In recent years, the total quantity of abalone produced on farms worldwide has increased significantly while abalone fisheries have declined. Fishery production was almost 20,000 metric tons (mt) in the 1970s but was only about 6,500 mt in 2015. Over the same period, farm production has increased from negligible quantities in the 1970s to 129,287 mt in 2015, the majority being produced in China and South Korea. Illegal exploitation, particularly in South Africa, Australia, and New Zealand, is still a major problem. Prices on the world market fell during the Global Financial Crisis, but now appear to be increasing again.

On Australian aquaculture farms, early life stages of abalone are reared under controlled abiotic and biotic conditions in an attempt to optimize individual growth and reduce potential stressors. Yet, physiological responses to the rearing conditions are largely unknown. This study tests if commercial stocking densities, light conditions, and oxygen levels influence the oxygen consumption rate (ṀO₂) of early life stages of Haliotis rubra and Haliotis laevigata hybrids at a standard commercial hatchery temperature of 16°C. Oxygen consumption rate of fertilized eggs and larvae in the trochophore, mid-veliger, and early benthic veliger stages were measured at densities from 100 to 2,400 individuals/ml, in light and dark conditions and oxygen levels of 100%–0% air saturation (%O₂sat). Neither density nor light conditions affected ṀO₂ of any of the tested life stages. Normoxic ṀO₂ varied across developmental stage and was higher in the actively swimming mid-veliger stages (114.92 ± 2.68 pmol O₂/ind/h) in comparison with less active earlier (49.48 ± 2.33 pmol O₂/ind/h) and later life stages (65.90 ± 3.05 pmol O₂/ind/h). Critical oxygen tensions, taken as the point at which animals could no longer maintain ṀO₂, ranged from 22.7%± 2.7%O₂sat in fertilized eggs to 14.0% ± 1.0% O₂sat in mid-veliger larvae. These results suggest that current conditions in Australian abalone aquaculture farms should not negatively impact the development of early life stages of hybrid abalones.

White abalone Haliotis sorenseni was listed as endangered in 2001 because of severe declines throughout southern California due to overfishing. Populations continue to decline despite the closure of the fishery in 1996. There has been little to no evidence of recruitment in southern California from population surveys and in artificial reefs targeting white abalone recruitment since the listing of the species. A 13-y time series of white abalone abundance in prime habitat, surveyed with a remote-operated vehicle, was used in a population viability analysis to quantify: (1) the population decline and (2) the time to reach a quasi-extinction threshold. The annual decline in the population is 12%, which is comparable to adult natural mortality rates for abalone species. The quasi-extinction threshold of 1,000 individuals is met within 15 y. These results confirm that the white abalone populations in southern California are at high risk of extinction, and highlight the importance of active stocking and restoration for the species. To inform restoration, a deterministic density-dependent size-based matrix model was developed to investigate different stocking scenarios, incorporating an innovative method for modeling low populations by setting the reproductive term as a function of adult density to mimic a reproductive Allee effect. A minimum density of 0.14 abalone/m² of stocked juveniles led to a maximum population growth rate (λ) of more than or equal to 1 for the model population within 10 y but that recovery was poor (mean λ_15–20 ≤ 1.0) over time if the level of juvenile stocking was less than 0.23 abalone/m² in the model population. The innovative approach of incorporating adult density into the reproductive term in the model quantitatively shows how low population densities can impact threatened and endangered species, and may be widely used for other species. These results can not only help guide stocking strategies but also allow for the quantitative evaluation of white abalone under the guidance of the IUCN Red List of Threatened Species, suggesting that white abalone should be considered Critically Endangered.

