Bryan McAllister’s personal reference notebook
July 30, 2026Short & citedBlog
Civic Viewpoint.
A quiet encyclopedia with a personal desk
Kept by Bryan McAllister — short guides, clear facts, and the Canadian angle when it matters.
Field Notes • Biology

Jellyfish

Jellyfish are gelatinous marine animals in the phylum Cnidaria, known for their bell-shaped bodies and stinging tentacles.

Updated July 30, 20261 min readCited sources

Jellyfish are gelatinous marine animals in the phylum Cnidaria, known for their bell-shaped bodies and stinging tentacles. They are not fish, but drifting ocean animals that feed mainly on small marine organisms such as plankton and crustaceans.

What it is

Jellyfish are cnidarians, not fish. Their soft, bell-shaped body and tentacles contain stinging cells called nematocysts, used to capture prey and defend against threats. They drift or swim in marine waters worldwide, including Canadian coasts.

Key details

Most adult jellyfish live only a few months in the wild, though some species can survive 1–2 years or longer in captivity. The lion’s mane jellyfish is the largest species. Jellyfish are carnivorous, eating zooplankton, small crustaceans, fish larvae, and other jellyfish.

Why it matters

Jellyfish occur in Canadian Atlantic, Pacific, and Arctic waters, affecting coastal ecosystems and swimmers. Some species can sting humans, with severity varying by species; wetsuits may reduce but not eliminate risk.

In short

  • Jellyfish are cnidarians, not fish.
  • They eat small drifting animals like zooplankton.
  • Most live only a few months in the wild.
  • Lion’s mane jellyfish is the largest species.
Canadian angle

Jellyfish occur in Canadian waters, including the Atlantic, Pacific, and Arctic regions, making them relevant to Canadian coastal ecosystems and swimmers.

Quick questions

What do jellyfish eat?
Jellyfish mainly eat zooplankton, small crustaceans, fish larvae, small fish, fish eggs, and sometimes other jellyfish.
How long do jellyfish live?
Most adult jellyfish live only a few months in the wild, though some species can live around 1–2 years or longer in captivity.
Are jellyfish fish?
No. Jellyfish are cnidarians, not fish.

Sources

  1. USA Today — https://www.usatoday.com/story/tech/science/2024/03/30/what-do-jellyfish-eat/72894348007/
    Supports: Jellyfish diet and typical lifespan information.
  2. Marine Conservation Society — https://www.mcsuk.org/news/jellyfish-your-questions-answered/
    Supports: Jellyfish diet, lifespan, and general facts about stings.
  3. Wikipedia — https://en.wikipedia.org/wiki/Jellyfish
    Supports: General classification, diet, and broad jellyfish overview.
  4. Oceana — https://europe.oceana.org/feature-about-jellyfish-0/
    Supports: Jellyfish as carnivores, diet, and marine habitat.
  5. HowStuffWorks — https://animals.howstuffworks.com/marine-life/how-do-jellyfish-eat.htm
    Supports: Largest jellyfish species commonly cited and feeding behavior.