Survival Of Spat Research Articles

Population dynamics of subtidal blue mussels Mytilus edulis and the impact of cultivation

Fishery on subtidal mussel beds and subsequent relying on culture plots in the same system is a common practice in bottom mussel culture. We address factors that determine the population dynamics of subtidal blue mussels Mytilus edulis L. and to what extent total (natural plus cultured) subtidal mussel biomass in the system is affected by fishery practices. Mussel size and density of spatially segregated natural and cultured subtidal mussel populations in the western Wadden Sea were measured over time in 2 field studies. Spatial patterns in survival rates showed better spat survival in areas with lower salinity and lower density of sea stars Asterias rubens. This suggests that mussel survival is negatively related to sea star distribution which is to a large extent controlled by salinity. The Asterias−Mytilus relation in the Wadden Sea is an example of the concept that environmental stress determines the successes of the prey by affecting the prey− predator relationship. Natural beds that escape predation are found at lower salinities, and mussels on these beds showed low growth rates, also because of lower food quality in these areas. Mussel culture is strongly affecting the population dynamics of the subtidal mussel population, through relay of mussels from natural mussel beds to culture plots. This activity increases mussel growth and survival, because food quality on culture plots is high and predation is controlled. Despite harvesting, mussel biomass production on culture plots was higher than on natural mussel beds, enhancing total subtidal mussel stock.

The use of biorefinery by-products and natural detritus as feed sources for oysters (Crassostrea gigas) juveniles

New research is currently underway to explore the potential of macroalgae for the production of biofuels. Marine biofuels in general and macroalgae in particular, offer a number of advantages over terrestrial biofuels including reduced competition for freshwater resources and for land use. Sugars can be extracted from macroalgae and processed into biofuels by anaerobic digestion and fermentation. This process generates significant waste biomass, which, if used, could improve the economic sustainability of the biorefinery sector. Bivalves' aquaculture relies heavily on the production of unicellular algae to feed juvenile individuals and this can represent a bottleneck for the bivalve industry especially in locations where sunlight is limited. Previous research explored the use of macroalgae derived digestate as alternative or integrative feed for juvenile bivalves, exploiting the notion that organic particulate matter (detritus) is an integral part of this animal class natural diet. The prospect of using waste products from the emerging biorefinery industry to solve a bottleneck for aquaculture businesses and, by so doing, improving profitability of both, is an exciting one. In this paper we describe the main nutritional profiles (Protein, Lipid, Carbohydrates and Fatty acids) of the tested diets and investigate the potential for the use of a biorefinery a by-product as replacement option for bivalves' production, by benchmarking it against aquaculture industry standards (live microalgae and commercially available algae paste) and natural detritus constituted by farmed sea urchin digesta. Both the digestate and the natural detritus supported the survival and growth of bivalve spat, especially when used at 50% inclusion rate, over the course of 4-week preliminary trials. Data suggest that a synergistic effect of the nutritional profiles of the diets employed may underpin the observed results. Statement of relevanceWith this study we compare the biochemical composition and suitability as oyster feed of the Single Cell Detritus produced by S. latissima enzymatic saccharification and natural detritus produced by sea urchin digestive action, with live microalgae as well as commercial algae paste. A comparison between biochemical composition and suitability as aquaculture feed between biorefinery by-products and natural detritus was, to our knowledge, lacking.Results indicate that both the digestate and the natural detritus supported the survival and growth of oyster spat, especially when used at 50% inclusion rate, over the course of 4-weeks trial.

Comparative growth and survival of spat of the Caribbean pearl oyster,Pinctada imbricatacultivated indoor with microalgae diets and outdoor with natural diet

We report the results of survival and growth in size and dry mass of spat of the Caribbean pearl oyster Pinctada imbricata cultivated under outdoor (field culture) and indoor (Laboratory) conditions. Field group fed on environmental seston. Laboratory groups were fed with mono, binary and ternary mixtures of three cultivated algae: Isochrysis galbana (Ig), Tetraselmis chuii (Ig) and the Chaetoceros sp. (Ch-A, isolated from north-eastern Venezuela). After 30 days of trial, fatty acid profiles of spat were determined along with growth in length and height shell, adductor muscle and soft tissue dry mass. During the field grow-out phase (field culture), samplings were performed at days 1, 15 and 30 to measure environmental variables of phytoplankton biomass (chlorophyll a), dissolved oxygen, seston, temperature and salinity. A significant increase in size and soft tissue mass occurred in spat fed the diets including the tropical diatom (Chaetoceros sp.). In contrast, monoalgal diets of Tc and Ig yielded no significant differences in size and mass of spat, compared with the field culture. These results suggest that nutritional requirements of cultivated spat for specific fatty acids of physiological importance for marine bivalves, such as: 16:0, 16:1n-7, 18:2n-6, 20:4n-6, 18:3n-3 and 20:5n-3, were satisfied from microalgal diets with Ch-A, alone or in combination, compared with spat fed from the field culture.

