Production and sinking rates for bio‐deposits of abalone (Haliotis discus hannai Ino)

Particle size distribution, organic content and the sinking velocity of bio‐deposits of abalone Haliotis discus hannai Ino were evaluated. The abalone was divided into three size classes according to shell length: Group B: 68.8 ± 2.8 mm, group M: 56.1 ± 2.3 mm and group S: 42.4 ± 2.8 mm. The faecal pellets had an amorphous shape, with a cross‐sectional area ranging from 0.01 to 2.64 mm². The mean cross‐sectional area varied among the size classes: 0.59 (B), 0.21 (M) and 0.12 (S) mm². The bio‐deposit organic content was similar among the groups (B: 18.3 ± 1.1%; M: 19.9 ± 0.9%; S: 19.3 ± 1.0%). Sinking velocity ranged from 0.5 to 2.3 cm s^?1. Larger abalone tended to have larger and thus faster‐sinking faecal pellets. The median sinking velocity for groups B, M and S was 0.9, 0.5 and 0.7 cm s^?1 respectively. The mean daily production rates for groups S, M and B were 2.8 ± 1.2, 3.4 ± 1.3 and 4.3 ± 1.8 g ind.^?1 respectively. Bio‐deposit production rate estimated to be between 134.4 and 206.4 mg m^?2 day^?1 in the bay. Our results suggest that the pellet size was within the appropriate size range for filter‐feeding bivalves.     

皱纹盘鲍食道的结构与功能

以组织学，组织化学，扫描电镜和透射电镜观察及酶活性测定等方法研究了皱纹盘鲍的食道，食道可分为前，中后，三段，中段又可分为食物通道和食道侧囊，食道粘膜上皮由纤毛柱状细胞，粘液细胞，闰状腺细胞，微绒毛细胞和分泌细胞组成，纤毛柱状细胞参与运输食物和分泌物，并呈现吸收细胞的结构特征；粘液细胞分泌中性和酸性粘多糖；颗粒状腺细胞内充盈分泌颗粒；微绒毛细胞呈现吸收细胞的特征；分泌细胞具有强的蛋白酶等酶活性，能以楔浆分泌形式分泌消化酶，该细胞还具有吸收和细胞内消化作用。食道中段还呈现3种植物多糖酶活性。     

Growth performance of disk abalone Haliotis discus hannai in pilot- and commercial-scale recirculating aquaculture systems

The study investigated the growth performance of abalone from juvenile to marketable size in a commercial-scale recirculating aquaculture system. The rearing system consisted of 12 raceways (4.0 × 0.8 × 0.6 m) with a protein skimmer and a submerged biofilter for juveniles and 10 raceways (6.6 × 1.3 × 0.6 m) with a protein skimmer and a trickling biofilter for on-growing. Sea mustard (Undaria pinnatifida) and kelp (Laminaria japonica) were fed to the abalone. The total weight of abalone in the recirculating aquaculture system at the juvenile stage increased from 22.0 kg (average shell length 24.5 mm) to 75.5 kg (average shell length 42.5 mm) after 180 days. Feed conversion ratios increased slightly from 13.7 for the first 90 days to 16.3 thereafter. The shell growth rate of juvenile abalone between 24.5 mm and 34.8 mm was 3.4 mm month⁻¹, while for juveniles between 34.8 mm and 42.5 mm it was 2.6 mm month⁻¹. The total weight of abalone in the recirculating aquaculture system for the on-growing stage increased from 100.0 kg (average shell length 44.0 mm) to 433.3 kg (average shell length 72.7 mm) after 570 days. The feed conversion ratios for the first 173 days, the next 320 days, and the last 570 days were 19.6, 22.1, and 24.8, respectively. The growth rate of the average shell length during the on-growing period was 1.5 mm month⁻¹. Total ammonia nitrogen (TAN) concentrations were stabilized below 0.12 mg l⁻¹ in the juvenile recirculating system and 0.14 mg l⁻¹ in the on-growing recirculating system after conditioning of the biofilters.     

