Shell Height Research Articles

From Isolated Valves to a Potential Marine Living Resource: History, Documented Distribution and Sustainable Population Enhancement Possibilities of the Smooth Scallop (Flexopecten glaber) on the Romanian Coast

Until recently, the smooth scallop Flexopecten glaber (Linnaeus, 1758) was considered absent from Romanian Black Sea waters, as only isolated valves were documented on beaches of the southern coast. Yet, in 2020, the first living specimens were collected by dredging at 25 m depth in Mangalia. Moreover, in the past three years, a considerable number of live individuals were also retrieved from beam-trawling operations targeting the gastropod Rapana venosa (Valenciennes, 1846) along the Romanian coast, indicating that there is a stable population here. This remarkable expansion of F. glaber in Romanian waters may be explained as a consequence of the Black Sea’s recovery from eutrophication, reduced predatory pressure from the declining population of R. venosa and changing climate conditions. Our research aimed at using all this novel information to document for the first time the occurrence and distribution of this bivalve on the Romanian coast, also considering perspectives for the development of a new type of shellfish mariculture, avoiding any pressure on the natural stock. In total, 386 F. glaber individuals were sampled during 2020–2023, at depths between 22.5 and 33.3 m. The abundance and biomass per station oscillated between 5 and 319 specimens and 51.5 and 7377 g, respectively. A subsample of 122 specimens was preserved and analyzed in the laboratory, revealing an average shell length of 53.54 mm (±4.13 SD) and an average shell height of 49.54 mm (±3.64 SD). The smooth scallop has both ecological and economic value, which makes it a viable candidate for sustainable aquaculture by collecting spat from the most abundant areas and subsequently placing “seedlings” in the appropriate polygons for stock recovery. Ultimately, commercial exploitation from aquaculture installations can be considered, provided a permanent healthy F. glaber population is established on the Romanian coast.

Somatostatin Receptor Gene Functions in Growth Regulation in Bivalve Scallop and Clam.

Bivalves hold an important role in marine aquaculture and the identification of growth-related genes in bivalves could contribute to a better understanding of the mechanism governing their growth, which may benefit high-yielding bivalve breeding. Somatostatin receptor (SSTR) is a conserved negative regulator of growth in vertebrates. Although SSTR genes have been identified in invertebrates, their involvement in growth regulation remains unclear. Here, we identified seven SSTRs (PySSTRs) in the Yesso scallop, Patinopecten yessoensis, which is an economically important bivalve cultured in East Asia. Among the three PySSTRs (PySSTR-1, -2, and -3) expressed in adult tissues, PySSTR-1 showed significantly lower expression in fast-growing scallops than in slow-growing scallops. Then, the function of this gene in growth regulation was evaluated in dwarf surf clams (Mulinia lateralis), a potential model bivalve cultured in the lab, via RNA interference (RNAi) through feeding the clams Escherichia coli containing plasmids expressing double-stranded RNAs (dsRNAs) targeting MlSSTR-1. Suppressing the expression of MlSSTR-1, the homolog of PySSTR-1 in M. lateralis, resulted in a significant increase in shell length, shell width, shell height, soft tissue weight, and muscle weight by 20%, 22%, 20%, 79%, and 92%, respectively. A transcriptome analysis indicated that the up-regulated genes after MlSSTR-1 expression inhibition were significantly enriched in the fat digestion and absorption pathway and the insulin pathway. In summary, we systemically identified the SSTR genes in P. yessoensis and revealed the growth-inhibitory role of SSTR-1 in bivalves. This study indicates the conserved function of somatostatin signaling in growth regulation, and ingesting dsRNA-expressing bacteria is a useful way to verify gene function in bivalves. SSTR-1 is a candidate target for gene editing in bivalves to promote growth and could be used in the breeding of fast-growing bivalves.

