Greenlip Abalone Research Articles

Modelling trends including effects of natural disturbance in an abalone dive fishery in Australia

AbstractFisheries management strategies usually do not consider secondary consequences of environmental shocks. A recent viral disease outbreak that decimated blacklip abalone populations in southern Australia had a much smaller impact on the region's less‐abundant greenlip abalone populations. Decreases in total allowable commercial catch (TACC) for blacklip abalone were partially offset by a transient increase in greenlip abalone TACC that peaked in 2010 and reduced to zero in 2013. A hypothesis that the greenlip abalone stock had declined was supported by a Bayesian analysis of catch rates (catch per unit effort, CPUE, as a proxy for biomass). The estimated decline is consistent with depletion of the relatively small and fragmented greenlip stock as an indirect consequence of the disease impact. Our analysis demonstrates a need to jointly monitor and manage substitute fisheries when one of the fisheries experiences depletion as a result of a natural disturbance event.Considerations for Management Hierarchical Bayesian models can determine whether a shock to a natural resource indirectly affects related resources via a transfer of exploitation effort; Greenlip abalone stocks in western Victoria were generally poor in quality and infrequently exploited prior to the disease outbreak. Their low productivity rendered them vulnerable to the sudden increase in exploitation pressure, which could not be sustained once CPUE declined to 40–50 kg h−1, after which fishing activity ceased; A CPUE of 40 kg h−1 could be a precautionary limit reference point for triggering future greenlip abalone fishery closures; An increase in greenlip abalone legal minimum length (LML) to at least 140 mm would improve quality and profit; It is important to protect substitute resources from secondary exploitation when imposing restrictions on exploitation of resources that are adversely impacted by natural disturbance events.

Impact of Vitamin K1on Tissue Vitamin K Levels, Immunity, and Survival of Greenlip Abalone,Haliotis laevigata, at Summer Water Temperatures

Summer mortality impacts the productivity of greenlip abalone, Haliotis laevigata, on land-based farms in South Australia. It is associated with high water temperature (greater than 23°C), low dissolved oxygen levels, increased bacterial loads, and immune system suppression during summer months. This study aimed to alleviate mortality rates of greenlip abalone by dietary intervention using vitamin K1 to support the innate immune system and oxidative status. Dietary vitamin K1 at 0.0, 0.5, 1.0, and 5.0 mg kg-1 was added to a commercially formulated diet mash. An additional diet containing 0.5 mg kg-1 of K3 was also used for comparison. Diets were fed to 3-y-old abalone (71.51 g; 79.91 mm) at 22 and 25°C water temperatures for 39 days. No mortalities were observed at 22°C; however, high mortalities were observed in all dietary treatments at the water temperature of 25°C. Compared with the negative control diet (0.0 mg additional inclusion ofK1 or K3 kg-1) at 25°C, the inclusion of vitaminK1 orK3 did not improve survival of greenlip abalone (P > 0.05). VitaminK1 inclusion level resulted in significant increases in vitamin K1 concentration of visceral organ and muscle tissues (P 0.05). Increasing water temperature to 25°C resulted in significant increases in serum catalase activity (22 K3) and vitamin K1 concentration in visceral organ (K1 >K3). In conclusion, vitaminK1 at the doses tested, resulted in significant increases in vitaminK1 concentration in visceral organ and muscle tissues, but failed to improve immune function, oxidative status, or survival of greenlip abalone at high summer water temperatures.

Seascape genomics reveals adaptive divergence in a connected and commercially important mollusc, the greenlip abalone (Haliotis laevigata), along a longitudinal environmental gradient.

Populations of broadcast spawning marine organisms often have large sizes and are exposed to reduced genetic drift. Under such scenarios, strong selection associated with spatial environmental heterogeneity is expected to drive localized adaptive divergence, even in the face of connectivity. We tested this hypothesis using a seascape genomics approach in the commercially important greenlip abalone (Haliotis laevigata). We assessed how its population structure has been influenced by environmental heterogeneity along a zonal coastal boundary in southern Australia linked by strong oceanographic connectivity. Our data sets include 9,109 filtered SNPs for 371 abalones from 13 localities and environmental mapping across ~800km. Genotype-environment association analyses and outlier tests defined 8,786 putatively neutral and 323 candidate adaptive loci. From a neutral perspective, the species is better represented by a metapopulation with very low differentiation (global FST =0.0081) and weak isolation by distance following a stepping-stone model. For the candidate adaptive loci, however, model-based and model-free approaches indicated five divergent population clusters. After controlling for spatial distance, the distribution of putatively adaptive variation was strongly correlated to selection linked to minimum sea surface temperature and oxygen concentration. Around 80 candidates were annotated to genes with functions related to high temperature and/or low oxygen tolerance, including genes that influence the resilience of abalone species found in other biogeographic regions. Our study includes a documented example about the uptake of genomic information in fisheries management and supports the hypothesis of adaptive divergence due to coastal environmental heterogeneity in a connected metapopulation of a broadcast spawner.

