Over the past few years, supplies of abalone from fisheries around the world have been gradually declining, whilst supplies from farms have been rapidly increasing. Illegal exploitation of abalone is still a problem in many parts of the world, although there is some evidence that some countries are taking steps to reduce poaching. The total world supply of abalone from all sources in 2010 was about 77,000 mt and this is expected to increase to more than 97,000 mt by 2012. This increase is largely due to increased farm production in China. To date, this has not had a very large effect on world markets because much of the Chinese production is consumed within China.

The performance of an agar-bound microparticulate diet (A-MPD) was evaluated on feeding postlarval abalone Haliotis asinina, focusing on the effects of agar concentrations and feeding frequencies. Larval abalone, obtained from the Southeast Asian Fisheries Development Center, Aquaculture Department hatchery, were reared in 60-L flow-through tanks with UV-filtered seawater. They were fed 1,200 mg A-MPD bound with either 5.0 mg/mL agar solution, 7.5 mg/mL agar solution, 10.0 mg/mL agar solution, and 12.5 mg/mL agar solution, or a natural diet consisting of diatoms at different feeding frequencies (daily, every other day, or every 2 d) starting at day 5. A 5 × 3 factorial experiment in a completely randomized design tested the effects of various treatments on postlarval settlement and survival after days 15 and 90. Scheffé's postcomparison test determined differences among treatments means. Postlarval settlement and survival were not significantly different in diets bound with higher agar concentrations and tested in 3 feeding frequencies. At lower levels of agar incorporation in diets, however, settlement and survival counts became significantly higher on daily feeding. Postlarval settlement and survival were significantly highest with abalone fed a diet bound with 7.5 mg/mL agar solution on a daily feeding frequency. Average percent weight loss in the feed was higher with lower levels of agar incorporation. Average particle size of both A-MPD and diatoms was 4–5 µm. Crude protein content of A-MPD was 42.7%; that of diatoms was 14.9%. A-MPD may be used as alternative food in abalone hatcheries with the incorporation of 7.5 mg/mL agar solution fed daily to abalone.

The Pacific abalone Haliotis discus hannai is a commercially valuable species in Korea. The commercial-scale production of the abalone in Korea began in the 2000s. As of 2011, abalone production reached about 7,000 t. The abalone production system in Korea is divided into 2 stages: seed production and rearing. Abalone seeds are produced at about 500 hatcheries, and almost all juveniles are reared using approximately 500,000 sea cages. Furthermore, a project to develop a breeding program for genetic improvement and environmental adaptation is being undertaken.

The effect of stocking density and cage design on the growth, survival rate, and feed conversion ratio was evaluated for the nursery (11–15 mm in shell length) and juvenile grow-out (26–30 mm in shell length) of the tropical abalone Haliotis asinina. Abalone were fed Gracilaria sp. within a randomized 2 × 3 factorial experiment using 2 stocking densities (Tl (500 pieces/m²) and T2 (1,000 pieces/m²)) and 3 cages (D1, box; D2, mesh cage; D3, prefabricated multitier trays). In addition, 3 stocking densities (T1, 50 pieces/m ; T2, 100 pieces/m; T3, 200 pieces/m) were evaluated in the prefabricated multitier trays. We found that, in the nursery experiment, 4-mo-old tropical abalone juveniles reared for 90 d showed no significant differences in growth (shell length and body weight) and survival rates among the 3 nursery cages used (Tukey's post hoc test, P > 0.05). Feed conversion ratio, however, was lowest for the high-density treatment T1D3 (7.8 ± 0.76) and was significantly different from the low density treatment T1D1 (11.32 ± 1.2) and intermediate density treatment T1D2 (12.39 ± 1.12; t-test, P > 0.05). Conversely, at higher densities (T2), the same trend applied with abalone reared in multitier basket systems (T2D3), having the highest growth rates and survival rates (29.3 ± 0.07 mm average shell length (ASL) and 5.16 ± 0.52 g average body weight (ABW)), followed closely by those reared in mesh cages (T2D2) and boxes (T2D1). Feed conversion ratio was also lowest for T2D3 (7.56 ± 0.79) and was significantly lower than T2D1 and T2D2. Between treatments, however, abalone reared at lower densities (T1) had significantly higher growth and survival than those reared at higher densities (T2), regardless of the nursery cage used, indicating an inverse relationship between stocking density, growth, and survival. For the grow-out study, tropical abalone reared in multitier trays at low densities (T1) attained the highest growth in shell length and body weight (49.7 ± 0.11 mm ASL and 29.8 ± 2.6 g ABW, respectively) at 180 d of culture, which was significantly greater than those reared in the high-density treatment (T3) with significantly smaller shell length and body weight (43.8 ± 0.18 mm ASL and 21.2 ± 2.0 g ABW), but not significantly different than the intermediate density treatment. This trend started from day 60 of culture onward when analyzed using Duncan's multiple range test (P > 0.05). Survival rates were not significantly different among stocking density treatments, nor were feed conversion ratios. We recommend, for nursery rearing of abalone juveniles, using multitier trays (D3) or boxes (D1) at 500 pieces/m² stocking density to attain a grow-out size of 26–30 mm in shell length in 90 days. A stocking density of 100 pieces/m² is recommended to grow abalone in multitier trays to attain a cocktail size of 50 mm ASL and 30 g ABW in 180 d with survival rates between 85.6% and 83.1%.

