Popular Science Monthly/Volume 82/June 1913/The Abalones of California
|THE ABALONES OF CALIFORNIA|
By Professor CHARLES LINCOLN EDWARDS
MEDICAL DEPARTMENT, THE UNIVERSITY OF SOUTHERN CALIFORNIA, ASSISTANT, CALIFORNIA FISH AND GAME COMMISSION
THE abalone belongs to a family of marine snails, the Haliotidæ, which has many representatives in the waters about Africa, India, Japan and the neighboring islands. Six species and one variety have been described from the Pacific coast of North America, but none from the Atlantic coast. Under the name of ormers, sea-ears, or earshells, this gastropod occurs on the coast of France and among the Channel Islands, but the species are most abundant in tropical and semi-tropical regions.
The abalone is of importance because of its beautiful shell, polished as an ornament, or manufactured into many kinds of novelties and jewelry. Gleaming with the iridescence of the rainbow and the aurora this lovely shell is fit to be the chalice of Eos. Pearls may be secreted around foreign particles accidentally, or designedly, introduced between the mantle and the nacreous layer of the shell. The mollusk Pholadidea may bore through the shell and cause the formation of the blisterpearl, or we may bring about the same result by inserting a prepared form. Then the meat, either fresh or dried, is of much, food value.
In the commercial fishery of abalones, one or more crews are employed, generally made up of Japanese, but sometimes of Chinese or American fishermen. The boat containing a crew is either rowed, or driven by motor, from the camp to the fishing grounds. The crew consists of the diver and his six assistants. When over the right bottom the diver is clothed with his suit, the helmet screwed upon the brass collar, the heavy lead breast and back weights adjusted, and the anvpump manned. One man takes the diver's signal rope, another the hose from the air-pump, and the diver, with a net attached to a rope and his shucking-chisel in hand, is assisted over the side, climbs down the short ladder and drops through the water to the bottom. If he finds the abalones plentiful, work is continued in depths of from twenty to sixty-five feet, in four-hour shifts. The man on the boat with the signal rope in hand follows the course of the diver by the constant stream of air-bubbles rising to the surface. When the kelp is thick one man has a knife on a long pole, with which he cuts the sea-weed and keeps the air-tube clear.The diver finds it an easy task to detach the abalone from the rock
if he pushes the shucking-chisel under the expanded foot before the animal is alarmed. If, however, the diver hesitates and the abalone contracts its muscular foot a powerful pressure is exerted. One or two cases have been reported of the drowning of Chinese fishermen who have had their hands caught by the abalone and thus held until overcome by the rising tide. The diver secures a net full of abalones, gives the signal and the mollusks are hoisted aboard and stowed below. The net, filled with about fifty green and corrugated abalones may be hauled up every six or seven minutes. During his shift below the diver gathers from thirty to forty basketfuls, each containing one hundred pounds of meat and shell, or altogether one and one half to two tons.
At Santa Catalina Island and later at San Clemente Island in company with a Japanese diver, I donned a diving-dress for submarine exploration. On one occasion the assistant failed to tighten the waist belt which is designed to keep the air in the upper part of the diving dress. The men at the pump worked with especial assiduity and as I dropped off the ladder the inflated rubber trousers turned my feet uppermost. Head down I went through sixty-five feet of water and then, not in a position for quiet reflection, remained some moments before the Japanese assistants concluded that my signals were not being made just for the fun of it. After being pulled to the surface, reversed and relieved of inferior inflation, a successful descent was made. The submarine journey is a wonderful experience. The bottom of the sea seems made of grains of gold and silver, shimmering in the penetrating sunlight. Upon the face of a precipice, large specimens of the green and corrugated abalones rest. The shell of each is covered with a luxuriant growth of algae, hydroids and tentacled tube-worms, which mask the creature from its enemies. All about are large fish which swim close and peer through the glass window of the helmet. An enormous sting-ray indifferently floats by. One has a fellow feeling with these unfrighted denizens of the deep in the fascination of observing their behavior under natural conditions.
In gathering abalones sometimes a crew is composed of six divers who work without suits up to a depth of twenty feet and some of them remain under water for as long as two minutes. These expert swimmers protect their eyes with glasses and wear cotton in their ears. They pry off the abalones with a shucking-chisel, often filling their arms on the way to the boat. Every two hours they return to the launch to be warmed at the fire. It takes the united efforts of these six men to equal the catch of one diver in a suit.