Comparison of three inert markers in measuring apparent nutrient digestibility of juvenile abalone under different culture condition and temperature regimes

A comparative research using three inert markers, chromic oxide, yttrium and ytterbium to measure the apparent nutrient digestibility of experimental feed in juvenile Hybrid abalone (Haliotis rubra X H. laevigata) and Greenlip abalone (H.laevigata) revealed that apparent digestibility of crude protein (ADCP) measured using yttrium and ytterbium in hybrid abalone were significantly different across the treatments. Protein digestibility measured in experimental tanks was higher than those measured in indoor and outdoor commercial tanks, regardless of inert marker used. Chromic oxide led to overestimated ADCP compared to when measured using yttrium and ytterbium. There were no significant interactions between temperature and inert markers when measuring ADCP and apparent digestibility of gross energy (ADGE). However, there was a significant difference of ADCP amongst inert markers when measured in greenlip abalone cultured at two temperatures. While measurements of ADge calculated using three inert markers shared the same value.

Growth and Nutrient Utilization of Greenlip Abalone (Haliotis laevigata) FedUlvaSp. Protein Extract

Greenlip abalone (Haliotis laevigata) are commercially farmed in land-based systems in southern Australia and are fed formulated diets that typically do not contain macroalgae. In a 90-day study, the growth and nutrient utilization of juvenile greenlip abalone (1.82 g, 23.23 mm) fed diets containing Ulva sp. protein extract (UPE) were investigated. Animals were fed one of the four formulated test diets containing graded levels of UPE (0%, 5%, 10%, and 20%) or a commercial diet that served as a control for the 0% basal diet. Diets were formulated to contain 37% crude protein, 5% lipid, and 17.5 MJ/kg gross energy. The specific growth rate and shell growth rate (µm/day) of abalone fed the four experimental diets were similar. Dietary inclusions of UPE supported the growth of juvenile greenlip abalone and may be used to reduce dietary inclusions of solvent extracted soybean meal, dehulled lupins, and wheat flour. Currently, UPE is cost prohibitive for commercial use in greenlip abalone diet. As UPE is a by-product of the macroalgae industry, the cost of UPE would likely become more economically viable as macroalgae production increases in the future to include in diets for greenlip abalone. Once economically viable, we recommend a dietary inclusion of up to 20% UPE meal for greenlip abalone.

Survival and Feeding of Greenlip Abalone (Haliotis laevigata) in Response to a Commercially Available Dietary Additive at High Water Temperature

Elevated mortality, triggered by increased water temperatures (>22°C) and associated factors, is a significant issue for land-based abalone farms in southern Australia. The aim of this study was to test the efficacy of the commercial animal feed product Orego-Stim (OS), containing oregano essential oil in reducing the mortality of 3-y-old greenlip abalone (Haliotis laevigata) exposed to high water temperature (25°C). Inclusion levels of 0.0 (commercial control diet), 0.5%, 1.0%, 2.0%, and 4.0% OS were added into a commercial feed formulation and diets were fed to 3-y-old greenlip abalone (67.98 g, 77.01 mm shell length) at two water temperatures (22°C and 25°C) for 47 days. Survival and immune parameters including phagocytic activity, total hemocyte count (THC), and activities of the enzymes superoxide dismutase (SOD) and catalase (CAT) were measured. Survival was high at 22°C with no significant differences in mortality between treatments. Irrespective of this, exposure to elevated water temperature (25°C) resulted in significantly higher mortalities for all diet treatments (P < 0.05), without any effect of diet. Low ferric reducing antioxidant potential values were observed for all diets. Phagocytic activity remained stable for all temperature and OS treatments (48.82% ± 1.31%). The dietary inclusion of OS and increased water temperature increased the THC compared with the commercial control diet treatment at 22°C. Superoxide dismutase was significantly elevated in greenlip abalone fed the commercial control (0.56 ± 0.08 U mL-1), and CAT was significantly higher when fed the 4.0% OS diet treatment at 25°C (18.93 ± 2.25 nmol min-1 mL-1). Despite failing to increase survival, OS significantly enhanced feed intake at both temperatures at 2.0% and 4.0% compared with the commercial control diet treatment, highlighting its ability as a feeding stimulant (P < 0.05).