Dose‐dependent protective effects of dietary selenium on abalone Haliotis discus hannai Ino against the toxicity of waterborne copper

This study was designed to assess the protective effects of dietary selenium (Se) on abalone Haliotis discus hannai Ino against the toxicity of waterborne copper (Cu). A 60‐day feeding trial was conducted in a static water system for abalone (initial weight: 3.17 ± 0.01 g) exposed to 0.02 mg L^?1 of waterborne Cu. The animals were fed one of the three experimental diets with 0.10, 1.31 and 4.20 mg kg^?1 of Se from Na₂SeO₃·5H₂O respectively. Results showed that the abalone fed 1.31 mg kg^?1 of dietary Se had the lowest Cu concentration in shell, muscle, mantle, gill, hepatopancreas and serum. Meanwhile, the significant lowest contents of malondiadehyde and protein carbonyl in hepatopancreas were also found in the treatment with 1.31 mg kg^?1 of dietary Se (P < 0.05). In addition, this treatment had significant higher glutathione content and thioredoxin reductase activity in hepatopancreas (P < 0.05). However, the activity of Se‐dependent glutathione peroxidase (Se‐GPx) was significantly decreased in the treatment with 4.20 mg kg^?1 of dietary Se (P < 0.05). In this treatment, the protein carbonyl content in hepatopancreas was significantly higher than that in the group with 1.31 mg kg^?1 of dietary Se (P < 0.05). In conclusion, in terms of anti‐oxidation and Cu accumulation, the protective effects of dietary Se on abalone against waterborne Cu were dose‐dependent. The 1.31 mg kg^?1 of dietary Se had this effect, but not 4.20 mg kg^?1 of dietary Se. Moreover, the latter increased the oxidative stress in abalone exposed to the waterborne Cu.     

Protective effects of dietary selenium on abalone Haliotis discus hannai against the toxicity of waterborne cadmium

This study was conducted to investigate protective effects of dietary selenium (Se) on abalone Haliotis discus hannai Ino against the toxicity of cadmium (Cd). A 60‐day feeding trial was conducted with abalone (initial weight: 3.17 ± 0.01 g), which were exposed to 0.34 mg/L of waterborne Cd. During a feeding trial, abalone were fed graded levels of Se at 0.10 (controls), 1.31, and 4.20 mg/kg diet respectively. Results showed that there was no significant difference in specific growth rate and survival rate of abalone among the three treatments. Compared with the controls, dietary Se significantly decreased Cd concentrations in serum, muscle, mantle, gill, mantle, and hepatopancreas of abalone. Besides, compared with the controls, dietary Se significantly increased metallothionein concentration in the hepatopancreas of abalone. Additionally, compared with the controls, dietary Se significantly decreased concentrations of malondiadehyde and protein carbonyl in hepatopancreas of abalone. Meanwhile, compared with the controls, dietary Se significantly increased activities of glutathione peroxidase, thioredoxin reductase, and thioredoxin peroxidase, and concentration of glutathione in the hepatopancreas of abalone. Based on the data above, in abalone, dietary Se showed protective effects against waterborne Cd.     

Shelter selection by juvenile Pacific abalone (Haliotis discus hannai Ino) as a function of food distribution and water flow velocity

Juvenile Pacific abalone (Haliotis discus hannai Ino) are currently reared in land‐based aquaculture systems until they reach the necessary size for seeding in the sea. One problem that this industry faces is that an uneven distribution of juveniles in tanks can lead to variations in the growth rate. Understanding the cues that affect the sheltering behaviours exhibited by juvenile Pacific abalone—namely, the food distribution and the water flow velocity—will help optimize abalone culture settings. In this study, a group of 1,000 juvenile Pacific abalone (distributed across three tanks) was visually observed and enumerated during six experiments that were conducted over a 5‐month study period. It was found that juvenile Pacific abalone preferred to shelter close to food sources when the food was unevenly distributed. When the food was evenly distributed, the juveniles tended to avoid areas of rapid water flow and distributed evenly across the sheltered areas receiving the equal water velocity. This distribution might be the confounding effects between water flow velocity and food stimulus. Based on these findings, it was recommend that the food and water velocity be evenly distributed in an abalone aquaculture system.     

皱纹盘鲍内脏酶的酶学性质及褐藻胶裂解酶的分离纯化

采用(NH4)2SO4分段盐析、透析、阴离子(DEAE-52)交换柱层析、SephadexG-200凝胶柱层析等分离纯化技术,通过SDS-PAGE电泳分析了皱纹盘鲍内脏酶的组成,结果表明鲍内脏酶主要含有两种褐藻胶裂解酶Ⅰ, Ⅱ,一种纤维素酶,一种琼脂酶。对酶的酶学性质分析结果表明两种褐藻胶裂解酶Ⅰ, Ⅱ的最适pH分别为8.6, 7.2,最适温度为35 ℃,分子量分别为35.2 ku, 67 ku;两种褐藻胶裂解酶的热稳定性比较差,且易受金属离子影响;纤维素酶的最适pH为5.0,最适温度为40 ℃。并确定了皱纹盘鲍内脏酶分离纯化的方法及参数,为进一步研究鲍内脏复合酶的性能提供了基础参数。图14表3参12 关键词：皱纹盘鲍; 褐藻胶裂解酶; 纤维素酶; 纯化 E-mail：wqk320@dlfu.edu.cn     