The effect of different strategies of opening water flow on the survival and growth of Haliotis rufescens 9-d postlarvae was evaluated using a randomized block design with 3 replicates for 63 days. Larvae were settled (1.5 µM gamma-aminobutyric acid) in 2-L plastic vessels (total area, 701 cm²) and were subjected to the following treatments: static conditions, static conditions with aeration (NF A), flow opened after 10 d, flow opened after 17 d, and flow opened after 24 d. The experiment was conducted at constant temperature (17.5 ± 0.5°C) and light intensity (∼750 lux). Water was changed daily in static treatments, and flow treatments received filtered seawater at ∼60 mL/min. Postlarvae were fed the benthic diatom Navicula incerta per standardized protocols. Every week, all organisms in each experimental unit were counted to estimate survival, and samples of 15 postlarvae were recorded under an inverted microscope and measured using digital image analysis. At the end of the experiment, greater survival occurred in treatment NF A (68.2%) and was the lowest in the treatment in which flow was opened after 10 days (26.9%); however, no significant differences were found (P > 0.37). The greatest growth rate was observed in the treatment in which flow was opened after 24 days (61.6 µm/d), and the lowest was seen in static conditions (47.6 µm/d and 44.6 µm/d for static conditions and NF A treatments, respectively). An inverse relationship between final growth rates and postlarval densities was found. Our results suggest that abalone postlarvae can be cultured successfully in static conditions with aeration, but feeding routines should be improved to allow high growth rates at high stocking densities.

The Tasmanian abalone biosecurity project was initiated by the Department of Primary Industries, Parks, Water and Environment (Wild Fisheries) and the Tasmanian wild abalone industry in response to an outbreak of abalone viral ganglioneuritis in the Victorian abalone fishery during late 2005. A formal risk assessment of abalone production activities in Tasmania was undertaken, the results of which were used to guide implementation strategies of the Tasmanian abalone biosecurity project. The risk assessment concluded that movements of live abalone in the wild fishery sector represented an unacceptable risk for spread of abalone herpes virus (AbHV) in Tasmanian State waters. Live-holding facilities in Tasmania routinely hold wild-caught live abalone in tanks preceding export. Prior to November 1, 2011, live-holding water was discharged to the marine environment without any treatment or consideration of potential pathogens. Currently, all processors that hold abalone that have been transported long distances must treat their live-holding discharge water to specifications set by the Department and outlined herein. There is limited information available on inactivation of AbHV; however, considering the magnitude of the risk and the value of the Tasmanian abalone fishery, the Department and industry have put measures in place to minimize the risk of potential spread of disease. The decontamination standards presented are based on available information relating to morphology, relative susceptibility, and hardiness of aquatic herpes viruses. The aim of treating water outflow from abalone processors is to avoid the spread of AbHV in Tasmanian State waters. Treatment, however, will also limit spread of other potential novel pathogens that may arise in the future.

Hatched larvae, juveniles, and adults of the Omani abalone Haliotis mariae were cultivated in land-based tanks with filtered running seawater during 3 experiments: (1) from January 2001 to December 2005, (2) from January 2006 to November 2009, and (3) from January 2009 to December 2011. Larvae and early juveniles were fed daily with diatoms, whereas late juveniles and adults were fed with artificial food and the green algae Ulva fasciata. Shell length and total wet weight from 40–80 randomly selected specimens in various experiments were measured monthly, and sex and gonad maturity stage were defined visually. The water parameters in tanks reflected the ambient condition of the Arabian Sea. The growth pattern of the abalone was very similar in the 3 experimental trials. Larvae and early juveniles have very fast growth rates, reaching an average 53–56 mm and 19–25 g after 1 y. Better results were obtained in the second and third experiments, when at the end of 2 y of rearing, abalone mean length was 67–72 mm and the weight was 46–54 g. At the age 3 y, abalone attained a mean length of 83–85 mm and a weight of 89–93 g. After 6 y, the abalone from the first experiment (2001 to 2005) showed, on average, 88.5 mm and 110.9 g. The length increments were the highest during the first year of the culture, whereas weight increments reached maximum values during the third (second and third trials) and fourth year (first trial) of rearing. After 4 y, abalone growth increments in weight decreased significantly. Males generally but not always have larger increments in length and weight when compared with females. During cultivation, a decrease in abalone weight was sometimes observed that, in most cases, coincided with decrease in water temperature during the southwest monsoon period (June to September). Some abalone sexually matured in tanks after 1 y, and mature males and females occurred almost year-round, with peaks in April to May and November to December. The length at first maturity was found to be 65.2 mm for males and 67.1 mm for females. Growth parameters for a von Bertalanffy function were calculated using data from different experiments. The growth rate coefficient in the first experiment was lower (K = 0.65), but in third experiment it appeared higher (K = 0.80) than in natural conditions from data other authors calculated based on length-frequency distribution analysis, which indicates faster growth rates of abalone in tanks when compared with those in the wild. Results of the trials showed that it is feasible to produce Omani abalone in land-based farms from eggs to commercial size during a 3 4-y cycle.