Assessment of scallop spat (Pecten novaezelandiae) transport, handling and tagging mortality for wild fishery enhancement, Golden Bay, New Zealand

The formerly lucrative Pecten novaezelandiae Southern Scallop fishery in New Zealand has experienced significant declines that have resulted in changes to spat handling and transport methods, with untested effects on spat survival. Experiments were carried out on board a harvest vessel to test the effects of spat handling, emersion, immersion and transport for up to 6h post-harvest. Spat were then transferred to lantern cages for 7 d with lantern and spat bag controls, and examined for mortality. Length frequency analysis revealed smaller spat (mean: 20.4mm ±0.3 95%CI) were more susceptible to handling and transport than larger individuals (mean: 25.9mm ±0.23), but ANOVA tests did not reveal any differences between emersed or immersed treatments that appeared related to handling stress. The most severe treatment, transporting spat for 3h at the bottom of a bulk bag to emulate crushing, had no detectable effect. Factors other than spat handling stress potentially responsible for the ongoing lack of recovery via enhanced spat in this fishery are discussed.

Increased Temperatures Combined with Lowered Salinities Differentially Impact Oyster Size Class Growth and Mortality

ABSTRACT Changes in the timing and interaction of seasonal high temperatures and low salinities as predicted by climate change models could dramatically alter oyster population dynamics. Little is known explicitly about how low salinity and high temperature combinations affect spat ( 75mm) oyster growth and mortality. Using field and laboratory studies, this project quantified the combined effects of extremely low salinities ( 30°C) on growth and survival of spat, seed, andmarket-sized oysters. In 2012 and 2013, hatchery-produced oysters were placed in open and closed cages at three sites in Breton Sound, LA, along a salinity gradient that typically ranged from 5 to 20. Growth and mortality were recorded monthly. Regardless of size class, oysters at the lowest salinity site (annualmean = 4.8) experienced significantly highermortality and lower growth than oysters located in higher salinity sites (annual means = 11.1 and 13.0, respectively); fur...

The by-products from marine biofuels as a feed source for the aquaculture industry: a novel example of the biorefinery approach

Through increased interest in the use of macroalgae for biofuel production, the concept of a biorefinery approach has been developed to improve its economic viability. This paper looks at the use of seaweed residue after enzymatic saccharification of the seaweeds Saccharina latissima, Alaria esculenta and Ulva lactuca as a novel feed component for the aquaculture industry. Chemical composition analysis was used to evaluate the impact of enzymatic treatment on the nutritional aspect of seaweed residue. During saccharification, the relative ash and carbohydrate content was reduced, but total nitrogen, total carbon and lipid content increased in all three species. In addition, the saccharification of S. latissima and A. esculenta resulted in the elimination of polyphenols, further enhancing the nutritional value of the residue. The residue supported the survival and growth of bivalve spat and commercially valuable sea urchins over the course of 3-week preliminary trials.

Further observations on the influence of husbandry practices on OsHV-1 μVar mortality in Pacific oysters Crassostrea gigas: Age, cultivation structures and growing height