Molecular identification of interspecific hybrids between Haliotis discus hannai Ino and Haliotis gigantea Gmelin using amplified fragment‐length polymorphism and microsatellite markers

Interspecific hybrids between Haliotis discus hannai Ino and Haliotis gigantea Gmelin were produced in this study. The hybridity of the interspecific hybrids was confirmed by using the methods of amplified fragment‐length polymorphism (AFLP) and microsatellite [simple sequence repeats (SSR)] markers. Five AFLP primer combinations were used to develop the AFLP profiles of H. discus hannai, H. gigantea and their reciprocal hybrids. AFLP analysis revealed that genetic variations of H. discus hannai and H. gigantea were relatively diverse and each species holds species‐specific bands. The AFLP profiles of reciprocal hybrids showed that all of the hybrids inherited bands specific to H. discus hannai and H. gigantea. Of a total of 20 microsatellite loci, which were selected from H. discus hannai microsatellite markers evaluated, eight loci were polymorphic in H. gigantea samples, with an average of 3.375 alleles per locus. Preliminary screening showed that, two of these eight microsatellite loci (Awb002 and Awb022) could be used as species‐specific markers to distinguish the hybrids and their parental species. Simple sequence repeats analysis showed that the reciprocal hybrids inherited one allele from each parent for both of the two SSR loci investigated. These data strongly suggest that the induced interspecific hybrid is a true hybrid between H. discus hannai and H. gigantea.     

Influence of 18:2n‐6/20:5n‐3 ratio in diets on growth and fatty acid composition of juvenile abalone,Haliotis discus hannai Ino

A 120‐day feeding trial was conducted to examine the effects of the ratio of dietary linoleic acid (LA, 18:2n‐6) to eicosapentaenoic acid (EPA, 20:5n‐3) on the growth and fatty acid composition of juvenile Haliotis discus hannai (initial shell length 10.23 ± 1.48 mm; initial body weight 0.13 ± 0.05 g) in a recirculation water system. Five semipurified diets with 35 g kg^?1 total lipid were formulated to contain graded LA/EPA ratios (1 : 0, 0.75 : 0.25, 0.5 : 0.5, 0.25 : 0.75, and 0 : 1, respectively). Twenty‐five juveniles were stocked in a rearing unit, a plastic basket (20 × 20 × 10 cm), as a replicate, and there were three replicates for each dietary treatment. The results showed that abalone survival rates were generally high (90.1–98.3%) and independent of the dietary treatments. However, abalone growth was significantly affected by LA/EPA ratio (P < 0.05). The LA/EPA ratio of 0.25 : 0.75 (Diet 4) produced the highest weight gain rate (WGR, 416.3%), closely followed by the ratio of 0 : 1 (Diet 5, 412.9%), the ratio of 0.5 : 0.5 (Diet 3, 399.7%) and the ratio of 0.75 : 0.25 (Diet 2, 372.1%), but no significant differences were observed among these treatments. The abalone fed the diet without 20:5n‐3 (Diet 1) had the lowest WGR (Diet 1, 363.8%), which was significantly lower than that of Diet 4. Fatty acid profiles in abalone body reflected those of dietary lipids, especially for the polyunsaturated fatty acids. The contents of arachidonic acid (AA; 20:4n‐6) in abalone tissues were positively correlated with dietary level of 18:2n‐6 (P < 0.05). Similar correlation was also observed between the level of docosahexaenoic acid (DHA, 22:6n‐3) in abalone tissues and the level of dietary EPA. It is suggested that abalone, H. discus hannai, have the capacity to synthesize 20:4n‐6 from 18:2n‐6, and maybe 22:6n‐3 from 20:5n‐3.     

