5 Types of Jellyfishes in Alaska
Yes, five species of jellyfish regularly occur in Alaskan waters, with Pacific Lion's Mane Jelly being by far the most commonly observed. These jellies thrive in the cold coastal and fjord waters of Southeast Alaska, Kenai Peninsula, and the Inside Passage. Most encounters happen aboard tour boats or from rocky shores between June and August, when water temperatures and food availability peak. This guide describes each species, how to identify them, and which Alaskan waters are most likely to have them.
By Tim, founder of Easy Street Markets. I maintain the wildlife database and verify every animal and source myself. Updated June 30, 2026.
- 5
- species recorded
- August, July, June
- peak months
Verified species, source iNaturalist
5 types of jellyfishes recorded in Alaska
5 jellyfish species have a verified observation record in Alaska across true jellyfish (class Scyphozoa), each with at least 10 confirmed sightings. The full list, ranked by how often each is recorded, is below.
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Plus 2 more recorded only rarely (fewer than 10 verified sightings). Counts from verified iNaturalist observations. Photos by iNaturalist observers, reused under the licence each observer chose.
More on jellyfishes in Alaska:
Real sighting data, source iNaturalist
1,741 verified observations on iNaturalist of jellyfish have been recorded in Alaska, most often in August, July, June.
Yes, five species of jellyfish regularly occur in Alaskan waters, with Pacific Lion's Mane Jelly being by far the most commonly observed. These jellies thrive in the cold coastal and fjord waters of Southeast Alaska, Kenai Peninsula, and the Inside Passage. Most encounters happen aboard tour boats or from rocky shores between June and August, when water temperatures and food availability peak. This guide describes each species, how to identify them, and which Alaskan waters are most likely to have them.
Pacific Lion's Mane Jelly: the giant of Alaskan waters
The Pacific Lion's Mane Jelly is by far the most frequently sighted jellyfish in Alaska, with 736 documented observations. These jellies are massive, with bell diameters often reaching 3 to 6 feet and tentacles that can trail 20 to 30 feet or longer. They appear reddish, orange, or brownish in color. The bell is divided into eight sections, with a thick cluster of arms and tentacles hanging from the center. Pacific Lion's Manes favor cool water between 45 and 55 degrees Fahrenheit and are abundant in Southeast Alaska's fjords and the Inside Passage. Despite their size, they are generally harmless to humans because their tentacles are designed to capture tiny fish larvae and plankton, not large prey. Boat tours through Kenai Fjords and glacier-viewing routes are ideal places to spot them.
Northern Sea Nettle: the sting you should avoid
The Northern Sea Nettle is the second most common jellyfish in Alaska, with 536 documented observations. These jellies have a distinctive bell shape with four prominent frilly oral arms (mouth extensions) around the base. The bell color ranges from clear with brownish tones to reddish or yellowish, depending on what plankton they have consumed. Northern Sea Nettles are smaller than Lion's Manes, typically 4 to 6 inches across the bell. Unlike the Lion's Mane, they deliver a noticeable sting to exposed skin and should be avoided during swimming or wading. They congregate in sheltered bays and fjords during summer months and are common in inside passages where warm, shallow water concentrates plankton. Wear protective clothing when entering water where they are known to occur.
What is the Greater Moon Jelly doing in Alaska?
The Greater Moon Jelly is the third most sighted species with 283 observations, making it a regular but less abundant presence in Alaskan waters. These jellies have nearly transparent or milky white bells typically 5 to 12 inches wide, with four horseshoe-shaped reproductive structures clearly visible through the bell. They prefer cooler, nutrient-rich waters and migrate seasonally into Alaska during spring and early summer. Unlike sea nettles, their sting is mild or absent for most humans, though sensitive individuals may feel minor irritation. Greater Moon Jellies often drift in loose aggregations and are commonly seen from beaches and boat tours in Southeast Alaska's northern passages during June and July.
