Ear Abalone Research Articles

The Potential of Donkey’s Ear Abalone (Haliotis asinina Linnaeus, 1758) as an Antibacterial Agent and Its Effect on Blood Cholesterol Reduction in Mice (Mus musculus Linnaeus, 1758)

The Potential of Donkey’s Ear Abalone (Haliotis asinina Linnaeus, 1758) as an Antibacterial Agent and Its Effect on Blood Cholesterol Reduction in Mice (Mus musculus Linnaeus, 1758)

Distinct impacts of growth band on the mechanical properties of abalone nacre under compressive and tensile stresses

In abalone nacre, growth bands occur periodically with the change of living environments. To explore the specific role of growth bands playing in the mechanical properties of nacre, the compressive and three-point bending behaviors of composites with growth bands in green abalone shell and pure nacre without growth bands in whitened ear abalone shell were comparatively investigated. It is found that the mechanical effects of growth bands under different stress states are significantly distinct, mainly attributing to the different responses of organic matrix interlayer in growth bands. Specifically, due to the remarkable ductility of thicker organic matrix interlayer under the action of compressive stress, the growth bands could be bent without fracturing in the region of kink band. However, the existence of growth bands leads to a lower interfacial strength, finally causing the fact that the composites with growth bands exhibit a lower strength but a higher toughness than pure nacre under uniaxial compression tests. Contrastively, both the strength and toughness of the composites are lower than those of pure nacre under three-point bending tests, since micro-cracks will be first initiated in growth bands on account of the weaker organic matrix interlayer under tensile stress. Therefore, the growth bands actually play different roles in the mechanical performances of nacre under compressive and tensile stresses.

First Histopathological Description of Parasites and Shell Conditions of the Donkey's Ear Abalone Haliotis asinina (Linnaeus, 1758) Cultured in Marine Cages and Land-Based Tanks in the Philippines

This study is the first attempt to assess parasitic infestations in grow-out cage culture and land-based grow-out tanks of the donkey's ear abalone Haliotis asinina in the Philippines. This histopathological study of the parasites was conducted from 2010 to 2013. Using 30 samples of abalones collected monthly from two sites, samples were measured and fixed in 10% formaldehyde in seawater, and routine histological techniques were used to identify the parasites. Water temperatures of the grow-out floating sea cages and the abalone hatchery facilities whose abalones were collected measured 27.5°C–32.5°C and 26°C–29°C, respectively; salinity in the area of the sea cages was 32–34 ppt, whereas salinity of the abalone hatchery was 32–35 ppt. Examination of the shell from cage-cultured abalones revealed the presence of burrowing polychaetes belonging to the families Serpulidae (prevalence, 32.5%) and Dorvilleidae (prevalence, 30%); on the other hand, only Dorvilleidae (prevalence of 28.5%) was detected in abalones from the hatchery. Histological examination revealed the presence of unknown ciliates (prevalence, 37.5%), Nematopsis sp. (prevalence, 17%), and metacestode Tylocephalum sp. (prevalence, 8.5%) from the grow-out cage-cultured abalones, whereas unidentified ciliates (prevalence, 32.5%) and Nematopsis sp. (prevalence, 10.5%) were detected from hatchery stock. The data collected showed that there was low-intensity infection and prevalence of parasites in abalones from grow-out cages and hatchery. These records of parasites constitute baseline information for future research work on abalones.

