Black Abalone Research Articles

Continued declines of black abalone along the coast of California: are mass mortalities related to El Niño events?

The intertidal black abalone Haliotis cracherodii has experienced mass mortalities along the coast of California, USA, since the mid-1980s. Mortality is due to infection by a pathogen that leads to a fatal wasting disease called 'withering syndrome', where the foot of the abalone atrophies until it can no longer adhere to the substratum. Massive die-offs due to withering syndrome were first noted on the Channel Islands in 1986, and by 1992 withering syndrome was observed near Point Conception on the mainland and was suspected to be spreading northward up the coast of California. The timing of the initial mass mortalities following the strong 1982 to 1983 El Nino and an isolated outbreak of withering syndrome in 1988 at Diablo Cove, north of Point Conception, following warm water dis- charge from a power plant, led to the hypothesis that the onset of mass mortalities due to withering syndrome may be triggered by elevated seawater temperatures. We surveyed black abalone popula- tions at 7 sites along the mainland coast of California (including 3 where withering syndrome was al- ready present) from 1992 to 2001, a period spanning 2 El Nino events, to determine whether (1) with- ering syndrome and associated declines of black abalone were spreading northward up the coast; and (2) these mass mortalities of black abalone could be related to elevated seawater temperatures during El Nino events. Mass mortalities of black abalone due to withering syndrome were observed at the 5 most southern sites (>90% decline in numbers in all size classes), but not at the 2 most northern sites, and there was a clear pattern of decline from south to north over time. Massive die-offs of abalone were not exclusively associated with times of elevated sea surface temperatures due to El Nino. Nev- ertheless, rapid declines of abalone at 2 sites coincided with the strong 1997 to 1998 El Nino, and de- clines during El Nino events were faster than those during non-El Nino years. Abalone at the 2 most northern sites, where only slight declines occurred during the 1997 to 1998 El Nino, may not have been infected by disease. It appears, therefore, that in the presence of the pathogen, warm water conditions associated with El Nino may accelerate the development of withering syndrome and the rate of decline of black abalone. Consequently, anthropogenic disturbances, such as discharges of heated water or global warming, may increase the incidence of this fatal disease.

Combined effects of pentachlorophenol and salinity stress on chemiluminescence activity in two species of abalone

The effect of pentachlorophenol (PCP) combined with salinity stress on hemocyte microbicidal activity was examined in two species of abalone. Microbicidal phagocytic function was determined in red ( Haliotis rufescens) and black ( Haliotis cracherodii) abalone after in vivo exposure to 25, 35 and 45‰ seawater salinity plus 1.2 mg/l PCP using luminol-dependent chemiluminescence (CL). Red and black abalone exposures of 3.5 and 6.5 h, respectively, were based on species-specific metabolic endpoints (MEPs) derived from previous nuclear magnetic resonance spectroscopy (NMR) data. Endpoints examined include total CL (CL total), peak CL (CL max), and the time to reach peak CL ( T max). Overall, black abalone CL was significantly greater than red abalone CL particularly at ambient and high salinities. High salinity alone had a dramatic effect on red abalone whereas black abalone demonstrated few salinity effects. While the addition of PCP stimulated CL max and CL total among red abalone at ambient and high salinities, PCP exposure inhibited CL max at each salinity and inhibited CL total at ambient salinity among black abalone. Black abalone generally did not demonstrate effects of PCP within the 3.5 h exposure period except at high salinity plus PCP, which caused a reduction of CL total. T max was greatly increased after PCP exposure at each salinity among red abalone but did not effect T max at any salinity tested among black abalone. No lysozyme activity was detected among red or black abalone after exposure to any of four different target particles tested either in the presence or absence of PCP. Overall, PCP in combination with salinity stress causes a modulation in the production of reactive oxygen species and this modulation varies between abalone species. Agents that decrease CL activity in hemocytes may reduce the antimicrobial potential of these cells thereby increasing susceptibility to infectious disease.

Population genetics of black abalone, Haliotis cracherodii, along the central California coast.

