Abalone resource decline and a recovery attempt in Chiba Prefecture, Japan.ABSTRACT Landings of abalone abalone (ăbəlō`nē), popular name in the United States for a univalve gastropod mollusk of the genus Haliotis, members of which are also called ear shells, or sea ears, as their shape resembles the human ear. (H. discus discus /dis·cus/ (dis´kus) pl. dis´ci [L.] disk. dis·cus n. pl. dis·ci A flat circular surface; a disk. discus pl. disci [L.] 1. , H. gigantea, and H. madaka) in Chiba Prefecture Chiba Prefecture (千葉県 Chiba-ken , Japan exceeded 700 t in 1966 and fluctuated between 600-800 t until 1978. The landings started to decline in 1979 and reduced to less than 100 t in 1997. Although landing of H. discus has been slightly increased since 2000, that of H. gigantea abalone is still decreasing. We analyzed the data of investigations on decline in abalone landings and have come up with "environment theory", "over-fishing theory" and "disease theory." In the environment theory various factors were considered, such as biomass decrease of purple sea urchin sea urchin, spherical-shaped echinoderm with movable spines covering the body. The body wall is a firm, globose shell, or test, made of fused skeletal plates and marked by regularly arranged tubercles to which the movable spines are attached. ; which is used as a shelter by juvenile abalone, sedimentation sedimentation In geology, the process of deposition of a solid material from a state of suspension or solution in a fluid (usually air or water). Broadly defined it also includes deposits from glacial ice and materials collected under the effect of gravity alone, as in talus flux increase, withering with·er·ing adj. Tending to overwhelm or destroy; devastating: withering sarcasm. with of seashore (Isoyake), oceanic dynamic change, predation predation Form of food getting in which one animal, the predator, eats an animal of another species, the prey, immediately after killing it or, in some cases, while it is still alive. Most predators are generalists; they eat a variety of prey species. damage, coastline development, and endocrine disruptors Endocrine disruptors are exogenous substances that act like hormones in the endocrine system and disrupt the physiologic function of endogenous hormones. Studies have linked endocrine disruptors to adverse biological effects in animals, giving rise to concerns that low-level , of which the sedimentation increase was thought to be the most influential factor. In the over-fishing theory, decrease in the number of reproductive adults due to reinforcement of the fishing intensity was considered to reduce the fertilization fertilization, in biology, process in the reproduction of both plants and animals, involving the union of two unlike sex cells (gametes), the sperm and the ovum, followed by the joining of their nuclei. success and caused the decline in recruitment. The disease theory was found to be not applicable because virus infection of seeds has not been reported in Chiba Prefecture. To solve the problems related to decrease in adult population number, various research approaches are possible: development of techniques to create suitable reproduction habitat, long term observation of reproductive conditions in a perpetual observation area, improvement of seed transportation and release methods, and development of fishing ground construction technology. We have been conducting research on the effects of leaving the fishing ground fallow fallow a pale cream, light fawn, or pale yellow coat color in dogs. for 5 y, and we are also investigating the amount of resources in different developmental stages. The present study summarizes the abalone landing decline factors in Chiba Prefecture and describes the present status of our research. KEY WORDS: fishing intensity, recovery, abalone, Haliotis INTRODUCTION In order for Chiba Prefecture to work on the investigation and the measure against production increase of abalone resources, the "abalone resource recovery project," which consists of administration, test research, and fisheries fisheries. From earliest times and in practically all countries, fisheries have been of industrial and commercial importance. In the large N Atlantic fishing grounds off Newfoundland and Labrador, for example, European and North American fishing fleets have long extension section was established in 1998. To clarify the causes of resource reduction, environmental theory; over-fishing theory; and disease theory were built and examined (Simizu & Tanaka 2001). ENVIRONMENTAL THEORY Biomass Decrease of Purple Sea Urchin Although juveniles are considered to hide under the prickle prickle /prick·le/ (prik´il) 1. a small, sharp spine or point. 