Stock enhancement of abalone, Haliotis asinina, in multi-use buffer zone of Sagay Marine Reserve in the Philippines

Donkey's ear abalone (Haliotis asinina) is a gourmet seafood export of the Philippines but its wild stock is at risk due to high fishing pressure. This paper aims to show evidences that abalone seeds produced in hatcheries can be used to rehabilitate its fisheries in multi-use buffer zones of marine reserves. This study released hatchery-reared abalone juveniles in a community-based resource enhancement site located in multi-use reef surrounding Molocaboc. This island is populated by fisherfolks who participated in protecting the 4000 m2 coralline release site. Molocaboc Reef comprise the buffer zone of Sagay Marine Reserve in Negros Occidental province in central Philippines. Data obtained during monthly monitoring of the release site from 2011 to 2016 showed that hatchery-reared abalone established together with its wild counterparts. Baseline wild abalone catch per unit effort (CPUE = 3 divers 1 h fishing) is 0.005/100 m2 in 2011. Mean monthly CPUE after release increased to 53 hatchery-reared and wild individuals combined. The mean shell length, body weight and body mass index of the hatchery-reared individuals (6.4 cm, 70.9 g, 10.5 g/cm) is not significantly different from those of the recovered wild stocks (6.9 cm, 85.0 g, 12.0 g/cm). The stocks recovered in the midst of undisrupted fishing activities in areas immediately outside and beyond the release site. Thus, mass production of seeds of overfished species is advised to repopulate degraded fisheries, improve catch of fisherfolks living within buffer areas of marine reserves and contribute to production and trade of high-value species.

Isolation and Characterization of Antimicrobial-Producing Bacteria from the Donkey's Ear Abalone Haliotis asinina

This study was conducted to isolate, test the antimicrobial potential, and characterize bacterial isolates from the gut of Haliotis asinina collected from cage culture and wild population. Isolation was performed using dilution spread plate method and antimicrobial property was determined using streak plate method against nine test microorganisms. Results showed that of the 29 isolates from the cage-cultured samples, five isolates showed the presence of antimicrobial property against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, and Candida albicans. Among the 30 isolates from the wild-caught samples, six isolates showed the presence of antimicrobial potential when tested against E. coli, S. aureus, B. cereus, B. subtilis, B. megaterium, and C. albicans. None of the isolates inhibited Aspergillus niger or Aspergillus flavus. The bacterial strain coded C28, isolated from cage-cultured abalone, and that inhibited the most test microorganisms was subjected to cultural, morphological, and physiological characterization. It was characterized as a bacterial strain closely related to the genus Pseudomonas. The results suggest that bacteria in the gut of H. asinina have potential antimicrobial properties where bacteria related to Pseudomonas spp. are present.

CO2-induced pH Reduction Hinders Shell Development of Early Larvae Donkey's Ear Abalone Haliotis asinina (Linnaeus 1758)

CO2-induced pH Reduction Hinders Shell Development of Early Larvae Donkey's Ear Abalone Haliotis asinina (Linnaeus 1758)

Effects of reduced pH on the early larval development of hatchery-reared Donkey's ear abalone, Haliotis asinina (Linnaeus 1758)

Declining pH levels caused by absorption of accumulating atmospheric CO2 in the ocean threaten the normal development of early life stages and particularly impair the ability of calcifying organisms to construct their shells. An experiment was conducted to determine the direct effects of reduced pH on % hatching of fertilized eggs, survival and developmental stages of trochophore larvae of the Donkey's ear abalone, Haliotis asinina. The ambient pH (7.97±0.02) of experimental seawater was reduced by bubbling food-grade CO2 to obtain the desired pH levels of 7.78±0.03, 7.60±0.03 and 7.40±0.02 as treatments. There were increasing negative impacts of reduced pH on the mean % hatched trochophores (97.6 at ambient pH conditions, 83.9 at pH7.78, 24.1 at pH7.60, and 1.4 at pH7.40). Significant impacts of reduced pH were also observed on mean % survival of trochophores (98.3 at ambient pH conditions, 84.9 at pH7.78, 24.1 at pH7.60, and 1.4 at pH7.40). Of the surviving trochophores, 23.2±3.2% (mean±sd) of those exposed to pH7.60 were morphologically deformed but in much lower pH treatment (pH7.40), all the trochophores were deformed. At pH7.78, only 63.3±3.7% of the surviving trochophores developed normally compared to 96.7±1.6% normal trochophores at ambient pH conditions. Normal trochophores have prototrochal cells and girdle fully developed and developing shell tissue. Malformed trochophores showed highly undefined morphological characters and cleavage failed to progress to further developmental stages. In conclusion, the early larval development of H. asinina was found to be highly sensitive to reduced pH levels projected for the end of the present century. Therefore, future rise in CO2 concentration in tropical marine waters will likely pose a significant threat to the natural population densities of this species. Statement of relevance•To understand how lower pH levels can affect this high-value haliotid species is critical because of the importance of this species to fishery and mariculture production;•The deleterious effects of reduced pH on the early larval development of (up to hatch-out stage) of the tropical abalone (H. asinina) were demonstrated in this study;•A significant decrease in hatching rates, increased larval mortality, delayed and abnormal development will most likely have great impact on the population dynamics of this species in their natural habitat;•All the observations in this study suggest that reduced pH can affect early larval development and survival of abalone in the coastal ecosystem; and•these negative effects on larvae may persist into juvenile and adult stages of abalone which would likely contribute to a severe reduction of their natural populations.