Recruitment is a central question in both ecology and fisheries biology. Little is known however about early life history stages, such as the larval and newly settled stages of marine invertebrates. No one has captured wild larval or newly settled red abalone (Haliotis rufescens) in California even though this species supports a recreational fishery. A sampling program has been developed to capture larval (290 µm), newly settled (290–2,000 µm), and juvenile (2–20 mm) red abalone in northern California from 2007 to 2015. Plankton nets were used to capture larval abalone using depth integrated tows in nearshore rocky habitats. Newly settled abalone were collected on cobbles covered in crustose coralline algae. Larval and newly settled abalone were identified to species using shell morphology confirmed with genetic techniques using polymerase chain reaction restriction fragment length polymorphism with two restriction enzymes. Artificial reefs were constructed of cinder blocks and sampled each year for the presence of juvenile red abalone. Settlement and recruitment were found to vary with year and site from 2007 to 2015. In some years such as 2010 and 2013, there were many larvae and newly settled abalone, whereas in other years there were none. The two exceptionally poor years for larval and newly settled abalone were 2012 and 2015 (warm El Niño years). In 2013, there was spatial concordance between two sites 18 km apart with respect to the sizes of the newly settled individuals suggesting they were spawned and settled on the same day. The methods developed here, quantifying early life history stages, may shed light on the “black box” of recruitment and help addresswhat are the drivers of good and bad recruitment years for red abalone in northern California.

A restoration program including wild population surveys, captive breeding, health monitoring, recovery site preparation, and recovery modeling has been implemented to restore white abalone (Haliotis sorenseni) populations in California. White abalone once supported a lucrative fishery and are now endangered, nearing extinction at less than 1% of baseline abundances. Recent deep water surveys indicate that populations continue to decline with no signs of recruitment, despite the closure of the fishery in 1996. Four sites with artificial reefs (n=12/site) in optimal white abalone habitat were established. No wild white abalone have been found at these sites. Captive abalone were spawned in the spring of each year from 2012 to 2015. Each year, the production of 1-y-old abalone has increased in the captive breeding program from approximately 20 in 2012, to 150 in 2013 and an estimated 2,000 in 2014. In 2015, the breeding program reached two milestones: (1) most successful spawning season to date and (2) the hatchery distributed 200 captive-reared abalone to 4 partner institutions within the White Abalone Recovery Consortium (WARC). The WARC is made up of federal and state agencies, universities, public aquaria, and aquaculture organizations, all committed to white abalone restoration. The next steps for the program include expanding the captive breeding program to increase production, monitoring abalone health and genetic diversity, and conducting stocking studies to enhance growth and survival in the ocean. The goal of the stocking program is to create a reproductive population in the wild to bring white abalone back from the brink of extinction.

Pacific abalone Haliotis discus hannai (Ino, 1953) aquaculture is a thriving and prosperous industry in China, producing more than 110,000 metric tons in 2013. In recent years, Fujian in the southern region of China has become the chief abalone farming center, accounting for 85% of the total Pacific abalone yield. The practice of transferring abalone to northern regions to oversummer emerged because of challenges in Fujian, such as fouling, high temperature stress, and unexpected extreme weather events. From the view of ecology and conservation biology, however, the potential ecological risks of this practice should be considered as the abalone shells could act as vectors of exotic organisms. In this study, oyster samples from the shells of live, farmed abalones were collected in Fujian in southern and Rongcheng in northern China. The oysters were identified using a recently developed molecular method. In addition, the fouling oysters on Pacific abalone transferred to the northern region were monitored in a field trial. Survivorship and growth performance of the fouling oysters on the transferred abalones were determined through investigation of digital images taken at 2-wk intervals during the oversummering period. Results of the molecular analysis showed that fouling oysters collected from southern and northern regions are Crassostrea angulata and Crassostrea gigas, respectively. The field trial demonstrated that approximately half of the C. angulata, from the southern region, were still alive after a 6-mo oversummering period in the northern region. Findings from this study have important implications for aquaculture, the management and monitoring of cultured populations of Pacific abalone, and the conservation of wild oyster species in China.