2. a tingling or smarting sensation.prick´ly of purple sea urchin to escape from predator predator an animal that derives its life support by predation. (Kojima 1974, Kojima 1981, Tanaka & Tanaka 1982), purple sea urchin is not necessarily distributed thoroughly in Chiba Prefecture (Anonymous 1980, Anonymous 1981), and abalone juveniles were observed to move out from underneath the spines of purple sea urchin in approach of eight armed starfishes(Coscinasterias acutispina). Therefore, decrease of purple sea urchin may not be a major reduction factor (Tanaka 2001). Sedimentation Flux Increase There is a report that sedimentation flux influences survival of abalone larvae Larvae, in Roman religion Larvae: see lemures. and juvenile (Yamada & Kamimura 1973, Sakamoto 1979, Sakamoto & Nanba 1980). Growth and survival rate of early juveniles are known to be better in filtered sea water. Withering of Seashore Seashore withering is reported to deteriorate de·te·ri·o·rate v. 1. To grow worse in function or condition. 2. To weaken or disintegrate. food conditions of abalone, causing malnutrition malnutrition, insufficiency of one or more nutritional elements necessary for health and well-being. Primary malnutrition is caused by the lack of essential foodstuffs—usually vitamins, minerals, or proteins—in the diet. and decline in abalone resources (Kawajiri et al. 1981, Tanaka & Tanaka 1986). There is a report that production of food seaweed seaweed, name commonly used for the multicellular marine algae. Simpler forms, consisting of one cell (e.g., the diatom) or of a few cells, are not generally called seaweeds; these tiny plants help to make up plankton. influences survival of H. discus hannai (Sakai 1962). However, in the Hamanamekawa and Kawaguchi area where the abalone fishery is performed, flora and the amount of sea oak and sea trumpet Sea´ trum´pet 1. (Bot.) A great blackish seaweed of the Southern Ocean, having a hollow and expanding stem and a pinnate frond, sometimes twenty feet long. 2. (Zool.) Any large marine univalve shell of the genus Triton. , which are the food items of abalone, did not differ between 1978 and 1998 (Tanaka & Simizu 2000). Ocean Dynamic Change In H. discus hannai, water temperature decrease by cold Oyashio current The Oyashio Current (also named 'Oya Siwo', the Kurile current, Japanese 親潮) is a cold subarctic ocean current that flows south and circulates counterclockwise in the western North Pacific Ocean. is one of causes of stock size decline (Shibuya 1984). The Chiba coast is under influence of warm Kuroshio current. Although winter water temperature has been rising slightly since 1986, abalone catch has begun to decrease since 1980 in Chikura areas (Tanaka & Simizu 2000). Thus, on the Chiba coast, water temperature may not be a reduction factor because ocean dynamic change and resource change do not synchronize See synchronization. . Predation Damage Octopus, crabs Crabs An informal or slang term for pubic lice. Mentioned in: Lice Infestation crabs Pubic lice, see there , star fish, snails, and fishes are known predators of abalone (Kojima 1981, Yamakawa 1990, Seimura et al. 1993, Anonymous 1976). However, detailed data of predation damage of abalone are not available. No correlation is found between landings of octopus and abalone (Simizu & Tanaka 2001). This may indicate minor importance of predation on abalone stock, but further studies are required. Coastline Development There has been no large scale coastal development in Chiba. Although there supposed to be some local fishery loss by the outflow of earth and sand, damages has been relatively minor. Endocrine Disruptors Abnormalities in the gonads of abalone, which are known to be caused by endocrine disruptors, may reduce reproductive activity of abalone (Horiguchi & Shiraishi 1999). However, histologic his·tol·o·gy n. pl. his·tol·o·gies 1. The anatomical study of the microscopic structure of animal and plant tissues. 2. The microscopic structure of tissue. abnormalities have not been observed in H. discus and a H. gigantea from Kawaguchi area (Simizu & Tanaka 2001). OVER-FISHING THEORY There are reports that describe abalone resource decline due to reinforcement of fishing intensity (Anonymous. 