Use of thraustochytrid Schizochytrium sp. as source of lipid and fatty acid in a formulated diet for abalone Haliotis asinina (Linnaeus) juveniles

The effects of using thraustochytrid Schizochytrium sp. as source of lipid and fatty acids in a formulated diet on growth, survival, body composition, and salinity tolerance of juvenile donkey’s ear abalone, Haliotis asinina, were investigated. Treatments consisted of diets either containing a 1:1 ratio of cod liver oil (CLO) and soybean oil (SBO) (Diet 1) or thraustochytrid (Diet 2) as source of lipid and fatty acids at 2 % level. Natural diet Gracilariopsis heteroclada (Diet 3) served as the control. No significant difference in growth was observed in abalone fed Diet 3 (SGR: 5.3 % BW day−1; DISL: 265 μm day−1) and Diet 2 (SGR: 5.2 % BW day−1; DISL: 255 μm day−1). Survival ranged from 78 to 85 % for all treatments and was not significantly different from each other. A 96-h salinity stress test showed highest survival of 84 % in abalone fed Diet 2 compared with those fed diets 1 and 3 (42 %). The high growth rate of abalone fed Diet 2 and high tolerance to low salinity could be attributed to its high DHA content (8.9 %), which resulted to its high DHA/EPA ratio of 10.5 %. These fatty acids play a significant role in abalone nutrition. The fatty acid profile of abalone meat is a reflective of the fatty acid profile of the oil sources in the diet. The present study suggests that the use of Schizochytrium oil in lieu of CLO and SBO can support good growth of abalone which is comparable with abalone fed the natural seaweeds diet.

Development of an integrated multi-trophic aquaculture (IMTA) system for tropical marine species in southern cebu, Central Philippines

This study presents the establishment of an integrated multi-trophic aquaculture (IMTA) system in the tropical open waters of southern Cebu, Philippines using a combination of locally available species, namely donkey’s ear abalone (Haliotis asinina) as fed species and seaweeds (Gracilaria heteroclada and Eucheuma denticulatum) as inorganic extractive species. The culture of Caulerpa lentillifera as a biofilter did not work in the open sea cultivation system using baskets. Monthly measurements of shell length, width and body weight of the cultured abalones, together with in situ measurements of physicochemical parameters to assess any changes in water quality, mainly nitrate, nitrite, ammonia and phosphate, were conducted over a year period from February 2013 to January 2014 in three designated stations (Abalone, Seaweed and Control Stations) at three different depths (surface, middle and bottom).Cage culture of abalone side by side with seaweeds in the open sea did not result in any significant water quality disturbance in the area—at least not in the current volume of caged abalones being used. Of the four inorganic compounds monitored in the field, nitrate and ammonia in the Seaweed Station were shown to have relatively lower year-round average values when compared with the Abalone Station, although in the case of nitrate, it was higher in the Control Station compared with the abalone and Seaweed Stations. Although this difference was not significant, it shows the red seaweeds, G. heteroclada and E. denticulatum, to be functioning as a natural filter for these two nutrients. In contrast, nitrite, and phosphate concentrations were not reduced indicating that the seaweeds were not effective biofilter for these two nutrients.The two-month old hatchery-bred donkey’s ear abalones can grow to a size of 53.8×28.2mm (L×W) and body weight of 37.8g after a period of 12 months. Any expansion of the farm into a much larger commercial-scale farm will have to be complimented with seaweeds stocked around it if only to mitigate possible build-up of excess inorganic wastes—to serve as both a natural filter and as a source of natural feed. The potential use of an organic extractive species has to be further studied under farm condition to achieve its full potential as an IMTA species.