Over the past three decades, the black abalone, Haliotis cracherodii, has experienced precipitous declines in abundance over portions of its range in southern and central California. The potential for recovery of these populations is dependent in part on dispersal processes; that is, can distant populations serve as sources of recruits to locales that no longer harbor H. cracherodii? Here we use population genetic analysis to assess levels of population subdivision and infer recruitment processes. Epipodial tissue samples were obtained from over 400 black abalone from seven geographic sites between Santa Cruz and Santa Barbara counties in central California. Allelic frequencies were determined for each population at three polymorphic enzyme-encoding loci (GPI, AAT-1 and PGM). Significant allelic frequency differentiation among sites was observed at all three loci. Genetic distance was found to be independent of geographic distance over the approximately 300-km sampling range. In addition, a limited number of DNA sequences (total N=51) were obtained for the mitochondrial cytochrome oxidase subunit I gene (COI) from five of the populations. Since the same common COI haplotype dominated each population, this analysis had little statistical power and failed to detect population structure. The observed level of population differentiation at allozyme loci was three-fold higher than that observed in California red abalone, H. rufescens. The species differ in their breeding period and it is suggested that the relatively short, summer breeding season of black abalone limits dispersal because larvae experience reduced variance in oceanographic conditions relative to red abalone that spawn year-round. Based on these results, rates of recolonization and recovery of locally depressed or extirpated black abalone populations are likely to be slow despite harvest restrictions.

Combined effects of pentachlorophenol and salinity stress on phagocytic and chemotactic function in two species of abalone

The effect of pentachlorophenol (PCP) combined with salinity stress on specific aspects of cellular immunity was examined in two species of abalone. Chemotactic and phagocytic ability (percent phagocytosis, % P; and phagocytic index, PI), as well as gross morphological characteristics, of hemocytes withdrawn from red ( Haliotis rufescens) and black abalone ( H. cracherodii) after in vivo exposure to 25, 35, or 45‰ seawater salinity plus 1.2 mg/l PCP were determined. Abalone exposures of 3.5 and 6.5 h, respectively, were based on species-specific metabolic endpoints (MEPs) derived from previous NMR data. Hemocyte chemotaxis was found to be augmented by low salinity in red but not black abalone, while high salinity seemed to reduce chemotactic ability in both species. PCP did not potentiate the effects demonstrated by salinity variations alone in red abalone, although chemotaxis was further compromised in black abalone exposed to high salinity stress combined with PCP. Although chemotactic ability was similar among both species, both % P and PI was greater among black abalone. Low salinity may offset the effects of PCP in red but not black abalone. Whereas red abalone demonstrated a reduction in phagocytic ability upon exposure to high salinity alone, black abalone appeared more resilient to high salinity stress alone. Furthermore, while the effect of high salinity plus PCP is subadditive among red abalone, high salinity seems to potentiate the effect of PCP on black abalone. Finally, hemocytes exposed to acute salinity variations plus PCP showed varying morphological characteristics when compared to controls. Over 30% of hemocytes of high salinity plus PCP exposed abalone remained rounded and generally unattached to glass slides with only a few pseudopod extensions. Hemocyte preparations incubated in rhodamine-conjugated phalloidin were observed with fluorescence microscopy and reveal an altered actin filament pattern. Overall, black abalone demonstrate greater phagocytic ability than red abalone both in the presence and absence of PCP. Furthermore, increases in salinity are accompanied with reduced phagocytic ability with red abalone demonstrating particular sensitivity to salinity variations. While PCP inhibits ATP synthesis, salinity variations may impose an additional stress on intertidal animals exposed to transient or seasonal environmental changes.

Withering Syndrome in Farmed Red Abalone Haliotis rufescens: Thermal Induction and Association with a Gastrointestinal Rickettsiales-like Prokaryote.

Withering syndrome (WS) is a chronic wasting disease responsible for mass mortality in wild populations of black abalone Haliotis cracherodii. The etiology of WS is uncertain with limited evidence for the role of a gastrointestinal Rickettsiales-like prokaryote (RLP). We documented for the first time the occurrence of animals with clinical signs of WS and associated morphological changes in another haliotid species, the red abalone H. rufescens. In this study, 60 juvenile red abalone (8 cm) were randomly selected from a farmed population raised at 14°C that was known to have low-intensity RLP infections but lacked clinical signs of WS. The abalone were held in triplicate containers receiving water of approximately 14.7°C (Control, Co) or 18.5°C (elevated temperature, ET) and were fed equally for 220 d. Survival was 100% (30/30) for the Co group and 67% (20/30) for the ET group. The ET group animals had higher RLP infection intensities and showed more clinical signs (mantle retraction, lower weight gain, lower condition index) and morphological changes (digestive gland degeneration) associated with WS. In trials conducted immediately before termination of the experiment, ET group animals fed at half the rate of Co group animals. Among ET group animals, the intensity of RLP infections in the posterior portion of the esophagus was positively correlated with WS clinical signs and morphological changes, whereas no correlations were present among Co group animals. During 1997-1998 and in conjunction with elevated seawater temperatures associated with El Niño, several abalone farms in California experienced a dramatic increase in the proportion of red abalone showing signs of WS. Examination of 66 red abalone from five commercial farms revealed that animals with more advanced RLP infections had more severe WS clinical signs and associated morphological changes. Collectively, these data demonstrate that RLP infection plays a key role in the etiology of WS in red abalone and that warm water enhances the severity of the pathogenic effects of RLP infection.