The abalone has a well-developed head and a powerful, adhesive, creeping foot. The shell is flattened, and the spire, which is such a prominent conical structure in most snail shells, is depressed and inconspicuous in this form. The last greatly enlarged whorl contains the body, especially characterized by the enormous columellar muscle, whose fibers run from their origin upon the muscle scar, or center of the shell, into the foot. Numerous contractile tentacles arise from the fringed epipodial fold, or ruff, around the base of the foot. The gills, alimentary system, reproductive glands, kidneys, heart and blood vessels and the pallial and visceral sections of the nervous system lie to the left of
|The Green Abalone Shell with Mask of Algæ.||Black Abalone. Shell removed, showing visceral mass terminating in the spiral cœcum posteriorly and the opened gill cavity to the left anteriorly.|
and behind the columellar muscle and foot. From the mouth cavity the gullet leads backward to the enlarged stomach, which is divided into two compartments, and receives the digestive juices from the large digestive gland at the hind end of the body. Two pairs of salivary glands pour their secretions into the buccal cavity. The intestine runs
Green Abalone Dissected. The gills, kidneys, heart and dorsal parts of mantle and columellar muscle have been removed and spiral cœcum turned over to the right.
anteriorly to the side of the head, there turns on itself and proceeds back to the stomach, where it again goes forward, passing through the ventricle of the heart, to terminate in the anus, which opens into the gill cavity. The shell is perforated, toward the left, by a series of openings lying above a slit in the mantle fold leading into the gill cavity, whence issues a stream bearing the excrement, respiratory and excretory wastes. Three tentacular processes from the edges of
Feeding Abalones from the Hand, a, b, grasping kelp with anterior processes of foot; c, drawing kelp under foot; d, eating hole in kelp.
the mantle cleft project through these holes. As the animal grows the apertures in the shell behind the respiratory cavity are closed up and new ones are formed at the anterior edge.The head terminates in a short snout on either side of which is a somewhat slender olfactory tentacle and slightly lateral to this a shorter and broader optic tentacle. Two elongated ganglia lying above the mouth cavity may be called the brain because they form the center for nerves from the eyes, olfactory tentacles, snout, lips and other parts of the head. The eye is a simple cup-shaped depression of the epithelium on the end of the tentacle. The cup is filled with a gelatinous lens and it has clear and pigmented retinal cells connected with fibrils from the
optic nerve. The shadow of a hand passing over the abalone in an aquarium causes the animal to contract the head end of the body. Hence the abalone differentiates various intensities of light and thus possesses a primitive sense of sight. The contractile tentacles running out in every direction from the ruff are end-organs of touch. Each has a nerve connected with either the right or left pedal cord. These two centers of innervation run through the middle of the foot for the greater part of its length and are connected by cross fibers. They not onlystimuli from the sense organs of the ruff, but govern the multitude of muscle fibers which form the foot.
Scattered all over the exposed parts of the body are long spindle shaped cells which may respond to such mechanical and chemical stimuli as to make of them indefinite end-organs of touch and smell. In the floor of the mantle cavity a water-testing sense organ, the osphradium, extends along the base of each gill. The cells of this simple end-organ are chemically stimulated in such manner that the abalone has sensations of smell, warning it to shut off the incurrent water, when foul or containing some poisonous matter.
If a piece of kelp is held motionless in front of the body, the animal soon responds by reaching out the cleft anterior portion of the foot. These finger-like processes grasp the sea-weed and pull it back beneath the mouth and foot, where it is firmly held. Cells in the mucous lining of the mouth cavity are stimulated so that the animal gets the sensation of taste. Covering the tongue is a long horny, file-like structure, the radula, with many thousands of chitinous teeth symmetrically arranged in transverse and longitudinal rows. The teeth are pointed backward, and as the tongue is thrust out and drawn in, the radula rasps a hole in the succulent kelp, carrying the fragments of food to the opening of the gullet. Two chitinous jaws, one at either side within the mouth, but united in the midline, serve as scrapers to hold back in the mouth cavity the particles of food adhering to the radula. This method of feeding abalones individually by hand is of importance in easily caring for the animals in confinement in aquaria or in enclosed pools, or live-boxes in marine farming.