Families of Pacific abalone (Haliotis discus hannai Ino) were initiated from fertilized gametes from broodstock taken from Japan and China. Three wild stocks from Hokkaido (Hkd), Iwate (Iwt), and Miyagi (Myg), Japan, and a local farmed stock (Zzd) at Zhangzidao Island, Dalian, China, were collected and conditioned at Zhangzidao Island during the winter in 2010. In 2011, 95 full-sib families generated by a single-mating method within each stock were tested for growth performance under a hatchery and sea-based culture system for a 1-y period. Progeny from the 4 stocks were reared in separated tanks under identical conditions until 5 mo posthatch, then 4,925 juveniles were tagged and evaluated in a growth trial that consisted of 2 replicate large pools. Growth data of juvenile abalone at the age of 1 y posthatch were collected and used to investigate differences among the stock in daily growth rate. Stock effect and full-sib effect on abalone daily growth rate from tagging to the end of the 1-y culture period were both significant. Variation among individuals within the full-sib families is comparable with the variation among stock. Top-ranked full-sib families based on 1-y growth performance were from varying Pacific abalone stock. The implications of the results is that, when comparing the performance of different H. discus hannai stock or initiating a selective breeding program for H. discus hannai, it is important to test many breeders from each stock. In terms of growth performance, top-ranked candidate F1 families from varying stock may be crossbred to generate F2 families if potential positive growth heterosis occurs.

Because abalone feed mainly on macroalgae, the disappearance of macroalgal beds would have negative effects on abalone. We investigated the relationship between abalone resources and quantitative or qualitative changes of algal beds in coastal waters around the Ojika Islands, Nagasaki Prefecture, southwestern Japan, from 1988 to 2011. During this period, the catch record of 2 abalone species—Haliotis discus discus and Haliotis gigantea—was examined, and the composition and abundance of macroalgae around the Ojika Islands was observed. The annual landing of abalone has decreased steadily from 91 mt in 1987 to 0.4 mt in 2011. The proportion of H. discus discus to the annual abalone landing has also changed; it was stable (30%–60%) between 1988 and 2000, less than 20% from 2004 to 2005, and increased from 2006, reaching more than 90% in 2010. The macroalgal beds have also changed during this period. The perennial Laminariales beds, consisting of Eisenia bicyclis and Ecklonia spp., had disappeared by 2003, shifting mostly to Sargassaceae (Sargassum macrocarpum) beds. After the Sargassaceae beds had disappeared by 2009, there have been no Laminariales or Sargassaceae beds except for spring algal beds (unusual perennial Sargassaceae beds that form dense stands from March to July and lose most thalli after maturing in August) in some fishing ports. The results suggest a differential detrimental effect of the disappearance of macroalgal beds on abalone, with different species having different effects. After 2009, when no perennial Laminariales or Sargassaceae beds were present, there were no mature individuals of H. gigantea, with no recruitment at the juvenile stage of the latter at major fishing grounds. Reformation of the macroalgal beds is indispensable to sustain or restore the H. gigantea population. On the other hand, because most H. discus discus are able to mature, they can sustain a viable population under this condition.

Gamma-aminobutyric acid (GABA) is a major neurotransmitter and effective settlement inducer in abalone aquaculture. This study aimed to explore the distribution of GABA within neural tissues of Haliotis asinina. Gamma-aminobutyric acid was found in neuronal cell type 1 of 3 major ganglia (i.e., cerebral, pleuropedal, and visceral ganglia) of both sexes. The distribution of GABA-immunoreactive (-ir) cells in the cerebral ganglion was concentrated mostly in the cortex region of the dorsal horn, whereas it was scattered throughout the pleuropedal ganglion, with more in the upper half. Gamma-aminobutyric acid-ir nerve fibers were found throughout the neuropils of the ganglia. The visceral ganglion had the least numbers of GABA-ir neurons compared with the other 2 ganglia. The cells were distributed mainly in the dorsal horn. We also observed GABA to be colocalized with 2 other neurotransmitters: serotonin (5-HT) and dopamine (DA). In the cerebral ganglion, fluorescence double staining of GABA and 5-HT, and GABA and DA showed immunoreactivity in separate cells and was also colocalized in the same cells. In the pleuropedal ganglion, the staining pattern was similar to the cerebral ganglion, but positive-staining cells were less numerous. In the visceral ganglion, GABA and DA, and GABA and 5-HT were colocalized in the same cell types. Overall, we found that GABAergic cells were most numerous in the cerebral ganglion of H. asinina. Further studies are required to determine the functions of these neurotransmitters in relation to their distribution.

