Survival Of Abalone Research Articles

ROS-mediated physiological activities and apoptotic effect on the survival of abalone (Haliotis discus hannai) under homoyessotoxin and ammonia stresses

Serious dinoflagellate blooms produce homoyessotoxin (homo-YTX) and ammonia (NH3-N) in eutrophic seawaters, posing threats to the healthy development of the mariculture industry. This study aimed to explore the toxicity mechanism of homo-YTX and NH3-N on the survival of abalone, which is important for the ecotoxicological research and cultivation of shellfish. The economy abalone Haliotis discus hannai was placed in homo-YTX (0, 2, 5, and 10 μg L−1) and NH3-N (0, 1.08, and 3.16 mg L−1) and a mixture of the two compounds to determine the survival rate (S), antioxidative responses, physiological activities, and apoptosis of abalone. Results show that the combination of homo-YTX and NH3-N increased the reactive oxygen species level, the malondialdehyde content, and the expression level of BCL2-associated X but decreased S; the activities of superoxide dismutase, catalase, adenosine triphosphatase, glutamic–pyruvic transaminase, xanthine oxidase, lactate dehydrogenase, and lysozyme; and the expression level of B-cell lymphoma-2. The activities of alkaline phosphatase and acid phosphatase in 10 μg L−1 of homo-YTX and 3.16 mg L−1 of NH3-N solutions and in the mixture of the two toxicants decreased. The caspase3 expression level was downregulated in 10 μg L−1 of homo-YTX. These results suggest that homo-YTX and NH3-N enhanced the oxidative stress and lipid peroxidation reactions, inhibited the energy supply, disrupted the metabolic and immune physiological functions, and activated apoptosis in the gills of abalone. ROS-mediated physiological activities and apoptosis were among the potential toxicity mechanisms of the interactive effects of homo-YTX and NH3-N on abalone.

Effects of dietary bile acids levels on growth performance, anti-oxidative capacity, immunity and intestinal microbiota of abalone Haliotis discus hannai

Abalone Haliotis discus hannai (initial weight: 38.79 ± 0.70 g) was used as the experimental animal in a 105-day feeding trial to investigate the influence of dietary bile acids levels on the growth, anti-oxidation, immune response and intestinal microbiota. Six isonitrogenous and isolipidic diets were prepared by adding 0 (control group), 15, 30, 60, 120 and 240 mg/kg of bile acids, respectively (named BA0, BA15, BA30, BA60, BA120 and BA240, respectively). It was found that survival of abalone between groups had no significant difference (P > 0.05). Compared to the control, significant improvements in weight gain rate (WGR) were observed in the groups of BA30 and BA60 (P < 0.05). Based on WGR, the broken line regression model analysis showed that the optimum demand for dietary bile acids for abalone was 35.47 mg/kg. Dietary bile acids increased the total anti-oxidative capacity and activities of catalase, superoxide dismutase, lysozyme and alkaline phosphatase, meanwhile decreased the content of malondialdehyde, alanine aminotransferase and aspartate aminotransferase activities in the cell-free hemolymph (P < 0.05). When bile acids were added to the diets, mRNA levels of genes related to pro-inflammatory factors and apoptosis in the digestive gland were down-regulated (P < 0.05). In contrast, the expression of genes related to anti-oxidation was significantly up-regulated (P < 0.05). The Firmicutes, Actinobacteriota and Proteobacteria were the most abundant phyla in intestine. And dietary bile acids significantly decreased the abundance of Actinobacteria and increased the abundance of Firmicutes (P < 0.05). In conclusion, supplementation of dietary bile acids within 120 mg/kg significantly increased the growth of abalone. The 34.62 mg/kg of dietary bile acids significantly increased the anti-oxidative capacity of abalone. Appropriate levels of dietary bile acids (34.62–61.75 mg/kg) promote the immunity of abalone. Application of appropriate levels of bile acids in diets (34.62 mg/kg) changed the intestinal microbiota and promoted the intestinal health of abalone.