The effect of commercial, natural and grape seed extract supplemented diets on gene expression signatures and survival of greenlip abalone (Haliotis laevigata) during heat stress

Summer mortality is a phenomenon associated with high temperature water spikes that can result in mass mortalities of abalone and other molluscs. This is a particular concern for aquaculture industries due to the economic impacts of such events. Diets containing algal supplements have been suggested as pre-emptive solutions for preventing these mass mortalities. The same has also been suggested for diets containing grape seed extract. This is due to their potential as a source of antioxidative compounds, which reduce the accumulation of harmful reactive oxygen species. This study aimed to identify functional genes associated with high survival in abalone fed diets high in antioxidative compounds during heat stress. Tentacle transcriptomes of 40 greenlip abalone (Haliotis laevigata) were investigated to determine the combined effects of differing diets and temperature on the gene expression responses by abalone. Here we compare the functional gene expression changes at 22°C and 25°C in abalone fed common commercial, live macroalgal (Ulva lactuca) and grape seed extract supplemented commercial diets as a means to understand the resulting high survival of abalone fed grape seed extract during heat stress. Twenty-four genes were differentially expressed between high survival promoting diets (macroalgae or grape seed extract supplemented commercial) relative to the purely commercial diet. Many of these genes have been suggested to be involved in antioxidant and innate immunity responses. The identification of these genes and their functional roles has enhanced our understanding of processes that contribute to summer stress resilience in abalone. Our study supports the hypothesis that diet and gene expression signatures may be indicative of the survival capabilities of abalone when exposed to heat stress.

Thermal Preference Increases During Larval Development of Pure and Hybrid Abalone

Temperature is one of the main factors influencing biological processes of ectothermic species. An optimum temperature of 16–18°C has been suggested for the development of early life stages of temperate Australian abalone, yet there are little physiological or behavioral data to support this suggestion. This study examines the acute thermal preferences (Tpref), swimming speeds (U), and oxygen consumption rates (ṀO2) of veliger larvae of blacklip abalone [Haliotis rubra (Leach, 1814)], greenlip abalone [Haliotis laevigata (Donovan, 1808)], and their interspecies hybrid. Thermal preference and U were measured in a thermal gradient with temperatures ranging from 12°C to 25°C, and ṀO2 was measured at 4–7 temperatures between 12°C and 32°C. Thermal preference increased in all three groups of abalone during development from a Tpref of 16°C in 1-day-old early veligers to a Tpref of 20°C in 3-day-old late veligers. Swimming speed increased with temperature in all three groups of abalone and increased with age in H. rubra and hybrids but not in H. laevigata. Veliger ṀO2 increased throughout the ecologically relevant temperature range in all three abalone groups. Higher temperatures were examined in hybrids, and it was found that ṀO2 reached a peak at 25°C and declined thereafter. These results align with the temperatures that veligers may experience in their natural habitat and provide support that current temperatures maintained at Australian aquaculture hatcheries are within optimal ranges for larval performance.

Epipodial Tentacle Gene Expression and Predetermined Resilience to Summer Mortality in the Commercially Important Greenlip Abalone, Haliotis laevigata

“Summer mortality” is a phenomenon that occurs during warm water temperature spikes that results in the mass mortality of many ecologically and economically important mollusks such as abalone. This study aimed to determine whether the baseline gene expression of abalone before a laboratory-induced summer mortality event was associated with resilience to summer mortality. Tentacle transcriptomes of 35 greenlip abalone (Haliotis laevigata) were sequenced prior to the animals being exposed to an increase in water temperature—simulating conditions which have previously resulted in summer mortality. Abalone derived from three source locations with different environmental conditions were categorized as susceptible or resistant to summer mortality depending on whether they died or survived after the water temperature was increased. We detected two genes showing significantly higher expression in resilient abalone relative to susceptible abalone prior to the laboratory-induced summer mortality event. One of these genes was annotated through the NCBI non-redundant protein database using BLASTX to an anemone (Exaiptasia pallida) Transposon Ty3-G Gag Pol polyprotein. Distinct gene expression signatures were also found between resilient and susceptible abalone depending on the population origin, which may suggest divergence in local adaptation mechanisms for resilience. Many of these genes have been suggested to be involved in antioxidant and immune-related functions. The identification of these genes and their functional roles have enhanced our understanding of processes that may contribute to summer mortality in abalone. Our study supports the hypothesis that prestress gene expression signatures are indicative of the likelihood of summer mortality.