Between May 2006 and February 2010, abalone viral ganglioneuritis caused by abalone herpes virus (AbHV) spread along the coast of Victoria, Australia, and devastated wild abalone populations, causing high mortality (up to 90% in some areas). However, some abalone from the affected populations survived the epizootic and thus may be naturally resistant to the disease. To test this hypothesis, abalone (Haliotis rubra) from 5 reefs within the geographical range for AVG were collected and tested for resistance to infection and disease. Thus, mature survivors (abalone ∼160 mm in length) and juvenile “new recruits” (abalone ∼70 mm in length) were exposed to the virus using an experimental infectivity model to determine the presence of any potential resistance to the virus. Exposure to AbHV was performed by immersion using 3 serial viral dilutions to ensure that abalone were exposed to at least 1 viral concentration that would provide a morbidity dose of intermediate level. Results indicated that morbidity curves for the wild abalone groups (both mature and juvenile) were similar to those of the susceptible, naive, farmed hybrid (Haliotis laevigata × Haliotis rubra) abalone (positive control) groups. Histological lesions typical of abalone viral ganglioneuritis, and viral DNA, were detected in moribund, challenged abalone, confirming AbHV as the causative disease agent. Results suggest that the surviving wild abalone are not resistant to AbHV and were probably not exposed to pathogenic doses of the virus during the initial outbreak that commenced in 2006.

Abalone is a highly regarded food in many cultures. It is consumed as a luxury food, valued for its unique sensory properties, which include both flavor and texture. The aim of this research was to understand the texture of abalone and to link textural attributes to the microstructure of the muscle tissue. Two different sources, and species, of abalone—wild (Haliotis rubra) and farmed (Haliotis laevigata)—were characterized structurally using light microscopy and confocal laser scanning microscopy. The structure at different length scales of the abalone foot muscle tissues was related to perceived texture by a trained sensory panel. The results of the microscopy work showed isotropic assemblies of interwoven muscle bundles with a diameter of approximately 20–40 µm. The muscle fibers consisted of bundles of aligned muscle fibrils, 2–4 µm in diameter, that were interconnected with anisotropic collagen. During steaming, the muscle fibers were observed to separate as a result of configurational changes of the protein. The sample from wild abalone was found by the sensory panel to be the most chewy, firm and springy. The size of the collagen-rich areas was linked to the texture perception, with the toughest pieces of meat displaying the largest collagen-rich areas. The size of the muscle fiber bundles also contributed to the perceived texture, in which samples containing larger bundles were perceived as more chewy than samples with fewer fibers per bundle.

Abalone is a highly valued food product in many countries, in large part a result of its unique sensory properties. Wild and cultured abalone both attract premium prices, but generally this is not based on sensory characteristics. Yet, abalone aquaculture is developing to provide an alternative to a dwindling supply of wild abalone, and this provides an opportunity to optimize the sensory properties if they are better understood. In most natural food products, farming practices and growing environment are responsible for the sensory properties of the final product; therefore, the comparison of both wild and aquacultured abalone's sensory characteristics could contribute to a better understanding of the impact of the growing and farming practices on the sensory properties. Our study focused on the development of a descriptive sensory analysis methodology to measure abalone sensory properties, and the observation of differences among the abalone sampled. Wild and aquacultured abalone were prepared according to a standardized cooking protocol. A sensory panel of trained assessors developed and defined a descriptive vocabulary and a method of assessment, and then quantified the sensory properties of abalone. A vocabulary of 16 terms describing aroma, texture, flavor, and aftertaste of the abalone was developed. Very significant differences were found between abalone sourced from the wild and aquacultured abalone from different sources. The wild-caught blacklip abalone, which were larger in size, were perceived as more firm, springy, and chewy, but also rated significantly higher in aroma, flavor, and aftertaste impact as well as earthy and metallic flavors. Significant differences in sensory properties were also found between cultured abalone fed different diets. Compositional analysis showed significant differences between abalone in their content of glycogen (range, 4.8%–23.2% of dry weight (DW)), moisture (69.4%–73.7% live weight), and taste-active free amino acids, especially glycine (3.4–18.2 mg/g DW) and glutamate (1.0–3.6 mg/g DW). Correlations were found between sensory attributes and some chemical compounds. This study indicates that growing conditions as well as growing techniques may have a large influence on abalone sensory characteristics. However, because the design of the study was not balanced for key growth or production variables, additional studies are required to identify and quantify which factors were most influential. The descriptive sensory method developed was successful in measuring the sensory properties of abalone and can now be applied more broadly.

