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Clam gardens are habitat modifications established by coastal Indigenous Peoples of northwest North America to enhance intertidal clam habitat productivity to provide secure and reliable local food resources. These gardens were established long ago and are mostly unmaintained in present times. To determine whether unmaintained clam gardens still provide a more productive and beneficial habitat than unmodified clam beaches, Pacific littleneck clams (Leukoma staminea) were transplanted to unmaintained clam gardens or unmodified reference beaches and then evaluated for growth, survival, and transcriptomic signatures of the gill and digestive gland after 16 weeks. All beaches in the study were characterized for sediment grain-size distribution, carbonate concentration, and organic content to identify sediment characteristics that may differ between clam garden and reference sites, as well as potentially contribute to differences in clam productivity. Clam growth and survival, sediment grain-size distribution, and carbonate and organic content were not significantly affected by unmaintained clam gardens. Wide variations in survival, growth, and sediment characteristics were observed among beaches. Examining across beach location resulted in the identification of significant negative effects of small rocks (2.00 – 4.75 mm), and silt (< 63 µm) on both growth and survival. Sand (250 – 500 µm) had a significant positive influence on both growth and survival while fine sand (125 – 250 µm) had a significant positive effect only on growth. Coarse sand (0.50 – 1.00 mm) had a significant positive effect on survival, while very fine sand (63 – 125 µm), carbonate, and organic content all had significant negative effects. To evaluate transcriptomic effects, ade novotranscriptome forL. stamineawas assembled. The final assembly contained 52,000 putative transcripts and those specific to each of the two tissues were identified. This revealed that similar functional categories were enriched in tissue-specific genes, but each tissue had its own transcripts comprising the categories. Transcriptomic analysis revealed differential expression in individuals from clam gardens, and although this effect was small in terms of the numbers of genes, specific response genes were identified consistently in both tissues. In summary, while the unmaintained clam gardens did not impact clam growth and survival over the 16 weeks of the study, it did have an effect at the level of the transcriptome. Furthermore, correlations of transcripts associated with either high or low survival provide new insights into ecological associations of these genes in this non-model organism. In summary, localized environmental factors are likely to have a greater influence on Pacific littleneck clam physiology, growth, and survival than the presence/absence of unmaintained clam gardens.

Anthropogenic particles (APs) generated from both natural and synthetic materials are widespread in the aquatic environment and contaminate seafood products, including shellfish. Depuration, involving the placement of filter-feeding shellfish in clean water for a period of time, often several days, is used to reduce contaminant concentrations, but the practicality of its use by the shellfish industry for APs has not yet been examined. In the present study, cultured adult Pacific oysters (Crassostrea gigas) were depurated for 10 days in a facility with limited airflow and filtered seawater. On average, there was a 73 % reduction in oyster AP concentration after 5 days, but no further reduction at 10 days, potentially due to the difficulty in depurating some particles or to re-contamination from the experimental environment. Long-term feasibility for industry will depend on future guidelines for safe AP consumption levels and the practicality and financial feasibility of creating and running clean facilities.

We assess the financial performance of an Atlantic salmon (Salmo salar) monoculture versus an Atlantic salmon, blue mussel (Mytilus edulis), and sugar kelp (Saccharina latissima) Integrated Multi-T...

Shellfish aquaculture often uses large amounts of plastic equipment and has been suggested as a potential source of microplastic contamination in the marine environment. To determine the influence of shellfish aquaculture on microplastic concentrations in bivalves and their environment, we compared microplastic particle (MP) concentrations in Manila clams Venerupis philippinarum and Pacific oysters Crassostrea gigas grown on commercial shellfish beaches with those in individuals of the same species grown on nearby non-aquaculture beaches in 6 regions of coastal British Columbia, Canada. MP concentrations did not differ between shellfish aquaculture and non-aquaculture sites for either bivalve species, sediment, or water samples. Plastic presence differed by site and oysters on sites with many synthetic anti-predator nets contained significantly, yet marginally, more MPs than those on sites without (0.05 vs. 0.03 g-1 dry-tissue weight on average). However, analysis of suspected MPs using Fourier-transform infrared spectroscopy indicated a predominance of fibres from textiles (including nylon and polyester), which are not typically used in shellfish aquaculture, suggesting that this may be caused by the larger average body weight of oysters grown at non-aquaculture sites rather than by the degradation of aquaculture infrastructure.