Individual Pattern Response to CO2-Induced Acidification Stress in Haliotis rufescens Suggests Stage-Specific Acclimatization during Its Early Life History

The red abalone Haliotis rufescens is a pivotal marine resource in the context of worldwide abalone aquaculture. However, the species has been listed as critically endangered partly because of the life-history massive mortalities associated with habitat climate changes, including short- and long-term ocean acidification. Because abalone survival depends on its early life history success, figuring out its vulnerability to acidification is the first step to establishing culture management strategies. In the present study, red abalone embryos were reared under long-term CO2-induced acidification (pH 7.8 and 7.6) and evaluated. The impairment prevalence was assessed during their larval stages, considering the developmental success, growth and calcification. The result in the stage-specific disturbance suggests that the body abilities evaluated are at the expense of their development stages, of which the critical threshold is found under −0.4 pH units. Finally, the settlement was short-term stressed, displaying the opposite to that observed in the long-term acidification. Thus, the early life history interacts through multiple pathways that may also depend on the acidification challenge (i.e., short or long term). Understanding the tolerance limits and pathways of the stress response provides valuable insights for exploring the vulnerability of H. rufescens to ocean acidification.

Combined effects of toxic Karenia mikimotoi and hypoxia on the juvenile abalone Haliotis discus hannai

Eutrophication in aquaculture areas concurrently leads to a high incidence of dissolved oxygen deficiency and toxic algal blooms. The combined effects of hypoxia and typical toxic algae on cultured organisms should be given sufficient consideration. Abalone breeding in China has greatly suffered from hypoxia and toxic Karenia mikimotoi blooms for many years. In this study, the individual and combined effects of the toxic dinoflagellate, K. mikimotoi, and hypoxia on juvenile abalone were determined based on abalone survival and oxidative stress indicators in their gills, hepatopancreas and hemolymph. The results showed that at a density of 106 to 3×107 cells/L, K. mikimotoi alone had a negligible influence on the survival of juvenile abalone under sufficient dissolved oxygen (DO) conditions. The 24 h-half lethal concentration (LC50) of DO alone for juvenile abalone was 0.75 mg/L in seawater. When K. mikimotoi was added at a density of 3×106 cells/L, the 24 h-LC50 of DO for juvenile abalone significantly increased to 2.59 mg/L, indicating obvious synergistic effects. The individual effects of hypoxia or K. mikimotoi on the oxidative stress indicators were limited, and only the superoxide dismutase (SOD) activity in the abalone gills significantly decreased under K. mikimotoi stress. However, the combined stress of hypoxia and K. mikimotoi led to significant changes in the antioxidant indicators in all tested tissues. The SOD activity in gills and hepatopancreas decreased, while the SOD and catalase (CAT) activity and malondialdehyde (MDA) content in the hemolymph increased due to the combined stress of hypoxia and K. mikimotoi. These results illustrated that the synergistic effects of hypoxia and K. mikimotoi caused serious oxidative damage in abalone and that the hemolymph exhibited greater sensitivity than did the gills and hepatopancreas. Further investigation found that K. mikimotoi increased the oxygen consumption rate in abalone and that hypoxia enhanced the hemolytic toxicity of K. mikimotoi. These results revealed that hypoxia and typical toxic algae cause synergistic harm to cultured organisms, which is expected to provide a new understanding of the destructive mechanisms of typical toxic algal blooms in aquacultural areas.

Dietary arachidonic acid affects the growth performance, fatty acid profile, immunity and resistance to heat stress in juvenile abalone Haliotis discus hannai Ino

A 93-day feeding trial was performed to evaluate the effects of dietary arachidonic acid (ARA) on the growth performance, antioxidative capacity, immunity and anti-stress capacity of juvenile abalone Haliotis discus hannai Ino with an initial mean body weight of 4.26 ± 0.11 g. Six practical diets with 0.04% (the control), 0.31%, 0.44%, 0.68%, 0.94% and 1.34% of ARA were designed. After the feeding trial, abalones were subjected to a heat stress test. The findings showed that the survival of abalone (91.7–96.7%) after the feeding trial was not significantly influenced by dietary ARA. The 0.31–0.44% of dietary ARA significantly increased the weight gain rate (WGR). The feed conversion ratio (FCR) was decreased by 0.31–0.68% of dietary ARA. The 0.44% of dietary ARA significantly enhanced the activity of trypsin, lipase and α-amylase in the intestine. Besides, dietary ARA supplementation significantly elevated the total antioxidative capacity and activity of superoxide dismutase, catalase and lysozyme in the cell-free hemolymph. Higher levels of dietary ARA (≥0.94%) significantly up-regulated the mRNA levels of nuclear factor κB, inhibitor of κBα and transcription factor AP-1 in the digestive gland. The 0.68% of dietary ARA significantly decreased the falling rate of abalone after heat stress. In conclusion, appropriate dietary ARA levels improved the growth performance and feed utilization of abalone. The optimal dietary ARA content for juvenile abalone was 0.52% based on the quadratic regression analysis of WGR. The 0.44–0.68% of dietary ARA improved the antioxidative capacity, immunity and anti-heat stress of abalone.