Abstract Management of mass mortality events associated with Ostreid herpesvirus-1 microvariant (OsHV-1 μVar) is vital for aquaculture of Crassostrea gigas . As a consequence, the understanding of transmission mechanisms and risk factors enabling husbandry solutions to be developed constitutes an international research priority. In this context, a longitudinal intervention study was set up in Woolooware Bay, Australia, during summer in 2012–2013. The primary objective was to improve the external validity of a study completed in 2011–2012 that demonstrated mortalities in adult oysters but not spat could be halved by reducing their immersion time in an inter-tidal tray cultivation system (by elevating growing height by 300 mm). It is unknown whether an even higher growing height (+ 600 mm) could further improve survival or benefit the survival of spat. Consequently Pacific oysters of different ages (9.5 and 17.5 month) were placed in inter-tidal and sub-tidal rearing structures (trays and baskets) at three different sites in the bay. Mortality, growth, infection prevalence and viral load were monitored for 8 months (October–May). As in the previous summer, the disease was not continuously active over time in Woolooware Bay; mortalities were observed mainly in November 2012 and March 2013. The mortality was highly correlated with the prevalence of OsHV-1, which was in turn highly correlated with viral load, confirming the strong relationship between the virus and oyster mortality. The protective effect of high growing height on adult oysters was confirmed, with a final cumulative mortality below 40%, associated with significantly lower infection prevalence. Even though infection prevalence was significantly lower in baskets than in trays considering all ages and all sites, the final cumulative mortalities for spat were high (> 60%) regardless of the height and the type of cultivation structure; other mitigation strategies need to be developed for young oysters. The disease showed temporal and spatial variability suggesting that substantial variations in exposure to the virus occurred within and between years.

Protection of Pacific oyster (Crassostrea gigas) spat from mortality due to ostreid herpesvirus 1 (OsHV-1 μVar) using simple treatments of incoming seawater in land-based upwellers

The microvariant genotype of Ostreid herpesvirus 1 (OsHV-1 μVar) has severely disrupted the production of Pacific oysters Crassostrea gigas in Europe, New Zealand, and Australia since its first detection in France in 2008. The disease occurs in the warmer months, recurs annually, and requires new management strategies. Larvae and spat are the most susceptible life history stages, which poses a threat to hatchery production. This is the first study to examine strategies to enable survival of spat in treated seawater in an OsHV-1 μVar endemic area. In 2013 and 2014, seven controlled experiments were conducted in which potentially infected estuarine water was pumped through an upweller nursery system housing spat. Controls died of OsHV-1 infection in 6 of 7 experiments. Filtration of seawater to 5 μm was protective, whereas filtration to 30 μm or 55 μm was not. UV irradiation was not required for protection after 5 μm filtration. Chilling water by 2–3 °C delayed the onset and reduced the mortality rate. Aging seawater for 48 h prior to use prevented mortality, but the mechanism, either sedimentation of particles or inactivation of OsHV-1, was not determined. Some oysters in treatments in which mortality was prevented contained low quantities of OsHV-1 DNA, suggesting that infections may have occurred. The results support a hypothesis that OsHV-1 is carried on particles rather than being uniformly distributed in water; the removal of the putative particulate vector of OsHV-1 from seawater using aging/sedimentation of water or filtration to 5 μm enabled C. gigas spat to survive despite the presence of OsHV-1 μVar in the water supply.

Corals Like It Waxed: Paraffin-Based Antifouling Technology Enhances Coral Spat Survival

The early post-settlement stage is the most sensitive during the life history of reef building corals. However, few studies have examined the factors that influence coral mortality during this period. Here, the impact of fouling on the survival of newly settled coral spat of Acropora millepora was investigated by manipulating the extent of fouling cover on settlement tiles using non-toxic, wax antifouling coatings. Survival of spat on coated tiles was double that on control tiles. Moreover, there was a significant negative correlation between percentage cover of fouling and spat survival across all tiles types, suggesting that fouling in direct proximity to settled corals has detrimental effects on early post-settlement survival. While previous studies have shown that increased fouling negatively affects coral larval settlement and health of juvenile and adult corals, to the best of our knowledge, this is the first study to show a direct relationship between fouling and early post-settlement survival for a broadcast spawning scleractinian coral. The negative effects of fouling on this sensitive life history stage may become more pronounced in the future as coastal eutrophication increases. Our results further suggest that targeted seeding of coral spat on artificial surfaces in combination with fouling control could prove useful to improve the efficiency of sexual reproduction-based coral propagation for reef rehabilitation.