Detection of Rickettsiales-like Prokaryotes by in Situ Hybridization in Black Abalone, Haliotis cracherodii, with Withering Syndrome

Detection of Rickettsiales-like Prokaryotes by in Situ Hybridization in Black Abalone, Haliotis cracherodii, with Withering Syndrome

Workshop “Emerging Diseases of Cultured Marine Molluscs in Japan”

A workshop entitled “Emerging diseases of cultured marine molluscs in Japan” was held by the Japanese Society of Fish Pathology in Sendai on 25th September 1999. This was aimed to have an overview of the researches on the mass mortality of cultured pearl oyster (Pinctada fucata martensii) occurring in Japan. Prior to the main subject, two diseases, amyotrophia of Japanese black abalone (Nordotis discus discus) and abnormal coloration of adductor muscle in Japanese scallop (Patinopecten yessoensis), were presented, both being suspected to be infectious diseases caused by filterable agents. Since 1994 mass mortalities of pearl oyster have occurred in western Japan, giving much economic losses to the pearl culture industry. Various factors such as blooms of toxic dinoflagellate Heterocapsa circularisquama, perkinsosis, virus or filterable agent infection, and environmental factors were suspected as causes of the mortality. In the workshop, invited speakers gave talks on the history of pearl oyster culture, results of epizootiological observations, histopathological examinations, microbiological examinations, and infection experiments, and their own views of the etiology of the disease. At present, although the causative virus has not been determined, the viral etiology seems to be most probable, and some environmental parameters such as high water temperature might affect the mass mortality.

A virus isolated from juvenile Japanese black abalone Nordotis discus discus affected with amyotrophia

A virus isolated from juvenile Japanese black abalone Nordotis discus discus affected with amyotrophia

Influence of salinity on the actions of pentachlorophenol in haliotis as measured by in vivo 31P NMR spectroscopy

The actions of pentachlorophenol (PCP) under various water salinities was investigated in live, intact red ( Haliotis rufescens) and black abalone ( H. cracherodii) by in vivo 31P nuclear magnetic resonance (NMR) spectroscopy. Based on PCP toxicity in red abalone (6 h LC 50 1.6 mg l −1; 6 h NOEL=0.8 mg l −1), animals were exposed in flowing seawater (14°C) to a sublethal PCP concentration of 1.2 mg l −1 and a water salinity of either 25, 35 or 45 ‰. Phosphagen changes in foot muscle were monitored by surface-probe localized 31P NMR. Upon PCP exposure, phosphoarginine (PA) levels declined and inorganic phosphate (Pi) levels concurrently increased. Dosing was terminated at a standard metabolic endpoint (MEP), defined as the time for the spectral peak height for Pi to reach one-half that of PA. This was on average 3.3±0.2 and 6.8±0.7 h at ambient salinity; 5.3±0.7 and 7.1±0.7 h for high salinity; and 4.0±0.5 and 6.5±1.0 h at low salinity, for red and black abalone, respectively. During recovery, all biochemical endpoints returned to normal; however, both onset and intensity of effects were influenced by changes in seawater salinity. Disposition of [U- 14C]PCP in both species was also examined to determine if the effects observed with NMR had a kinetic basis. Three sets of abalone ( n=3) from each species were exposed to each salinity (25, 35 and 45 ‰), plus 1.2 mg l −1 of [U- 14C]PCP. Red abalone were exposed for 3.5 h and black abalone for both 3.5 and 6.5 h (they represent the lowest average MEP for both species). Residues were quantified via tissue digestion and liquid scintillation counting. The 3.5 h total concentration factors (TCFs) for red abalone were not significantly different among the three salinities ( P>0.05) and ranged from 104 to 133. However, low salinity seemed to deter the uptake of [U- 14C]PCP in black abalone, as the TCF was over three times lower for abalone exposed to 25 ‰ at both 3.5 h (TCF=19±11) and 6.5 h (TCF=38±8) than at 35 ‰ (3.5 h TCF=62±6; 6.5 h TCF=119±11) and 45 ‰ (3.5 h TCF=67±14, 6.5 h TCF=115±8). Furthermore, the 3.5 h TCF for red abalone exposed to PCP at all salinities was similar to the 6.5 h TCF for black abalone exposed at 35 and 45 ‰. Thus, black abalone appear to have greater resistance to the combined effects of PCP and salinity variations, which appears to be due to slower uptake of the biocide. While PCP is a potent uncoupler of mitochondrial oxidative phosphorylation, use of varying water salinities simulated an additional stress imposed on intertidal animals by transient or seasonal environmental changes.