Microplastic particles (MPs) are widely distributed in seawater. Fibrous MPs (microfibres) are often reported as the most commonly encountered shape of particle. To estimate MP concentrations in seawater, samples are often collected using towed nets (generally 300-350-μm mesh) and may underestimate the amount of microfibres present, which may pass through the mesh due to their narrow width. We compared the potential microplastic particle (PMP) concentration estimates provided by two different seawater sampling methods conducted at three commercial shellfish farms and three unfarmed sites in Baynes Sound, British Columbia, Canada. The methods were: 10-L bucket samples sieved through 63-μm mesh in situ and subsequently filtered through an 8-μm polycarbonate membrane; and 1-L bulk samples collected in jars and subsequently filtered to 8 μm. The jar samples yielded PMP concentrations averaging approximately 8.5 times higher than the bucket samples per L of water (at the site level), largely driven by differences in the number of microfibres. There was no significant difference in PNP concentration between shellfish farms and unfarmed sites. An analysis of MP concentrations and mesh sizes reported in the literature suggests that using a 300-350-μm mesh may underestimate total MP concentrations by one to four orders of magnitude compared with samples that are filtered through much smaller mesh sizes (e.g.100 μm), despite the effect of sample volume. Particles300 μm in diameter make up a large component of MPs commonly found in fish and invertebrates. As such, common sampling practices fail to adequately measure a biologically relevant class of MPs, thereby undermining the ability to quantify ecological risk. We suggest that seawater sampling methods be designed to filter to10 μm (the approximate width of many microfibres), either using pressurized pumps for large-volume samples, or by using sufficient replication of small-volume discrete samples.

Provisioning and regulatory ecosystem services of Pacific geoduck clam (Panopea generosa) culture were simulated for an intertidal shellfish farm in Eld Inlet, South Puget Sound, Washington, USA. An individual geoduck clam growth model was developed, based on a well-established framework for modeling bivalve growth and environmental effects (AquaShell™). Geoduck growth performance was then validated and calibrated for the commercial farm. The individual model was incorporated into the Farm Aquaculture Resource Management (FARM) model to simulate the production cycle, economic performance, and environmental effects of intertidal geoduck culture. Both the individual and farm-scale models were implemented using object-oriented programming. The FARM model was then used to evaluate the test farm with respect to its role in reducing eutrophication symptoms, by applying the Assessment of Estuarine Trophic Status (ASSETS) model. Farm production of 17.3 t of clams per 5-year culture cycle is well reproduced by the model (14.4 t). At the current culture density of 21 ind m−2, geoduck farming at the Eld Inlet farm (area: 2684 m2) provides an annual ecosystem service corresponding to 45 Population-Equivalents (PEQ, i.e. loading from humans or equivalent loading from agriculture or industry) in top-down control of eutrophication symptoms. This represents a potential nutrient-credit trading value of over USD 1850 per year, which would add 1.48% to the annual profit (USD 124,900) from the clam sales (i.e. the provisioning service). A scaling exercise applied to the whole of Puget Sound estimated that cultured geoducks provide a significant ecosystem service, of the order of 11,462 PEQ per year (about USD 470,600) in removing primary symptoms of eutrophication, at the level of the whole water body. The modeling tools applied in this study can be used to address both the positive and negative externalities/impacts of shellfish aquaculture practices in the ecosystem and thus the trade-offs of the activity.