1984, Nonaka 1987, Tachiyama et al. 1998, Horii 1998). In Chiba Prefecture, the possibility that introducing wet suit to diving fishery and/or other elements caused the over-fishing cannot be denied. The habitat density of 1-y-old abalone was remarkably decreased in 1989 as compared with 1978 (Tanaka & Simizu 2000), indicating the decrease of new recruitment. In Australian greenlip abalone (Haliotis laevigata), high density of broodstock is known to be indispensable for fertilization success (Babcock & Keesing 1999). Decrease in the number of reproductive adults due to reinforcement of the fishing intensity was considered to reduce fertilization success and caused the decline in recruitment. DISEASE THEORY Although wild abalone may die of virus infection passed on by infected in·fect tr.v. in·fect·ed, in·fect·ing, in·fects 1. To contaminate with a pathogenic microorganism or agent. 2. To communicate a pathogen or disease to. 3. To invade and produce infection in. artificial seeds, no virus infection has been reported in the process of the seed production in Chiba Prefecture. Therefore, virus infection does not seem to be major reduction factor of abalone resources. In summary, the main causes of the abalone resource reduction in Chiba Prefecture seem to be related to over-fishing and we took a measure against recovery based on this conclusion. Solution for Resource Recovery Improvement of Abalone Seed Release Method The recovery rate of the released seeds in Chiba Prefecture is estimated to be 8.8% (Sakamoto et al. 1986). By improving the release method, the survival rate, and therefore recovery rate, may be increased. The survival rate of abalone seeds can be maximized by the use of a release basket (Fig. 3) (Nishima & Ito 1989, Tanaka & Sakamoto 2001). To date, divers Several; any number more than two; different. Divers is a collective term used to group a number of unspecified people, objects, or acts. It is used frequently to describe property, as in divers parcels of land. have released abalone by hand in Chiba Prefecture. However handling can damage the seeds. The introduction of a release basket can make transporting and releasing of seeds more efficient. A study of this method was performed to test its effects. The release basket, which is used for H. discuss hannai release in Iwate Prefecture Iwate Prefecture (岩手県 Iwate-ken (Anonymous. 1990), can accommodate about 1500 individuals of seeds (~3-cm SL). The examination was carried out in a developed area with about 200 concrete boards (60 cm x 60 cm) in Hamanamekawa area in November 2001. [FIGURE 3 OMITTED] Effect of the release basket was examined. The use of the release basket increased the recapture recapture n. in income tax, the requirement that the taxpayer pay the amount of tax savings from past years due to accelerated depreciation or deferred capital gains upon sale of property. (See: income tax) RECAPTURE, war. rate of H. gigantea, whereas the effects were not clear in H. discus (Table1). To mitigate the predator damage of released seeds, water temperature should be low. Use of the release basket, which can make it possible to carry out the release without diving in the winter, may be effective. Development of Suitable Reproduction Habitat We have been conducting research on the effects of catching abalone every 3 y. One research area 1,000 [m.sup.2], and was developed with about 1,500 sheets of the concrete plates (80 x 60 x 10 cm). About 20,000 H. discus seeds were released in one area, and the recovery rate was examined after 3 y. Three sets of areas established and "catch rotation during 3 years" is carried out. The amount of recoveries been 300-400 kg per one area on average (Table 2), 700 kg maximum, which is about 2,000 individuals. In an average fishery ground, the benefit of seeding greatly exceeds the cost. This type of catch rotation fishery can expect not only increased recovery of released abalone but it is also functions in the maintenance of high parents density. Early Ecology of Abalones in Chiba Coast To attain suitable and effective resource control and enhancement, investigation of resource change mechanisms is indispensable. The occurrence of planktonic plank·ton n. The collection of small or microscopic organisms, including algae and protozoans, that float or drift in great numbers in fresh or salt water, especially at or near the surface, and serve as food for fish and other larger organisms. larvae Tidal tidal /ti·dal/ (ti´d'l) ebbing and flowing like the waters of the oceans. tid·al adj. Resembling the tides; alternately rising and falling. the flow was investigated, and abalone larvae were collected