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= Haliotis sorenseni = The white abalone (Haliotis sorenseni) is a species of large plant-eating sea snail native to the west coast of North America. White abalone are marine gastropods with a muscular “foot” and a thin spiral shell. The white abalone is an endangered species in the United States. Prior to commercial fisheries, indigenous people along California’s coast consumed white abalone for thousands of years. White abalone shells from 7,400 years ago have been discovered near human settlements. These shells were traded along routes from southern California to east of the Mississippi River. White abalone fishing was banned in California in 1997; however, the species is considered an expensive delicacy and consequently is a popular target of poachers.

In 2001, the white abalone was the first marine invertebrate species to be listed in the Endangered Species Act. Currently, white abalone are being maricultured to produce juveniles that can be returned to the ocean to stabilize the population.

Behavior
White abalone are slow-moving bottom dwellers. They have a muscular foot which helps them attach to rocks and move along the ocean floor. While young abalone (called cryptic abalone) may move tens of meters per day, adults tend to decrease in activity as they increase in size.

Habitat
The white abalone is the deepest dwelling of eight species of California abalones, living at depths from 80 to 200 ft (24–61 m). The depth distribution of white abalone has changed so that most remaining organisms are in areas that are too deep to be fished. The depth at which white abalone are found is limited by light level and substrate availability. Lower sea temperatures reduce the survival rate of white abalone larvae. White abalone are found on open rocks and boulders between sand channels. These sand channels may be important for the movement and concentration of drift macroalgae, as well as a variety of red algae, upon which white abalone are known to feed. White abalone tend to be located near the rock-sand interface of large rocks.

Diet
The white abalone is a known herbivore, grazing mainly on macroalgae, such as Laminaria farlowii and Agarum fimbriatum, as well as several species of red algae. Young abalone eat benthic diatoms, bacterial biofilms, and algae on coralline algae substrate. White abalone also eat Chondracanthus exasperates, Macrocystis pyrifera, and Palmaria mollis. White abalone can capture kelp that are fixed to rocks or drifting along the seabed. White abalone tend to eat more attached brown algae than drift algae.

Reproduction
White abalone reproduce by broadcast spawning, or the free release of eggs and sperm into the water. A significant number of sperm are required to fertilize an egg. Fertilized eggs hatch into larvae after one day and spend 5 to 14 days as non-feeding zooplankton. Larvae that survive eventually become adults and attach to hard substrates in intertidal and subtidal areas. Due to the difficulty of fertilizing eggs, high numbers of adult male and female abalone are necessary to ensure successful production of larvae. Low population densities and recruitment failure from Allee effects have hurt reproductive success rates in recent years.

Shell
White abalone have a flattened, oval-shaped shell with a row of 3-5 pores that are used for respiration, waste removal, and reproduction. These holes collectively make up the selenizone, which forms as the shell grows. White abalone shells can grow to a length of about 10 inches (25 cm), but are usually within the range of 5–8 inches (13–20 cm).

Anatomy
The bottom of the white abalone's foot is orange and contains a muscle used for attachment and movement. The white abalone also has a tan-orange epipodium, an extension of the foot with sensory tentacles.

Life History
White abalone have a lifespan of 35 to 40 years. Adults become sexually mature at the age of four to six years old. The life cycle of white abalone involves larval stages. Fertilized eggs hatch into larvae, which eventually metamorphose into adults and migrate from plankton to a hard substrate. As broadcast spawning gastropods, white abalone reproduce by releasing their eggs and sperm into the surrounding water. White abalone tend to spawn between the months of February and April.

Historical and Present Range


Historically the white abalone ranged geographically from Point Conception, California to Baja California, Mexico, and was found especially on offshore islands such as Santa Catalina and San Clemente Islands.

In the northern part of the California range, white abalone were reported as being more common along the mainland coast. However, in the middle portion of the California range, they were noted to occur more frequently at offshore islands. At the southern end of the range, in Baja California, Mexico, white abalone were reported to occur more commonly along the mainland coast but were also found at a number of islands including Isla Cedros and Isla Natividad.

It remains unknown whether this distribution pattern was due to limited available habitat along the mainland coast or because of overfishing in more accessible mainland regions.