The South African abalone Haliotis midae Linnaeus is the most important aquaculture species in South Africa. Marker-assisted selection is envisioned to play an integral part of the genetic improvement program of abalone, and therefore the generation of linkage maps for quantitative trait loci analyses are necessary. This study reports on a first-generation linkage map for H. midae based on microsatellite and single nucleotide polymorphism (SNP) markers. Ten full-sib families were screened with a total of 508 molecular markers derived from genomic and expressed sequence tag sequences. Linkage maps were constructed for each of the families and combined to create an integrated linkage map. The integrated linkage map consists of 186 markers that included 116 microsatellites and 70 SNPs. These markers mapped to 18 linkage groups, which corresponds to the haploid chromosome number of H. midae. The average genome length was estimated at 1,312 cM, displaying an average marker interval of 6.88 cM with 80% genome coverage. The female map is 1.16-fold longer than the male map, indicating differences in recombination rate between the sexes. The association of markers with known genes as well as with transposon elements was also investigated. This study resulted in the first linkage map constructed for any haliotid in which both microsatellite and SNP markers were used, and the results provide a framework for future applications in quantitative trait loci identification.

The implementation of abalone aggregations as a tool for stock enhancement has been under discussion. For this purpose, understanding the self-recruitment capacity of managed reefs based on the amount of larval retention is an important task to evaluate potential success. Under the hypothesis that every reef is mostly self-restored within a short spatiotemporal scale because of a rather reduced planktonic period, the practice of aggregating mature adults of pink abalone in a reef would improve local recruitment. This study assessed local replenishment within an abalone reef of pink abalone Haliotis corrugata at Bahía Asunción (El Riíto reef), a location on the west coast of the Baja California Peninsula, where an aggregation of adult abalone was studied. A parentage analysis was carried out between adults transplanted to El Riíto and the juveniles collected from the same site by comparing their genetic profiles at 8 microsatellite DNA loci. The parentage tests defined successfully the status of more than 97% of the juveniles, revealing that approximately 4% of them could have been produced within the aggregation area. Because not all the potential parental abalone were collected, this self-recruitment proportion in the aggregation experiment was possibly underestimated. The suitability of parentage analyses, based on genetic markers as a robust alternative for the assessment of future aggregations, is discussed.

In this study, shell length, shell width, shell height, apex height, and body weight of reciprocal hybrid abalone (Haliotis discus hannai ♀ × H. gigantea ♂ (DG) and H. gigantea ♀ × H. discus hannai ♂ (GD)) were measured, and the correlation coefficients were estimated. Path coefficients, determination coefficients, and correlation index were calculated. The results showed that phenotypic correlations between morphological traits and body weight in reciprocal hybrids were positive. The association of the morphological traits and body weight were found to be different in these 2 hybrid abalone. For DG, shell height was highly correlated with body weight among the 4 shell morphological traits, whereas shell width was highly correlated with body weight in GD. Multiple regression equations were obtained to estimate shell length, Χ;₁ (in millimeters); shell width, Χ;₂ (in millimeters); apex height, Χ;₃ (in millimeters); and shell height, Χ;₄ (in millimeters); against body weight, Y (in grams) of reciprocal hybrids (DG and GD). For DG: Y = -181.723 2.4327Χ;₁ 1.2548Χ;₂ 1.2128Χ;₃ 2.2128Χ;₄; for GD: Y = -241.131 3.1122Χ;₁ 2.0166Χ;₂ 1.7543Χ;₃ 2.7312Χ;₄. These results will help abalone breeding practices and be useful for selecting growthrelated traits in genetic breeding program of hybrid abalone.