using the Kitahara plankton plankton: see marine biology. plankton Marine and freshwater organisms that, because they are unable to move or are too small or too weak to swim against water currents, exist in a drifting, floating state. net in Ftomi area in 1979 and 1980. The spawning season of abalone was considered to start in late October and end in February, and it became clear that spawning is induced by low atmospheric pressure atmospheric pressure or barometric pressure Force per unit area exerted by the air above the surface of the Earth. Standard sea-level pressure, by definition, equals 1 atmosphere (atm), or 29.92 in. (760 mm) of mercury, 14.70 lbs per square in., or 101. and rapid water temperature changes. Eggs and larvae were found to be accumulated in the whirlpool whirlpool, revolving current in an ocean, river, or lake. It may be caused by the configuration of the shore, irregularities in the bottom of the body of water, the meeting of opposing currents or tides, or the action of the wind upon the water. region (Tanaka & Ishida 1986). To compare with the past conditions, larvae were collected by the Kitahara plankton net in 2001 and 2002 (Table 3). The densities of H. discus and a H. gigantea were 0.4 ind./[m.sup.-2] and 0.5 ind./[m.sup.-2] respectively in 1987 and were 0.01 ind./[m.sup.-2] and 0.02 ind./[m.sup.-2] in 1998. Despite the fact that there were larger amount of resources 20 y ago, the numbers of larvae collections of the larvae in 2001 and 1980 were in the same level. The occurrence of larvae is a key factor in understanding abalone stocks, yet it is the most elusive. It is necessary to carry out studies on methodology. The occurrence of postlarvae Occurrence of postlarvae of abalone has been investigated since 1977. We collect natural stones and concrete hoards (20 x 20 x 2 cm) to extract the juveniles at least once a week in the Kawaguchi area from late October to December, which is the breeding season Breeding season is the most suitable season usually with favorable conditions and abundant food and water when wild animals and birds (wildlife) have naturally evolved to breed to achieve the best reproductive success. of abalone. The number of annual accumulation of postlarvae ([m.sup.-2]) was the highest in 1977 (i.e., 277) and gradually decreased thereafter to 0-7 in the 1990s (Tanaka & Kasai 2000). This trend seems to be in parallel with the trend of abalone stock abundance: systematic accumulation of knowledge of ecology and methodology is necessary. CONCLUSION For abalone stock enhancement, improvement in the survival and recovery rates after the release is raised as a short-term objective, and it is necessary to steadily advance and spread the technologies introduced in this study. Moreover, because the current status of fisheries will not fall to growth-over-fishing if the present legal size (i.e., 12 cm) of capture is kept (Simizu 2000), appropriate measures such as enlightenment on fisheries association consciousness, poaching poaching: see cooking. prevention and shell length restriction observance, and an improvement of fisheries management Fisheries management is today often referred to as a governmental system of management rules based on defined objectives and a mix of management means to implement the rules, which is put in place by a system of monitoring control and surveillance (MCS). system, are indispensable. At the same time as a mid and long-term objective, the early ecology of abalones and a resource change mechanism need to be elucidated towards the increase in natural juvenile, production. Accumulation of the systematic knowledge is desirable.
TABLE 1.
Comparison of recovery rates between two release basket and diving, in
H. discus and H. gigantea.
At Release
Nov. 7, 2001
Shell Length
Method Species N (mean [+ or -] SD nm)
Release basket 1000 29.8 [+ or -] 1.4
Diving H. discus 996 29.8 [+ or -] 1.4
Release basket H. gigantea 990 27.8 [+ or -] 1.4
Diving 959 27.8 [+ or -] 1.4
At Release At Recapture
Nov. 7, 2001 Dec. 4, 2001
Weight Recapture/rate
Method (g) N (%)
Release basket 3.7 [+ or -] 0.5 332 33.2
Diving 3.7 [+ or -] 0.5 354 35.5
Release basket 2.8 [+ or -] 0.5 622 62.8
Diving 2.8 [+ or -] 0.5 486 50.7
At Recapture
Dec. 4, 2001
Shell Length Weight
Method (mean [+ or -] SD nm) (g)
Release basket 30.4 [+ or -] 1.7 3.6 [+ or -] 0.8
Diving 30.2 [+ or -] 1.6 3.7 [+ or -] 0.6
Release basket 28.9 [+ or -] 1.6 2.8 [+ or -] 0.5
Diving 29.0 [+ or -] 1.8 3.0 [+ or -] 0.6
TABLE 2.
Landings of abalone in rotation fisheries grounds.