Recognizing the physiological changes of invertebrates during early life is essential to understand the species biology. Studies describing the development of early stages of Omani abalone (Haliotis mariae) are scarce. Therefore, this article presents the first detailed description of embryonic and larval development of the Omani abalone (H. mariae). The eggs obtained by a successful artificial spawning using a combination of hydrogen peroxide and ultraviolet irradiated- seawater, were observed carefully under compound microscope. The chronicle order of the embryonic and larval development of 26 distinct stages, from fertilization until reaching the presettlement stage when the larvae are competent and distinguished by formation of the third tubule tentacle, were illustrated. The changes during several stages were documented and photographed. The eggs were spherical, green, and negatively buoyant at the beginning then became planktonic; average fertilized egg diameter was 185 ± 7 µm. Hatching occurred at 9 h 16 min after fertilization, whereas larvae were competent at 46 h 48 min post fertilization. The average seawater temperature during the embryonic and larval observation was 24.7°C ± 1.0°C. The survival rate prior to settlement was 24.2%. This study provide a first detailed informative illustration of embryonic and larval development of Omani abalone (H. mariae), assisting in understanding the biology and ecology and supporting steps toward sustainable development of the aquaculture and management of this species.

A refined formulated feed for the grow-out culture of tropical abalone Haliotis asinina was evaluated to assess its suitability for a shorter culture period (<8 mo). Refinement procedures focused on the application of additional binder (sodium alginate), use of different feed forms (molo and noodle forms), and incorporation of Spirulina spp. as alternate protein source in partial replacement of other protein sources. Groups of 22 postlarval abalone with mean initial shell length (SL, 29 ± 0.01 mm) and weight (5.67 ± 0.06 g), harvested from the mollusc nursery of Southeast Asian Fisheries Development Center, Aquaculture Department in Tigbauan, Iloilo, were stocked each as replicate in five plastic trays measuring 31.7×43.5×9.0 cm. The trays were suspended in five 1×2×1-m concrete land-based tanks representing the five dietary treatments. Abalone were fed either the refined formulated diet,molo form(RF-M), refined formulated diet, noodle form(RF-N), unrefined formulated diet, noodle form(UF-N), unrefined formulated diet, molo form (UF-M), and seaweed (NF), as the reference diet. Formulated diets and natural food were given at 2%–3% and 10%–15% (wet weight) of the body weight, respectively, once daily at 1600 h for 180 days. Water qualitymeasurements weremaintained at desired levels. A flow-through filtered seawater systemwith continuous aeration was provided in each tank. A parametric one-way analysis of variance (ANOVA) and Tukey's post hoc test were used to test the differences in abalone SL, weight gain (WG), and specific growth rate (SGR) while nonparametric Kruskal-Wallis test was used for daily growth increase in SL (DGSL) and feed conversion ratio (FCR) among the various dietary treatments. Percent diet water stability and apparent digestibility coefficient for dry matter (ADMD) and apparent digestibility of seaweed as ingredient were, likewise assessed. A Hedonic scale taste test analysis was done to assess differences in abalone meat quality. Highest mean WG (239.17% ± 26.05%), mean SL increase (91.51% ± 3.28%), DGSL (2,296.67 µm/day), SGR (4.04 ± 0.27) were attained with abalone fed RF-N. Values, however, were not significantly different (P > 0.05) for all growth parameters in RF-M except for percent increase in SL at 74.25 ± 3.11. Abalone given UF-N and UF-M showed significantly lower mean WG and SL. Survival was high and was significantly different (P < 0.05) between treatments. The highest FCR was obtained with abalone fed seaweeds. Apparent digestibility for dry matter of both the RF and UF were high at 95.67% ± 1.17% and 95.95% ± 0.45%, respectively. Apparent digestibility of ingredient seaweed was 99.4% ± 1.38%. Regression analysis of data showed better percent water stability for RF (57%; R² = 0.954) compared with UF (38%; R² = 0.790) after 24 h. Meat quality of the final product assessed through Hedonic scale taste testing and one-way ANOVA did not show any significant variations in taste, texture, color, odor, and general acceptability. Results have demonstrated that the refinement done on the formulated feed may enable the abalone to grow to its marketable size of about 5–6 cm in a shorter culture period (180 days) in concrete land-based tanks.