Effects of reduced pH on the growth and survival of postlarvae of the donkey’s ear abalone, Haliotis asinina (L.)

High atmospheric CO2 levels primarily from burning fossil fuels have increased CO2 concentration in the surface water of the ocean, this in turn has resulted in a drop in seawater pH known as “ocean acidification” (OA) and presents a potential threat to calcifying marine organisms. Up to the present, however, the impacts of OA on the early developmental stages of tropical abalone were not known. For the first time in the Philippines, we investigated the direct effects of reduced pH on the growth and survival of the postlarvae of the donkey’s ear abalone, Haliotis asinina L. H. asinina is the only commercial species of haliotid in the country. We reduced the ambient pH (7.99) of experimental seawater by bubbling food-grade CO2 to obtain the desired pH levels as expected by the year 2100. Survival of H. asinina postlarvae was negatively affected by reduced pH. Mean survival of postlarvae significantly decreased from 86.3 % at ambient conditions to 47.2 and 18.3 % at pH 7.62 and 7.42, respectively, after 20 days (P 0.05). Mean shell lengths of postlarvae also differed significantly among treatments and across exposure period (P = 0.000 for both). Postlarvae reared at pH 7.62 and pH 7.42 exhibited smaller shell size (138 and 124 µm, respectively) compared to those at ambient conditions (175 µm). Postlarvae reared at pH 7.81 showed larger shell length (162 µm) compared to the postlarvae reared at pH 7.42 (124 µm). Across time, significant increase in shell size from day 5 to day 20 was observed only in postlarvae reared at ambient conditions (P = 0.000) and in the pH 7.81 treatment (P = 0.006). Daily growth rate decreased significantly from 2.83 µm day−1 (ambient) to 0.95 and 0.30 µm day−1 at pH 7.62 and 7.42, respectively. Our results suggest that growth and survival of postlarval H. asinina was found to be sensitive to reduced pH of seawater. This implies that future decrease in pH unit of the world’s oceans will most likely threaten the natural population of this economically important species.

ONGROWING TECHNIQUES FOR JUVENILE DONKEY EAR ABALONE (HALIOTIS ASINIA) AT PEMENANG WATERS, NORTH LOMBOK, INDONESIA

Abalone is one of the most prized sea delicacies in the world. In Indonesia, although donkey ear abalone (Haliotis asinina) forms a valuable fishery, little is known about its culture techniques. A study has been conducted to find out the most suitable technique for ongrowing donkey ear abalone, for to the local farmer in Indonesia. Juveniles used in study were collected from the southern Lombok coastal waters. They were reared in different type of structure (CNC = circular net cage and TNC = tyre net cage) and set at different depths. Juveniles were fed ad-libitum by macroalgae, Gracilaria spp. Results of the study showed that juveniles of donkey ear abalone have a better growth when cultured offshore in a TNC than in CNC. To gain a better growth, juveniles abalone need to be reared in cages which provided more shelter and less light. Donkey ear abalone was considered a hardy species, survival rate was not influenced by the type of structure (CNC or TNC) and setting position (depths).

Evidence for sexual attraction pheromones released by male tropical donkey's ear abalone (Haliotis asinina), (L.)