Kawaguchi Hiraiso
Catch Rate * Catch Rate *
Area (kg) (%) (kg) (%)
P1 517 74.4 269 89.2
P2 185 76.7 738 92.9
P3 517 70.9 603 89.7
K1 153 86.6 588 86.9
K2 136 62.1 686 97.2
K3 585 91.7 414 90.5
mean 349 77.1 550 91.1
The amount of recoveries 269 501
Senda Okawa
Catch Rate * Catch Rate *
Area (kg) (%) (kg) (%)
P1 245 85.1 448 71
P2 170 55.8 540 93.1
P3 176 69.6 179 68.6
K1 376 88.7 306 85.4
K2 437 91.4 434 92.7
K3 479 97.5 398 89.4
mean 314 81.4 384 83.4
The amount of recoveries 255 320
Shiramazu
Catch Rate *
Area (kg) (%)
P1 105 46.4
P2 266 62.8
P3 245 69.5
K1 270 95.1
K2 309 93.2
K3 296 88.4
mean 249 75.9
The amount of recoveries 189
Fishing was annually rotated in two groups: P1-P3 and K1-K3.
* Rate: ratio of released abalone in the landings
TABLE 3.
Occurrence density of abalone larvae in Futomi area, Chiba Pref.
Mean Density
(ind./[m.sup.3])
Number of Egg and
Year Investigation Veliger Trochophore
1979 10 27.8 34.7
1980 9 1.3 19.1
2001 10 1.0 --
2002 7 0.4 --
ACKNOWLEDGMENTS The authors thank Dr. Toyomitsu Horii and Dr. Satoshi Watanabe, National Research Institute of Fisheries Science, for their critical reading of this manuscript. LITERATURE CITED Anonymous. 1990. Discharge fishery advanced use technical development enterprise. In: Aomori, Iwate, Akita, Kanagawa & Fukuoke, editors. Abalone seeds-and-saplings discharge manual. Anonymous. 1980. Large-scale multiplication multiplication, fundamental operation in arithmetic and algebra. Multiplication by a whole number can be interpreted as successive addition. For example, a number N multiplied by 3 is N + N + N. place development-work results-of-an-investigation report in the 1979, 1980 r (East Awa area: H. discus). Chiba Prefectural pre·fec·ture n. 1. The district administered or governed by a prefect. 2. The office or authority of a prefect. 3. The residence or housing of a prefect. Government, Fisheries Research Center. 1-182. Anonymous. 1981. 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Some eat both plant and animal matter; others eat only one type of food. , and the elucidation e·lu·ci·date v. e·lu·ci·dat·ed, e·lu·ci·dat·ing, e·lu·ci·dates v.tr. To make clear or plain, especially by explanation; clarify. v.intr. To give an explanation that serves to clarify. of substance. An endocrine-disruptors research presentation meeting summary, pp. 65-66. Horii, T. 1998. About the increase of fish catch intensity and the miniaturization min·i·a·tur·ize tr.v. min·i·a·tur·ized, min·i·a·tur·iz·ing, min·i·a·tur·iz·es To plan or make on a greatly reduced scale. min of a fish catch individual which were produced by H. discus seeds-and-saplings discharge. Suisanzo Shoku. 46(1):13-17. Kawajiri, M., T. Sasaki & Y. Kageyama. 1981. Extensive deterioration de·te·ri·o·ra·tion n. The process or condition of becoming worse. of the Ecklonia kelp stands and death of the plants, and fluctuations in abundance of the abalone off Toji, Southern Izu Peninsula Izu Peninsula Peninsula, central Honshu, Japan. It extends 37 mi (60 km) into the Pacific Ocean and consists largely of volcanic rock and highly eroded volcanoes. It is part of the Fuji-Hakone-Izu National Park, and its hot springs and warm winter climate are major tourist . Bull. Shizuoka Pref Fish. Exp. Stn. 15:19-30. Kojima, H. 1974. The habitat of young black-abalone. Haliotis discus discus Reeve REEVE. The name of an ancient English officer of justice, inferior in rank to an alderman. 2. He was a ministerial officer, appointed to execute process, keep the king's peace, and put the laws in execution. in Kaifu-gun. Tokushima prefecture. Nippon Suisan Gakkaishi 10(6):155-160. Kojima, H. 1981. Mortality of young Japanese black Japanese black breed of cattle developed by crossing one of the indigenous breeds of Japanese cattle with European cattle. Black, horned (some polled), small, fine-boned; used principally for meat, some draft, occasionally milk. Similar breeds are Japanese brown, Japanese polled. abalone Haliotis discus discus after transplantation. Nippon Suisan Gakkaishi 47(2): 151-159. Nishima, K. & T. Ito, & O. Ezaki. 