Bacteriophage therapy for the control of Vibrio harveyi in greenlip abalone (Haliotis laevigata)

Bacteriophage therapy has demonstrated promising results towards the control of bacterial infections within the aquaculture industry as an alternative therapy to antibiotics. This current research describes the efficacy of bacteriophage therapy in controlling vibriosis within abalone (Haliotis laevigata). Two bacteriophages were isolated and used in in vitro assays to determine the effect of each specific phage on the growth of specific Vibrio harveyi isolates. To demonstrate efficacy, an in vivo bioassay was performed using abalone (H. laevigata) at a water temperature of 24°C. Characterisation of the two isolated phages revealed they were from the family, Siphoviridae. The phages had different antimicrobial abilities towards different Vibrio harveyi isolates in the in vitro assays and the bioassay demonstrated improved survival of abalone treated with bacteriophage. The results of the bioassay showed that the negative control and phage control were statistically identical, with 100% survival, but they were different from the positive bacterial control, with a 0% survival. The bacteria + phage treated group showed increased accumulative survival of 70% compared to the positive control. This is the first study to demonstrate the efficacy of bacteriophage therapy treatment for abalone. The study demonstrates that if abalones are treated with bacteriophage shortly after Vibrioharveyi infection, the accumulative survival could be significantly increased.

Colour change of greenlip abalone (Haliotis laevigata Donovan) fed formulated diets containing graded levels of dried macroalgae meal

This study evaluated the effects of supplementing dried macroalgae meal on the shell, foot and lip colour in terms of colour hue, saturation and brightness and pigment concentration in greenlip abalone Haliotis laevigata. Two species of dried macroalgae meal (Ulva sp. and Gracilaria cliftonii) at four levels (0% basal diet, 5%, 10% and 20%) of dietary inclusion were fed to the abalone (2.89±0.01g; shell length 22.41±0.06mm) for 92days. The abalone fed G. cliftonii meal developed brown-red colour on the shell and the increased inclusion of algal meal resulted in darker brown shells, whereas abalone fed Ulva sp. meal or the basal diet exhibited light green shells. Although foot hue and foot brightness were not influenced by the type and level of inclusion of dried algal meal, the foot colour saturation of abalone fed ≥10% macroalgal meal was significantly higher than those fed the basal diet. Abalone developed a green lip when fed ≥10% of G. cliftonii meal, whereas lip colour did not change when fed Ulva sp. meal inclusion, compared to the basal diet, and exhibited milky lip colour. Although diet pigments varied with the species of macroalgae and inclusion level, β-carotene was the major pigment in the tissue of abalone fed all test diets and its content increased significantly with the inclusion level of macroalgae in the diet. Abalone fed the basal diet had significantly lower tissue β-carotene than those fed the diets with macroalgal inclusion. This study suggests that the inclusion of ≥5% G. cliftonii can produce a brown-red shell and the inclusion of ≥10% G. cliftonii intensifies the green colour of the lip. The brown-red colour mark on the shell by feeding macroalgal meal may be used as a harmless shell-marking method for ranching, stock enhancement or growth study in the wild. Statement of relevanceFeed manipulation can change abalone shell, foot and lip colour.

Ventral Videographic Assessment of the Feeding Behavior of Juvenile Greenlip [Haliotis laevigata(Donovan, 1808)] and Hybrid (H. laevigata×Haliotis rubra) Abalone in Response to Dietary and Temperature Manipulation

ABSTRACT 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 (...