As food the abalone is one of the best of our marine mollusks. Detached from the shell, the visceral mass and mantle fringe are trimmed off from the large central muscle, which is then cut transversely into slices. These small steaks, when beaten four or five times with the flat side of a meat-cleaver and then fried in butter, are tender and delicious. The meat is also equally delectable when served as a chowder or minced. Besides supplying the local market the mollusks may be shipped across the continent, for when individuals are placed one on top of the other, in a sort of a living nest, they will survive for as long as six days without water, feeding upon the organisms and organic slime covering the shells upon which they rest. While the American market is not sufficiently developed to create an active demand
for fresh abalones yet in a dried state many are shipped to China. After being gathered from the rocks by the diver and taken into camp, the shells are removed and the abalones thrown into vats of salt water and left for two or three days. In this manner, the pigmented mantle fringe is removed and the meat preserved. The abalones are next washed in large tubs by means of wooden paddles and then cooked for one half hour in water almost at the boiling temperature not only for sterilization, but to give the meat the desired rounded shape. With dip-nets the Japanese workmen remove the abalones to baskets and
carry them to the drying frames, where they are laid out in trays in the sunshine. After four or five days, or longer, if the temperature falls, the partly dried abalones are cooked in water for the second time for one hour. Next they are smoked in charcoal smoke for from twelve to twenty-four hours, and then for the third time placed in boiling water mainly for rinsing. Now the} r are dried for a period of six weeks and after a final cleansing bath in luke-warm water made ready for shipment. During the process of drying the meat loses nine tenths of its original weight. While hard and tough, like dried beef, it may be sliced with a sharp knife and eaten with relish. When dried the meat brings from twelve to fourteen cents a pound for the green and corrugated species, and from eight to ten cents for the black abalone. Most of the dried abalone goes to China and there finally, at retail, brings seventy-five cents per pound. A camp of fourteen Japanese fishermen brings in thirty tons, or more, of the fresh abalone in a month. There is considerable business in canning abalone for the California markets as well as for New York and Honolulu. The abalone of Japan, the awabi, is a smaller species and the holes of the shell are relatively large, so that only the central part is of value, chiefly for use in inlaying. Gathering abalones is especially carried on by women divers, who swim out to the fishing grounds and work in depths of from six to eight fathoms. Pearls are not often found, but the meat is dried and sold as dark red disks strung on sticks.
The familiar polished abalone shells have gone all over the world and everywhere are highly esteemed as ornaments. The shell is polished by grinding it first on a carborundum wheel until the desired colors are reached. The shell is then surfaced by a wheel of felt sprinkled with carborundum dust glued to the wheel. Finally it is
|Polished Black Abalone Shell.||Shell of the Corrugated Abalone. The unpolished posterior half showing incrusting worm tubes.|
polished with a wheel made of many layers of cotton on the edges of which tripoli has been rubbed. This wheel is revolved about twenty-two hundred times per minute. The quality of being easy, or hard, to grind and polish is spoken of by the manufacturers as the texture of the shell.The shells are Sorted into two classes, but ordinarily classes one and two are mixed together. At Avalon, in 1870, when the meat sold for five cents a pound, the green shells brought eighty dollars a ton. At the present time the green shells are sold at one hundred and twenty-five to one hundred and eighty dollars a ton, the black, at eighty to one hundred dollars a ton, and the red, at forty to seventy-five dollars a ton. The black shells, with especially good pearly centers, bring from three hundred to five hundred dollars a ton. Owing to the increasing scarcity
of good green shells, there is a growing tendency to use the centers of the red shells for jewelry.
When the shells are cut into ornaments, as many as fifteen pieces, including one scimitar-shaped paper-knife made from the lip, or rim, may be produced from one shell of about twenty-two inches in circumference. At an average retail price of fifty cents for each of these pieces the products of the shell would realize seven dollars and fifty -cents.
The blister-pearls are more or less extended elevations of the inner,
pearly layer of the shell, formed by the secreting cells of the mantle in defense of the invading, boring mollusk, Pholadidea parva. They occur mostly in the red abalone, with only one blister-pearl in about a thousand shells of the green or black species. A crab, which infests the abalone at certain seasons, may be the cause of such formations, and one exhibited the complete outline of such a crab. Frequently the blister pearls are formed over sea-urchin spines, chiton or razor-clam shells,
pebbles and other foreign bodies retained beneath the mantle. Sometimes a diseased visceral hump is cut off and covered by nacre, making a huge blister-pearl.