Egg-yolk Jelly and Brown-rimmed Moon Jelly: the rare species
These two species are less frequently encountered. Egg-yolk Jellies have a distinctive yellow or orange bell, usually 2 to 4 inches across, with eight rounded lobes. With only 31 documented observations, they are present but genuinely rare in Alaskan waters. Brown-rimmed Moon Jellies, with 16 observations, are even more uncommon and have a transparent bell with a brown-tinted rim and brown oral arms. Both species are small and cause little to no sting risk. They may appear in specific fjords during peak plankton blooms in mid to late summer but are not reliable sighting subjects for most visitors.
How do you tell these jellyfish apart at sea?
The easiest way to identify jellyfish at distance is by size and color. Pacific Lion's Manes are distinctly large and reddish or orange, visible from a distance on boat tours. Northern Sea Nettles are smaller and more brownish or yellowish, with visible frilly mouth arms beneath the bell. Moon Jellies are nearly transparent or milky and smaller still, often requiring closer viewing to spot. Egg-yolk Jellies are bright yellow or orange and tiny. Pay attention to the bell shape: Moon Jellies have a simple, round bell, while Sea Nettles have a more dome-like shape with prominent tentacles. In dark water or from a distance, color alone often tells the story. Boat naturalists on Southeast Alaska tours will point out species and explain what you're seeing.
When in the year are Alaskan jellyfish most visible?
June through August are the peak months for jellyfish sightings in Alaska, with August typically offering the highest concentrations. Water temperature, plankton availability, and seasonal currents all increase jellyfish populations during mid to late summer. Spring arrivals (May to early June) show building numbers, while September begins a decline as water cools and food becomes scarcer. Winter months have very few observations because cold water temperatures and reduced light suppress plankton blooms that jellyfish depend on. For maximum visibility, book tours or plan shore visits in late June through late August. Early morning boat trips often yield better sightings because calmer water makes jellies easier to spot.
Which parts of Alaska have the most jellyfish?
Southeast Alaska's Inside Passage is by far the most reliable region for jellyfish sightings. Glacier-fed fjords in areas like Kenai Fjords, Glacier Bay, and Tracy Arm-Fords Terror concentrate both plankton and jellyfish populations. The cold meltwater creates ideal feeding conditions, and tour boats pass through these areas daily during summer. Southeast Alaska's numerous protected passages funnel currents and concentrate food and jellies in predictable patterns. Coastal areas near Juneau, Ketchikan, and the Gulf of Alaska also have strong populations. Lakes and enclosed bays in Southeast tend to have higher jellyfish densities than open ocean areas, making them better viewing sites from smaller boats or shore locations.
Are there any safety rules for viewing jellyfish in Alaska?
Jellyfish are marine animals and deserve respect. Avoid touching any jellyfish, even if it appears dead on a beach, because tentacles retain venom and can sting hours after beaching. Stay at least arm's length away and never attempt to capture one for photos. When swimming or wading, wear protective clothing such as wetsuits or rash guards in areas where Northern Sea Nettles are known to occur. Follow your boat naturalist's or guide's instructions about safe viewing distances. If stung, remove any visible tentacle pieces with a card edge (not bare fingers), rinse the area with vinegar if available, soak in hot water to reduce pain, and seek medical attention for severe reactions. Most Alaskan jellyfish cause minimal harm if avoided.
What role do jellyfish play in Alaska's marine ecosystem?
Jellyfish are a key food source for many Alaskan marine animals. Sea turtles, sunfish, and some seabirds actively hunt jellyfish. Larger fish such as lingcod and some salmon populations also consume jellyfish and their eggs. In turn, jellyfish larvae and small jellies feed on copepods, fish eggs, and larval fish, making them both predators and prey in the nutrient cycle. When plankton blooms occur (driven by spring snowmelt and nutrient upwelling), jellyfish populations explode because their food becomes abundant. Jellyfish also help regulate small fish and copepod populations, preventing any single species from dominating. They are a natural part of Alaska's cold-water marine food web and indicate a healthy, productive ocean system.