Aquaculture Performance and Genetic Diversity of a New [(Crassostrea hongkongensis ♀ × C. gigas ♂) ♂ × C. hongkongensis ♀] Variety of the Oyster "South China No. 1" in Beibu Gulf, China.

Crassostrea hongkongensis is an economically important bivalve found in various parts of the South China Sea. A new interspecific backcross ([(Crassostrea hongkongensis ♀ × C. gigas ♂) ♂ × C. hongkongensis ♀]) variety was bred by the South China Sea Institute of Oceanology which named "South China No. 1". This study aims to explore the effects of stocking density on the growth performance of "South China No. 1", compared their growth performance and genetic diversity to C. hongkongensis, and found the best place breeding site for "South China No. 1" in Beibu Gulf. The results showed that stocking a density of 20 oysters/substrate can significantly increase the shell height, shell width, total weight, survival rate, daily shell height gain and daily body mass gain. It was found that the shell height and total weight of "South China No. 1" cultured in Fangchenggang were significantly higher than that of those in Beihai and Qinzhou from September 2018 to November 2018. Similarly, the shell width of oysters in Fangchenggang and Qinzhou was also significantly higher in September 2018, and the interaction between site and stocking density had significant effects on the shell width in March 2018 and November 2018. In addition, the shell height and shell width of "South China No. 1" were significantly higher than that of C. hongkongensis in all three sites. At all three sites, the phytoplankton community structure was mostly dominated by Bacillariophyta. In the Hardy-Weinberg equilibrium test, for the seven populations and ten microsatellites, in 10 of the 70 groups, the segregation distortion was significant. These results suggest that a stocking density of 20 oysters/substrate can promote the shell height, shell width and total weight of "South China No. 1" in Beibu Gulf, China. "South China No. 1" has better growth performance compared with C. hongkongensis. Fangchenggang is a suitable place to cultivate the "South China No. 1" breed according to the total weight and sum of all algal genus abundances. The results of this study can be used as a reference to further understand the stocking density and genetic diversity of the "South China No. 1" breed in Beibu Gulf, China.

Suggestion of Correlations to Obtain Shell and Tube Side Nusselt Numbers in Coiled Heat Exchangers

In coiled tube heat exchangers increase in curvature ratio and effective contact of shell fluid with coil surface led to better thermal characteristics. This work addresses study of thermal performance, shell and tube heat transfer coefficients (ho and hi). Also, mathematical correlations are predicted to obtain shell and tube Nusselt numbers (Nuo and Nui). In the designing of compact coiled heat exchangers consisting of straight helical coil (SHC), conical coil (CC) and spiral coil knowledge of Nuo and Nui is necessary whereas mathematical correlation to calculate Nuo considering variations in shell geometry is not found. Five heat exchangers consisting of three cone coils (angle, ϴ = 30°, 50° and 70°), spiral coil (ϴ = 0°) and SHC (ϴ = 90°) are tested. Using Wilson plot method ho and hi are obtained for wide range of tube side Reynolds numbers (Rei = 3700 - 21000). It is observed that, highest ho is obtained for ϴ = 30°CC with better thermal performance. Lowest ho is obtained for ϴ = 90°SHC. Ratio of height of shell, Hs and diameter of shell, Dso is considered in prediction of single correlation as: Nuo = 16.55.Reo0.55.Pro0.4 *(Hs/Dso)0.096. Comparison with experimental findings shows variation of 0-14%. Similarly two correlations are proposed as: Nui = 0.0512.Rei0.80.Pri0.4.CRave0.18 and Nui = 0.0365.Dei0.815.Pri0.4.CRave-0.3. A fair agreement is found with existing researchers.

