Donkey's Ear Abalone Research Articles

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.

REARING OF JUVENILE DONKEY-EAR ABALONE (Haliotis asinina) IN FLOW-THROUGH TANKS WITH THE ADDITION OF DIFFERENT SUBSTRATES

This study investigated the effects of the addition of coral rubble and polyvinylchloride (PVC) guttering as substrates on the growth of donkey-ear abalone (Haliotis asinina) reared in a flow-through water system. The tanks were100 cm long x 50 cm wide x 40 cm deep, filled with sea water up to 30 cm high. Hatchery-produced abalone with a mean initial shell length of 30.9 ± 0.1 mm and wet weight of 5.5 ± 0.1 g were stocked at 25 individuals/tankthat corresponded to stocking densities of ca. 50 abalone/m2 of the bottom area of the tank. Juvenile abalonewere provided with an excess red seaweed Gracilaria spp daily over 175 days. The results show that growth and growth rates in shell length and wet body weight were not significantly different between treatments (P>0.05). Survival rates of juveniles reared in the tank with the addition of coral rubble and/or PVC guttering were 100%, but 98% for juveniles in the tank without the addition of substrate. The average daily growth rates of shell length and wet body weight were 0.087+0.037 mm and 0.088+0.044 g for juveniles reared in the tank with the addition of coral rubble; 0.081+0.030 mm and 0.077+0.032 g for juveniles reared in the tank with the addition of PVC guttering; and 0.082+0.032 mm and 0.078+0.039 g for juveniles reared in tank without addition of substrates.

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.

Effects of chemical cues on larval survival, settlement and metamorphosis of abalone Haliotis asinina

Low larval survival, poor settlement, and abnormal metamorphosis are major problems in seed production of donkey-ear abalone Haliotis asinina. We examined the effects of chemical cues including epinephrine, nor-epinephrine, and serotonin on larval survival, settlement, and metamorphosis in order to determine the possibility of using these chemicals to induce the problems. The results show that epinephrine could enhance metamorphosis rate at 10−6 mol/L only but higher concentrations (10−3−10−4 mol/L); and nor-epinephrine could inhibit the performance significantly, and serotonin could increase significantly the performance at a wide-range concentration (10−3–10−6 mol/L). Treatment with serotonin at 10−5 mol/L for 72 hours resulted in the highest settlement rate (42.2%) and survival rate (49.3%), while at 10−4 mol/L for 72 hours resulted in the highest metamorphosis rate (38.8%). Therefore, serotonin may be used as a fast metamorphosis inducer in abalone culture.

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.

Induction of larval settlement and metamorphosis in the donkey-ear abalone, Haliotis asinina Linnaeus, by chemical cues

The effects of the chemical inducers, gamma-aminobutyric acid (GABA) and potassium chloride (KCl), on the larval settlement and metamorphosis of the donkey-ear abalone, Haliotis asinina, was investigated. H. asinina larvae (5–6 h post-hatch) were exposed to a range of GABA (0.125–2.00 μM) and KCl (1.00–12.00 mM) concentrations for 72 h. Results of the dose response experiments showed that settlement and metamorphosis vary according to the dose levels of the inducer compounds. Under controlled laboratory conditions, 0.45–0.50 μM and 6.0 mM seemed to be the optima for GABA and KCl, respectively, as these concentrations elicited the greatest number of postlarvae that metamorphosed, settled or survived. However, GABA generally promoted better attachment and metamorphic response as well as survival than KCl in H. asinina postlarvae.

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.

Grow-out culture of tropical abalone, Haliotis asinina (Linnaeus) in suspended mesh cages with different shelter surface areas

Thisstudy investigated the effects of shelter surface area (SSA) on the feeding,growth and survival of the donkey-ear abalone, Haliotisasinina reared in mesh cages (0.38×0.38×0.28m) suspended in flow-through tanks (water volume = 6m3). Cages had sections of polyvinylchloride (PVC) thatprovided shelters with surface area of 0.22 m2, 0.44m2 and 0.66 m2.Hatchery-produced abalone with initial shell length of 32 ± 1mm and wet weight of 7.5 g were stocked at 50individuals cage−1 that corresponded to stocking densities ofca. 227, 113 and 75 abalone m−2 of SSA. The ratios of sheltersurface area to cage volume (SSA:CV) were 5.5, 11 and 16.5. Abalones wereprovided an excess red seaweed Gracilariopsis bailinae(= Gracilaria heteroclada) at weekly intervals overa 270-day culture period. Feeding rates (18–20% of wet weight), foodconversion ratio (26–27) and percent survival (88–92%) did notdiffer significantly among treatments (p > 0.05). Body size at harvest rangedfrom 56 to 59 mm SL and 52 to 57 g wet body weightwith significant differences between abalone reared at SSA 0.22m2 and 0.66 m2 (p < 0.05).Abalone reared in cages with 0.66 m2 SSA grewsignificantly faster at average daily growth rates of 132 μm and188 mg day−1. Stocking densities of 75–113m−2 SSA in mesh cages suspended in flow-throughtanks resulted in better growth of abalone fed red seaweed.

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.