Chicken by‐product meal as a replacement to fish meal in juvenile abalone (Haliotis discus hannai Ino 1952) feed

AbstractThis study aims to assess the effect of replacing anchovy meal with chicken by‐product meal (CBM) in juvenile abalone (Haliotis discus hannai) feed. Five diets were formulated to contain 0 (CBM0), 25 (CBM25), 50 (CBM 50), 75 (CBM75), and 100% (CBM100) CBM in replacement to 24% fish meal (FM). Dried Saccharina japonica, which is the natural food for this species of abalone was also prepared. Each diet was fed to triplicate groups of abalone. 1260 abalone assigned into eighteen cages were fed for 16 weeks. After the 16‐week feeding trial, 30 abalones from each cage were exposed to air for 24 h, and survival was monitored for 7 days. Results showed that weight gain and specific growth rate of abalone fed the CBM0 (185.4 ± 12.83% and 0.93 ± 0.040%/day, respectively) diet were significantly (p &lt; 0.04 for both) higher than those of abalone fed the CBM100 (139.0 ± 6.36% and 0.78 ± 0.024%/day, respectively) diet. Shell length and width of abalone fed the CBM0 diet were significantly (p &lt; 0.003 and p &lt; 0.02, respectively) longer and wider than those of abalone fed the CBM75 and CBM100 diets. Survival of abalone during the 7‐day post‐observation period after the 24‐h air exposure exhibited no remarkable (p &gt; 0.1 for Log Rank and Wilcoxon tests) difference among all formulated diets according to the analysis of the Kaplan–Meier survival curve. In conclusion, CBM can replace FM up to 50% in an abalone diet without compromising growth performance and survival.

Substitution effect of broccoli (Brassica oleracea var. italica) by‐product for Saccharina japonica in feeds on growth, carcass chemical composition, and air exposure resistance of abalone (Haliotis discus, Reeve 1846)

AbstractSubstitutability of broccoli by‐products (BBP) for Saccharina japonica in feed on growth, carcass chemical composition, and air exposure resistance of abalone (Haliotis discus) was investigated. One thousand and two hundred sixty abalones were randomly assigned into 18 cages (3 cages/diet; 70 abalone/cage). Two hundred g/kg of S. japonica was included in the control diet (BBP0). The BBP250, BBP500, BBP750, and BBP1000 diets were prepared by substituting 250, 500, 750, and 1000 g/kg of S. japonica with an equal amount of BBP. Additionally, dry S. japonica was prepared. Abalone were fed daily for 7 days a week for 16 weeks. Following the completion of the feeding trial, 20 abalone from each cage were exposed to air for 20 h prior to being monitored for the following 5 days. The greatest weight gain and specific growth rate (SGR) were achieved in abalone fed the BBP250 diet. Superior survival was obtained in abalone fed the BBP250, BBP500, BBP750, and BBP1000 diets to abalone fed the S. japonica control diet. The BBP250 and BBP500 diets achieved the highest survival of abalone. BBP appears to be a novel replacer for S. japonica in abalone diets, and 250 g/kg replacement of BBP for S. japonica produced the best weight gain and SGR.

Abiotic Stress Tolerance of Juvenile Small Abalone Haliotis diversicolor aquatilis (Obunjagi) to Gamma Irradiation