Land-based grow-out of greenlip abalone (Haliotis laevigata) in Australia is predominantly practiced using a single-diet feeding strategy, despite geographical and seasonal differences in water temperature that influence feed intake and growth. This 12-wk study investigated the interactions between 2 abalone year classes (1 y old, 1.8 g; 2 y old, 22.9 g), 3 water temperatures (14°C, 18°C, and 22°C), and 4 dietary protein levels (1 y old: 27%, 30%, 33%, and 36% crude protein; 2 y old: 24%, 27%, 30%, and 33% crude protein) to evaluate the potential to use diets to suit specific water temperatures and aged animals. Diets were formulated to be isoenergetic (∼12.5 MJ/kg digestible energy), and contain fat levels of ∼3.6% and digestible protein levels ranging from 17.99%–28.57%. Feed was fed to excess daily and uneaten food was collected. Temperature significantly affected the specific growth rate of both year classes of abalone. There was no significant effect of dietary protein level on specific growth rate; however, abalone compensated for a reduction of dietary protein by consuming more feed. This observation was evident with significant increases in feed conversion ratios as dietary protein levels decreased for both year classes. With the exception of abalone grown at 14°C, when protein deposition decreased with increasing dietary protein level, protein deposition increased with an increase in dietary protein for both year classes. For 1-y-old abalone, as temperature increased from 14-22°C, the optimum crude dietary protein levels increased from -29%-∼35%. For 2-y-old abalone, the optimum crude protein level appeared to be less, and increased from 24% at 14°C to 34% at 22°C. There is scope to use multidiet feeding strategies in the production of greenlip abalone.

The land-based culture of greenlip abalone Haliotis laevigata in southeastern Australia is carried out using seawater that is prone to seasonal temperature fluctuations and is done almost exclusively using artificial feeds. Although some nutrition research has been done to identify the optimum dietary protein level, typically farms use only 1 diet for grow-out after the juveniles are weaned. Little consideration has been given to the effects of fluctuating water temperatures and dietary protein levels on the morphology of the gastrointestinal tract (GIT) of abalone. Because these factors are known to impact growth in other aquatic species, it is important that they are investigated further to improve growth in abalone species. In this study, the histological changes of the GIT of greenlip abalone in response to 2 water temperatures and 4 dietary levels of crude protein (juvenile, 27% and 36%; subadult, 24% and 33%) for juveniles (1.75 g) and subadults (22.93 g) were investigated. The epithelial thickness of the stomach and crop; intestinal villus height, width, and area; lamina propria height; and stomach, crop, and intestinal neutral and acidic goblet cell numbers were measured. The stomach epithelium was significantly thicker at 14°C than 22°C in both juveniles and subadults, whereas the crop epithelium was significantly thicker at 22°C than 14°C in juveniles. The crop epithelial thickness of subadults was reduced by increasing dietary protein; however, juveniles did not show the same response. Juvenile abalone were more sensitive to temperature fluctuations than subadults, whereas significant effects of dietary protein levels were only observed in subadults. The alterations in the morphology of the GIT did not appear to be detrimental to the health and growth of the abalone. Further research is required to investigate the interactive effects of water temperature and dietary ingredients, particularly in regard to antinutritional factors, on the morphology and function of the GIT to improve our understanding of abalone physiology.

This study reports the first classification of cytological structures in developing gonads of cultivated Haliotis midae. Gonad tissue from animals ranging from 6–48 mo of age was evaluated histologically. The process of oogenesis was divided into 9 distinct stages according to the size and histological structures of each cell type, whereas spermatogenesis was divided into 5 distinct stages. Six-mo-old animals showed initial development of germinal epithelium, whereas at 12 mo of age, the gonad cavity was visible. In 18-mo-old males, spermatogonia and primary spermatocytes were identified, whereas in 24-mo-old males, all cell stages of spermatogenesis were present. Oogonia and stage 1 oocytes were seen in the gonad cavity of an 18-mo-old female, whereas in the gonad of 2-y-old females, all stages of oogenesis could be distinguished, although mature oocytes were not abundant.

Fluctuations in reproductive performance (i.e., spawning success, hatching rate, larval survival) are a common occurrence in abalone breeding programs, in particular during the early stages of their development. Such fluctuations affect the numbers of families available for progeny testing and selection, and can have consequences for genetic gains and inbreeding. We used stochastic computer simulations to understand how genetic gains and levels of inbreeding are affected when greenlip (Haliotis laevigata) breeding programs encounter varying severity and frequency of reproductive failure. We simulated breeding programs for greenlip abalone with both conservative and aggressive selection approaches over 35 y (10 generations). Without reproductive failure, genetic improvements of 36%–55% could be achieved after 10 y of selection in a single trait in a commercial abalone breeding program with a conservative selection approach, and gains of twice that could be achieved with a selection approach that allowed high rates of inbreeding. A conservative selection approach would be sustainable even at high rates of reproductive failure, whereas a more aggressive approach would lead to nearly twice the recommended level of inbreeding. It was concluded that breeding programs for greenlip abalone may be buffered against unexpected fluctuations in reproductive performance if the selection approach is chosen strategically.