This multifactorial study used a newly developed ventral videography technique to investigate the feeding behavior of 18-mo-old juvenile greenlip abalone (21.1 g, 55.6 mm), and hybrid abalone (23.4 g, 57.6 mm) fed either a formulated commercial diet or live Ulva sp. at 18°C and 22°C. Feeding behavior was scored in terms of the following activities: quiescence, alertness, moving, feeding, distance traveled, velocity, and homing. There was a significant effect of diet type and temperature on feeding behavior of abalone. Both types of abalone were more active and exhibited the highest velocity when fed the formulated diet at 22°C. Greenlip abalone spent a larger proportion of time feeding on Ulva sp. than on the formulated diet, regardless of the water temperature. In contrast, no significant difference was observed in the proportion of time feeding between diet types for hybrid abalone. Both types of abalone rapidly located and consumed Ulva sp. when feed was introduced into the aquaria at 1600 h (light phase). In contrast, abalone predominantly commenced feeding on the formulated diet in the dark phase, indicating the potential of Ulva sp. as feed attractant in abalone diet, to promote feeding. The mode in which abalone consumed feed also differed between diets. Abalone fed the formulated diet nibbled intermittently on random chips, whereas when fed Ulva sp., abalone engulfed entire individual fronds before moving on to the next available frond. Greenlip and hybrid abalone exhibited homing behavior at the completion of the dark phase, which was more pronounced in abalone fed Ulva sp. This new information may assist in refining feed design and feeding practices for the culture of these two types of abalone.

The objective of this study was to examine gonad development and reproductive cycle of the abalone Haliotis discus hannai at three main abalone aquaculture farms (Uljin, Wando, and Jeju Island) in Korea to obtain information on artificial seed production. The sex ratio (female:male) was approximately 1:1 without significant difference among the three regions or between females and males. Average gonad index was the highest during July in Uljin and Jeju Island and during August in Wando. There was no definitive seasonal change in condition index and meat weight index throughout the year in the three regions. The gonad of H. discus hannai displayed seasonal change histologically, thereby enabling us to distinguish the following stages: inactive (November–December), early active (January–March), late active (March–April), ripe (May–July), spent (August–October), and degenerative (October–November). The main spawning period of H. discus hannai was determined to be during September–October in Uljin and Wando, and August–September in Jeju Island.

Pacific abalone Haliotis discus hannai is one of the most important species of shellfish aquaculture. The annual production of cultured abalone exceeded 100,000 t in 2013, and the Pacific abalone was the main farmed species. The genetic diversity of hatchery stocks of H. discus hannai in most areas of China, however, remains unknown. The exchange of Pacific abalone in China was not only among hatcheries but also between southern and northern areas, and the Japanese population was widely used for the production of seed. Both practices may have led to the production of mixed seeds, and the difference between populations may be not significant, which could result in inbreeding and loss of potentially valuable alleles. Therefore, it is necessary to assess the current genetic characterization of hatchery populations. For the analysis, a total of 10 populations were obtained from different hatcheries: Dalian, Qingdao, and Changdao in the northern coastal areas; and Xiapu, Lianjiang, Putian, Zhangpu, Jinjiang, Dongshan, and Shanwei in the southern coastal areas. Five populations were added as the control: Ja (the F1 population of H. discus hannai introduced from Japan), KDH (the F1 population of H. discus hannai introduced from Korea), KDD (the F1 population of Haliotis discus discus introduced from Korea), ST (the F1 population developed from the cross of H. discus discus and H. discus hannai), and Red (the Pacific abalone with red shell). The data of 14 microsatellite primers were all highly polymorphic while the degree of variability was different at each locus. In all the studied populations, the number of alleles ranged from 2 to 17, and the number of effective alleles ranged from 1.032 to 10.169. The principal component analysis result showed that all populations were dispersed except KDD and ST, which clustered in the second and third quadrants. A neighborjoining tree indicated that most populations were closely related. Moreover KDH, KDD, and ST were less related to the others because of the different genetic background. The estimates of effective population size (N_e) using the linkage disequilibrium methods demonstrated that the N_e of eight populations was less than 50, and the other two populations were close to 50. In conclusion, by the previous studies, the current analyses present that these cultured populations of Pacific abalone in China have lost their genetic diversity to some extent, and the difference among populations was not significant. Thus, for the sustainable development of the aquaculture, the genetic diversity should be monitored every year and inbreeding should be controlled.