Effects of dietary grape seed extract, green tea extract, peanut extract and vitamin C supplementation on metabolism and survival of greenlip abalone (Haliotis laevigata Donovan) cultured at high temperature

A major problem confronting the abalone farming industry in Australia is elevated mortality during summer months. Recent research suggests that temperature-induced tissue breakdown allows bacteria entry to the host, and nutritional supplementation can alleviate this breakdown. The aim of this study was to alleviate mortality of greenlip abalone, Haliotis laevigata, cultured at high summer water temperatures (25°C) by dietary intervention using graded levels of peanut skin extract (PE; 0.5, 1.0, 2.5 and 5%), green tea extract (GTE; 0.5, 1.0, 2.5 and 5%) and vitamin C (1.0% vitamin C; 1.0% vitamin C+1.0% GTE; and 1.0% vitamin C+1.0% PE) in a commercial diet; these supplements contain antioxidant and bioactive compounds. The commercial diet containing 5.0% Australian grapeseed extract (GSE) fed at 25°C was also included as a negative temperature/positive diet control due to improved survival and health of abalone at high temperatures in our previous study. Three-year-old abalone (49.21g; 70.26mm) were fed the commercial diet at 22°C (positive temperature control), and the commercial diet (negative temperature control) and test diets at 25°C for 38days. Abalone survival was 85% for the commercial diet at 22°C, whereas survival of abalone was significantly reduced to 40% when fed the commercial diet at 25°C. There were no significant differences in survival of abalone fed the commercial diet at 22°C and those fed 5.0% GSE, 0.5% GTE and 2.5% GTE diets at 25°C. Supplements did not significantly affect oxygen consumption, ammonia excretion rates and total hemocyte count. Abalone fed 5.0% GTE had significantly lower phagocytic activity than those fed the commercial control diet at 22°C. Supplementation with PE and vitamin C had no beneficial effects on survival, while GTE holds promise as a potential dietary additive to enhance the survival of abalone at higher water temperature. This study confirms that supplementation of 5.0% GSE in the commercial diet also improves the survival of greenlip abalone cultured at high summer water temperature in the laboratory setting. Statement of relevancePurported to have diverse health benefits including antioxidant, antimicrobial, anti-inflammatory, and anticarcinogenic properties, 5% Australian grape extract, graded levels of green tea extract, peanut skin extract and vitamin C were supplemented in a commercial abalone diet in order to improve survival of greenlip abalone at high water temperature.

Setting quotas using provisional data: a case study from the South Australian abalone fisheries

ABSTRACTStock assessments of quota or effort managed fisheries in which the duration of the fishing season is 12 months are invariably delivered well into the subsequent fishing season. As a result, quotas are frequently based on year-old data. This delay is often unavoidable because it may take months to collect, collate and analyse data necessary to assess fishery performance. The South Australian fisheries for blacklip (Haliotis rubra Leach, 1814) and greenlip abalone (H. laevigata Donovan, 1808) have addressed this issue by using provisional data on current stock status to inform application of the harvest strategy decision rules that set the quota for the next year. The primary index of relative abundance for these fisheries is catch per unit effort (CPUE). Our study uses 25 years (1988–2012) of CPUE data to quantify the differences between the provisional and complete-season CPUE estimates at the spatial scales used to assess the fisheries. We demonstrate that, in most cases, there was a strong relationship between the provisional and complete-season CPUE estimates for both species, with little evidence of bias. As the provisional CPUE estimates were a reliable and accurate predictor of the complete-season CPUE estimates, this provides a high degree of confidence in using provisional CPUE estimates to set quotas, thereby overcoming the difficulty of basing decisions on aged data. These findings are likely to be applicable to other fisheries, particularly those where much of the annual catch is obtained (or effort expended) in a short time period at the commencement of the fishing season.

Dietary inclusions of dried macroalgae meal in formulated diets improve the growth of greenlip abalone (Haliotis laevigata)

Wild greenlip abalone predominantly consumes macroalgae, but under culture conditions in Australia, they are fed formulated diets. Dried macroalgae meals are promising ingredients for abalone diets. In this 92-day study, the growth, feed utilisation and digestive enzyme activities of greenlip abalone (Haliotis laevigata; 2.89 g) fed dried macroalgae meals (Ulva sp. meal or Gracilaria cliftonii meal) in formulated diets were investigated. Seven experimental formulated diets, a basal diet (0 % diet) and three inclusion levels of Ulva sp. meal (5, 10 and 20 % inclusions) and Gracilaria sp. meal (5, 10 and 20 % inclusions) were used. Diets were formulated to contain 35 % crude protein, 5 % crude lipid and 17.5 MJ kg−1 gross energy. A commercial diet was also fed to abalone and compared with the 0 % diet. Growth and feed conversion ratio (FCR) of abalone fed the 0 % diet and commercial diet were similar. Abalone fed 5 % Gracilaria sp. meal or Ulva sp. meal exhibited superior growth to abalone fed 0 %. However, increasing dietary Gracilaria sp. meal inclusions (>10 %) led to further growth improvements but impaired protein and energy retentions. In contrast, abalone fed >10 % Ulva sp. meal inclusions exhibited similar growth to those fed 0 and 5 % Ulva sp. Although Ulva sp. and Gracilaria sp. meals are currently not commercially viable, this study clearly demonstrates the potential to develop abalone feeds with inclusions of dried macroalgae meal. We recommend a dietary inclusion of 10 % Gracilaria sp. meal or 5 % Ulva sp. meal to improve abalone growth.