The free pearls have the color of the inside layer of the shell, varying from white, to green, or pink, according to the species. They sell from fifty cents, for the smaller ones, to one hundred and twenty-five dollars for one of twenty-five grains. Occasional pearls are so large and of such fine quality as to sell for five hundred, or even one thousand dollars. The free pearls are frequently found within the stomach. During the year 1912, over eighty-six thousand blister pearls and four thousand free pearls have been obtained from the abalone fishermen.The origin of pearls has been a matter for speculation during many
(a) Black abalone shell with pearl form inserted, (b) Head of shell pearl form on inner side of black abalone shell, (c) culture pearl formed in the green abalone in seven months.
nacre which we now know serve as minute prisms to split up the white light into the rainbow tints so beautiful when reflected from the surface of the pearl. In the middle of the nineteenth century from an investigation of the fresh-water mussels of Turin Lake, Filippe proved that the stimulus for pearl formation in that species is a trematode worm. Other naturalists, Küchenmeister, 1856, Möbius, 1857, Kelaart and Humbert, 1859, Garner, 1871, Dubois, 1901, and Giard, 1903, have contributed to our knowledge of the origin of pearls from parasitic nuclei. In 1902, Jameson traced the life history of a Distomum from its first host, a duck, to a clam as its second host, and he succeeded in
|Interior View of the Red Abalone Shell, showing pearly center within the muscle scar.||Shell of the Green Abalone. The anterior portion polished.|
inoculating the edible mussel, Mytilus, by placing it with parasitically infected mollusks and thus artificially induced the formation of pearls. Herdman, in 1903, found in the pearl-oysters of Ceylon that a tapeworm larval cyst may become a pearl nucleus, or that in some cases the secretions may he deposited around sand grains, bits of mud or a fish or some other small animal, in pockets of the mantle epidermis, or again about calco-spherules near the muscle insertions. The surface finally becomes polished, or takes the "orient," and thus reflects the opaline and nacreous tints so highly prized.
The production of culture pearls dates back to the fourteenth century in China and it is probable that the Arabs had a similar industry. The Chinese open the shell of the river-mussel, push back the mantle and introduce metal images of Buddah which are covered with nacre in the course of six months. Linné drilled a hole through the shell and inserted a pellet of limestone on the end of a silver wire so that the nucleus might be kept free from the shell during the secretion of nacre. In more recent times the secretion of culture pearls has been induced in pearl-oysters by similar methods in various countries. Bouton, in 1897, at Roscoff, France, bored small holes through the shell of the abalone and inserted forms made of mother-of-pearl. After some months beautiful pearls were secreted, their size being in proportion to the length of time of the culture.
In our red abalone a boring mollusk, Pholadidea, penetrates the shell from the outside. It files its way, by means of sharp teeth on its shell and possibly by the secretion of sulphuric acid. The burrow enlarges, as the Pholadidea, growing in size, digs its way in. When near the inner pearly layer of the abalone shell, the host resists the oncoming Pholadidea by secreting more nacreous matter. Thus the defensive wall, eaten by the Pholadidea, grows inwardly as a mound shaped projection, the blister-pearl. In imitation of this natural process, a hole is drilled through the abalone shell and a form is inserted. This form, made of shell, is shaped like a long-shanked collar button and so placed that the expanded curved base lies against the pearl-secreting mantle. The shank projects from the outer surface of the abalone shell and is there made fast by aluminum wire, to which a metal tag, bearing the serial number, is attached. In some cases the wire has corroded, with the loss of the tag. In later experiments the numbers have been filed upon the shell. The black abalone has been used in most cases, although a few experiments have been made upon the green abalone. Holes have been drilled through various parts of the shell and different numbers of forms inserted. In addition, spherical forms, without shanks, have been placed beyond the mantle cavity near the visceral hump. I have succeeded in raising abalone culture
pearls in one hundred and thirty-three days. These pearls, however, are thin layers of nacre, foimed over a horny basis, which is the first material to be secreted. In the natural process of continued deposition they increase in thickness and solidity and consequently in value. One produced in a green abalone in seven months shows good form and luster. My average time for drilling a hole in the abalone shell, inserting the form and wiring it in place with the numbered metal tag, is eight minutes. This working time might be decreased by an expert laborer doing nothing else, so that the business of raising pearls would be of interest and profit. Mr. C. B. Linton has succeeded in producing similar culture pearls by drilling a hole through the shell center, pushing in a round ball, made from shell, and filling the outside end of the hole with beeswax and cement.
Based upon the fact that each ton of abalone shells represents a certain value of manufactured jewelry and novelties, it is possible to estimate the value of the abalone industry. Shells of the black abalone are sorted into two classes. Each ton of those with fine, pearly centers will make novelties and jewelry worth, at retail, four thousand dollars. The class known as button shells, with plain mother-of-pearl surface, represents a final value of one thousand dollars and the shells of the green abalone, three thousand dollar?. For the fiscal year ending in July, 1912, the following shipments were made from Long Beach and represent the given valuations in manufactured products: thirteen tons of pearl center black abalone shells, fifty-three thousand dollars; forty tons of button black abalone shells, forty thousand dollars; fourteen tons of dried abalone meats at two hundred dollars a ton, twenty-eight hundred dollars; a total of ninety-five thousand eight hundred dollars. The shipping statistics are not complete for the other California ports, but it is demonstrable that the abalone industry may be developed into one of great value.