In many marine invertebrates, the relationship between egg production and/or number of competent larvae and subsequent recruitment is often unknown. Estimating such relationship is critical for informing the management and conservation of exploited species because it determines a natural population's response to exploitation. In the current study, recruitment rates of abalone Haliotis fulgens and Haliotis corrugata were recorded by means of postlarval collectors inside and outside 2 marine reserves in 2 subsequent years. At the same time and locations, theoretical reproductive outputs were computed by combining estimates of abalone densities and size structure with literature data on size-dependent fecundity and size at sexual maturity. We found that observed settlement rates correlated positively and significantly with estimated reproductive output, suggesting that greater production of eggs by large and fecund individuals can result in predictably high recruitment rates. In addition, the slope of the linear relationship suggests that the proportion of eggs that settle and metamorphose to become postlarvae is between 0.2% and 0.3%. Although affected by great uncertainty, this value constitutes a unique estimate of larval survival for the genus Haliotis in a natural environment.

Hatchery-reared abalone outplanted into the wild at higher than ambient densities often experience very high levels of mortality as a result of density-dependent predation by natural predators. We conducted 2 experiments to assess the effectiveness of different methods of reducing predation on outplanted northern abalone (Haliotis kamtschatkana). During the first experiment, we removed small predators from brick-filled habitat cages that excluded large predators. The survival rates of juvenile abalone (mean shell length (SL), 22 mm) were greater in cages from which sea stars and other predators were removed periodically than in control cages. During the second experiment, we constructed 30 fenced 1 -m² outplanting plots and assigned 10 randomly to be controls and 20 to be filled with 1 of 4 complex substrates (0.3-m layer of cobbles, 0.3-m layer of boulders, 0.9-m layer of cobbles, and 0.9-m layer of boulders). We then released 30 large juvenile abalone (mean SL, 51.5 mm) into each plot. The number of live outplanted abalone remaining in the complex substrate plots was significantly greater than in the control plots during the first 6 days. Surveys of a 4-m radius around each plot showed that emigration was lower from complex substrate plots than from control plots, and fewer shell fragments were found. The addition of complex substrate to plots provided crypsis from large predators but also resulted in significantly higher densities of small predators. Outplanting lower densities of abalone into larger plots of natural high-substrate complexity might attract fewer predatory sea stars and crabs, and thus result in higher survival rates.

Historically, Point Loma had the highest fishery landings of pink abalone (Haliotis corrugata Wood 1828) along the California coast. The current status of the population in this key location is described using population and aggregation surveys from 2004 to 2007. We developed a size-based matrix model to assess the recovery potential of this low-density population. We incorporated fecundity parameters into the model, modified by empirical nearest-neighbor distance, aggregation size, sex ratio, and size-frequency data, to evaluate their influence on the population growth rate. We found the density of the population (∼170 abalone/ha) is an order of magnitude less than the minimum spawning density (2,000 abalone/ha) used by the California Department of Fish and Wildlife for abalone management. The average aggregation size was ∼2 abalone, and more than 50% of the abalone were solitary (no neighbors within a 2.5-m distance). The average nearest-neighbor distance was greater than 5 m in all 3 y, corresponding to an estimated fertilization success rate of ∼20%. The per capita recruitment potential was 1.3–5.3 recruits per female in 2006 and 2007. Population growth rates (λ) from the models including aggregation characteristics were 12%–18% less than the models with no aggregation information. A further 12% reduction in λ occurred between models assuming high and low fertilization success (high, 1.04/y; low, 0.91/y), showing that inclusion of aggregation characteristics has a large impact on population viability analyses. Under the International Union for the Conservation of Nature threat categories, a population with a λ of 0.91 would be classified as endangered. Based on these results, we define recovery targets for pink abalone as (1) aggregation size ≥ 5 abalone and (2) nearest-neighbor distance less than 1.6 m. We suggest aggregation characteristics will be important to include when quantifying recovery goals for depleted populations of species susceptible to reproductive Allee effects.

Abalone restocking in the peninsula of Baja California, Mexico, has been practiced for more than 2 decades by fishermen cooperatives. We describe the methods used to produce and release abalone larvae and seeds by these organizations, and provide their recent production statistics. From 2005 to 2011, 2.2 million seeds (>15 mm) and 692 million competent larvae were produced by 6 cooperative hatcheries and released in their fishing grounds. Of these, 90.1% of the seeds and 80.7% of the larvae corresponded to Haliotis fulgens, whereas the figures for Haliotis corrugata were 9.9% and 19.3%, respectively. The research conducted in Mexico on the evaluation of the impact of restocking is also addressed. Preliminary results suggest that less than 5% of the seeds stocked are incorporated into commercial catches.