Effects of grazing by herbivorous gastropod (Trochus niloticus) on the survivorship of cultured coral spat

The technology in the production of sexual coral propagules for coral reef restoration is being actively developed recently to address concerns on the low genetic diversity in coral populations restored through transplantation of coral materials derived from fragmentation. In this study, we produced coral spat attached to rubble and determined the effect of the addition of hatchery-reared trochus, a herbivorous gastropod, at two densities (one and two trochus per cage, equivalent to four and eight trochus per square meter, respectively) on the survivorship of the spat cultured in cages at the hatchery and in situ nursery. After 5 weeks of culture in the hatchery, spat survivorship was significantly higher in the two per cage trochus treatment (18.3% ± 6.7%, mean ± sd) than in the control (5.5% ± 1.7%), with the one per cage trochus treatment having intermediate spat survival (12.6% ± 7.9%). The enhanced spat survivorship, though not apparent in the in situ nursery culture, is attributed to the grazing effect of trochus as significantly lower turf algal cover was observed in rubble placed in two per cage trochus treatment (44.8% ± 3.2%) than in the one per cage trochus treatment and control (80.2% ± 6.5% and 76.3% ± 5.0%, respectively). This study demonstrates that trochus can be used to control algal cover and enhance survivorship of coral spat in caged culture, at least in the hatchery, for the production of sexually derived transplant materials for coral reef restoration.

Age–size structure of common bivalve mollusc populations in the White Sea: the causes of instability

Inter-annual fluctuations in the recruitment rate and size–age structure are typical for marine bivalve beds. Until now there is no common opinion about the causes of this variability. One of them may be related to the adult–larval interactions in mollusk populations. To test this suggestion and to reveal the possible causes of inter-annual instability in bed recruitment level we analyzed the long-term (9–30 years) dynamics of the size–age structure of 22 populations of 9 bivalve species in the White Sea. Inter-annual variability in the successful recruitment was typical of most studied bivalve beds. This phenomenon was apparently caused, on the one hand, by the intensity of molluscs’ intraspecific interactions, and on the other (no less), by the juvenile survival in their first winter. The bivalve stationary beds in the White Sea are likely the exception from the general rule. They can be formed in case of a relatively stable level of annual recruitment with a decrease in intensity of intraspecific competition. However, in this case, the stability of the bed size–age structure can be easily disrupted under unfavourable conditions for spat survival in their first winter.

Effective size of refugia for coral spat survival

While the importance of the refuge structure for coral spat survival is increasingly recognized, little information is available regarding its effective size or dimensions. Accordingly, the present study examined the effective size of refugia using spats of two reef coral species, Echinophyllia aspera and Favites abdita. Coral spats settling on plates with three sizes of refugia (5, 15, and 25mm wide, and all 4mm deep) were monitored over a 2-year experimental period. The results were similar for both coral species: a higher survival rate was found for coral spats in smaller refugia. The 2-year survivorship in the 5-mm refugia (E. aspera: 1.5%, F. abdita: 12%) was more than one order of magnitude higher than those in the two larger refugia. Considered together with previous information, the effective size of refugia for the survival of coral spats may be on the scale of millimeters.

Effect of the fatty acid EPA and DHA in the conditioning of the scallop Nodipecten nodosus (Linné, 1758)

This study tested the diet enrichment with fatty acid EPA and DHA during the broodstock conditioning of scallops Nodipecten nodosus in hatchery. For this, before the conditioning the animals were induced to spawning and then were placed in tanks for maturation of 30days, and subjected to five treatments: (1) Cm100%, (2) Cm+DHA, (3) T-Iso100%, (4) T-Iso+EPA e (5) Mix (mix of the microalgae Isochrysis sp., Chaetoceros muelleri and Skeletonema sp., in the rate 50:25:25, respectively). After the conditioning, the animals were induced to spawning. The sexual stage by histology, spawning, larviculture and settlement was evaluated. The treatment T-Iso+EPA in broodstock showed 100% of the animals mature, stage 2B (advanced pre-spawning), higher yield in larvae D, pediveliger and spat. These results indicate that broodstock feeding with T-Iso+EPA provides a positive effect on the maturation, as well as a higher larvae and spat survival in hatchery.

Caging enhances post-settlement survival of juveniles of the scleractinian coral Acropora tenuis