Abalones are edible shellfish and a valuable food source in Asian countries. Although substances from abalone have bioactivities, such as anti-oxidation and anti-inflammation, anti-metastatic effects of abalone have not been fully revealed. Gastric cancer is a common malignant cancer, but prognosis is poor because of its high metastatic characteristics. In this study, a novel peptide (A2) from abalone (Haliotis discus hannai) was applied to investigate its antimetastatic effects in MKN-28 gastric cancer cells. Enhanced activities of glycogen-synthase kinase 3β(GSK-3β) by A2 treatment contributed to modulation of β-catenin; hence, β-catenin signaling was downregulated, and translocation of β-catenin to the nucleus was repressed. Moreover, cellular protrusions including lamellipodia and filopodia were disrupted through downregulation of Rac1 and Cdc42 in response to A2 in MKN-28 cells. It is suggested that A2 inhibits cell migration through controlling levels of β-catenin, GSK-3β, and also induced disorganization of lamellipodia and filopodia. Therefore, A2 possesses therapeutic properties to treat gastric cancer.

The evaluation of abalone (Haliotis spp.) restocking programs might be improved by the use of microchips attached to seeds [ca. 20–30mmshell length (SL)]. Preliminary studies were conducted to standardize thismethodology and to assess tag retention and the potential impacts of tagging red abalone (Haliotis rufescens) seeds (initial averages: 26 mm SL, 2.5 g total weight) with passive integrated transponder (PIT) tags (9×2mm, Biomark, HPR Plus Reader). Tags were placed in previously made grooves in the shells and glued with a cyanoacrylate adhesive fast cured with sodium bicarbonate. Laboratory trials showed that metabolic rate increased in tagged seeds compared with untagged controls (t = 4.74, P = 0.009) immediately after the tagging procedure, but this effect was not significant after 3 h (t= 1.43, P = 0.23). Food (Macrocystis pyrifera) consumption after 24 h was similar by seeds marked with PIT tags, plastic tags, both tags, and untagged controls (F= 0.12, P = 0.94). Tag retention and survival was 100% after 108 days in all treatments and no effects were detected on growth rates in length (range=0.92–1.11 mm/mo, F= 0.72,P= 0.57) or weight (range= 0.30–0.44 g/mo, F=2.44,P= 0.16). Results from a small-scale field experiment in tide pools, suggest that the detection of planted abalone seeds can be significantly improved when these are marked with PIT tags, compared with those marked with conventional plastic tags. Improvements should, however, bemade regarding antenna design and reading distance to optimize the use of this technology to evaluate restocking programs.