Primary Culture of Hemocytes From Japanese Black Abalone Nordotis discus discus.

Primary Culture of Hemocytes From Japanese Black Abalone Nordotis discus discus.

Studies on the feeding attractants for fishes and shellfishes. XXVI. Probable feeding attractants in allspice Pimenta officinalis for black abalone Haliotis discus

The attraction activity of allspice Pimenta officinalis was statistically estimated based on the exploratory and feeding behaviour of the black abalone Haliotis discus. The ether fraction (oils) from the water extract of allspice was the most attractive. The essential oil of allspice was separated into four fractions (phenolic, acidic, neutral and basic) by extraction using a mixture of pentane-dichloromethane (1:1, v/v). The neutral fraction was the most attractive. This fraction was further separated into eight fractions using Silicagel 60 (Merck) with a series of pentane-ether mixtures of various ratios. The fraction eluted with a pentane-ether solution at a ratio of 50:50 was the most attractive. A gas chromatogram of the eluate showed the presence of many diverse components. Each peak was identified by combined gas chromatography-mass spectrometry. Among the components identified, ten representative specimens were selected and examined for their attraction, ϱ-cymene, β-elemene and α-terpineol were effective attractants, while β-elemene was the most attractive. The attraction activity of β-elemene increased appreciably at higher concentrations. Other components that were weak or not effective attractants were β-caryophyllene, eugenol, methyl eugenol, linalool, linalool oxide, terpinen-4-ol and β,-γ-terpineol.

Recent declines of black abalone Haliotis cracherodii on the mainland coast of central California

Recent declines of black abalone Haliotis cracherodii on the mainland coast of central California

Association of Prokaryotes with Symptomatic Appearance of Withering Syndrome in Black Abalone Haliotis cracherodii

Withering syndrome (WS) is an epizootic fatal wasting disease that is devastating California Channel Island populations of block abalone Haliotis cracherodii. Our studies suggest a strong pathogen-disease association. The pathogen is an intracellular prokaryote that infects epithelial cells lining the gut and enzyme secreting cells of the digestive diverticula. It multiplies by binary fission in round to oval, basophilic, membrane-bound colonies teeming in the cytoplasm. Infection of the digestive diverticula is accompanied by a complete loss of digestive enzyme granules and metaplasia of enzyme secretory cells to a morphology similar to epithelium lining the gut. Extensive infection of digestive diverticular cells and the resultant deficiency in digestive enzymes correlates to the degree of pedal muscle atrophy and the severity of signs associated with WS. Electron microscopically the intracellular pathogen is a rodshaped, ribosome-rich, gram-negative, prokaryote with a trilaminar cell wall consistent with the order Rickettsiales. Microbiological and protozoological methods produced no patterns that implicated other types of microbes. Chemical analysis of tissue from animals from a population with WS did not support an association between WS and environmental pollutant exposure to polycyclic aromatic hydrocarbons, polychlorinated biphenyls, or chlorinated pesticides.