Since the mid-1990s, extremely low numbers of isolated survivors have been identified along the mainland coast in Santa Barbara County and at some of the offshore islands in the middle portion of the range, indicating that the current range of white abalone in California may be similar to what it was historically, albeit at dramatically reduced population sizes.

No critical habitat has been declared for the white abalone out of concern that this information would serve to attract the attention of poachers.

No recent information on current range is available for Baja California. The white abalone population in Mexico is thought to be depleted based on commercial fishery data, but the status of the species in Mexico remains largely unknown.

Historical and Present Population Size
Although there were once millions of white abalone along the coast of California, that number has been reduced so dramatically that the species could become extinct within a decade unless extraordinary recovery measures are implemented. The Scripps Institution of Oceanography conducted surveys of white abalone deep water habitat in the early 1970s which found high concentrations of about one white abalone per square yard. Such densities were comparable to the abundance of shallower species of abalone found in previously unfished or protected areas. Unfortunately, the high demand for the species led to a "boom-and-bust" fishery, which devastated the population of this species in seven years.

Conservation Status
[[File:Haliotis_sorenseni_2.png|right|thumb|375x375px|California Commercial White Abalone Haliotis sorenseni Landings for 1972–1992. The price exponentially increased as catch decreased. Even taking fishing effort into account, the volume of abalones fished is inversely proportional to the price (power regression model, F40,2 = 139.96; p < 0.0001).

Open squares - commercial catch per unit effort

Left y-axis - thousands of pounds of shell per vessel

Filled circles - price of Haliotis sorenseni

Right y-axis - USD per pound.]]

History of Endangered Species Act Listing
The U.S. National Marine Fisheries Service (NMFS) designated the white abalone as a candidate to be listed as an endangered species under the Endangered Species Act on July 14, 1997. Alongside the Scripps Institution of Oceanography, NMFS conducted a comprehensive status review of the species from August 1998 to March 2000. The NMFS received two petitions in 1999 to list the white abalone as an endangered species, and published a proposed rule to list the white abalone as an endangered species on May 5, 2000. With the final decision published on June 28, 2001, the white abalone became the first marine invertebrate to be listed under the Endangered Species Act, and its classification as an endangered species has remained unchanged since then.

Human Impact
The population of white abalones was drastically reduced in the 1970s due to overfishing by a short-lived commercial fishery that unsuccessfully tried to limit its burden on the population with size limits and seasonal restrictions. Although the fishery was closed in the 1980s, and fishing for white abalone has been illegal in California since 1997, the population in the wild has yet to show significant signs of recovery.

Major Threats
The biggest threat to white abalones is their low reproduction rate. As a broadcast spawner, the white abalone depends heavily upon high population density for successful reproduction. Currently, however, the remaining population is so fragmented that spawning in the wild is unlikely or even impossible. Other ongoing challenges facing white abalone recovery are poaching and a disease known as withering syndrome that has slowed attempts at captive breeding and propagation.

Current Conservation Efforts
The white abalone is one of the U.S. National Marine Fisheries Service’s “Species in the Spotlight,” an initiative designed to identify marine animals most at risk of extinction and prioritize their recovery efforts. As part of this program, the NMFS published a 5-year action plan on January 1, 2016 which details four key components for white abalone recovery. The first is the expansion of a captive breeding program currently being coordinated by the NMFS West Coast Region in association with the University of California at Davis’ Bodega Marine Laboratory. Next, these captive bred abalone need to be introduced to kelp forests in the wild where they can enhance existing populations and allow for higher broadcast spawning success rates. An extensive framework for tracking the demographics of enhanced white abalone populations is necessary to monitor success of the program and make necessary adjustments. Finally, the NMFS seeks to strengthen its outreach program to ensure that consistent messages about the goals of white abalone recovery are being presented to the public and potential private partners.

Although the species is not listed on the International Union for Conservation of Nature (IUCN) Red List, proactive conservation programs are required as new recruitment has been minimal. An isolated population was observed to have a 75 percent population decline from 2002 to 2010. Restoration programs are also concerned about the influence of the bottleneck effect on the genetic diversity of the white abalone.