Integrated culture of bivalves at marine finfish farms may help lessen nutrient loading while producing a commercially-valuable crop and increasing the farms' social license to operate. Integrated culture of filter-feeding bivalves at salmon farms may also provide natural mitigation of the occurrence of planktonic sea lice larvae. This study assessed the growth of Pacific oysters (Crassostrea gigas) cultured at a commercial Atlantic salmon (Salmo salar) farm in British Columbia (BC) and the extent to which the cultured oysters contributed to mitigation of the occurrence of the salmon louse (Lepeophtheirus salmonis). Oysters were deployed in trays at 1-, 3-, and 6-m depths around one end of the farm and at a reference site approximately 150 m away. The height, length, and width of the shell and weight [whole wet, soft-tissue wet, dry, and ash-free dry (organic) weights] of oysters were measured at intervals following deployment. Salmon louse reduction was assessed monthly by comparing the water-borne density of larval sea lice among three bivalve cages and three controls (non-bivalve cages), and by examining oyster digestive tracts for L. salmonis DNA using PCR. All seven oyster-size variables increased significantly over time with significant effects of depth and position around the farm. In general, oysters at 1 and 3 m were significantly larger than those at 6 m. Side of the fish cage was used as a blocking factor in the experimental design and had a significant effect on final oyster size; at the end of the study, oysters at the farm were either significantly larger or not significantly different than oysters at the reference site, depending on the side of deployment. There was no significant variation in mean larval density due to time or treatment (bivalve versus non-bivalve). Larval lice densities were highest in January 2014. However, at that time there was no evidence of L. salmonis DNA in oyster digestive tissues.

Planktonic and parasitic sea lice (Lepeophtheirus salmonis and Caligus clemensi) were examined at a commercial Atlantic salmon (Salmo salar) farm near the Broughton Archipelago, British Columbia (BC) from December 2012 through March 2014. Parasitic sea lice were counted on a minimum of 20 fish in three pens per month. Surface seawater salinity ranged from 19 to 35 PSU. Parasite abundance was highest in winter, peaking in January 2013 at 6.5 ind fish− 1 (motiles were 14.3% L. salmonis, 85.7% C. clemensi) and February 2014 at 3.3 ind fish− 1 (motiles were 96.5% L. salmonis, 3.5% C. clemensi). SLICE® (emamectin benzoate) administered in both winters rapidly reduced parasitic sea lice numbers. Monthly parasite abundance was significantly correlated with the density of sea lice larvae (nauplius and copepodid stages) (r2 = 0.65, p = 0.01) suspended in the water column of the salmon pens. Larval density was calculated monthly via triplicate vertical plankton hauls within six pens, as well as at a reference site approximately 150 m away. Larval density at the farm peaked in January 2013 (mean ± SE: 1.3 ± 0.6 ind m− 3) and January 2014 (1.0 ± 0.3 ind m− 3). Sea lice nauplii were found in all samples at the reference site in densities similar to those observed within pens. Overall, the majority (87.8%) of sea lice in the plankton samples were nauplii, with copepodids comprising 5.2% and motile stages 1.8%. Surprisingly, the remaining 5.2% of planktonic sea lice were chalimus stages of C. clemensi, and were found both before and after SLICE® administration. For comparison, L. salmonis nauplius densities were estimated from established relationships between water temperature and salinity, the number of female lice present, and the approximate number of fish on site. These estimated densities were significantly (t = 3.41, p = 0.009) higher than actual nauplius densities observed at the farm, suggesting that sea lice larvae quickly dispersed from the farm after hatching. This study provides information on all sea lice stages present throughout an Atlantic salmon production cycle in BC (through two SLICE® treatments) and the first report of planktonic chalimus stages of C. clemensi, a commercially-relevant though relatively under-studied sea louse species.