Contribution of the TGFβ signaling pathway to growth of Pacific oyster (Crassostrea gigas)

Growth mediated by the transforming growth factor β (TGFβ) signaling pathway is a key trait in understanding environmental adaptability and species stability. The aim of the present study was to identify the TGFβ signaling pathway members and their expression patterns in different sized Pacific oysters (Crassostrea gigas). Nine oysters were selected for each of two groups: group L (shell height 77.57 ± 7.55 mm, shell length 49.96 ± 4.79 mm) and group B (shell height 43.58 ± 2.74 mm, shell length 33.25 ± 2.78 mm). Using a bioinformatics approach, 37 protein sequences of TGFβ signaling pathway members were classified in C. gigas, including 19 species for this species, nine ligands, five receptors, and five Smads. The mRNA expression levels of TGFβ pathway members in oysters of different sizes showed that both the TGFβ/activin/Nodal and BMP/GDF/MIS subfamilies are involved in the growth regulation of C. gigas. In the first subfamily, there was one possible signaling pathway: INHBA - TGFBR1/BMPR1B/ACVR1 - BMPR2 - Smad3/Smad1, 5, 8. In the second subfamily, there were three possible signaling pathways: BMP2 - BMPR1B - BMPR2 - Smad1, 5, 8; BMP4 - BMPR1B - BMPR2 - Smad1, 5, 8; and BMP7 - ACVR1/BMPR1B - BMPR2 - Smad1, 5, 8. Principle components analysis identified Bmp3, I-Smad, Bmp4, INHBA, and Smad3 as biomarkers of growth in the TGFβ signaling pathway of C. gigas, implicating the TGFβ pathway in the growth of C. gigas.

Comparative analysis on growth performance, survival and harvest traits between offspring from wild and mass-selected populations of Crassostrea nippona

Crassostrea nippona has recently been recognized as a preferred alternative to C. gigas in summer due to its firm flesh and high glycogen content. To promote industrial development, the mass selective breeding program was initiated to improve growth performance of C. nippona in 2014. Although a steady genetic gain of approximately 10% for growth traits was achieved in each of the first three generations of the selected strains, little is known about the cumulative genetic progress in desired traits contributed by the selective breeding in the genetic improvement program. In this study, the aquaculture performance of the selected population was comprehensively evaluated by comparing the production performance and reproductive traits of the progeny (WF1 and SF4) from the wild population and the third-generation selected line in commercial farming environments. The results showed that the diameters of eggs from both populations were at similar levels, but the fertilization and hatching rates of the progeny from the selected lines were significantly higher than those of the wild population (P < 0.05). At larval stages, the shell height and cumulative survival rate (CSR) of individuals from SF4 were consistently superior to that of WF1, especially on day 6 post-fertilization, in which CSR of the improved C. nippona was increased by 25.08% compared to that of wild oysters. Meanwhile, a significant 12.10% enhancement in the metamorphosis rate was observed in SF4 when compared with WF1. During the grow-out stage, SF4 displayed distinct advantages in growth performance and survival compared to the wild strain, with 23.19, 33.48, 34.18 and 79.11% improvement in shell height, body weight, CSR and final yield at harvest on day 800, respectively. Meanwhile, relative brood amount (RBA) associated with initial development of offspring was found to be significantly higher in SF4 compared with WF1 (P < 0.05). Remarkably, the gonadal development, sex ratios and biochemical composition of oysters from both populations were at similar levels at final harvest, implying that high-intensity artificial selection had no significant effect on reproductive characteristics and nutritional quality of C. nippona. The encouraging results in the present study suggest that the overall genetic progress contributed by genetic breeding is considerable in the fast-growing strain of C. nippona, and such gains are expected to continue to increase with further selective breeding.

