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White abalone - breeding back from the brink

As part of the health protocol for white abalone that are transferred between captive holding facilities, these are being treated for the removal of shell-boring organisms by applying paraffin wax to the animals' shells. Pictured from left to right are Susan Wang (NMFS Southwest Regional Office), Dr. James Moore (California Department of Fish and Game and BML), and Steve Blair (formerly of the Aquarium of the Pacific). Credit: Melissa Neuman, NOAA.

In 2001, white abalone received the dubious distinction of being the first marine invertebrate listed as endangered under the ESA. Once numerous off the West Coast south of Point Conception to Baja California (with historical estimates of more than 300,000 individuals off the coast of California), this marine mollusk will likely number fewer than 1,000 within 10 to 15 years.

A critical recovery action that may help avert the extinction of the species is the development of a captive propagation and enhancement program to reintroduce captive-grown white abalone back into the wild. Although there are significant hurdles to overcome, researchers with NOAA Fisheries and our partners are making headway.

A short-lived fishery

Unlike their better known relatives of pink, green, red, and black abalone, white abalone live at deeper depths of about 70 to 200 feet. Here, the species was more protected from recreational and commercial fishing until the advent of compressed air diving technology in the early 1960s. Intense commercial harvesting of white abalone began in 1969 and peaked in 1972 at about 143,000 pounds of white abalone per year. Just 6 years later, the fishing industry caught less than 5,000 pounds.

The Lonely Abalone

A likely reason for the inability for white abalone to rebound is their need to be close to each other when reproducing. White abalone are considered “broadcast spawners,” shooting eggs and sperm into the water by the millions when environmental conditions are right. One female can release as many as 10 million eggs at one time, but must be within 2 meters of a spawning male for fertilization to occur. The relatively short duration but high impact of the fishery diminished the density of the species, making it difficult for the remaining individuals to reproduce. Unfortunately it appears that there have been few, if any, offspring produced since the late 1960s or early 1970s.

From 2002 to 2004 NOAA began research cruises off southern California at Tanner Bank and other locations to estimate the number of remaining white abalone in prime areas and locate important habitat where captive-raised abalone could be reintroduced. Scientists found plenty of good habitat, but no young offspring and very few adult abalone close enough to reproduce.

Follow-up surveys were conducted in 2008 and 2010 with discouraging results. The number and density of white abalone had declined precipitously since the previous survey, indicating that more animals were dying than being reproduced in the wild. These results suggest that the wild population is approaching extinction and therefore immediate active restoration actions are necessary to reverse the downward trend. These actions are critical to species’ recovery and require a secure and stable funding source.

Captive breeding, combating extinction

The Bodega Marine Laboratory (BML), under the auspices of NOAA Fisheries and in partnership with five other facilities, oversees a program to determine if captive propagation and enhancement is an effective recovery tool for restoring wild, self-sustaining populations of white abalone. Analyses by BML indicate that one significant outplant of abalone (approximately 20,000 juveniles) to the recovery area would be the most effective approach to initiate recovery, as opposed to successive outplants of a smaller number of animals.

The first successful spawning in more than a decade occurred in 2012 at the Aquarium of the Pacific and at the University of California, Santa Barbara. Although the embryos developed normally into swimming larvae, only one batch survived and successfully settled on substrate to grow into juveniles. BML is currently monitoring the growth and survival of these juveniles and initiating requests to collect additional broodstock to increase the chances for successful future spawning. They are also exploring methods for improving settlement success.

There is still a long way to go. However, with persistence, dedication, and a bit of ingenuity, we may just be able to help breed white abalone back from the brink of extinction.

Updated: November 22, 2013