Impacts of harmful algal blooms (HABs) have increased in frequency, intensity, and geographical distribution in the last several decades. Detection methods to date largely depend on microscopic observations which require expertise and time-intensive processes. In this study, we apply microscopic observational methods, quantitative real-time polymerase chain reaction (qPCR), and metabarcoding with multiple markers ( i.e. 16S, 18S-dinoflagellate and 18S-diatom, and large subunit (LSU) rDNA) on cultured (N=30) and field (N=24) samples containing suspected harmful algae ( e.g ., Alexandrium spp., Chattonella sp., Chrysochromulina spp., Dictyocha spp., Heterosigma akashiwo , Protoceratium reticulatum , Pseudochattonella verruculosa, Pseudo-nitzschia spp., and Pseudopedinella sp). Good detectability was found using previously published TaqMan assays for A. tamarense , H. akashiwo , and P. verruculosa . Overall, the multiple marker metabarcoding results were superior to the morphology-based method for detection and identification of harmful taxa, with the notable exception of taxa from the silicoflagellate group ( e.g. Dictyocha spp.), which had better detection by morphology. Metabarcoding results depended greatly on the marker type applied, which highlights the value of a multiple-marker approach. The combined results of the 18S and the LSU markers closely corresponded with morphological identification of targeted species and provided the best overall taxonomic coverage and resolution. The most numerous unique taxa were identified using 18S-dinoflagellate amplicon (N=167) and the best resolution to species level occurred using LSU (N=60). This work is the first report of HAB species identification in Canada using a combination of morphological, metabarcoding, and qPCR approaches. These results emphasize the benefit of applying molecular techniques to detect HAB taxa and highlight the current necessity of using multiple markers for accurate detection of the diverse groups that cause HABs.

In a field study, five different stocking densities ( i . e . 0, 30, 60, 90, 120 ind. net − 1 or 0, 2.46, 4.91, 7.37, 9.82 ind. m − 2 ) of adult green sea urchins ( Strongylocentrotus droebachiensis ) were randomly assigned to 30 predator-exclusion nets ( i . e . n = 6) around cultured mussels ( Mytilus spp.) to test the effect of urchin density on biofouling intensity (percent net occlusion) and urchin/mussel growth. After 174 days of culture, nets in all treatments containing sea urchins were significantly less fouled than those in the control treatment without urchins. Fouling intensities on nets with the two highest stocking densities of urchins (90 and 120 ind. net − 1 ) were approximately 40% less than that on nets with urchins held at the lowest stocking density (30 ind. net − 1 ) and 45% less than that on nets without urchins. The differences in fouling intensity among nets with 60, 90, and 120 ind. net − 1 were not statistically significant. While fouling was significantly reduced in the presence of urchins compared to the control treatment with no urchins, it was not completely eliminated since they were only able to access the inside surface of the nets. Sea urchin somatic and gonad growth declined with increasing stocking density, but there was no significant difference in mussel growth at the different urchin stocking densities. Mussels and sea urchins can be successfully co-cultured with no food input, but there may be a trade-off between the effectiveness of biofouling control and sea urchin growth. Statement of relevance This paper examined the use of sea urchins ( Strongylocentrotus droebachiensis ) to mitigate biofouling in mussel ( Mytilus spp.) aquaculture and the effect of sea urchin density on biofouling coverage and mussel growth. Treatments containing sea urchins showed significantly less fouling than a control treatment without urchins. Urchin density had no significant effect on mussel growth.

Using net enclosures in an earthen pond, we established three culture treatments with the sea cucumber Apostichopus japonicus and the Chinese white shrimp Fenneropenaeus chinensis: monoculture of sea cucumbers (C), monoculture of shrimp (S), and co-culture of the two species (CS). We measured levels of suspended particulate matter in the water column; total organic matter, total organic carbon, total nitrogen, and carbon/nitrogen ratios in both settling particles and the sediment; and chlorophyll a levels in the sediment. We then compared these variables between the three treatments. We also examined growth, survival, and yield of the two species in the different treatments. From June to September, the mean monthly suspended particulate matter sedimentation rates in the CS and S treatments were significantly (P