Feasibility exploration and comparative analysis of interspecific hybridization between Crassostrea hongkongensis and Crassostrea dianbaiensis

Interspecific hybridization plays a significant role in the genetic improvement of oysters in aquaculture, with the main objective being to obtain progeny that inherit the desirable traits of both parents and establish a stable inheritance pattern. Crassostrea hongkongensis is well-known for its large size and excellent meat quality. However, it exhibits poor resistance to external environmental changes and a high mortality rate. To address these shortcomings, this study conducted a 2 × 2 interspecific hybridization between Crassostrea dianbaiensis and C. hongkongensis. D larvae from C. hongkongensis ♀ × C. dianbaiensis ♂ (HD) and C. dianbaiensis ♀ × C. hongkongensis ♂ (DH) crosses were successfully hatched. However, the hatching index of both groups was lower than that of C. hongkongensis ♀ × C. hongkongensis ♂ (HH) and C. dianbaiensis ♀ × C. dianbaiensis ♂ (DD) groups. The average shell height of DH on the 15th day was only 111.50 ± 6.31 μm, and all individuals were dead by the 18th day. Despite experiments being repeated many times, no attached DH larvae were obtained. Compared with intraspecific hybridization, HD grew slower in the larval stage and had a lower survival rate, but the shell height of HD was slightly higher than that of HH on the 450th day (P > 0.05). The cumulative survival rate of HD throughout the growth period was higher than that of HH and DD, demonstrating a clear hybrid advantage in terms of relative yield and survival rate, especially higher than that of C. hongkongensis. Moreover, the gonads of HD can develop normally and produce gametes, and the color of the inner shell and body is between that of C. hongkongensis and C. dianbaiensis. These results indicate that HD effectively improved the survival rate of C. hongkongensis, demonstrating its great application potential and promising prospects in aquaculture.

Morphometry and length-weight relationships of the freshwater pearl mussel Parreysia corrugata (Muller 1774) (Bivalvia: Unionidae) from Daya River, Odisha, India

Allometry in the freshwater mussel Parreysia corrugata was studied from east-flowing riverDaya, Bhubaneswar, India. The results indicated that shell length (SL)-shell height (SH) andshell length-shell width (SW) relationships for P. corrugata were SH = 0.876 + 0.932SL andSW = 0.625 + 0.898SL. Greater correlation was found between SL and SW than between SLand SH. The length-weight, height-weight and width-weight relationships of P. corrugata wereestablished as TW = 0.00038SL2.80, TW = 0.0006SH2.95 and TW = 0.0023SW2.97 respectively.The t-test value of b indicated an isometric growth pattern in the width-weight and theheight-weight relationships. The highest r2 value was obtained for shell length-total weightand shell height-total weight equations. Present study will be helpful in strengthening theknowledge on interrelationship between the morphometric variables of P. corrugata and alsoin comparing with the earlier studies to know the existence of spatial or temporal variabilityin the morphometry of this species. This information can also be used to better understandthe biology of P. corrugata and to improve the management of this species. Keywords:Conservation, Daya River, Length-weight relationships,Morphometry

A new species of freshwater snail of Fenouilia (Gastropoda, Pomatiopsidae) from northern Guangxi, China, based on morphological and DNA evidence.

A new species of pomatiopsid freshwater snail, Fenouiliaundata Chen & He, sp. nov., is described from Guangxi, China, based on morphological and molecular evidence. The new species can be distinguished from its congeners by the following combination of characters: shell with low, prosocline, rounded axial ribs and fine spiral striae, broader than high; aperture broader than shell height; radula with lateral teeth have only two or three faint, wavy ridges on inner side. A molecular analysis of partial mitochondrial COI and 16S DNA sequences supports the systematic position of the new taxon.

A Comparative Study of Mercury Bioaccumulation in Bivalve Molluscs from a Shallow Estuarine Embayment.