Catch per unit effort (CPUE) is widely used as an index of abundance in the assessment of abalone fisheries even though it has often been considered unreliable. This is because, it is susceptible to hyperstability and influenced by factors other than stock abundance such as increased fishing efficiency, market demand for particular product, weather, diver habits, and putative rotation of fishing grounds. These factors introduce uncertainty to the use of CPUE as an index of relative stock abundance, with some of these factors causing hyperdepletion of the index. In the western and southern zones (WZ and SZ) of South Australia, commercial fishers recently suggested that declining CPUE in 2014 was attributed to a fishing season with poor weather, and in particular higher than average swell, rather than to declines in stock abundance. To evaluate the effect of weather on CPUE in the SZ and WZ daily, logbook catch and effort data were linked with swell and wind observations. Analysis demonstrates that, although the observations of extrinsic factors were correct, fishers avoided diving on days with unsuitable weather conditions. Consequently, the observed decrease in CPUE is not likely to have been affected by weather-related hyperdepletion, and therefore managers should not rule out interpreting recent declines in CPUE as reflecting decreases in stock abundance. This highlights the independence of CPUE to the effects of the extrinsic factors evaluated and challenges some of the reasoning provided for it not being a reliable index of abundance. Further exploration of the effects of other factors that may affect CPUE, as well as the link between this index and fishery-independent estimates of abundance, are needed to determine the weighting it should receive in the stock assessment process.

Over the past decade, Australian abalone were produced using a range of commercially formulated grow-out diets with crude protein (CP) levels ranging from 27% to 30% throughout their production cycle. Recent research identified higher optimal dietary CP levels of greater than or equal to 35%for younger than 1-y-old abalone at higher water temperatures (20–22°C). To validate the results of the laboratory-based research, the current trial was designed to investigate the effect of feeding two different commerciallymanufactured diets (standard-protein diet, 32%CP, versus a high-protein diet, 39%CP) to hybrid abalone (Haliotis laevigata ×Haliotis rubra; initial weight: 3.10 g) on growth performance, feed utilization, and sales revenue under on-farm conditions. During this 18-mo trial, abalone were cultured using normal commercial practices over two summer periods at Great Southern Waters abalone farm (Indented Head, VIC, Australia). A significant improvement in specific growth rate (SGR) led to a 9% improvement in biomass gain for abalone fed with the high-protein diet. This improvement was achieved with no differences in survival, and minimal difference in feed input between diets. In addition, the feed conversion ratio of abalone fed with the high-protein feed was 7.1% superior to that of animals fed with the standardprotein diet. On the basis of a farmgate value ofAUD35/kg abalone, for an additional feed input cost ofAUD2/m² slab tank/y, a 9.5%increase in basic annual sales revenue (AUD44/m2 slab tank/y) was achieved feeding the high-protein diet. In addition, due to an increased SGR by feeding the high-protein diet, the duration of a typical 3-y production cycle for hybrid abalone may be shortened by up to 3.4 mo. By adopting the high-protein diet, farmers may also harvest abalone sooner, and reduce exposure to one less summer. This may reduce heat-related mortalities and further improve productivity, and when combined with savings made with biomass and feed efficiency gains, a more than 10%improvement in productivity across the entire grow-out period for hybrid abalone may be achieved.

Recently, cultivation of the Pacific abalone Haliotis discus hannai (Ino, 1953) in China has developed rapidly, boosted by innovations in low-cost seed production and highly efficient sea-based culture systems. Seed production of Pacific abalone differs between northern and southern China and is dependent on sufficient quantities of broodstock, excess quantities of freshly cultured diatoms during the nursery phase, and tank hygiene and newly designed attachment methodology during the intermediate culture phase. Innovations in grow-out systems for Pacific abalone, such as stock enhancement in northern regions and commercial application of cage culture methods in southern regions, have further contributed to the success of Pacific abalone farming in China. There are still challenges in Pacific abalone-farming industry in China. First, mass mortality during the nursery and postlarval culture stages hinders seed production in northern and southern regions. Second, extreme weather events, including cold waters in northern regions and typhoons and red tides in southern regions, have occurred more frequently during recent years, and these events often cause high mortality of adult abalone during the grow-out phase. Finally, Pacific abalone H. discus hannai is an introduced species from northern regions, and, therefore, summer mortality remains a major problem in most bays of southern China; moreover, the survival rate from seed to market size varies widely among growing areas. The future direction in development of Pacific abalone farming in China will be also discussed.