The nutritional value of eight species of microalgae for larvae and early post-set juveniles of the Pacific geoduck clam, Panopea generosa , was evaluated. The microalgae tested included two prymnesiophytes, Pavlova lutheri (PL) and Tisochrysis lutea (TL); two chlorophytes, Dunaliella tertiolecta (DT) and Tetraselmis suecica (TS); and four diatoms, Chaetoceros calcitrans (CC), Chaetoceros muelleri (CM), Phaeodactylum tricornutum (PT), and Thalassiosira pseudonana (TP). These microalgae were first tested as mono-species diets on both larvae and early post-set juveniles. The resultant best-performing mono-species diet was then tested as the major component in mixed- (bi-, tri-, and tetra-) species diets. Further experiments examined the possibility that the best-performing mixed-species diet could be improved by adding another algal species. The optimal diet, with the fewest number of algal species to support the best growth, was the bi-species diets of CC + TL for larvae and CM + TL for early post-set juveniles. The fatty-acid profiles of juveniles were influenced by the diets. Although no clear pattern between the level of any particular nutrient and growth and development of juveniles was evident, it appears that a balanced mixture of various dietary nutrients is important. Attention was given to the ratios between n − 3 and n − 6 fatty acids and between eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). The best-performing diets, including the optimal one, had a n − 3/n − 6 ratio of 2.17–3.03 and an EPA/DHA ratio of 1.28–3.25 for larvae and 1.84–2.58 and 1.84–2.63, respectively, for early post-set juveniles. Results of this study can be applied to improve the commercial hatchery production of geoduck seed. Statement of relevance Nutritional value of microalgae for young geoduck clams.

The performance of deposit feeders in integrated multi-trophic aquaculture (IMTA) was analysed through the application of mathematical models. Loading of organic particulates to the benthos as a result of finfish cage culture and shellfish suspended culture was analysed by means of a deposition model (ORGANIX), and an individual model for growth and environmental effects was developed for the California sea cucumber Parastichopus californicus . Following validation, the model was combined with existing models for finfish, shellfish, and macroalgae into a framework for simulation of IMTA interactions at the local scale. Several scenarios for different culture combinations and densities were simulated using the Farm Aquaculture Resource Management (FARM) model, using a layout which reflects typical stocking densities and spatial occupation in Europe and North America. The model allows an analysis of the different sources and fate of particulate organic matter associated with distinct culture groups. Our results illustrate the production enhancement for deposit feeders cultivated below both finfish (600%) and shellfish (150%). Furthermore, sea cucumbers are responsible for a significant removal of the particulate organic carbon loading to the bottom, reducing the gross load by up to 86% for finfish culture and 99% for shellfish culture. The role of cultivated seaweeds in reducing the dissolved nitrogen concentration in the farm area was also examined—no significant reduction in ambient nutrient concentration was observed, but the added nitrogen provides a clear stimulus (22% increase) to kelp production. By contrast, shellfish grown in suspended culture in the vicinity of finfish cages show very little change in individual growth or harvestable biomass. This work helps to analyse the ecological and economic potential of various forms of IMTA, and the role of co-cultivation in direct extraction and re-use of materials and energy at both the local (farm) and system (bay, estuary) scales. Statement of relevance Analysis of the ecological and economic potential of various forms of IMTA, and the relevance of co-cultivation in direct extraction and re-use of materials and energy at both the local (farm) and system (bay, estuary) scales. FARM model framework applied to understand the roles of suspended bivalve culture and benthic deposit-feeder culture in mitigating the negative externalities of finfish culture.

Re: Facets-2020-0025 The title of the paper was published incorrectly. The correct title of the paper is Comparing metabarcoding and morphological approaches to identify phytoplankton taxa associated with harmful algal blooms The article has been corrected accordingly. The publisher apologizes for this error.

The Pacific geoduck Panopea generosa is the largest burrowing clam in the world and adults can live up to a meter below the sediment surface. To extract these clams, harvesters use pressurized water jets to dislodge surrounding sediments. This type of disturbance could have significant effects on the local benthic environment, but has been little examined. The present study was conducted on one intertidal and one subtidal plot to assess potential effects of commercial-scale geoduck harvesting on the sedimentary benthic environment and nearby eelgrass beds. Sediment samples were collected inside the impacted plots and at intervals up to 75 m away while eelgrass sampleswere collected adjacent to the impacted plots and at intervals up to 50maway, seasonally over 2 y.Harvest of the subtidal plot occurred at one year and mock harvest of the intertidal plot occurred after one preimpact sample. Sediment and infaunal qualities examined included: grain size, percent organics, total nitrogen, total organic...