In estuarine food webs, bivalve molluscs transfer nutrients and pollutants to higher trophic levels. Mercury (Hg) pollution is ubiquitous, but it is especially elevated in estuaries historically impacted by industrial activities, such as those in the U.S. Northeast. Monomethylmercury (MeHg), the organic form of Hg, is highly bioaccumulative and transferable in the food web resulting in the highest concentrations in the largest and oldest marine predators. Patterns of Hg concentrations in marine bivalve molluscs, however, are poorly understood. In this study, inorganic Hg (iHg), MeHg, and the total Hg (THg) in soft tissues of the northern quahogs (Mercenaria mercenaria), eastern oysters (Crassostrea virginica), and ribbed mussels (Geukensia demissa) from eastern Long Island sound, a temperate estuary of the western North Atlantic Ocean was investigated. In all three species, concentrations of THg remained similar between the four sampling months (May, June, July, and September), and were mostly independent of animal size. In quahogs, MeHg and iHg displayed significant (p < 0.05) positive (iHg in May and June) and negative (MeHg in July and September) changes with shell height. Variability in concentrations of THg, MeHg, and iHg, both inter- and intra-specifically was high and greater in quahogs and oysters (THg: 37, 39%, MeHg: 28, 39%, respectively) than in mussels (THg: 13%, MeHg: 20%). The percentage of THg that was MeHg (%MeHg) was also highly variable in the three species (range: 10-80%), highlighting the importance of measuring MeHg and not only THg in molluscs.

Effects of polystyrene nanoplastics on the amino acid composition of Asian Clam (Corbicula fluminea)

Because the effect of nanoplastics (NPs) on muscle nutrition is poorly understood, a systematic study of the growth performance, tissue damage, and amino acid composition of Asian clam (Corbicula fluminea) under polystyrene nanoplastic (PS-NP) treatment was performed by combining short- and long-term treatments together. The primary results showed the shell length, height, and width increased as time progressed, whereas the body weight of C. fluminea revealed no significant difference between the PS-NP–treated clams and the blank control during the entire experiment. Histopathology analyses manifested the inflammatory cell infiltration and vacuolization rates of gill, gut, gonads, and muscle were elevated under PS-NP treatment in comparison with those of the blank control, indicating PS-NP–induced tissue damage occurred irreversibly. Downregulated SOD activity and upregulated CAT and GPX activities were detected, accompanied by increased MDA and GSH levels, suggesting PS-NPs induced tissues damage associated with its role as an antioxidant system disruptor. Levels of four bitter amino acids (Val, Met, Ile, Leu) significantly increased in the PS-NP-treated group compared to levels in the blank control, which was the dominant variation in muscle nutrition. As a result of these changes, the meat quality of C. fluminea decreased, which is a novel discovery of this work.

Discovering new living Pinna nobilis populations in the Sea of Marmara

Fan mussel (Pinna nobilis) is one of the largest bivalve species in the Mediterranean Sea. The situation of the species is critical as it faces widespread mass mortality attributed to pathogens in various parts of the Mediterranean Sea. The Sea of Marmara (SoM) offers a unique environment for fan mussel populations, with some areas hosting alive populations. This study aims to explore and describe new P. nobilis populations in the SoM that are known to be not affected by mortality. An area of 28,200 m2 at 47 stations along the 105 km coastline in the southern part of the SoM was explored using underwater visual transects. A total of 544 alive fan mussels were recorded during the underwater surveys, ranging in total shell height from 11.8 to 31.4 cm. The mean density was estimated as 5.3 ind 100 m−2 although maxima of 18.8 ind 100 m−2 were recorded in some stations. These density hotspots were distributed from the shoreline to a 10 m depth range and 100 m distance from the shoreline in sandy and seagrass meadow habitats. The presence of juveniles provided evidence of successful recruitment. The distribution pattern and recorded mortalities were attributed to hydrodynamic factors and intense human activities. Potential environmental factors (low salinity and temperature) in the SoM may control or delay the possible spread of the lethal pathogens. Favorable conditions result in mussels’ resilience and survival mechanisms. The SoM offer a promising larval reservoir for the recolonization of affected areas, such as those found in the Aegean Sea, through larval exportation.