Much has been said recently in the newspapers concerning the threatened extermination of the abalone. That this is a real danger, and not an idle theory, is apparent to any one familiar with the facts. For instance, near Avalon, Santa Catalina Island, not more than twenty years ago, the green and corrugated abalones were so thick that they rested upon one another four or five deep, all over the rocks. After much searching in this locality during the last year I was unable to find a single specimen. The shells brought up by the divers of the glass-bottomed boats, and eagerly bought by the tourists, have been placed in position previously by the enterprising management. Great shell heaps on San Clemente, San Nicholas and other islands prove the abundance of abalones during the centuries of Indian occupation. Some of the red shells found are unusually large, measuring from twenty to thirty inches in circumference. Necklaces of large abalone pearls have been found with the remains of Indians. If only well preserved, some of these pearls at present would be worth as much as five hundred dollars.
In many places where the abalone was formerly abundant, the large individuals of legal size are taken and it may be true, as in the case of the American lobster, that in this manner the most prolific breeders are sacrificed. We do not yet know anything about the breeding habits and embryology of any species of abalone, and hence are not certain as to the best months for a closed season. In time, without doubt, we shall be able to artificially propagate the abalone, as has been done with the oysters, clams, lobsters and other useful animals. The government breakwater, at the mouth of Los Angeles harbor, at San Pedro, has become a natural breeding ground for black abalones which creep back under the great stone blocks and thus escape the gatherers, who are stripping every accessible niche and cranny along the coast at each low tide during the open season.
Reservations have been established at Monterey Bay and Venice, but the present laws are inadequate for their best development. By act of the city trustees, the Venice breakwater has been made a biological reservation under the control of the marine biological station of the University of Southern California and guarded by a deputy of the State Fish and Game Commission. As an aquacultural experiment I have placed colonies of several hundred black abalones and seventy-five of the green species upon the submerged rocks. A large concrete livebox has been suspended by a block and tackle hoisting apparatus at about the mid height of the tide. The open top is covered by heavy galvanized iron meshwork, while through several holes in thethe dirt is cleaned out by the flow of the tide. The box is so heavy that one may stand upon any part of it and do the necessary work in feeding and observing the animals within. Forty abalones under experimentation and for growth records are kept in the live-box and a group of two or three times that number might easily be maintained in good condition. Near Venice the ocean is shallow, for it is three miles out to the sixteen-fathom line. The trawling of our motor-sloop, the Anton Dohrn, has demonstrated that in most places the fauna of the sandy bottom is poor. Better results may be looked for when reservations are located on the rocky coast, where great beds of kelp thrive just within the deep-water line. The kelp is not only important as food for abalones, but within its wide spreading fronds a world of living things thrive. In such a region the plankton is richer and these microscopic plants and animals generate food for the larger swimming and bottom-dwelling forms.
The establishment of laws for the regulation of aquaculture and the concomitant protection of marine and fresh-water organisms is of primary importance. The formation of reservation districts for absolute closure during successive periods of years, within which we may have, every five or ten miles, smaller perpetual biological reservations for breeding centers, will solve the problems of preservation in a better manner than the present laws for closed and open seasons. In Germany the Elster River pearl mussel beds and in France the marine mussel and oyster fisheries have been saved and developed by proper legislation and governmental supervision. In this country the business of oyster propagation and farming has been profitably established under such well-developed laws as those of Connecticut. It would be difficult to attempt an estimate of the remarkable achievement of the Bureau of Fisheries in the field of aquaculture. The shad, the salmon and now the fur-seal have been saved from extermination. So abalones may be raised in the sea as easily as chickens upon the land. The coastal waters must be surveyed for leasing by the state and then a police force organized to guard the marine farms from all the poaching pirates. It can not be emphasized too often that in direct ratio with the increase of population the neglected food resources of land and sea must be conserved and developed. The company manufacturing rubber and fertilizer and extracting iodine from kelp should only be allowed to cut the seaweed under such restrictions as will preserve the natural home and food supply of all the countless dependent organisms. The inherent tendency of man to rob the earth and sea in order to promote his own selfish interests must be restrained for the larger benefit of his fellows and the salvation of his descendants from want. The sea is the last great field for human exploration and exploitation. We know so little of its vast resources that we can scarcely dream of the possible future industries which will arise under a wisely administered system of aquaculture.