1989. Research-II about fish-farm-izing of useful seashore Animals about the discharge method of H. discus seeds and saplings. Bull. Fukuoka Pref. Fish. Exp. Stn (15). Nonaka, T. 1987. Change of an abalone fish catch--II Relation with fish catch regulation. Cultivation Technical Research Report. 16(2):149-154. Sakai, M. 1962. Ecological studies on the abalone, Haliotis discus hannai ino-III. Study on the mechanism of production of the abalone in the region of Onagawa bay. Nippon Suisan Gakkaishi 28(9):891-898. Sakamoto, H. 1979. 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The Consideration of the Abalone Stock Decrease Factor in Chiba Prefecture. Bull. Chiba pref. Fish. Exp. Sin. 57:229-235. Tachiyama, T., K. Fukagawa & N. Shirohara. 1998. Consideration of the resource change factor of H. discus in the Chikuzen Ocean. Bull. Fukuoka Fish. & Marine Tech. Res. Cen. 8:31-35. Tanaka, T. 2001. The insect damage test of the abalone seed by the existence of the Anthocidaris. Bull. Chiba pref. Fish. Exp. Stn. 57:221-227. Tanaka, T. & J. Sakamoto. 2001. A Comparison between recovery rate and discharge size, technique of abalone seed. Bull. Chiba pref. Fish. Exp. Stn. 57:237-239. Tanaka, T. & K. Tanaka. 1982. About the abalone young clam place of the beach Namegawa. Bull. Chiba pref. Fish. Exp. Stn. 40:83-97. Tanaka, T. & S. Ishida. 1993. abalone the appearance situation of a flouting larva larva, in zoology larva, independent, immature animal that undergoes a profound change, or metamorphosis, to assume the typical adult form. Larvae occur in almost all of the animal phyla; because most are tiny or microscopic, they are rarely seen. . Bull. Chiba pref. Fish. Exp. Stn. 41:1-10. Tanaka, T. & S. Kasai. 2000. On grounding situation of the abalone at Chikura, Chiba Chikura (千倉町; -machi) is a town located in Awa District, Chiba, Japan. As of 2003, the town had an estimated population of 12,599 and a density of 343.86 persons per km². The total area was 36.64 km². Prefecture. Bull. Chiba pref. Fish. Exp. Sin. 56:31-33. Tanaka, T., T. Simizu & H. Mita. 2000. Changes of the biota biota /bi·o·ta/ (bi-o´tah) all the living organisms of a particular area; the combined flora and fauna of a region. bi·o·ta n. The flora and fauna of a region. on the rocky shores Rocky shore is an intertidal area on seacoasts where solid rock predominates. Rocky shores are biologically rich environments, and make the ideal natural laboratory for studying intertidal ecology and other biological processes. of Sotobo Coast, Chiba Prefecture. Changes of the Biota on the Rocky Shores of Sotobo Coast, Chiba Prefecture. Tanaka, K. & T. Tanaka. 1986. Changes of the biota on the rocky shores of Sotobo Caost, Chiba Prefecture. Bull. Chiba pref. Fish. Exp. Stn. 56:35-45. Tanaka. K., S. Ishida & T. Tanaka. 1986. On the weight loss of abalone around Mera Shoal in the Southern Coast of the Boso Peninsula I. On the distribution of abalone. Bull. Japan Sea Natl. Fish. Res. Inst. 36: 49-57. Yamada, N., N. Kamimura & T. Otaki. 1973. Fundamental studies on the prevention of seawater seawater Water that makes up the oceans and seas. Seawater is a complex mixture of 96.5% water, 2.5% salts, and small amounts of other substances. Much of the world's magnesium is recovered from seawater, as are large quantities of bromine. pollution in the Coast of Izu Peninsula Shizuoka Prefecture-II. Bull. Shizuoka pref. Fish. Exp. Stn. 6:53-57. Yamakawa, K. 1990. The wear factor in the discharge early stages of abalone seeds and saplings. Fisheries Engineering 26(2):33-39. KANAKO UCHINO, ** TOSIATU SIMIZU, TANEO TANAKA, AND TERUKAZU SHIBATA Chiba Prefectural Government, Fisheries Research Center ** Corresponding author. E-mail: k.uchn2@mc.pref.chiba.jp |
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