Wild populations of Pacific oysters (Magallana gigas) emerge during the blob heatwave in south Puget Sound, Washington USA

Marine heatwaves have altered ecosystems globally, including changing community composition and facilitating the spread of invasive species. In south Puget Sound, Washington (USA), non-native Pacific oysters (Magallana gigas) have been farmed extensively for almost a century and grown in enhancement sites, however, they have only recently recruited in the wild. This study explores how the appearance of Pacific oysters was related spatially (eight sites) and temporally (decade) to warmer summer water temperatures in south Puget Sound and compares oyster persistence across five sites where recruitment occurred. The largest recruitment event from 2012-2020 was in the summer of 2015, in the middle of the east Pacific Blob marine heatwave which led to warm water temperatures off the west coast of North America. Throughout the study period, the number of oyster recruits each year was positively correlated with warmer water temperatures. Oyster population densities differed across the five sites where recruitment occurred and generally declined after 2015, but showed no site by year interactions, which is consistent with spatially-variable recruitment and similar post-recruitment survival. Mean oyster shell heights also differed among sites, which could reflect different growth trajectories or recreational harvest patterns. This study supports the claim that warming sea surface temperatures may interact with species introductions to change modern biogeography.

Growth, survival and reproductive traits of chemical induced and tetraploid-derived triploid Hong Kong oysters (Crassostrea hongkongensis)

Chemical induction (inhibition of polar body II release) and crossing between tetraploid and diploid oysters (mating triploids) are 2 distinct and typical methods for obtaining triploids, and systematic comparative analysis on the phenotypic traits of these two triploids is rare. We tracked and compared the growth, survival, reproductive characteristics and ploidy composition of diploids, induced triploids, and mating triploids, and conducted interaction analysis between genotypes and sites. The results showed that the shell height of larvae showed a significant decrease trend of 3 NTD > 3 NCB > 2 N, while the D larval rate and survival rate of 3 NCB were the lowest, which may be related to the long-term effects of CB toxicity. During offshore farming, from the 180th to 700th day, the shell heights of the three groups followed a significantly decreasing order at both sites, namely 3 NTD > 3 NCB > 2 N (except on the 270th day at Beihai site), and the triploid advantage of shell height in 3 NTD was generally higher than that in 3 NCB, with the same trend in the whole weight. Genotypes and sites always had significant effects on shell height, but their interactions were not significant. The incremental survival rates of the 2 triploid groups were higher than that of the diploid at both sites on the 270th and 700th day, while that of the 3 NTD was significantly higher than the 3 NCB only on the 270th day. In addition, both triploids had some individuals fertile and could produce mature gametes, but the proportion was much lower than that of diploids. Triploid gonadal development is characterized by feminization and a high proportion of hermaphroditism. The fertility ratio and gamete production of 3 NTD were higher than that of 3 NCB, but the relatively high fertility of 3 NTD had no significant effect on its growth and survival. Ploidy composition tracking found that the ploidy composition of 2 N and 3 NTD groups was stable, but the ploidy composition of 3 NCB varied over time. These results indicate that 3 NTD has better performance and higher triploid advantages than 3 NCB, making it more suitable for the commercial production and promotion of triploid C. hongkongensis.

Influence of ploidy, genetic and environment on production traits of the Pacific oyster Crassostrea gigas

Pacific oysters, Crassostrea gigas, are one of the most widely farmed shellfish. To meet demand, the advantages of growth and increased sterility are currently being exploited in the commercial culture of triploid C. gigas. However, the extent of the triploid advantage can vary, environmental conditions and rearing methods. In the present study, the performance of diploid and triploid oysters was compared at two sites (Rongcheng and Rushan) to determine whether the triploidization would result in any advantage on production traits that could be utilized for aquaculture of this species. Triploid oysters were also produced using the wild broodstock and selected line to verify whether selectively bred oysters maintain their improved traits after triploidization. In this study, we found that the survival advantage of triploid is “site-dependent” and that Rongcheng's triploids did not exhibit significantly higher cumulative survival than diploids. Notably, incremental survival of triploid oysters was consistently higher than that of diploids during the second summer, which may be related to gonad development and spawning in diploids. At both sites, growth traits (shell height and individual weight) were always higher for triploids than in diploids in both the selected and control groups, which is strong evidence of a superior growth advantage for triploids. In addition, we found that the production performance (growth, survival and yield) of the selected group was consistently better than that of the control group (either diploid or triploid), suggesting that the superior traits of diploids can be converted to triploids through ploidy manipulation. Our results support the notion that yield can be further optimized by reducing mortality through a selective breeding program coupled with triploid production to increase growth rates. This study provides meaningful information on the potential of triploid C. gigas for oyster culture in northern China.