Frequently asked questions
What is the Greater Moon Jelly doing in Alaska?+
The Greater Moon Jelly is the third most sighted species with 283 observations, making it a regular but less abundant presence in Alaskan waters. These jellies have nearly transparent or milky white bells typically 5 to 12 inches wide, with four horseshoe-shaped reproductive structures clearly visible through the bell. They prefer cooler, nutrient-rich waters and migrate seasonally into Alaska during spring and early summer. Unlike sea nettles, their sting is mild or absent for most humans, though sensitive individuals may feel minor irritation. Greater Moon Jellies often drift in loose aggregations and are commonly seen from beaches and boat tours in Southeast Alaska's northern passages during June and July.
How do you tell these jellyfish apart at sea?+
The easiest way to identify jellyfish at distance is by size and color. Pacific Lion's Manes are distinctly large and reddish or orange, visible from a distance on boat tours. Northern Sea Nettles are smaller and more brownish or yellowish, with visible frilly mouth arms beneath the bell. Moon Jellies are nearly transparent or milky and smaller still, often requiring closer viewing to spot. Egg-yolk Jellies are bright yellow or orange and tiny. Pay attention to the bell shape: Moon Jellies have a simple, round bell, while Sea Nettles have a more dome-like shape with prominent tentacles. In dark water or from a distance, color alone often tells the story. Boat naturalists on Southeast Alaska tours will point out species and explain what you're seeing.
When in the year are Alaskan jellyfish most visible?+
June through August are the peak months for jellyfish sightings in Alaska, with August typically offering the highest concentrations. Water temperature, plankton availability, and seasonal currents all increase jellyfish populations during mid to late summer. Spring arrivals (May to early June) show building numbers, while September begins a decline as water cools and food becomes scarcer. Winter months have very few observations because cold water temperatures and reduced light suppress plankton blooms that jellyfish depend on. For maximum visibility, book tours or plan shore visits in late June through late August. Early morning boat trips often yield better sightings because calmer water makes jellies easier to spot.
Which parts of Alaska have the most jellyfish?+
Southeast Alaska's Inside Passage is by far the most reliable region for jellyfish sightings. Glacier-fed fjords in areas like Kenai Fjords, Glacier Bay, and Tracy Arm-Fords Terror concentrate both plankton and jellyfish populations. The cold meltwater creates ideal feeding conditions, and tour boats pass through these areas daily during summer. Southeast Alaska's numerous protected passages funnel currents and concentrate food and jellies in predictable patterns. Coastal areas near Juneau, Ketchikan, and the Gulf of Alaska also have strong populations. Lakes and enclosed bays in Southeast tend to have higher jellyfish densities than open ocean areas, making them better viewing sites from smaller boats or shore locations.
Are there any safety rules for viewing jellyfish in Alaska?+
Jellyfish are marine animals and deserve respect. Avoid touching any jellyfish, even if it appears dead on a beach, because tentacles retain venom and can sting hours after beaching. Stay at least arm's length away and never attempt to capture one for photos. When swimming or wading, wear protective clothing such as wetsuits or rash guards in areas where Northern Sea Nettles are known to occur. Follow your boat naturalist's or guide's instructions about safe viewing distances. If stung, remove any visible tentacle pieces with a card edge (not bare fingers), rinse the area with vinegar if available, soak in hot water to reduce pain, and seek medical attention for severe reactions. Most Alaskan jellyfish cause minimal harm if avoided.
What role do jellyfish play in Alaska's marine ecosystem?+
Jellyfish are a key food source for many Alaskan marine animals. Sea turtles, sunfish, and some seabirds actively hunt jellyfish. Larger fish such as lingcod and some salmon populations also consume jellyfish and their eggs. In turn, jellyfish larvae and small jellies feed on copepods, fish eggs, and larval fish, making them both predators and prey in the nutrient cycle. When plankton blooms occur (driven by spring snowmelt and nutrient upwelling), jellyfish populations explode because their food becomes abundant. Jellyfish also help regulate small fish and copepod populations, preventing any single species from dominating. They are a natural part of Alaska's cold-water marine food web and indicate a healthy, productive ocean system.
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