A management strategy evaluation framework was used to simulate multiple populations making up a management or quota zone for Australian blacklip abalone (Haliotis rubra). The simulation was conditioned on the properties of blacklip abalone and its fishery on the east coast of Tasmania. Abalone are well known for exhibiting spatial heterogeneity in their biological properties. Each population in the simulation was represented by a size-based population dynamics model and had biological properties of growth, maturation, emergence from crypsis, and mortality specific to each population; the range of these properties varies to different degrees in the different quota zones around Tasmania. The simulation was used to compare the effects of applying different legal minimum length (LML) regulations on the fishery. Because of spatial heterogeneity in growth, a single LML within a zone has always been a compromise between underprotecting some populations and overprotecting others. The simulation was used to determine the protection afforded the overall mature biomass and the variation likely among different populations, and how these populations then responded to exploitation. In addition, when setting an LML within a zone, an analysis was made, using the simulation, of the potential trade-offs between the total allowable catch (TAC), the number of abalone needed to take that TAC, the proportion of the mature biomass protected by the LML, and the stock depletion level after fishing with different LMLs but the same TAG.

Population declines of pink (Haliotis corrugata) and green (Haliotis fulgens) abalone in southern California forced the closure of the fisheries in 1995. Overfishing was the main factor contributing to decreasing landings, and in 2004 both pink and green abalone were identified as species of concern. Translocation of adults, moving solitary abalone together to create dense aggregations, is one of the strategies that has been proposed to overcome Allee effects and to enhance spawning success and recovery. Pink (n = 35) and green (n = 113) abalone were tagged and translocated to recovery sites with preexisting pink (n = 13) and green (n = 26) abalone. Translocation and preexisting abalone were tagged and monitored to determine their long-term survival, persistence at the site, and movement at 2 islands in southern California. The mortality associated with the tagging and translocations was low (<5%) including 1 dead pink abalone and 5 dead green abalone. The density of translocated pink abalone at 2 sites remained fairly stable, decreasing slightly from 0.84 abalone/m² to 0.72 abalone/m² after 391 days and 0.56 abalone/m² to 0.44 abalone/m² after 133 days. In contrast, translocated green abalone densities at 2 sites decreased dramatically from 0.51 abalone/m² to 0.08 abalone/m² after 405 days and 0.62 abalone/m² to 0.01 abalone/m² after 388 days. Pink abalone persistence was high and immigration was rare, whereas green abalone persistence was low and immigration into the sites was common. We find that pink abalone are optimal candidates for translocation given their high rate of site fidelity, but green abalone are not. Furthermore, our results demonstrate how important species-specific behaviors are to the success of translocation efforts, supporting the use of pilot studies prior to implementation of large-scale translocation recovery actions.

A time series abundance analysis of adult and juvenile Haliotis fulgens living in the central region of Baja California Sur, México, was performed and its potential application to fishery management as a predictor of future catches was assessed. The juvenile time series consisted of 13 y (1996 to 2008) of semiannual sampling of abalone juveniles from 2 sites in Bahía Tortugas, Baja California Sur, whereas the adult time series encompassed 15 y (1996 to 2010) at the same fishing area. The time series were based on separate density and biomass surveys of the abalone population conducted annually by the Instituto Nacional de la Pesca for setting catch quotas in all abalone fishing areas. Various lagged linear regressions and quadratic regressions were tested to explore the correlations between 1-y-old recruits and ≥ 3-, 4-, and 5-y-old adults; the reverse order was also evaluated (adults of various ages and 1-y-old recruits). The only significant quadratic regression captured the 3-y delay between ≤ 1-y-old juveniles and 4-y-old adults (r = 0.702, P = 0.014). Smoothed series for both adults and recruits revealed that the abundance of recruits ≤ 1 y old was reflected 3 y later in the abundance of 4-y-old adults. The importance of a predictive model such as this one lies primarily in its good approximation of future catches, enabling the anticipation of population increases or recruitment failures that may impact the fishery.

Field studies that attempt to estimate the mean growth rates of individuals in a population usually yield unbalanced data and various forms of sampling error. If these data are a poor representation of a population, then the estimates of growth rates may also be unrepresentative of the population. We present an assessment of the performance and uncertainty in 4 growth models—the von Bertalanffy, Gompertz, inverse logistic, and Schnute models—fitted to data with various scenarios of sampling error. The performance of each model was determined by comparing highest likelihoods outcomes to known case outcomes. A Monte Carlo simulation framework was used to generate data consisting of 8 typical scenarios of sampling error common in tag-recapture data. Each growth model was evaluated according to 2 metrics: the error rate (i.e., a metric for model uncertainty) and the prediction error (i.e., the accuracy of biological predictions such as age). Results indicate that an inadequate size range in the data (i.e., a lack of juvenile size classes) would often lead to a high error rate. When negative growth increment data are included, the K parameter of the von Bertalanffy model increased, and the L∞ decreased. The inverse logistic model sometimes produced absurd parameter estimates but nevertheless generated the lowest prediction errors. A high prediction error can potentially have far more serious implications to fishery stock assessments than is currently appreciated. Given widespread use of the von Bertalanffy and Gompertz models, selected solely on the basis of model selection criteria, it is clear that greater care and scrutiny are warranted in the selection of growth models in the presence of sampling error.