Studi kelimpahan dan morfometrik pada kerang darah (Anadara granosa) di Perairan Motadikin Kabupaten Malaka

Anadara granosa is one of the fisheries commodities that is abundant in various regions, especially tropical areas. The high use of blood cockles by the community in Motadikin waters is considered to result in a decline in the population of blood cockles in nature, thereby increasing population growth. This research aims to examine the abundance and morphometric features of blood cockles in Motadikin waters, Malaka Regency. This research was carried out for 1 month in Motadikin waters, Malacca Regency using the transect method. The number of transects used was 3, the distance between transects was 25 m and each transect used 6 quadrants with a size of 1x1 m and the distance between each quadrant was 5 m. The results of the research showed that the abundance of blood clams in Motadikin Waters was an average of 5-7 individuals/m2 and the average The average abundance found on substrates covered with mangroves (I) is higher than on sandy substrates alone (II). Meanwhile, morphometric measurements of blood clams in Motadikin waters are dominated by blood clams with a length range of 3.2 cm - 3.9 cm, with a shell height of 1.4 cm - 2.7 cm, an umbo height of 1.1 cm - 1.2 cm, shell thickness 2.4 cm - 2.6 cm and ligament length 2.4 cm - 2.7 cm.&#x0D; &#x0D; Keywords: Anadara granosa, abundance, morphometrics, motadikin waters.

Abundance of Vibrio aestuarianus, water temperature, and stocking density are associated with summer mortality of Pacific oysters in suspended culture

High mortality rates of cultured Pacific oysters (Crassostrea gigas) during the summer months have regularly occurred on oyster farms in British Columbia, Canada over the last 10 years, but little is known about the microbial and environmental conditions that contribute to such mortality events. The objective of the study was to determine correlative factors associated with the onset of a summer mortality event in oysters (mean ± SD shell height: 14.2 ± 0.5 mm) grown in suspended culture at four stocking densities (150, 300, 450, 600 oysters tray−1) from May 11 to September 17, 2018. Variables examined included both biotic (oyster growth, mortality, reproductive development, and microbiome (approximately every week); Vibrio and harmful algal species abundance) and abiotic (temperature, salinity, turbidity, dissolved oxygen, pCO2, pH, and aragonite saturation) ones. Both the absolute abundance of V. aestuarianus and the relative abundance of Vibrio spp. increased with observed oyster mortality and declining health. Mortality was highest on August 12 and associated with a prior period of elevated temperatures (i.e., increasing temperatures from early July to early August) and increased oyster growth/reproductive development. At that time, systemic mixed microbial infections and necrotic gill tissue in histological cross sections were observed in 19% of oysters that appeared healthy macroscopically. Cumulative percent mortalities per tray ranged from 34 to 75%, the highest-density trays having significantly less mortality and smaller shell width, shell length, and gonad length than lower-density trays. This study demonstrates the significant impact of summer mortality on Pacific oysters and highlights the biotic (host growth, reproductive development, and microbiome composition as well as Vibrio spp. abundance) and abiotic (water temperature) factors associated with the observed mortality in this region.