The production of live microalgae can be a critical constraint to economic bivalve culture due to high production cost, culture instability, and batch variability. The integration of alternatives to live algae is consequently a current trend in bivalve aquaculture, but dietary alternatives remain unexplored for the culture of the Pacific geoduck clam ( Panopea generosa ). To investigate the feasibility of substitution of live algae for juvenile geoduck feeding, the present study replaced a positive control microalgal diet [ Chaetoceros muelleri (CM) and Tisochrysis lutea (TISO)] with various levels (0, 25, 50, 75, 100% substitution by ash-free dry weight) of the spray-dried heterotrophic thraustochytrid Schizochytrium sp. or the spray-dried cyanobacterium Spirulina ( Arthrospira platensis ). Feeding trials (14 days) were conducted on two sizes of juvenile geoducks [mean initial shell length: 2.47 mm (trial 1); 4.00 mm (trial 2)]. Geoduck growth and survival were measured to quantify treatment success and proximate (total protein, carbohydrate, lipid) and fatty acid analyses were conducted on diets and final geoduck tissues. Growth rate was significantly higher in individuals fed Spirulina than in those given Schizochytrium sp., but algal-replacement treatments resulted in significantly reduced growth in comparison to the control of live algae (i.e. 0% substitution) at substitution levels of 25% and higher or 50% and higher, depending on geoduck size and growth variable. The superior diet of live microalgae contained a polyunsaturated fatty acid Σn–3 / n–6 ratio of 2.9, a value which appears to be conserved in the bivalve literature (range: 2.0–3.3). Tissue analyses suggested limited digestion of spray-dried derived protein and carbohydrate, but indicated general lipid/fatty acid sequestration. Based on these findings, the dietary incorporation of spray-dried Schizochytrium or Spirulina in juvenile geoduck culture is not recommended. It is proposed that additional potential dietary alternatives attempt to mirror the nutritional composition of the combination of the live microalgae CM and TISO since this diet elicited the best growth rate in both the present study and previous research examining the effect of various microalgal species on juvenile geoduck growth.

This research examined the individual effects of temperature and ration on growth and survival of juveniles of the Pacific geoduck Panopea generosa Gould, 1850, in two separate experiments. Growth parameters measured included shell length, daily shell increment, individual total body wet weight, specific growth rate, individual total body dry weight, and total body ash-free dry weight (AFDW). Larvae in all treatments were fed a binary microalgal diet of Chaetoceros muelleri and Tisochrysis lutea mixed at a 1:1 ratio by AFDW. The temperature experiment examined the effect of four temperatures (7°C, 11°C, 15°C, and 19°C) using two geoduck cohorts. One cohort was comprised of larger juveniles (mean initial shell length ± SE, 3.22 ± 0.05 mm) and the other included smaller individuals (0.54 ± 0.01 mm) which were cultured for 28 days and 21 days, respectively. Using a separate cohort, the foodration experiment examined the effect of nine rations (0.0, 1.0, 2.0, 4.0, 8.0, 16.0, 32.0, 64.0, and 128.0 × 1...

The coralline red algae, Lithothamnion glaciale, Phymatolithon laevigatum, P. rugulosum, and Corallina officinalis, induced >85% of laboratory-reared larvae of Strongylocentrotus droebachiensis to metamorphose. Larvae must contact live L. glaciale or its spores for metamorphosis to occur; the inducer is not sensed in the water column. However, aqueous extracts of L. glaciale can induce metamorphosis, suggesting that the inducing factor is chemical. Neither ashed nor boiled L. glaciale induces metamorphosis, indicating that the factor is heat-labile and that thigmotaxis, per se, is not important in the response. The amino-acid, γ-aminobutyric acid (GABA), which induces settlement of other marine invertebrate larvae, also induces significant rates of metamorphosis of S. droebachiensis at concentrations ≥ 10-4 M. A reduction (with antibiotics) in the number of live bacteria on the surface of L. glaciale does not affect the rate of metamorphosis of larvae.