Colour changes of greenlip abalone (Haliotis laevigata Donovan) fed fresh macroalgae and dried algal supplement

Abalone colour is an important market trait in the seafood industry. Two experiments were conducted over 93days to test the effect of diet on the colour of the foot and shell of 1-year old greenlip abalone Haliotis laevigata. In Experiment 1, a commercial control diet and two species of fresh macroalgae (Gracilaria cliftonii and Ulva sp.) were used and each macroalgae species was either non-enriched or enriched with nutrients in the culture media. The shell of abalone fed the commercial diet and fresh Ulva sp. was green but abalone fed fresh G. cliftonii developed a brown shell. The fresh G. cliftonii increased shell colour purity while fresh Ulva sp. increased shell brightness. Feeding abalone with either fresh Ulva or fresh G. cliftonii produced yellowish foot. Nutrient enrichment of algae did not significantly affect the pigment contents in both macroalgae and abalone, and had minimal impact on the colour of shell and foot. With the exception of zeaxanthin, the pigment contents were significantly lower in fresh G. cliftonii than in fresh Ulva sp. Moreover, β-carotene was the main pigment in abalone fed both species of fresh macroalgae. In Experiment 2, the inclusion of dietary dried algae affected abalone colour. Three diets including a commercial control diet, a diet containing 3% dried Spirulina sp. and a diet containing 10% dried Ulva sp. were used. The shell of abalone fed dried Spirulina sp. was yellow-brown with higher colour purity while the shell remained light green in abalone fed dried Ulva sp. or the commercial control diet. The colour of abalone foot became bright yellow when abalone fed dried Ulva sp. Abalone fed dried algae contained β-carotene as the principal pigment. This study indicates that fresh macroalgae and dried algae supplementation in feed can change the colour of abalone foot and shell. Feed effect on shell colour was far more than on tissue colour. Feeding abalone with fresh G. cliftonii contributes to the formation of brown colour on the shell. Statement of relevanceFeed manipulation can change abalone shell and foot colour.

Effects of Broodstock Age and Sperm Collection Time over a Natural Spawning Period on Sperm Cryopreservation in Farmed Greenlip Abalone, Haliotis laevigata

ABSTRACTThis study investigated the effects of broodstock age (2‐ and 3‐yr‐old), and sperm collection time at the beginning, middle, and end of a natural spawning period, on the ability of sperm to tolerate cryopreservation in farmed greenlip abalone, Haliotis laevigata. The quality of sperm was assessed by motility, fertilization rate, plasma membrane integrity, mitochondrial membrane potential (MMP), and acrosome integrity (AI). The sperm collected at the middle of a natural spawning period had significantly higher quality than those collected at the beginning and the end of the spawning period in terms of plasma membrane integrity, MMP, and AI of fresh and post‐thaw sperm, post‐thaw sperm motility, and fertilization rate. No significant difference was found between 2‐ and 3‐yr‐old animals in most quality parameters evaluated. The results suggested that sperm collected during the middle of the spawning season should be used for cryopreservation. The efficiency of genetic improvement programs can be further enhanced by using sperm collected from 2‐yr‐old abalone which has a similar ability to tolerate cryopreservation as 3‐yr‐old counterparts.