Jwa, M.S. and Hong, C.-Y., 2023. Abiotic stress tolerance of juvenile small abalone Haliotis diversicolor aquatilis (obunjagi) to gamma irradiation. Journal of Coastal Research, 39(1), 55–62. Charlotte (North Carolina), ISSN 0749-0208. In South Korea, the small abalone (obunjagi), Haliotis diversicolor aquatilis, is a prominent commercial seafood species. However, summer circumstances frequently impede abalone productivity, emphasizing the need for suitable approaches to promote abalone viability. The purpose of this study was to see if the survival rate and physiological responses of juvenile H. diversicolor aquatilis changed after exposure to low-level 60Co-gamma irradiation under high temperature (HT) and low salinity (LS) stress conditions (20 Gy). For this research, juvenile small obunjagi, H. diversicolor aquatilis, were obtained from Jeju City fishing vendors, Korea. Before the experiment, all abalone samples were acclimated for 7 days in a seawater-filled tank at 23°C ± 0.3°C and 32 ± 0.2 psu under starvation conditions. Seventy abalones (20 male and 50 female) were gamma irradiated and 30 abalones (10 male and 20 female) were used as controls. After 6 weeks of malnutrition, abalone survivability and the quantity of cardiovascular hemocytes rose dramatically after 20-Gy exposure compared with the control (0 Gy). The viability of abalone was dramatically reduced by HT stress but not by LS stress. The initially improved immune response-mediated hormetic impact might be connected to abalone survival rate under famine and HT stress, and the hormesis-induced gamma radiation exposure strategy will successfully raise abalone productivity throughout summer.

Comparative evaluation on the effects of dietary docosahexaenoic acid on growth performance, fatty acid profile and lipid metabolism in two sizes of abalone Haliotis discus hannai Ino

A 93-day feeding trial was conducted to comparatively evaluate the effects of graded levels of dietary docosahexaenoic acid (DHA) (0.06%, 0.46%, 0.99%, 1.57%, 1.95% and 2.25%) on growth performance, fatty acid profile and lipid metabolism in two different sizes of abalone Haliotis discus hannai (initial body weight: 2.83 ± 0.03 g and 26.81 ± 0.17 g, respectively). Results showed that 0.99%–1.95% of dietary DHA contents significantly increased the weight gain rate (WGR) in large size of abalone (P < 0.05), while the WGR in small size of abalone was significantly increased by the 0.46%–0.99% of dietary DHA contents (P < 0.05). There was no significant difference in the survival of abalone among all the six groups (P > 0.05). Based on the WGR, the optimal dietary DHA content for large and small size abalone were estimated to be 1.32% and 0.88%, respectively. Dietary DHA supplementation significantly increased the activities of trypsin and lipase in the intestine, the content of ∑n-3 polyunsaturated fatty acids (PUFA) and ∑n-3/n-6 PUFA ratio in digestive gland in both sizes of abalone (P < 0.05). The total glyceride concentration in the cell-free hemolymph in two sizes of abalone was decreased. In large size of abalone, 1.95%–2.25% of dietary DHA reduced the lipid content in digestive gland. Lipogenic genes in the digestive gland, including sterol regulatory element binding protein-1 (srebp-1) and diacylglycerol acyltransferase, were up-regulated in the 0.46%–1.57% DHA group (P > 0.05). The mRNA expression levels of hormone sensitive lipase (hsl) and carnitine palmitoyl transferase-1 (cpt-1) of lipolytic genes in the digestive gland were significantly increased in the 0.46% and 0.99% DHA groups, respectively (P < 0.05). In the small size of abalone, the lipid content in digestive gland and soft body decreased significantly in the 1.95% and 2.25% DHA groups, respectively (P < 0.05). Lipogenic genes in the digestive gland, including srebp-1 and acetyl-CoA carboxylase, were significantly down-regulated in the 0.99%–1.95% DHA group (P < 0.05). Lipolytic genes in the digestive gland, including hsl and cpt-1, were not significantly different from the control group (P > 0.05). In conclusion, based on the WGR, the dietary DHA requirements for large and small size of abalone were estimated to be 1.32% and 0.88%, respectively. Dietary DHA reduced lipid deposition in both sizes of abalone by promoting lipid decomposition and inhibiting lipid synthesis.

Dietary inclusion effect of citrus peel by-product as an additive on the growth performance, body composition, and various stress resistance of juvenile abalone (Haliotis discus) compared to ethoxyquin