The tropical donkey's ear abalone (Haliotis asinina) is routinely collected in many parts of the Indo-Pacific and has significant potential for commercial aquaculture. Although its reproductive cycle has been investigated, no studies have reported the use of chemical signals to coordinate reproduction and spawning. Using a bioassay designed with one caged individual, whilst the other is free to roam, we investigated the presence of attraction pheromones released from mature individuals. Only mature females were attracted to caged mature males with all other treatments showing no significant attraction. Those mature females also took significantly less time to reach the mature males than other pairings. Temperature influenced the response with the maximum number of positives occurring between 25 and 31°C, which coincides with the optimum physiological temperatures and the spawning times for this species. We have also shown that the attraction pheromone is present in mature male testes and induces stereotypical pre-spawning behaviours (sweeping epipodial and cephalic tentacles) as well as attracting females. Some individuals also moved towards the surface of the water, this may also be a pre-spawning behaviour. This is the first time that a sexual attraction pheromone has been reported for any haliotid species and is likely to have a critical function in the synchronization of spawning in the wild between sexes.

Temperature and size range for the transport of juvenile donkey's ear abalone Haliotis asinina Linne

Live transport of hatchery-produced juvenile donkey's ear abalone Haliotis asinina Linne was examined to evaluate the effect of transportation on the survival of juvenile abalone. Simulated transport experiments were conducted to determine the appropriate temperature using 5, 10 and 20 g L−1 of ice to air volume for 8 h and the appropriate size using two size groups (Size A, 15–20 mm, 0.5–1.3 g, and Size B, 30–35 mm, 5.3–8.5 g) up to 24-h out-of-water live transport. Survival was significantly higher (P<0.001) when 10 g L−1 of ice was used to decrease the temperature to the range of 17–23 °C. At this temperature, both size groups subjected to simulated transport for 8 and 10 h had 100% survival after 48 h, while mortality occurred in abalones subjected to 16 and 24 h of simulated transport. The Size B abalone subjected to 24 h of transport had significantly higher survival (64.4 ± 2.9%) (P<0.001) than the Size A abalone (5.5 ± 1.6%) after 48 h. Live juvenile abalone were successfully transported to the field applying the protocols developed in the lab experiment. This study serves as a guide for handling and shipping live juvenile abalone.

Stock Enhancement of Threatened Species in Southeast Asia

Natural populations of global inshore fisheries are coming under heavy pressure, primarily due to overexploitation and habitat degradation. Stock enhancement of hatchery-reared seeds is perceived as an alternative strategy to enhance the regeneration process. The Aquaculture Department of the Southeast Asian Fisheries Development Center in the Philippines has been implementing activities related to stock enhancement of donkey's ear abalone (Haliotis asinina), mud crabs (Scylla spp.), giant clam (Tridacna gigas), and seahorses (Hippocampus spp.). Seed production techniques for abalone including a diet tagging method were established, and juvenile abalone were released and monitored in a marine protected area. Mud crabs conditioned before release had higher recapture rates compared to the non-conditioned crabs, which can be translated to higher survivorship. Giant clams stocked at 8–10 cm shell length have high survival 4 mo after stocking (90%), with initial mortalities occurring within the first few days due to transportation stress. Seed production trials for seahorse have begun.

A survey of stock of the donkey’s ear abalone, Haliotis asinina L. in the Sagay Marine Reserve, Philippines: evaluating the effectiveness of marine protected area enforcement