Chemoattractant effects of sugars and their related compounds on black abalone Haliotis discus

The chemoattractant properties of sugars and their related compounds were statistically estimated on the basis of an exploratory behavior of black abalone Haliotis discus. Six monosaccharides, three disaccharides, six sugar alcohols, six glycosides and two artificial sweeteners were tested. The active compounds were: glucose and galactose (monosaccharides), maltose (disaccharides), sorbitol, mannitol, maltitol, dulcitol and erythritol (sugar alcohols), all the glycosides, and saccharin (artificial sweeteners). Maltose, dulcitol and particularly phyllodukin showed the highest activity. The chemoattractant properties of maltose and phyllodukin increased as concentrations increased. The activity of phyllodulcin was higher at all concentrations tested than that of maltose.

Kinetic and Structural Adaptations of Cytoplasmic Malate Dehydrogenases of Eastern Pacific Abalone (Genus Haliotis) From Different Thermal Habitats: Biochemical Correlates of Biogeographical Patterning

ABSTRACT We measured the effects of temperature on cytosolic malate dehydrogenases (cMDHs) from the shell muscle of five species of eastern Pacific abalone, genus Haliotis, found at different latitudes and/or tidal heights. The apparent Michaelis–Menten constant (Km) of coenzyme (nicotinamide adenine dinucleotide, NADH) was conserved within a narrow range (11–21 μmol l−1) at physiological temperatures for all species. However, elevated temperatures perturbed the Km of NADH for cMDHs of the two species living at higher latitudes and/or lower tidal heights [Haliotis rufesens (red) and H. kamtschatkana kamtschatkana (pinto)] to a much greater extent than for cMDHs of congeners from lower latitudes and/or higher tidal heights [H. fulgens (green), H. corregata (pink) and H. cracherodii (black)]. The apparent Arrhenius activation energies for the cMDHs of these five species showed a similar interspecific divergence. Furthermore, green, pink and black abalone have cMDHs that are more resistant to thermal denaturation than are cMDHs of red and pinto abalone. Native gel electrophoresis showed that cMDHs of red and pinto abalone had identical mobilities, whereas cMDHs of green, pink and black abalone are distinct both from each other and from that of the two cold-adapted species. These data suggest that cMDHs from the abalone species living in warm habitats are adapted to function optimally at higher temperatures than are the cMDHs of the two species living in cooler habitats. The relationships suggested by these criteria are in agreement with other studies that used morphological and molecular indices to predict abalone phylogeny. These results therefore provide further evidence that interspecific variation in protein structure and function may be driven by natural selection based on only small (i.e. several degrees Celsius) differences in average body temperature, and that such selection is an important element of the mechanisms of species formation and the maintenance of biogeographic patterning.

Effects of Temperature on Mitochondria From Abalone (Genus Haliotis): Adaptive Plasticity and its Limits

ABSTRACT The effects of temperature on mitochondrial oxygen consumption, membrane fluidity and cytochrome c oxidase activity were measured for five species of eastern Pacific abalone (genus Haliotis) found at different latitudes and tidal heights. Mitochondria were isolated from freshly collected individuals and from specimens that had been acclimated in the laboratory to temperatures spanning the extremes of each species’ known habitat temperature range. The temperatures at which Arrhenius plots of respiration rate of mitochondria from freshly collected abalone exhibited sharp breaks in slope were found to correlate with the habitat temperature at the time of capture of each species. Membranes isolated from freshly collected abalone living at warm temperatures (Haliotis cracherodii and H. corregata) were significantly less fluid (as determined by the fluorescence polarization of the probe 1,6-diphenyl 1,3,5-hexatriene) than were membranes from species captured at cooler temperatures (H. rufesens and H. kamtschatkana kamtschatkana). Laboratory acclimation significantly shifted the temperature of mitochondrial thermal inactivation in an adaptive manner in the eurythermal species, H. fulgens, H. corregata and H. rufesens, but did not alter this property significantly for mitochondria from the stenothermal species, H. k. kamtschatkana. Laboratory acclimation resulted in temperature-compensatory changes in membrane fluidity in all species except H. rufesens. The temperatures at which cytochrome c oxidase activity was inactivated also shifted in an adaptive manner in some species. Acclimation of mitochondrial respiration, membrane fluidity and cytochrome c oxidase activity occurred only over the ranges of temperature at which each species is common, suggesting that there is a relationship between acclimatory ability and the biogeographical distribution of congeneric species.