Dietary additive can effectively improve growth performance and stressor resistance of aquatic animals. Dietary inclusion effect of citrus peel by‐product (CPB) as an additive on the growth, body composition, and various stress resistance of juvenile abalone (Haliotis discus) was investigated, and compared to commercial antioxidant (ethoxyquin). A total of 2880 juvenile (initial weight of 3.3 g) abalone were randomly assigned into 24 net cages. Seven formulated diets supplemented with 0, 5, 10, 20, 30, and 50 g/kg CPB and 0.01 g/kg ethoxyquin were formulated, and referred to as the CPB0, CPB5, CPB10, CPB20, CPB30, CPB50, and EQ diets, respectively. Finally, dry Saccharina japonica was prepared to compare the formulated diets on growth of abalone. All experimental diets were assigned to triplicate groups of abalone. Abalone were daily fed to satiation for 16 weeks. After the 16-week feeding trial, sixty abalone from each cage were subjected to the 20-h air, 12-h low salinity at 25 psu, and 20-h high temperature at 30 °C exposure stressors, respectively, and then survival was monitored. Abalone fed all formulated diets produced superior weight gain, specific growth rate (SGR), shell growth to abalone fed the S. japonica. Dietary inclusion levels of CPB linearly improved weight gain of abalone. However, there was no difference in chemical composition of the soft body of abalone fed all experimental diets. Diets supplemented with CPB or EQ improved survival of abalone when subjected to the 20-h air and high temperature exposures. In conclusion, CPB was a very effective additive as growth enhancer as well as stress reducer in abalone diet. Abalone fed the CPB50 diet attained the highest weight gain, SGR, and stress resistance subjected to the 20-h air and high temperature exposures.

A Comparison of Eucheuma cottonii Seaweed Cultivation in Monoculture and Polyculture Systems

Seaweed is a commodity that has high economic value and benefits. The implementation of seaweed cultivation is quite short and the export market opportunities are wide open because the need for seaweed is quite large. This study aims to determine the growth rate of seaweed with monoculture and polyculture cultivation systems and the survival rate of abalone in polyculture cultivation. The research used an experimental method with Completely Randomized Design (CRD) consisting of two treatments and three replications. The cultivation system in this study was seaweed monoculture Eucheuma cottonii with an initial weight of 100 gr and 100gr seaweed polyculture with abalone Haliotis squamata, each polyculture culture net bag containing 50 abalones. The value of the specific growth rate of monoculture seaweed was 2.21%/day, lower than the specific growth rate of polyculture, which was 3.61%/day. T-test analysis showed the value of sig = 0.049 &lt; = 0.05, which means that there is a significant difference between the treatment of monoculture cultivation and polyculture cultivation. The abalone growth rate value ranged from 0.78-0.91%/day and the abalone survival rate ranged from 68-76%. Changes in environmental conditions affect the condition of abalone and seaweed so that the survival value of abalone is quite low and seaweed is infected with an ice-ice disease which causes a decrease in seaweed weight gain in the final week of the study period.

Replacement of dietary fish meal by soybean meal on growth performance, immunity, anti-oxidative capacity and mTOR pathways in juvenile abalone Haliotis discus hannai Ino

This study aimed to evaluate the effects of replacing fish meal with soybean meal (SBM) on growth performance, immunity, anti-oxidative capacity and mTOR pathway in juvenile abalone Haliotis discus hannai Ino. Five isonitrogenous (about 29% of crude protein) and isolipidic (about 4% of crude lipid) experimental diets with graded levels of fish meal replaced by SBM (0, 25, 50, 75 and 100%, respectively) were fed to abalone (initial body weight: 21.87 ± 0.07 g, initial shell length: 53.18 ± 0.18 mm) for 16 weeks. These experimental diets were named as SBM0, SBM25, SBM50, SBM75 and SBM100, respectively. The results showed that: 1) There was no significant difference in survival of abalone among all the treatments. The highest weight gain rate was found in the SBM50 group, and the group did not significantly differ from those in the SBM75 and SBM100 groups. 2) Replacement of fish meal by SBM linearly and quadratically increased the crude lipid content in muscle of abalone, which reached its highest level in the SBM50 group. 3) Trypsin activity in the digestive gland of abalone fed SBM25 diet was significantly higher than that of other groups. 4) The highest total anti-oxidative capacity and superoxidase activity in digestive gland were found in the SBM50 group. 5) The highest mRNA levels of pi3k and eif-4e, and the lowest level of 4e-bp in muscle were found in the SBM50 group. There was no significant difference in the mRNA level of mtor in the muscle among all the groups. 6). The lowest expression level of nf-κb and the highest expression level of mytimacin 6 in digestive gland of abalone were observed fed SBM50 diet. A significant quadratic trend was found in the mRNA levels of il-16 with increasing levels of dietary SBM. Meanwhile, the mRNA level of β-defensin was linearly decreased after total replacement of fish meal by SBM. Take the growth, antioxidation, immune and mTOR pathway into account, 50% replacement of dietary fish meal by SBM was recommended for abalone.