Influences of dietary antimicrobial peptide APSH‐07 on the growth performance,immune response and vibriosis resistance of abalone Haliotis discus hannai Ino

A 115‐day feeding trial and subsequently a 10‐day challenge test with Vibrio parahaemolyticus were conducted to investigate the effects of dietary antimicrobial peptide APSH‐07 on growth performance, immune response, antioxidative status and vibriosis resistance of abalone Haliotis discus hannai (initial body weight: 2.06 ± 0.01 g; initial shell length: 25.42 ± 0.18 mm). Four artificial diets were designed with 0 (artificial diet control), 7.5, 15.0 and 22.5 mg/kg of APSH‐07, respectively. The brown alga Laminaria japonica was used as the live food control. Results showed that the specific growth rates of abalone in the groups with 7.5 and 15.0 mg/kg dietary APSH‐07 were significantly higher than those in the controls (p < .05). The total haemocyte counts and respiratory burst activity in haemolymph of abalone in the group with 7.5 mg/kg of dietary APSH‐07 were significantly higher than those in the groups with 0 and 22.5 mg/kg of dietary APSH‐07 (p < .05). The gene expression levels of Mn‐superoxide dismutase and thioredoxin peroxidase 2, and the activities of glutathione peroxidase in the group with 7.5 mg/kg of dietary APSH‐07 were significantly higher than those in the other groups (p < .05). Cumulative mortality of abalone after the challenge test was significantly decreased in the group with 7.5 mg/kg of dietary APSH‐07 supplementation. Supplementation of 22.5 mg/kg dietary APSH‐07 significantly increased the cumulative mortality. In conclusion, 7.5 mg/kg of dietary APSH‐07 supplementation had the better growth performance, higher antioxidation, immune and disease resistance capacity of abalone. Excessive supplementation of dietary antimicrobial peptide APSH‐07 (22.5 mg/kg) had significantly negative effects. Further studies are needed to determine the optimal level of dietary APSH‐07 supplementation for abalone.     

Effects of the initial size, stocking density and sorting on the growth of juvenile Pacific abalone, Haliotis discus hannai Ino

During winter months, a novel overwintering mode of transferring juvenile abalones to open seawaters in southern China rather than keeping them in closed land-based nursery systems in northern China is a popular practice. The initial size, stocking density and sorting are among the first considerations when establishing an abalone culture system. This study aimed to investigate the effects of these factors on the growth of juvenile Pacific abalone, Haliotis discus hannai Ino, during overwintering. Juvenile abalones were reared in multi-tier basket form for overwintering in open seawaters in southern China for 106 days. The daily growth rates (DGRs) in the shell length of all experimental groups ranged from 67.08 to 135.75 μm day⁻¹, while the specific growth rates (SGRs) were 0.2447–0.3259% day⁻¹. Variance analysis indicated that both DGRs and SGRs in shell length were significantly affected by the initial body size and stocking density. Furthermore, the effects of stocking density on DGRs and SGRs varied with the initial size. However, sorting abalones according to their initial sizes may not be necessary in practice as sorting did not alter growth significantly at all densities in this study. Factors potentially affecting abalone growth such as genetic control and intraspecific competition were discussed.     

皱纹盘鲍微卫星多重PCR体系构建及其在家系鉴定中的应用

为提高微卫星分型效率,从以往报道的皱纹盘鲍微卫星中筛选出易扩增、特异性好的微卫星位点进行组合扩增,并通过优化退火温度、反应体系、引物浓度等条件,开发了4组多重PCR扩增体系.运用CERVUS3.0软件对12个皱纹盘鲍全同胞家系的372个子代进行家系鉴定,验证了这4组多重PCR在家系鉴定中的效率.结果发现,仅用1组微卫星多重PCR模拟和实际家系鉴定的成功率分别为86％和90％,两组则达到100％.结果表明,微卫星多重PCR技术能准确地把任意子代鉴定至其所属家系,可以进行大批量家系材料分析,具有较好的应用价值.     

The growth and carbon allocation of abalone (Haliotis discus hannai) of different sizes at different temperatures based on the abalone‐kelp integrated multitrophic aquaculture model

The integration of shellfish and seaweed is an important and successful IMTA model. The IMTA of abalone and kelp has been well‐practiced in Sanggou Bay, China. In the present study, the growth and carbon allocation of abalone (Haliotis discus hannai) of different sizes (S, small; M, medium; L, large) fed kelp (Laminaria japonica) were investigated at different temperatures (10, 14, 18 and 22°C). A two‐way ANOVA showed that both size and temperature significantly affected the specific growth rate (SGR), food consumption (FC), feed conversion ratio (FCR) and apparent digestion rate (ADR) of abalone (p < 0.05), and significant interactions between the two factors were detected (p < 0.05). Curve estimation showed a significant quadratic relationship between SGR and temperature in each size class (p < 0.05). The two‐way ANOVA also showed that both size and temperature significantly affected all the measures of carbon allocation (p < 0.05) except for the carbon lost in metabolism (p > 0.05). All the measures of carbon allocation increased with the increasing temperature. It was concluded that it was better to culture H. discus hannai with a body weight less than 15 g at 20–22°C, and more than 15 g at 15–20°C to achieve good growth. The growth carbon of kelp around the abalone farm should be more than the metabolic carbon expenditure, which means the growth of kelp around the abalone farm should be more than 23.06%–61.91% of food consumption to maintain a carbon sink IMTA system without any carbon release.     