Marine protected areas (MPA) are tools for integrated coastal management (ICM); they have gained worldwide acceptance as a strategy for resource restoration and conservation. Research must gauge the effectiveness of MPA implementation in promoting fisheries recovery. This study investigated the effectiveness of enforcement in the Sagay Marine Reserve (SMR), western Philippines, in promoting the recovery of abalone stock. Enforcement of protection in the SMR is accomplished through the bantay-dagat (sea patrol), which utilizes reef watchtowers to deter illegal activities. The abalone populations in two protected reefs (well-enforced protection) and two open access reefs (poorly enforced protection) in the SMR were surveyed using 50 m×2 m belt transects. Abalone density was significantly greater, and abalone were larger, on protected than on unprotected reefs. However, we found that recruitment appeared limited at all sites, and that abalone tended to be sexually mature at small sizes. This may indicate that the population has been near a critical threshold, that recent climatic events may have suppressed recovery rates, and/or that enforcement and rule compliance was low and with continued poaching. Nevertheless, the results of this study agree with findings of other research that a properly enforced no-take MPA can promote recovery of local stocks. Moreover, the investment of funds by the local government in monitoring activities (in this case, watchtowers) is necessary to achieve MPA objectives.

Reproductive performance of hatchery-bred donkey's ear abalone, Haliotis asinina , Linne, fed natural and artificial diets

Hatchery-bred donkey's ear abalone, Haliotis asinina, Linne broodstock were given diets consisting of natural food, seaweed (SW), Gracilariopsis bailinae, D1; combination of SW and artificial diet (AD), D2; and AD alone, D3. Equal numbers of 1 : 1 female and male abalone were stocked in 24 units, 60 L tanks with eight replicate tanks per dietary treatment. Reproductive performance, e.g. number of spawnings, instantaneous fecundity and egg hatching rates, was monitored over 270 days. The mean number of spawnings was not significantly different among treatments. The mean instantaneous fecundity and percent hatching rates were significantly higher in abalone fed D2 or D3 compared to those given D1. Survival of abalone broodstock fed D1 was, however, significantly higher at 88% than those fed either D2 or D3 at 75%. Fatty acid analysis showed that the n-3/n-6 fatty acid ratios of abalone hepatopancreas reflected those of their diets. Mature abalone ovary had n-3/n-6 fatty acid ratio of 1.3. A higher amount of essential nutrients in the artificial diet such as protein, lipid and the highly unsaturated fatty acids, e.g. 20 : 4n-6, 20 : 5n-3, 22 : 6n-3 in abalone fed D2 or D3, may have influenced the increased reproductive performance.

Studies on the reproductive biology of the Donkey's ear abalone, Haliotis asinina Linné

The sex ratio, initial size at sexual maturity, spawning period, time interval between successive spawnings and fecundity of the Donkey's ear abalone, Haliotis asinina were studied. The sex ratio of wild abalone (>60 mm shell length) collected from Panagatan Cays, Antique, Philippines was approximately 1:1. Sexual maturity was first attained at a size of 35.0 mm and 35.9 mm for hatchery-reared male and female abalone, respectively, and 40.6 mm for wild-caught male and female specimens. Based on calculated gonad bulk indices and histological observations, wild-caught abalone appeared capable of spawning during most months of the study period except June for males and May–June for females, during which most specimens collected were at a resting stage. This abalone species is a serial spawner with an asynchronous spawning behavior. Hatchery-reared abalone have short time intervals between successive spawnings of 13–15 days. Ripe females measuring 58.1–69 mm in shell length may release about 150,000 to 600,000 eggs per spawning.

Growth of the ass's ear abalone (Haliotis asinina Linné) on Heron Reef, tropical eastern Australia

Growth of ass's ear abalone (Haliotis asinina) was measured in situ (mark-recapture of adults) and in aquaria (juveniles) on Heron Reef, Queensland. A growth curve (y = 4.27L2.03 e-u, where y is the growth rate, L is the shell length, and u = 0.27L0.88) fitted to these data indicated a sigmoidal age-length relationship. It is estimated that H. asinina may grow from 2 mm to 35.6 mm in shell length in six months and 55.0 mm in one year. These growth estimates are consistent with temporal shifts in the size-frequency distributions of juveniles in the field. Peak growth rates, estimated at over 120 mm year-1 in young abalone (approximately 3-4 months of age), are the highest recorded for any abalone species.