Dietary effect of substituting Saccharina japonica with cabbage extract by‐product on the growth, body composition and air exposure of juvenile abalone (Haliotis discus hannai Ino 1952)

Dietary substitution effect of cabbage extract by‐product (CEB) for Saccharina japonica on the growth, body composition and air exposure stressor of juvenile abalone (Haliotis discus hannai) was determined. A total of 1260 abalone were randomly distributed into 18 net cages (seventy per cage). Five formulated diets were prepared. The control (CEB0) diet contained 20% S. japonica powder. Twenty-five, 50%, 75%, and 100% of S. japonica were substituted with the equal amount of CEB, referred to as the CEB25, CEB50, CEB75 and CEB100 diets, respectively. Ultimately, dry S. japonica was prepared to compare formulated diets on growth of abalone. Each diet was randomly assigned to triplicate groups of abalone and fed to abalone every other day for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure for 24 h, and then survival was monitored for the next 6 days. All formulated diets achieved greater weight gain and specific growth rate (SGR) than those of abalone fed the S. japonica. Weight gain and SGR of abalone linearly improved with dietary increased substitution levels of S. japonica with CEB. Shell growth of abalone tended to agree with growth rate. The chemical composition of the soft body of abalone was not affected by the experimental diets. Survival of abalone fed all formulated diets was (P < 0.05) higher than that of abalone fed S. japonica at the end of the 6-day post observation period after the 24-h air exposure. In conclusion, S. japonica could be completely (100%) substituted with CEB in abalone feeds when 20% S. japonica was included. Substitution of S. japonica with CEB in feeds could improve growth of abalone, but lower feed cost.

Substitution effect of Saccharina japonica with beet leaf by-product in feed on the growth and chemical composition of the soft body of juvenile abalone (Haliotis discus hannai Ino 1952) subjected to air exposure

Dietary substitution effect of beet leaf by-product (BLB) for Saccharina japonica on the growth and soft body composition of abalone (Haliotis discus hannai) subjected to air exposure was determined. A total of 1260 juvenile abalone was randomly distributed into 18 containers. Five experimental diets were prepared. The control (Con) diet contained 20% S. japonica. Twenty five percent, 50%, 75% and 100% S. japonica were substituted with equal amount of BLB, referred to as the BLB25, BLB50, BLB75 and BLB100 diets, respectively. The dry S. japonica was also prepared to compare effect of formulated diets on growth of abalone. The experimental diets were fed to triplicate groups of abalone for 16 weeks, and then exposed to air for 24 h. Survival of abalone was monitored for the next 6-day post observation period after the 24-h air exposure. Weight gain and specific growth rate (SGR) of abalone fed with formulated diets were greater than those of abalone fed with the S. japonica. The greatest weight gain and SGR were obtained in abalone fed the BLB25 diet, followed by the BLB50, BLB75, BLB100 and Con diets, in that order. The maximum values of weight gain, SGR, shell length and shell width of abalone were estimated to be approximately 42.3%, 43.5%, 39.8% and 33.7% of substitution level of BLB for S. japonica in abalone feed. The chemical composition of abalone soft body was not affected by the experimental diets. Survival of abalone fed with formulated diets was higher than that of abalone fed with the S. japonica at the end of the 6-day post observation period. In conclusion, S. japonica could be completely replaced with BLB in abalone feed without retardation of growth and survival of abalone subjected to the 24-h air exposure. The greatest weight gain and SGR were obtained in abalone fed the BLB25 diet.

No evident effect of domestication on the anti-predator behaviour of European abalone (Haliotis tuberculata): Implications for stock enhancement programs