Age-dependent response of digestive enzyme activities to dietary protein level and water temperature in greenlip abalone (Haliotis laevigata)

Proteases, lipases and carbohydrases are digestive enzyme sub-classes that influence the digestive capacity of abalone. In a 12-week study, the effects of age, water temperature and dietary protein levels on digestive enzyme activity in greenlip abalone (Haliotis laevigata) were investigated. One- and 2-year old abalone were fed diets with crude protein (CP) levels from 24 to 36% (18.0–28.6% digestible protein) and cultured at 14, 18 and 22°C. Diets were formulated to be isoenergetic (12.5MJkg−1 digestible energy) and isolipidic (3.6% crude lipid). Trypsin, α-amylase and lipase activities were measured, and were influenced differently by abalone age, water temperature and dietary protein levels. Lipase and α-amylase activities significantly increased as water temperatures were raised. In contrast, trypsin activity was not affected by water temperature. Trypsin activity of 2-year old abalone was significantly lower (53%) than that of 1-year old abalone. The α-amylase activities of 1-year old abalone were significantly up-regulated as dietary protein levels increased. In contrast, 2-year old abalone down-regulated α-amylase activity by 55% when fed 33% CP, compared to abalone fed 30% CP. The significant trypsin activity down-regulation in 2-year old abalone compared to 1-year old animals provides further support to reducing dietary protein for 2-year old abalone to optimise cultured greenlip abalone production. Significantly higher α-amylase activity in 1-year old abalone as starch levels were reduced indicates a compensatory effect in abalone fed carbohydrate deficient diets. Further research is recommended to optimise the protein to energy ratio for different age classes of greenlip abalone, especially when fed high dietary protein levels.Statement of relevance: Results may contribute to further diet development research

Growth and feed utilisation of greenlip abalone (Haliotis laevigata) fed nutrient enriched macroalgae

Wild greenlip abalone predominantly consume macroalgae, but are fed formulated diets under culture conditions. This study aims to (i) investigate the effect of nutrient enrichment (non-enriched and enriched) and fresh macroalgae type (Ulva sp., Gracilaria cliftonii, and an equal combination of Ulva sp. and G. cliftonii) on the growth and feed utilisation of greenlip abalone and (ii) compare the performance of abalone fed fresh macroalgae to those separately fed either one of the three commercial formulated diets. Abalone were fed to excess at 16:00h daily, and uneaten feed was collected the following morning. Nutrient enrichment increased the protein level for Ulva sp. and G. cliftonii from 5.3 to 27.7% and 12.9 to 38.1%, respectively. The growth of abalone fed G. cliftonii was superior to animals fed Ulva sp. The effect of enrichment was macroalgae species-dependent. While abalone fed enriched Ulva sp. exhibited superior growth to those fed non-enriched Ulva sp., animals fed non-enriched and enriched G. cliftonii exhibited similar growth. However, abalone fed non-enriched G. cliftonii had superior apparent protein deposition and protein efficiency ratio, compared to animals fed enriched G. cliftonii. Feeding an equal mix of Ulva sp. and G. cliftonii had a positive synergistic effect on abalone growth, compared to animals fed mono-specific algae. Abalone fed each commercial diet exhibited improved growth and feed utilisation compared to animals fed fresh macroalgae. The results of the current study suggest that the use of fresh G. cliftonii as a source of carbohydrates may spare protein when feeding formulated diets to abalone. When formulated diets are unavailable or are inappropriate to feed abalone, a mix of enriched Ulva sp. and G. cliftonii may be used. However, feeding fresh macroalgae alone to cultured greenlip abalone should be avoided, if growth is the parameter of interest and we recommend that commercial formulated diets be fed to cultured greenlip abalone. Statement of relevanceAbalone diet development with fresh macroalgae.

Temperature-Dependent Feed Consumption Patterns for Greenlip (Haliotis laevigata) and Hybrid (H. laevigata × Haliotis rubra) Abalone Fed Fresh Macroalgae or a Formulated Diet

ABSTRACT Because of the nocturnal and slow feeding activity of abalone, farmed abalone are typically provided with feed throughout the night. Understanding the nocturnal feeding patterns of abalone is fundamental to feed management and productive abalone farming. In this study, the apparent feed consumption for greenlip abalone (Haliotis laevigata) and hybrid abalone (H. laevigata3Haliotis rubra) fed fresh Ulva sp. or a commercial formulated diet at 18°C or 22°C were investigated at night. Abalone were exposed to low light intensity (3.4 Lux) from 7:00 AM to 7:00 PM and darkness from 7:00 PM to 7:00 AM. Abalone were fed to excess daily at 4:00 PM and feed intake was determined at 7:00 PM, 10:00 PM, 1:00 AM, 4:00 AM, and 8:00 AM. When Ulva sp. was added to the tank, greenlip and hybrid abalone immediately displayed a feeding response, which was not observed in abalone fed the formulated diet. Abalone consumed Ulva sp. at a linear rate from 4:00 PM to 8:00 AM. In contrast, the apparent feed consumption rate...