Creature Feature: Red Abalone

A healthy red abalone. Harvest of red abalone is closed in Northern California until April 2021. Photo: Athena Maguire.
A healthy red abalone. Harvest of red abalone is closed in Northern California until April 2021. Photo: Athena Maguire.

Haliotis rufescens

Red abalone are single-shelled gastropod marine mollusks related to snails and sea slugs. They are the largest species of abalone in the world and most certainly the largest of the eight found in California waters (red, green, pink, black, white, pinto, flat, and threaded abalone).

While they are found from Sunset Bay, Oregon to Bahia Tortugas, Baja California, Mexico, this article will focus on the Northern California region (from the Oregon border to San Francisco). Red abalone inhabit the rocky shores and kelp forests and are found in intertidal and shallow subtidal waters and out to 40-50-foot plus depths.

The pursuit of this tasty mollusk is traditional subsistence for tribal cultures and is both food and thrill of the hunt for divers and rock pickers.  Unfortunately, it can also be a deadly endeavor due to the nature of the environment where abalone is found,  hazardous ocean conditions, and a diver’s poor judgement or health when seeking out a legal 7-inch or trophy (10-inch or larger) abalone. Predators to abalone include sea otters (pre-over hunting), recreational abalone divers and shore pickers (pre-closure), and poachers.

The lateral ridge or fold alongside the foot of the gastropod, also known as epipodium, is usually black, however it is not uncommon to find them with a barred black and cream color pattern. The surface of the epipodium is smooth and the edge is broadly scalloped. The area around the foot and tentacles are black and the foot or sole is tan to grey. The single shell surface with red edge is generally brick red but frequently the color is masked by encrusting organisms and there are three to four open moderately elevated pores above shell surface.

Abalone are herbivores and their primary diet is bull kelp. The first foods eaten by very young abalone, those in the post-larval settlement stage, are encrusting coralline algae and bacteria. They usually graze on the diatoms or single cell algae. When juvenile abalone get about 2 inches long, they begin to feed on drifting kelp.

The fecundity of abalone (ability to produce), increases exponentially with size. Young females produce a few hundred thousand eggs per year, when older they can produce 10-15 million. On average, abalone are sexually mature when the shell length reaches 5 inches. They are broadcast spawners—releasing their eggs and sperm into the water column through the shell pores with hopes they find each other. Reflecting the seasonal availability of kelp, spawning season is from April to July, peaking in May. When one abalone starts to spawn, it usually triggers spawning of others in the aggregation, an occurrence that causes more opportunities for fertilization to take place. It is essential that a minimum density of spawning abalone are no more than 5 feet apart for successful broadcast spawning.

Fertilized eggs, or zygotes, sink to the seafloor, where they hatch into planktonic microscopic larvae in about 24 hours. The larval mollusks are free-swimming, using cilia to move up in the water column where they remain for several days to a week before starting to search for a suitable surface or substrate on which to attach. When settlement occurs, swimming stops and growth into an adult abalone begins.

Tagging studies indicate red abalone take about 12 years to reach the legal harvesting size of  7 inches, but growth rates are highly variable. Abalone grow nearly one inch per year for the first few years, and much slower after that. It takes about five years for a red abalone to go from 7 to 8 inches. It has been noted that it could take up to another 13 years to yield another inch. Because of this, many years are needed to replace each abalone harvested. Some sources indicate red abalone can live 30 to 55 years or more.

The explosion of purple urchins following the star-fish die off, along with kelp loss, has resulted in starving conditions for abalone along the Northern California coastline. Photo: Athena Maguire.
The explosion of purple urchins following the star-fish die off, along with kelp loss, has resulted in starving conditions for abalone along the Northern California coastline. Photo: Athena Maguire.

Beginning in 2014, sea star wasting disease emerged, which eliminated the sunflower starfish (the biggest predator to purple sea urchins). Combined with unusually warm water trends, this resulted in the loss of kelp and an explosion of purple sea urchins (which compete for the same food source as abalone). The California Department of Fish and Wildlife has described this occurrence as a perfect storm of conditions, resulting in high abalone mortality. The remaining abalone are starving, atrophied, and are no longer reproducing. These conditions led to the closure of the abalone season in Northern California for 2018. With an existing moratorium in Southern California, this was the first time the entire state was closed to abalone harvest. In response, Oregon closed their small abalone fishery in 2018 for three years to prevent potential impacts from a sudden influx of harvestors from California.

The CA Fish and Game Commission voted unanimously in December 2018 to extend the sunset reopening date from April 1, 2019 to April 1, 2021, as the conditions have not proven viable enough to open the fishery.  Furthermore, the long-term Red Abalone Fishery Management Plan (RAFMP) to amend the current Abalone Recovery and Management Plan (ARMP) is still in development and will determine how to re-open the closed fishery for future opportunities.

For more information and to sign up for updates, visit the CA Department of Fish and Wildlife at www.wildlife.ca.gov, and the CA Fish and Game Commission  at  www.fgc.ca.gov. For peer-reviewed information about the RAFMP from the Ocean Science Trust, visit www.oceansciencetrust.org.

An informational FGC video from its February 2016 meeting about the ‘Perfect Storm’ and abalone decline can be found here: www.youtube.com/watch?v=P42Gm1AiWQw.

Brandi Easter has been advocating for recreational divers on fishery issues since 1999.