs in laboratories called spiking or pithing. Another technique in APEC Air shipment of live and fresh fish and seafood guidelines is described as follows: "A cut is made toward the front of the flatfish severing the major artery and the spinal cord. Placement of the cut is made to preserve the greatest amount of flatfish flesh. This paralyzes the flatfish. A second cut is made in the tail to hasten the removal of blood. Flatfish are then chilled slowly to maintain circulation and facilitate the bleeding process. After the flatfish have been bled, they are transferred to a salt/ice water slurry and chilled to −12°C." Ikejime has been successfully used manually in the tuna and yellowtail industries, along with limited use in sport and game fishing, as it provides a rapid slaughter technique. An alternative to death by exsanguination, ikejime is used and the fish put straight into ice or flash-freezing.

References

Illustrations

Worked examples

Example 1 — a first encounter with Ikejime

Start with the simplest possible case. Write down what Ikejime claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ikejime before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ikejime ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ikejime

In research: Ikejime appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ikejime in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ikejime is common in secondary-school and first-year university syllabi. It links to neighbouring topics Animal killing, Fishing equipment, Japanese cuisine terms, so understanding it makes those chapters shorter.
In everyday life: Look for Ikejime outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ikejime in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ikejime means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ikejime out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ikejime in simple terms?

Ikejime (活け締め) or ikijime (活き締め) is a method of killing fish that maintains the quality of its meat. The technique originated in Japan, but is now in widespread use.

Why does Ikejime matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ikejime?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ikejime.