Low cost, simple approaches leading to enhanced numbers of viable, mature corals on reefs are prerequisite to active reef rehabilitation at even modest spatial scales. Mass culture of coral larvae to settlement, utilising improved knowledge of major coral spawning events, promises to be relatively straightforward, but very significant mortality in the early post-settlement period remains a major hurdle. This study was conducted to examine the effect of herbivore exclusion on the survival of 6 week old coral spat of Acropora tenuis (Dana, 1846) reared ex situ at a site in north-western Philippines. Coral spat were placed on the reef approximately 6 weeks after settlement in three treatments, caged, open-sided cage and no cage at two depths (4 m and 9 m). Mean survival of coral spat was significantly higher at the deep sites compared to the shallow sites. Among treatments, survival was significantly lower in the uncaged treatment (4.7% ± 2.6% and 10.5% ± 4.5%, mean ± SE in shallow and deep respectively) compared to the open-sided cage (18.6% ± 5.0% and 22.5% ± 7.1%) and fully caged treatment (17.0% ± 4.5% and 33.0% ± 6.0%) after 3 months. The results indicate that removal of coral spat by grazers may have reduced survival in the uncaged treatment, although the fact that survivorship was not significantly reduced in the open-sided cage treatments suggests that the presence of the cage also had some effect on survival. It is possible that the open-sided cage prevented access by larger fish that may have actively removed coral spat or that shading provided by the cage enhanced spat survival. Further research is needed to see if survivorship in cages decreases at a later stage due to overgrowth by other biota and whether survivorship is enhanced if spat are settled on more complex surfaces that provide refuge from grazers. This study demonstrates that using cages to exclude herbivores and corallivores and/or to provide shading may be beneficial to survival during the early stages when rearing corals in situ for reef rehabilitation.

Survivorship of fast-growing coral spats depend less on refuge structure: the case of Acropora solitaryensis

Previous studies have demonstrated the importance of refuge structure from grazers on settlement substrata in survivorship of scleractinian coral spats. The present study reports some evidence showing that the importance of refuges varies depending on growth speed of coral spats. Survival of spats of the fast-growing scleractinian coral, Acropora solitaryensis that had settled on plain surfaces of settlement plates or in artificially-made micro-crevices (MC) serving as refuges on the plain plate surfaces was monitored in situ over the first year of life. Survival rate of A. solitaryensis spats dropped rapidly to less than 50% during the first two months but stabilized afterward and maintained high values both in MC (33%) and on the plain surfaces (17%) by the end of the one year experimental period. The higher spat survival rate observed in MC confirmed refuge effects on spat survivorship while many spats surviving on plain surfaces, which were not seen in slow-growing coral species in a previous comparable study, suggest that spats of fast-growing coral species that can attain a large enough size to survive damage from grazers early may depend less on refuge structure on settlement substrata. This may allow fast-growing coral species to extend potential areas for successful recruitment, more regardless of surface structure of settlement substrata, promoting its population development.

Effect of algal diet and temperature on survival, growth and biochemical composition of spat of the lion's paw scallop Nodipecten subnodosus

To find the best conditions for production, spat of the scallop Nodipecten subnodosus were grown for 10 weeks at 23, 26 or 29 °C, and fed with 2:1 mixtures (cell:cell) of Chaetoceros calcitrans with Pavlova lutheri or Isochrysis sp. (diets M1 and M2) or with a 1:1 mixture of P. lutheri and Isochrysis sp. (diet M3). Mortality was 100% after 4 weeks at 29 °C. Survival was significantly higher with diet M1 than with the other diets, and was 51 and 46% at 23 and 26 °C, respectively. With diets M2 and M3, the respective percentages of survival were 39.39 and 33.84% at 26 °C and 23.03 and 19.85% at 23 °C. The best growth in shell height was with diet M2, but there were no differences in final organic weight between diets M1 and M2; diet M3 gave the lowest spat growth. The highest protein content was with diet M1 at 23 °C. This diet gave the lowest carbohydrate contents of the spat at both temperatures, and the lowest spat lipid content at 23 °C. The fatty acid composition of spat was related to that of the respective diets, and there was no evident relation between dietary fatty acids and spat growth. Our results indicate that N. subnodosus spat should be kept at 26 °C and fed a mixed diet containing C. calcitrans and either P. lutheri or Isochrysis sp.