2种养殖模式对鲍营养成分与低温胁迫响应的差异比较

为研究不同养殖模式中的皱纹盘鲍(Haliotis discus hannai Ino)的营养成分与低温胁迫响应的差异,采用南北接力养殖鲍和北方底播养殖鲍作为研究对象,于2021年9月取样测量了肌肉组织中的总糖、蛋白质、有机物总量和氨基酸含量等营养成分和低温胁迫下的耗氧率和心率等生理指标。结果显示,底播养殖个体的总糖含量为(3.20±0.00)%、有机物总量为(27.60±3.70)%、必需氨基酸含量为(4.19±0.09)%,均显著高于南北接力养殖的个体(P<0.05)。低温胁迫条件下,南北接力养殖和底播养殖个体的耗氧率分别为(0.017±0.006)和(0.018±0.009) mg/(g·h),无显著差异(P>0.05);然而,底播养殖个体的心率为(12.82±1.72) BPM,显著低于接力养殖个体[(18.11±2.79) BPM] (P<0.05)。研究表明,不同养殖模式显著影响皱纹盘鲍养殖个体的营养价值及其响应低温胁迫的生理过程,底播养殖个体有着更高的营养价值和低温耐受能力。此外,心率可作为高敏感性的指标应用于研究鲍等贝类响应低温胁迫的生理机制。     

Study on an integrated eco‐aquaculture system for rearing the yellow seahorse,Hippocampus kuda Bleeker

Seahorse aquaculture is challenged by insufficient feeding supply and lack of biological and nutritional knowledge, resulting in low survival rate and poor economical profitability. We report here an integrated eco‐aquaculture system in which the yellow seahorse and its natural prey were co‐cultured with fertilized water and seaweed in cement ponds. In the first stage, urea (10 g m^?3) and chicken manure (50 g m^?3) were used to fertilize the cultured water, 5–7 days later, rotifer and micro‐crustaceans were flourishing. Then, seahorse juveniles were stocked at 200 ind m^?3. After 2 weeks, seaweed Gracilaria lichevoides was transplanted into the ponds to regulate water quality, light and to provide holdfast attachment for seahorses. The optimal density of G. lichevoides was controlled between 0.5 and 2 kg m^?3. The introduction of seaweed provides the habitat for natural food of seahorse. Within the cluster of the seaweed, small crustacean density was over 450 individuals per 100 g of fresh weight. Initial size of seahorse juvenile was 1.03 ± 0.091 cm, After the 146‐day rearing period, seahorse survival rates were 70.8%, 57.7% and 42.5%, and body standard lengths were 11.33 cm, 10.84 cm and 10.04 cm in the integrated eco‐aquaculture system (GFA) and in monoculture systems of FA (fertilized + feeding) and BA (only feeding) respectively. This system incorporated traditional Chinese aquaculture technique in which feedings nature food organisms were cultivated by fertilization and ecological regulation. Results from these preliminary experiments suggest that the integrated system could be technically feasible, suitable and exemplary.     

A novel konjac glucomannan–xanthan gum binder for aquaculture feeds: the effect of binder configuration on formulated feed stability,feed palatability and growth performance of the Japanese abalone,Haliotis discus hannai

As part of a programme to develop sustainable diets for macroalgivores, a 3‐month experiment was conducted to determine the effects of konjac glucomannan–xanthan gum (KX) binder configuration on formulated feed stability, feed palatability and growth performance of juvenile, hatchery‐reared, Haliotis discus hannai. This study was conducted in a recirculation facility in which four KX binder configurations were evaluated in a series of isonitrogenous experimental feeds and freshly harvested Laminaria digitata was included as a natural feed type. Dry matter leaching of the experimental feed treatments was assessed with no significant difference in the dry matter leaching between treatments observed. No differences (P > 0.05) were found in percentage survival, daily food consumption (DFC) and linear growth rate (LGR) between treatments. Food conversion efficiency (FCE), specific growth rate (SGR) and body weight/shell length (BW/SL) ratio were significantly higher when offered L. digitata. Trends showed that the best performing KX feed in terms of FCE, LGR, SGR and BW/SL ratio was produced with the 2% KX; 1 : 1 binder.     