Stock-enhancement programs for the European abalone (Haliotis tuberculata) might be an efficient way to restore collapsed natural populations or preserve fishing activities. Specifically, this practice consists of releasing hatchery-reared juveniles from wild or farmed broodstock into natural environments. However, the process of selection and adaptation to farming conditions may result in domestication, thus leading to genetic and behavioural changes in farmed animals. Therefore, evaluating the effects of the domestication process on juveniles is a critical first step toward the development of successful abalone stock-enhancement programs. To this end, the behaviour and survival of sixteen-month-old H. tuberculata juveniles from wild and from farmed broodstock (the product of three generations of shell-length based selection) were compared. We used three assays at different spatial and temporal scales: (1) short-term responses to simulated contact with predators, (2) the activity pattern in the presence of a natural predator (the velvet crab Necora puber) in aquariums during a 2-week trial, and (3) survival in large mesocosms in the presence of predators during a 3-week trial. No significant effects of the broodstock origin of the juveniles were detected on any of the studied parameters (P > 0.05). In addition, the estimated size effects were small compared to the overall mean for most of the variables, suggesting that the domestication process was too recent to induce important behavioural changes in juveniles from farmed broodstock.Introducing crabs into the mesocosms significantly decreased abalone survival rates (P < 0.05). In the activity pattern trial, most of the abalone mortality in aquariums with crabs (55%) occurred within the first three days, which was largely attributed to initial exploration of areas outside of shelters by the abalone. In the second week, abalone spent much less time moving when crabs were present (P < 0.05).These results suggest that juveniles from both origins would likely have the same survival rates if released in the wild. The commonly reported high abalone mortality immediately after seeding is likely due to a lack of hiding behaviour or exploration of the new environment during the first few days of exposure to predators in the wild. Therefore, current release systems may need to be adjusted to the ethological characteristics of abalone juveniles to avoid high mortalities due to an initial lack of predator avoidance.

Dietary substitution effect of Saccharina japonica with residues of citrus juice production in formulated diets on the growth, body composition and air exposure of juvenile abalone (Haliotis discus, Reeve 1846)

Dietary substitution effect of Saccharina japonica with residues of citrus juice production (RCJP) on the growth and body composition of abalone (Haliotis discus) subjected to air exposure was determined. A total of 1260 abalone were randomly distributed into 18 net cages (seventy per cage). Five formulated diets were prepared. The control (RCJP0) diet included 20% S. japonica. The percentages of 25, 50, 75 and 100 of S. japonica were substituted with the same amount of RCJP, referred to as the RCJP25, RCJP50, RCJP75 and RCJP100 diets, respectively. Finally, dry S. japonica was prepared to evaluate the formulated diets on growth performance of abalone. Each diet was randomly assigned to triplicate groups of abalone. Abalone were daily fed to satiety with little leftover for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure stressor for 20 h, and then survival was monitored for the next 120 h. All formulated diets achieved significantly greater weight gain and specific growth rate (SGR) than those of abalone fed the S. japonica. Weight gain and SGR of abalone linearly improved with an increased substitution levels of S. japonica with RCJP in feeds. The greatest weight gain and SGR were obtained in abalone fed the RCJP100 diet. The shell growth and soft body weight of abalone also linearly increased with dietary substitution levels of S. japonica with RCJP. The chemical composition of the soft body of abalone was not affected by the experimental diets. Survival of abalone fed all formulated diets, except for the RCJP0 diet was significantly higher than that of abalone fed the S. japonica at the end of the 120-h post observation. In conclusion, S. japonica could be entirely (100%) replaced with RCJP in formulated abalone diet. The greatest growth performance was obtained in abalone fed the RCJP100 diet.

The expression patterns of HSP70 and HSP90 genes of abalone (Haliotis squamata) using 2-phenoxyethanol as an anaesthetic during transportation

The packaging of abalone (H. squamata) (39.65 ± 0.24 mm TL) for long-term transportation (&gt;8 hours) requires the addition of substances that provide an anesthetic effect so that it could reduce stress and maintain survival rate post transportation without having to repack. The objective was to investigate the expression pattern of HSP70 and HSP90 genes of abalone during transport with the addition of 2-phenoxyethanol. Abalone was packed using a styrofoam box with dimensions (42.5 x 75.5 x 27.5 cm3), containing 2 pcs of 10L Polyethylene (PE) plastic bags. The plastic bag consisted of 2 pcs of 25cm, 4-inch Polyvinyl Chloride (PVC) pipe for abalone attached. Both ends line enclosed with screen net and tied with rubber bands. Abalone density was 50 heads/pipe. Transportation tests were carried out using a dry system and wet system with and without the addition of 2-phenoxyethanol (PK, KK). Data analysis was done by paired sample ttest and ANOVA with a 95% confidence interval. The results showed that the best abalone survival (85%) was obtained in wet transport + 2-phenoxyethanol (PB) (p&lt;0.05) within 24 hours of transportation.

The Effects of Modified Clay on Abalone (Haliotis discus hannai) Based on Laboratory and Field Experiments.

