Posted on July 27 2021
Red abalone were once a popular recreational free divers and rock pickers pastime in Northern California ocean waters. They are the largest abalone species worldwide with an average width of seven to twelve inches and prized as a food delicacy and for their beautiful shells.
These gastropod marine mollusks were previously legal for divers to take during a specific season. Unfortunately, several unfavorable factors came together in the last few decades to create a steep decline in their numbers. Abalone season has been closed since 2017 and will remain so for a few more years based on a recent season closure extension.
Red abalone in California
Red abalone have a single smooth shell with a rich red shell coloring. Their long lifespan helps them reach 35 to 54 years on average as they live out their sedate lives in the waters between Oregon and Baja. As subtidal creatures, they can be found at about 40 meters in depth along rocky crevices and drifting kelp (their preferred source of food).
These gentle herbivores had only two main impacts to their populations until recent years. Those were sea otters and humans as natural predators.
Why red abalone are at risk
Humans as a predator led naturally to overharvesting. Once prolific across the coasts, their numbers declined as more were collected in increasing numbers for food and shells.
They also suffered from fatal disease. Withering syndrome, also known as WS, is a disease caused by bacteria invading and targeting the abalone digestive tract lining. That bacteria, Candidatus Xenohaliotis californiensis, essentially causes abalone starvation by preventing digestive enzyme production. The abalone will begin to consume its own body mass in an attempt to survive. But that only further weakens the abalone, and it will either become an easy target for otters or eventually starve.
Warming waters have also impacted red abalone numbers. Global warming trends cause ocean temperature increases. This is detrimental to red abalone sperm production, and directly influences their population increase or decrease.
In a sad twist of fate, sea otter conservation efforts also have an effect on red abalone. Sea otters influence red abalone density, size, and behavior, which all impacts their sustainability. The scientific community has considered creating separate categories of marine protected areas for the two, in order to ensure each species can thrive.
Other reasons for the declining populations include poachers, purple sea urchins competing for food, toxic algae blooms, and decimation of kelp forests.
These stressors and more directly influenced the decision to close abalone season back in 2017. The California Fish and Game Commission had tightened regulations in prior years to reduce overharvesting, yet it just wasn’t enough to stabilize the red abalone population. And while many had hoped it would soon reopen, another delay has been announced. The next red abalone season is scheduled for April 1, 2026.
Nurturing the species for a comeback
The decision to delay abalone season for four more years will likely help red abalone recover to some extent. Despite this, there must be more we can do. Scientists continue to delve into reasons for the declining numbers and identify more solutions. One graduate student at California State University, Fullerton has been doing just that.
Marissa Velarde Wu studied and researched red abalone spawning behaviors and characteristics along with research professor Danielle Zacherl. Their work is focused on female spawning behaviors and body movements to someday inform repopulation, restoration, and conservation efforts.
Protecting our oceans and marine life
Conservation efforts are more important than ever to protect our oceans and the colorful marine life in them. Each action we take, from steps to reduce climate change, lessen pollution, or creating awareness, helps to ensure the future of species such as the red abalone.
Have you seen red abalone during your dives? What did you observe about their population growth or decline? Share your story in the comments below.