Abalone

An Intriguing Snail

One of the most alluring residents of the bull kelp forests of the northern California coast is the red abalone. There are also smaller white and black abalone whose numbers have fallen drastically in their coastal zones farther south, and the pinto or northern abalone can be found through British Columbia and into Alaska, but the red abalone holds a special place in the hearts, minds and mouths of Californians, both native and non-native. Abalone is a marine mollusk that, like sea urchin, loves to eat kelp and algae. Abalone are part of the great diversity of organisms, from fish, marine mammals, sponges, tunicates, to other algae and invertebrates that create the dynamic world of the kelp forest. In fact, abalone’s domed shells provide additional real estate possibilities for a variety of algae and are often seen sporting both encrusting and articulated pink coralline algae. 

Abalone are naturally abundant around Monterey, California and the word “aulon,” traces back to the Indigenous Rumsen people of that area, which then got converted to “abulon” by the Spanish. In Latin, the genus Haliotis means sea ear, and while there are many species of abalone in the world’s oceans, all within this same genus, along the California coast the reds are not only the largest, but have the greatest range. They can be found from Oregon to Baja California in Mexico, with six other smaller species, white, black, green, pink, pinto, and flat, found in more limited ranges.

Abalone are marine snails that look unlike most snails we know. Their spiraled shell has been flattened to a cap of calcium carbonate that covers the fleshy foot. This foot emerges from the domed shell with a flouncy edge and waving tentacles, and attaches strongly to rocky underwater surfaces. It is a powerful foot force, holding firmly to its substrate. The abalone shell has a row of respiratory pores, or holes, that run along one edge of the shell, and when found whole or in parts along a rocky shore, the glittering iridescence of the insides, the nacre, makes it impossible not to pick up with wonder. When building their shells, abalone shift from one polymorph of calcium carbonate to the other, making calcite for the outer shell then switching abruptly to depositing aragonite for the colorful interior. Light bounces between the layers of aragonite creating the shimmering iridescence that has been coveted by humans through deep time, a testament to our abiding predilection for beauty. The exterior of the red abalone is brick red, the shells tough and durable, prized for toolmaking; their interior prized as decoration for masks, sculptures and regalia by California and Pacific Northwest Indian tribes up and down the coast and traded extensively inland. In fact, the earliest sea fur traders found that picking up easily-found abalone shells in Monterey were the best items to use for trade with tribes farther north when bartering for sea otter pelts. 

Abalone, like urchins, are detritivores, living in deep cracks in the rocky ocean terrain or on the sides of boulders, waiting for drift algae or kelp to come their way. In a healthy kelp forest, drift algae is abundant and abalone populations thrive. If kelp is in short supply, abalone will go looking for it. One of the saddest sites is a photograph of a large abalone climbing up the denuded stalk of urchin-ravaged understory kelp.

How do Abalone Reproduce?

Abalone are broadcast spawners like sea urchins. Females and males release millions of egg and sperm through the pore holes in the shell, creating what looks like wisps of smoke into the surrounding ocean. This release stimulates nearby abalone to spawn, creating a spawning event, dramatically increasing the probability of fertilization. But other red abalone of varying sexes need to be nearby, within about 5 feet, for fertilization to be successful. Fertilized eggs hatch into planktonic, free-floating larval veligers that, after a week or so, start looking for a suitable substrate (especially loving coralline algae encrusting on the rocks), to settle upon to then grow into its adult form. Cracks in rocks, or undersides of boulders are popular, but sometimes the best place to grow as a tiny abalone and be protected from predators is in between the spines of a sea urchin. Like urchins, abalone are long-lived once they reach maturity, easily living 30–40 years.

Abalone spawning is not a regular thing however. It can be enormously successful, creating a cohort of abalone that will feel like an overwhelming abundance in population, but given environmental conditions—warming oceans, increasingly acidic waters, dispersed populations of males and females—it can also fail. There is no guarantee of a renewing cohort of abalone regularly filling age gaps in populations. R-selected species are prone to population spikes and crashes, depending on disease, predation and other factors. At Bodega Marine Lab, even the experts are stymied by their inability to predict when the abalone in their tanks will spawn. The misunderstanding of abalone reproduction as well as the politicization of California abalone fisheries management in the mid-20th century led to massive overfishing of abalone, mining any remaining resilience out of the remnant populations of white and black abalone. The decline of the bull kelp forests off the Northern California coast from 2016 onward compounded recreational fishery pressures, resulting in a parallel decline in red abalone populations, as their habitat and food source disappears.

Abalone are a coveted food as well as a coveted shell. That meaty foot is prized protein and has been eaten by humans since the earliest traversing of the kelp highways along the continents’ edges. Abalone themselves show up as fossils from 12,000 years ago onward and their shells, made into crude projectile points, are markers of the earliest human/prey relationship. Abalone appear abundantly in the earliest shell middens allowing for an image of Indigenous Californians, collecting a substantial food source from the near shore waters, easily carried in its own shell container.