Measurement of Significant Marine Paleotemperature Variation Using Black Abalone Shells from Prehistoric Middens

The archaeological record from the last millennium in southern California indicates that a period of significant cultural change was associated with a reported marine paleoenvironmental disruption ca. 1150-1250 A.D. A lengthy warm-water anomaly may have in part precipitated more complex sociopolitical and economic responses. We develop independent verification of the perturbation (originally deduced from sediment core data) using archaeological data. Respiratory pore number allometry in the black abalone shell is known to vary clinally in modern populations in response to temperature-induced variation in rate of growth. We use developmental trajectories of abalone from dated, stratified archaeological deposits to reconstruct prehistoric seawater temperatures.

Studies on feeding repellents for fishes and shellfishes

The present study on chemotaxis activity was conducted between May 1989 and March 1990. In order to establish a chemotaxis index, with special reference to a repellence index of food for black abalone Haliotis discus, a logistic curve y=g/{1+ exp [-r(j-a)]}, where g, r and a are constants, was applied to time-courses of abalone responses to fresh and spoiled algal extracts. The time-courses were respresented by the number of individuals (yi) displaying three behaviors (entering. leaving and remaining in a test compartment with algal sample) over time (j=1 to 10, 2-min intervals). Repellence and attraction specimens were prepared from a homogenate of green laver Ulva pertusa allowed to spoil for 2, 4 and 6 d at 40°C, and from fresh homogenate, respectively. Of 32 time-courses (estimated according to a method whereby the observed number was weighted by j for each behavior, involving 30 individuals), 32 “entered”, 19 “left” and 19 “remained” time-courses fitted the curve at the 0.10 level, as determined by a chi-square test. A general evaluation of repellence and attraction, determined by observable behavior, agreed well with the difference in a between the dummy (control) and specimen curves, and with the ratio of a in the dummy curve to a in the specimen curve, for logistic curves fitted to the “entred” time-course. The difference was >0 and the ratio was >1 in the repellence index, and <0 or <1 respectively in the attraction index. The validity of the indexes was ascertained using food specimens prepared from three kinds of algae.

A method for estimating mortality rate and divers' sighting rate for tagged abalones.

This paper proposes a method for estimating the mortality rate and divers' sighting rate by taking the effect of movement of abalones into consideration, from the data of the number of alive and dead abalones counted by divers at survey day and the initial number of tagged abalones. The abalones are classified into four states by the combination from the elements as alive or dead and observable or unobservale. The probabilities for the states at survey day t are presented by a stationary Markov chain. The probabilities which an abalone is sighted alive or dead at t are given by the products of the probabilities of the divers' sighting and the probabilities for the alive or dead states in the observable. The log-likelihood function L is obtained from the multinominal distribution. The unknown parameters are estimated. by maximizing L. The variance-covariance matrix of the estimates is approximately given by the inverse of the information matrix. The values of the parameters for maximizing L are found by Davidon's variable metric method. Furthermore, the method is applied to the data of Japanese black abalone Haliotis discus discus in the coast off Chiba Prefecture. The estimates of the mortality rate per day are about 3.2% for group 1 (10-24mm) and 0.64% for group 2 (22-30mm). The true values of the sighting rate for alive abalones are 41% at one day after releare, 23% at six, 20% at fourty five for group 1, and 37%, 15% and 13% for group 2, respectively. The limitations of the application and the modification of the method are discussed.

Studies on the Feeding Attractants for Fishes and Shellfishes-XIX. Attraction Activities of Herbal Crude Drugs for Abalone, Oriental Weatherfish, and Yellowtail.

The attraction activities of herbal crude drugs were statistically estimated on the basis of exploratory behavior of three aquatic test animals; the black abalone Haliotis discus, the oriental weatherfish Misgurnus anguillicaudatus, and the yellowtail Seriola quinqueradiata. Among twenty-three herbal crude drugs, the common attractive drugs for all test animals were following three drugs; Herba plectranthi (En'meisou in Japanese) and Phellodendron bark (Ohbaku) of bitter stomachic, and sweet Hydrangea leaf (Amacha) of corrective. The most potent attractive drugs were Amomum seed (Shukusha) of fragrant and pungent stomachic for abalone, guarana seed (Garana) of cardiac stimulant for oriental weatherfish, and Gentian (Genchana) of bitter stomachic for yellowtail. The attraction activity of each of these drugs increased appreciably with the increase in concentration (0.1-3.0%) for oriental weatherfish and yellowtail, but decreased at high concentrations for abalone.