The abalone industry has suffered immense economic losses due to the occurrence of harmful algal blooms (HABs). Among the methods for mitigating HABs, modified clay is considered the most promising strategy and has been successfully used for field applications in many countries, and its environmental effects have become a subject of global concern. The effects of modified clay on the survival, growth, nutritional quality, and oxidative stress indicators of abalone were studied based on both laboratory and field experiments. The results showed that modified clay at 3-10 times the concentrations used for HAB treatment did not affect the survival of abalone. During the laboratory experiments, the increases in abalone shell length and weight nonsignificantly decreased with increasing concentrations of modified clay at 1-15 d, whereas the weight of abalone in the experimental groups increased rapidly during the recovery period at 16-30 d. The growth and nutrition qualities of abalone in field experiments showed negligible differences between the control and experimental groups. Catalase (CAT) activity in the hepatopancreas and superoxide dismutase (SOD) activity in the gills were significantly affected by certain concentrations of modified clay at individual time points, whereas the malondialdehyde (MDA) content decreased in all experimental groups within 96 h. The removal of bacteria and the mitigation of water quality decline were among the effects of modified clay that contributed to the decrease in MDA content. The present study showed that modified clay had no obvious adverse effects on the survival, growth, quality, or oxidative stress indicators of abalone at the experimental concentrations, thus providing a reference for the field application of modified clay in typical aquaculture areas. Environ Toxicol Chem 2020;39:2065-2075. © 2020 SETAC.

Dietary substitution effect of Undaria pinnatifida with onion extract by-product on growth, chemical composition and air exposure stress of juvenile abalone (Haliotis discus, Reeve 1846)

Effect of dietary substitution of Undaria pinnatifida with onion extract by-product (OEB) on growth, body composition and air exposure stress of juvenile abalone was determined. One thousand and eighty juvenile abalone were randomly distributed into 18,100 L net cages (sixty per cage). Five formulated diets were prepared. Twenty percent U. pinnatifida was included into the control (Con) diet. Twenty five, 50, 75 and 100% U. pinnatifida were substituted with an equal amount of OEB, referred to as the OEB25, OEB50, OEB75 and OEB100 diets, respectively. Finally, dry U. pinnatifida was prepared to compare formulated diets on growth performance of abalone, referred to as the Undaria. Each diet were randomly assigned to triplicate groups of abalone and fed to abalone once a day to satiety with little leftover for 16 weeks. After the 16-week feeding trial, abalone were subjected to air exposure for 24 h and survival was monitored for the next 4 days. Weight gain and specific growth rate (SGR) of abalone fed all formulated diets were greater than those of abalone fed the Undaria. The greatest weight gain and SGR were obtained in abalone fed the OEB50 diet, followed by the OEB75, OEB25, Con and OEB100 diets, in that order. Weight gain and SGR of abalone fed the OEB100 diet were lower than those of abalone fed the Con diet. Shell length, width and height and soft body weight of abalone tended to agree with growth rate of abalone. No difference in the chemical composition of the soft body of abalone was observed. The survival of abalone fed the OEB25, OEB50, OEB75 and OEB100 diets was higher than that of abalone fed the Undaria and Con diet at the end of 4-day post observation after 24-h air exposure. In conclusion, U. pinnatifida up to 75% could be replaced with OEB in abalone feed when 20% U. pinnatifida was included. The greatest growth performance was obtained in abalone fed the OEB50 diet.

Improved growth and survival of post-larval Haliotis midae in response to probiotic biofilm diets

The bacterium Vibrio midae SY9, shown to enhance the nutrition and health of juvenile Haliotis midae, was investigated as a probiotic for H. midae during the post-larval phase of development. Using a randomized box design, we conducted three independent laboratory-scale experiments in which post-larval H. midae (mean shell length 2.7 mm) were fed three different artificial biofilm diets. The diets consisted of alginate and either the probiotic V. midae K811 only (diet 1), a mixture of the benthic diatom Cocconeis sp. and Vibrio midae K811 (diet 2) or Cocconeis sp. only (diatom control diet). Abalone survival was monitored over 25 days, and growth was quantified by measuring abalone shell length. Results confirmed that V. midae K811 has a probiotic effect on post-larval H. midae by significantly improving survival and promoting a three-fold increase in the growth rate of these animals. This study also demonstrated that post-larval H. midae can survive and grow on a bacterial biofilm diet lacking diatom cells which might suggest that bacteria could replace diatoms as the principle food source for post-larval H. midae.