Effects of microalgae diets on growth, proximate, and fatty acid composition of black mussel, Mytilus galloprovincialis

AbstractThis study evaluates the growth, proximate, and fatty acid composition of black mussel, Mytilus galloprovincialis fed four marine microalgae (Pavlova lutheri, Nannochloropsis oculata, Diacronema vlkianum and Rhinomonas reticulata) diets for 21 days. Black mussel is a common bivalve species that has been recognized as important for marine aquaculture with increasing production in the last two decades. The mussel group fed N. oculata showed a significantly lower survival rate than the other groups (p &lt; 0.05). Shell height, length, and width of mussels were measured. The height and length of the mussel group fed N. oculata were statistically higher than other experimental groups (p &lt; 0.05). Shell width did not show any significant differences among groups (p &gt; 0.05). The microalgae N. oculata showed the highest protein content whereas P. lutheri had the highest crude lipid content among dietary treatments. The group fed P. lutheri showed significantly higher protein, lipid, and ash contents among experimental groups (p &lt; 0.05). The D. vlkianum diet enhanced the highest docosahexaenoic acid level in black mussels. Black mussel fed P. lutheri showed the highest eicosapentaenoic acid and polyunsaturated fatty acid levels. Arachidonic acid was found to be similar among experimental groups. In our study, P. lutheri and D. vlkianum had outstanding results on survival, growth, and essential fatty acid accumulation in mussel culture.

Morphological Trait Correlations, Gonadal Development Characteristics and Pleopod Nutrient Compositions of the Whelk Volutharpa perryi perryi

The aim of this study was to clarify the “morphological-trait–body weight” correlation, gonadal development characteristics, and pleopod (main edible part) nutrient composition of the whelk (Volutharpa perryi perryi). Live body mass (BM), soft tissue mass (STM), and eight other morphological traits of the whelk were measured, and path coefficients, correlation indices (R2), and coefficients of determination were then calculated. Gonadal development characteristics were investigated by histological observation. Pleopod nutrient composition was analyzed by standard biochemical assays. The results indicated that (1) shell aperture width (SAW) and body whorl height (BWH) were positively correlated with both live BM and STM (p &lt; 0.01), and shell height (SH) was positively correlated with both live BM and STM (p &lt; 0.01) in male whelks; (2) similar gonadal development characteristics were observed in both female and male whelks; and (3) pleopod nutrient composition was consistent in both female and male whelks, whereas sex-specific variation in pleopod nutrient content was observed in the whelks. The observations in this study will provide theoretical support for the development of the whelk aquaculture industry.

Growth and Survival of Scallops Austrochlamys natans (Philippi, 1845) and Zygochlamys patagonica (P. P. King, 1832) in Suspended Systems and Land-Based Tanks in Chilean Patagonia

The southern scallop (Austrochlamys natans) and the Patagonian scallop (Zygochlamys patagonica) are vital species in the fisheries of Chilean Patagonia. However, overfishing has led to stock depletion, necessitating research for stock restoration and commercial production. This study aimed to evaluate the growth and survival of these scallops in suspended systems and land-based tanks across various Patagonian regions. Eight experiments were conducted, three with southern scallops and five with Patagonian scallops. For southern scallops, two experiments involved suspended systems at different shell heights and three tested land-based tanks at various temperatures (9, 11, and 13°C). Patagonian scallop experiments included one suspended system in an endemic area, land-based tanks with different temperatures (9, 11, and 13°C), and three suspended systems outside the species’ endemic zone. In suspended systems, southern scallops grew from 15.1 to 42.7 mm (shell height) in 322 days, with a rate of 0.085 mm/day and a survival rate of 43.7%. Patagonian scallops reached 46.0 mm shell height in 466 days, with a growth rate of 0.079 mm/day and a survival rate of 57.2%. Experiments in controlled-temperature tanks revealed that 13°C was the lethal temperature for southern scallops. Notably, higher growth rates occurred at temperatures between 9 and 11°C. Both species show potential for future commercial cultivation, contributing to Chilean aquaculture diversification.