Effects of dietary α‐lipoic acid on the growth and antioxidative responses of juvenile abalone Haliotis discus hannai Ino

A feeding experiment was conducted to determine the effects of α‐lipoic acid (LA) on the growth and antioxidative responses of juvenile abalone Haliotis discus hannai Ino. Six purified diets supplemented with 0, 200, 400, 800, 1600 and 3200 mg kg^?1 of LA, respectively, were fed to abalone for 16 weeks in a flow‐through water system. The results showed that the weight gain ratio (WGR) increased with the dietary LA levels, and reached the highest value in the group with 800 mg kg^?1 dietary LA supplement. Glutathione peroxidase activity in the 800 mg kg^?1 dietary LA group was significantly higher than that in the dietary LA‐deficient (0 mg kg^?1) group. Superoxide dismutase activities in the 200, 400 and 800 mg kg^?1 groups were significantly increased. Supplements of 200, 400 and 800 mg kg^?1 dietary LA elevated the total antioxidative capacity significantly. The glutathione level in the hepatopancreas increased significantly with the dietary LA supplements in a dose‐dependent manner (except for the 200 mg kg^?1 group). Catalase and malondialdehyde in the hepatopancreas were not significantly affected by dietary LA. In conclusion, dietary LA promoted the growth and stimulated the antioxidative defence capacity of abalone. Based on the data of WGR, the optimal dietary LA supplement for juvenile abalone was found to be 709 mg kg^?1 using piece‐wise linear analysis.     

Consumer interest in social sustainability issues of whitefish from capture fisheries in the north‐east Atlantic

Capture fisheries in the north‐east Atlantic account for approximately 10% of all fish consumed from capture fisheries globally. The literature shows that consumers show considerable interest in social sustainability of products in general and of fish specifically. This interest, however, has not yet been investigated for fish from the north‐east Atlantic. The first objective of this study, therefore, was to investigate whether consumers are interested in social sustainability issues of whitefish from the north‐east Atlantic by determining preferences for four social sustainability issues with distinct benefits in relation to a known reference point (i.e. approach to overfishing). The second objective of this study was to determine to what degree case‐specific and general psychographic consumer characteristics explain preferences for these issues. Choice modelling results from an online survey among 457 Dutch consumers show that consumers have the strongest preference for the environmental sustainability issue approach to overfishing. In addition, results on the social sustainability issues showed that consumers prefer fish welfare over product quality, worker safety and local employment, indicating that in this case, consumers place animal benefits over personal, worker and community benefits. The case‐specific psychographic characteristic concern contributed most to explaining preferences for the environmental sustainability issue, whereas the general psychographic characteristic personal relevance contributed most to explaining preferences for the social sustainability issues. This result is likely explained by the principal focus on MSC certification in markets for fish products, which caused consumers to form opinions (e.g. concern) on overfishing, but not on social sustainability.     

Impacts of the 2011 mega‐earthquake and tsunami on abalone Haliotis discus hannai and sea urchin Strongylocentrotus nudus populations at Oshika Peninsula,Miyagi, Japan

On 11 March 2011, a massive tsunami generated by a mega‐earthquake with a moment magnitude of 9.0 hit a wide area of Pacific coast of northeast Japan. We observed and analyzed the effects of the earthquake and tsunami event on populations of the abalone Haliotis discus hannai and sea urchin Strongylocentrotus nudus at Tomarihama in Miyagi, where we have carried out regular surveys since January 2008. Before the event, algal forests dominated by the brown macroalga Eisenia bicyclis had developed in the survey area shallower than 5 m in depth, where adult abalone >50 mm in shell length (SL) inhabited. Juvenile abalone <20 mm SL and juvenile and adult urchins inhabited the deeper area dominated by crustose coralline algae (CCA). After the event, although no apparent decrease was observed in the brown macroalgal population, the mean density of adult abalone >50 mm SL, mainly inhabiting the algal forests, was reduced by more than half. The impact of the tsunami was more profound in the CCA area than in the macroalgal forest. Juvenile abalone and urchins largely decreased to 14 and 5% of the densities just before the event, respectively. The distribution pattern of juvenile abalone and urchins could be a cause of the marked decrease, because most of these animals inhabited the CCA area where the disturbance by the massive water movement was not reduced by the effects of the macroalgal forest.