Photo credit: Oscar Del Valle Ayala (Peru) Via: Wilder Rodriguez Arteaga (Peru)
Review: Abdel Rahman El Gamal (Founder of the website)
Introduction: The red abalone, Haliotis rufescens, is a snail-like, univalve species of a very large edible sea snail; it is a marine gastropod mollusk in the family Haliotidae. Historically, red abalone has been the most important commercial species of abalone that was harvested in the California while in the present; it is the only species of abalone still legally supports the recreational free-dive. This species may live for 20 years.
Distribution and habitats:
Geographic range: The red abalone can be found along the west coast of North America, from southern Oregon to Baja California, and Mexico. Due to overfishing, the stocks of red abalone have very much declined along the Pacific coast.
Habitat: The red abalone is found from the intertidal zone down to at least 100 feet but most abundant attached to rocky areas with kelp from 20 to 40 m depth. The red abalone prefers water from about 7 – 15 Celsius.
Description: Red abalone, Haliotis rufescens are the largest of all the abalone species in the world whereas its shell diameter can reach up to 30 cm. The abalone shell is large and thick of brick red to pink color with 3-4 oval, open pores which are located on one side of the shell and are moderately elevated above the shell surface. Through these holes, the abalone breathes and discharges wastes which fill up and are replaced by new holes as the abalone ages. The red abalone has myopic eyes on the end of retractable stalks, long jet-black tentacles, and a large cupped mouth.
Food Habits: Red abalones are algae grazers and feed primarily different plants from plankton, macro-algae, large brown algae such as bull kelp, and giant kelp. Their feeding habits are supported by their rasp-like teeth and extruding tongue changing in their feeding as they grow. During their early and juvenile stages, they feed upon diatoms and bacterial films attached to substrates, then after Coralline algae. As they grow they increasingly rely on drift algae. Red abalones exhibit remarkable skill at capturing and manipulating strands of kelp. They stay in their location waiting for food to drift by. When food becomes scarce, they will move looking for their food.
On the other hand, an abalone once feeling a possible predator, it pulls its shell over its soft body making the matter very difficult for most predators to remove the abalone from its substrate.
In regard to farmed abalone, many abalone farms use high quality specific manufactured food that leads to the production of high quality meat.
Reproduction and life history: This species becomes sexually mature at the age from 4-6 years, and they spawn throughout the year with a peak period. The sexes of this abalone are separate. The gonads of the females are green and those of the male, yellowish. During spawning, abalone broodstock broadcast their eggs and sperm into the ocean. Males eject sperm and females eject eggs. Fecundity as measured in the number of gametes produced is directly related to female size; a large female may have over 12 million ripe oocytes whereas smaller/younger females will produce less number of eggs.
If the temperature is optimum (14-16 o C), red abalone larvae hatch about one day after fertilization, develop into a morphologically mature veliger larvae after three days and are capable of metamorphosis after about seven days. Red abalone settlement and metamorphosis are by compounds released from coralline algae, which the young abalones graze upon. Within 2 months, the larvae develop into small sized adults while by the age of 1 year, an abalone reaches about 25 mm long, and within 4 years it reaches sexual maturity.
Utilization of red abalone
Fishery: The human uses of red abalone dates to thousands of years ago starting with shells which have been used to make a variety of fishhooks, beads, ornaments, and other artifacts.
Moreover, because of the high quality meat, there has been a growing demand on some abalone species including the red abalone which has been sorted as a luxury and expensive food especially in to the Pacific Coasts of Mexico and the United States.
Because of the overfishing and the destruction of most wild populations of abalone, abalone farming has become a booming business.
Farming: Because of the high demand on popular abalone species including red abalone, the farming of abalone began to exist especially this species is well suited for farming, both land based and ocean based operations. The red abalone has been favored due to its productive traits as well as the best meats to shell ratios which the species enjoys. It is claimed that abalone farming has little environmental impact because of its feeding habits which rely mainly on fast-growing kelp, which regrows quickly upon harvest.
Threats and conservation efforts
Threats: The red abalone population has been drastically reduced as a result of over exploitation whether via commercial fishery or sport divers. The predation especially by sea otters and rock crabs has contributed to the decline of red abalone stocks. Diseases have also affected the red abalones.
Conservation measures: Even though most of the following examples of conservation measures for red abalone are related to California fishery, these regulations could be applied elsewhere. The followings are the protocols taken towards the conservation of the stocks of red abalone:
Developing and enforcing the fishing laws that specified the minimum size of fished abalone (20 cm in diameter)
Prohibiting the canning of abalone and prohibiting the shipment of fresh or frozen meat out of state
Closing the commercial fishery of red abalone such as in 1997
Limiting the recreational abalone fishery to specified locations
Launching an Abalone Recovery and Management Plan (ARMP) in 2005
Specifying legal fishing gears to ensure the catch of legal abalone size. In some abalone fishery, the minimum legal size for red abalone is 17 cm (7 inches). Moreover, fishing quota per day or per year has been established
References: Wikipedia, http://www.wallawalla.edu, Animal Diversity Web, Ecology and Evolutionary Biology, Fish Tech
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