UCSD - University of California - San Diego

03/24/2026 | Press release | Distributed by Public on 03/24/2026 12:17

Birch Aquarium Celebrates First-Ever Red Octopus Settlement Success

Published Date

March 24, 2026

Article Content

Birch Aquarium at Scripps Institution of Oceanography at UC San Diego is celebrating a historic milestone in cephalopod care with the successful settlement of more than 15 Red Octopuses(Octopus rubescens). Experts believe this is the first time this species has been hatched, raised and "settled" in aquarium care. These are the same octopuses the aquarium announced hatching last October.

A tiny "settled" Red Octopus explores its surroundings at Birch Aquarium. Photo: Jordann Tomasek.

"This is an exciting opportunity to be a pioneer in the largely unknown early life stage of Red Octopuses. It has been incredibly fun and rewarding to watch them develop over the past six months," said Maddy Tracewell, Senior Aquarist of Animal Health. "When they first hatched, they looked like tiny aliens. Now they finally look like a real octopus, and I'm so excited and amazed!"

Octopus settlement remains one of the most mysterious phases in a cephalopod's life, largely because scientists have rarely observed this transition from a free-swimming, planktonic stage to a benthic, "settled" lifestyle on the seafloor. The aquarium's breakthrough offers a rare, detailed glimpse into the early life stages of the Red Octopus, helping scientists better understand octopus settlement as a whole

A Cephalopod Crash Course

A female Red Octopus cares for thousands of eggs. Photo: Jordann Tomasek.

This journey began last summer when Tracewell discovered a female Red Octopus guarding thousands of eggsbehind the scenes. This moment marked the start of a months-long, intensive crash course in raising cephalopods.

From reaching out to scientists worldwide, reviewing countless research papers, consulting aquarium colleagues and more, Tracewell discovered that while little is known about raising this species, two things were immediately clear.

"Our main challenges were going to be creating the right flow to replicate a pelagic environment and providing a steady supply of live food for the octopus babies, or paralarvae," said Tracewell.

Go With The Flow

Octopus species are classified by egg size, which shapes their life strategies. Red Octopuses are a "small-egg" species that produce thousands of tiny eggs, which hatch into planktonic paralarvae. These paralarvae spend several weeks drifting with ocean currents, remaining suspended in the water column as they grow and develop. Without sufficient water flow, they will not survive.

Red Octopus paralarvae spend several weeks drifting with ocean currents. Photo: Jordann Tomasek.

"Only small-egg octopus species go through this planktonic paralarvae stage that drifts with the currents," said Tracewell. "Caring for them during that stage is extremely difficult, which makes raising this species in aquariums especially challenging."

For context, large-egg species like the California Two-Spot Octopus hatch as miniature adults, skipping the planktonic stage entirely and immediately "settling" on the sea floor.

To address this flow challenge, Tracewell consulted one of the world's leading experts on octopus paralarvae, Dr. Dan Shigeki, Professor at Tokyo University of Marine Science and Technology.

"I was so happy to share our research on octopus biology with Birch Aquarium, as it may help deepen our understanding of the unique characteristics of octopuses, which are truly fascinating animals," said Shigeki.

While it took some trial and error, Tracewell - guided by Shigeki's expertise - built her own upwelling systemto provide proper flow for the babies. With this system, water gently flows from the bottom of the tank upward, keeping the paralarvae suspended in the water column. Once the flow was established, the team focused on the next challenge - finding a reliable food source.

Fast Food

The aquarium typically feeds many of its juvenile species with live Brine Shrimp. However, during research on raising octopuses, the team learned that Brine Shrimp lack a specific fatty acid essential for the development of octopus paralarvae.

Photographing the tiny, juvenile Red Octopuses alongside a ruler allows the team to measure their size accurately. Photo: Jordann Tomasek.

They pivoted to Mysid Shrimp, another readily available live food commonly used at the aquarium. However, the shrimp proved to be too fast for the octopus paralarvae to catch.

With no other readily available options, the aquarium started a Grass Shrimp culture. And, in true Goldilocks fashion, this shrimp turned out to be just right.

"The Grass Shrimp zoea, or babies, were the perfect size, nutrient profile and speed for the paralarvae," said Tracewell. "Once we finally had a steady supply of zoea, everything began to click!"

Secrets of Settlement

Octopus settlement occurs over several months and progresses through three distinct stages: a pre-settlement "tactile" phase, a settlement "hiding" phase and a post-settlement "ninja" phase.

The most reliable way to determine an octopus's settlement stage is by both counting the number of suction cups on each arm and measuring the ratio of the mantle length to the total body length. While this may sound straightforward, it's anything but.

A juvenile Red Octopus is measured along a ruler to track its growth and estimate when it will settle. Photo: Jordann Tomasek.

"These octopuses are extremely tiny, basically microscopic," explained Tracewell. "It's impossible to measure these sorts of things with your naked eye."

Weekly photoshoots with the babies provided the aquarium with an incredible resource of highly detailed images documenting their journey from eggs to hatchlings and, eventually, through all three stages of settlement. These photos allowed Tracewell to count suction cups, measure mantle length relative to total body length and track the development of chromatophores.

When an octopus hatches, it is essentially born with a species-specific pattern of "founding chromatophores," which scientists can use to identify its species. By sharing these images with octopus researchers worldwide, the aquarium provided new insights into the development and patterns of the founding chromatophores of Red Octopuses.

Senior Aquarist for Animal Health, Maddy Tracewell, looks at a photograph of the newly hatched Red Octopuses. Photo: Jordann Tomasek.

"Not many places have had the opportunity to document this life cycle in such detail, so our goal was to document anything and everything. We wanted to show just how incredible this transformation is from start to finish," said Tracewell.

Tracewell estimates that it took about five months for them to develop from hatchlings to settled. Although they have now officially settled, they still need a bit more growing to do before any can be viewed by the public. For now, they'll remain behind the scenes.

Red Octopuses typically live for about two years and can grow to about 20 inches as adults. This local species is found along the Pacific coast, from Central Alaska down to Northern Mexico.

UCSD - University of California - San Diego published this content on March 24, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on March 24, 2026 at 18:17 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]