Response and condition of larvae of the scallops Nodipecten subnodosus and Argopecten ventricosus reared at the hatchery with different seawater sources

Larvae of the scallops Nodipecten subnodosus and Argopecten ventricosus were reared at a hatchery under five seawater sources: (1) filtered seawater, as the control group; (2) pasteurized seawater; (3) seawater taken from a well; (4) synthetic seawater, and (5) seawater containing a commercial probiotic (Epicin). The quality of each seawater source was measured in terms of counts of Vibrio pathogenic bacteria, levels of nitrites, nitrates, and ammonium, and content of suspended and organic matter. Overall response of larvae under each treatment was measured in terms of growth, survival, biochemical composition, and recruitment rate of spat. Differences in all these parameters, as a function of the seawater source, were analyzed with one-way ANOVA. Larvae survived more, grew faster and larger, had higher protein levels, and recruited more in filtered seawater (in N. subnodosus) and pasteurized seawater (in A. ventricosus), but significant differences between treatments were slight. In A. ventricosus cultures, filtered seawater favored significantly higher Vibrio counts than pasteurized seawater, but this result did not affect the response and condition of larvae. The well seawater treatment ranked third in terms of low bacterial counts, high nitrate levels, larvae showing relatively high survival and growth rates, and spat reaching the settlement stage (only in A. ventricosus ). The synthetic seawater and Epicin treatments did not yield satisfactory results for any of the indicators measured. In fact, in the Epicin treatment, larvae survived only the first days of hatchery cultivation and settlement occurred only in A. ventricosus. The results from these first set of trials are useful for planning additional experiments aimed to improve the protocol of seawater use at our research hatchery.

Micro-crevice structure enhances coral spat survivorship

This study examined effects of microstructure (hereafter termed “micro-crevices”) on the surface of settlement substrata, which provides refuge for minute coral spats from grazing and, hence, could enhance coral spat survivorship. Survival of coral spats settling on plain tile-surfaces or in artificially-made micro-crevices on the tile-surfaces were monitored in situ using three scleractinian coral species; Echinophyllia aspera, Favites pentagona, and Platygyra contorta. All coral spats settling on the plain tile-surfaces died without traces of skeleton within the first four months of the experiments while some spats that settled in the micro-crevices still survived by the end of the one-year experimental period with survival rates of up to 12%. The results demonstrated the role of micro-crevice structure enhancing coral spat survivorship in the three coral species. Hence, given grazing activity, micro-crevice structure may be a significant factor influencing development of scleractinian coral communities.

Survival and growth of hatchery-produced postlarvae and spat of the Caribbean scallopsArgopecten nucleusandNodipecten nodosus

A study was made of the growth and survival of postlarvae and spat of Argopecten nucleus and Nodipecten nodosus produced in the laboratory and exposed to different conditions of settlement and culture. An evaluation was made of the different types of collection substrates (onion-bags, artificial-grass, fibreglass-plates), two types of settlement inducers (epinephrine, low temperature), and two culture environments (sea, laboratory). The results showed that larger numbers of postlarvae were obtained in artificial-grass collectors than on fibreglass-plates or in the onion-bags. The growth of the A. nucleus postlarvae was not affected by the collector type, while that of N. nodosus was higher on fibreglass-plates, and lesser in the onion-bags. Both thermal and chemical stimulation of the competent larvae resulted in recovery of a greater percentage of postlarvae. The growth of postlarvae of A. nucleus was better in groups exposed to the two methods of settlement induction, while those of N. nodosus remained unaffected by this treatment. The survival of the postlarvae and spat was greater in the laboratory than at sea except in the case of A. nucleus postlarvae attached to collectors, whose survival was similar in both environments. The growth of postlarvae and spat was greater in the sea than in the laboratory.

Nutritional value of Pavlova spp. (Prymnesiophyceae) for spat of the Cortez oyster Crassostrea corteziensis during late-nursery culturing at the hatchery

Three Pavlova species were evaluated for their nutritional value as diets for growth and survival of the Cortez oyster Crassostrea corteziensis spat during late-nursery cultivation at a hatchery. Microalgae were provided as monospeci¢c diets (Pavlova salina, P .s p. C50 andP. sp. C53) and in binary combinations of diets112,1 1 3a nd 213 at 80^90 10 3 cells mL 1 for 21 days. Juveniles experienced high survival rates and grew well with all dietary treatments, but binary diets yielded greater survival and growth of spat. From the three binary treatments, Diet 6 (P .s p. C50 andP. sp. C53) promoted signi¢cantly (Po0.001) fastest growth of juveniles in shell height (0.19 mm day 1 ), shell length (0.14 mm day 1 ), total wet weight (0.04 g day 1 ) and dry weight of meat biomass (0.024 g day 1 ). For all shell dimensions, the lowest growth rates occurred with Diets 2 (P .s p. C56 alone) and 3 (P. sp. C50 alone). These results highlight the importance of testing microalgal diets for bivalve spat rather than just relying on published nutritional values.