The effects of mono-species and bi-species microalgal diets on body length, survival and metamorphosis of auricularia larvae of the California sea cucumber, Parastichopus californicus, were tested in two separate laboratory feeding experiments. The first examined eight single species of microalgae – Chaetoceros calcitrans (Cc), Chaetoceros muelleri (Cm), Dunaliella tertiolecta (Dt), Isochrysis sp. (Tahitian strain: TISO) (Ti), Pavlova lutheri (Pl), Phaeodactylum tricornutum (Pt), Tetraselmis suecica (Ts) and Thallassiosira pseudonana (Tp). The second experiment took the five most effective single species from the first experiment (i.e. Cc, Cm, Dt, Pl and Ti) and presented them in all possible binary combinations. In the first experiment, Cc was determined to be the best diet on the basis of generating a significantly higher metamorphic rate (65.5 ± 4.2%, mean ± SD) than any other species and leading to one of the best survival rates (72.3 ± 7.6%) and greatest body lengths (831.6 ± 5.6 μm at day 14). In the second experiment, diets containing Cc generally produced the highest survival and metamorphic rates and greatest body lengths (except Cc/Cm) of all mixed diets, although no bi-species treatment was ever significantly superior to a control of Cc alone. Of the various mono-species and bi-species diets evaluated for rearing auricularia larvae of P. californicus, Cc (either alone or mixed with other species) is recommended.

The combined effects of initial stocking density (2, 5, 10 individuals [inds]/mL) and feed ration (5×103, 20×103, 40×103, 100×103 cells·ind−1·d−1) on growth, survival, and ingestion rate of larval geoduck clams Panopea generosa fed Isochrysis sp. (Tahitian strain, TISO clone) were assessed. All three measurements were significantly affected by stocking density, ration, and their interaction. Growth rate ranged from 2.15 to 3.85 μm/d in the various treatments. It increased with stocking density at 5×103 cells·ind−1·d−1, was significantly higher at 5 than at 2 inds/mL at 20×103 cells·ind−1·d−1, and was significantly higher at 2 and 5 than at 10 inds/mL at 40×103 and 100×103 cells·ind−1·d−1. Growth rate increased with increasing ration up to 40×103 cells·ind−1·d−1 at 2 and 5 inds/mL, but decreased with increasing ration at 10 inds/mL. Percent survival over the experiment duration (23 d) ranged from 7% to 56% in the various treatments and generally decreased with increasing stocking density. There was...

The effect of ration on Panopea generosa gonad development was tested over 52 days. Clams were fed Isochrysis sp. and Chaetoceros muelleri (50 : 50 cell count) at rations of 0.8 × 109, 2.4 × 109, 4.0 × 109, 5.6 × 109, 7.2 × 109 and 10.0 × 109 cells clam−1 day−1 (R1, R2, R3, R4, R5 and R6, respectively). The highest ration (R6) caused a 25% die-off within 3 days and was discontinued. Ration did not significantly affect condition index, gonadosomatic index, connective tissue occupation index or oocyte diameter. Clams fed the R5 ration (85% of which spawned from day 26 to 52) were more spent than clams in any other treatment with significantly fewer oocytes mm−2 than those fed the R1, R2 and R3 rations and significantly lower levels of sperm occupation than clams fed any other ration. Spawn percentages were low from day 26 to 52 in R1, R2 and R4 (15, 0 and 0%, respectively). Clams in the R3 treatment had a similar spawn percentage (100% from day 26 to 52) to those in the R5 treatment yet maintained gonads in a more ripened condition with higher levels of gamete occupation, making R3 the most likely ration to maximize gamete output over time.

Four microalgal species [Dunaliella tertiolecta, Phaeodactylum tricornutum, Tetraselmis suecica, Thalassiosira pseudonana], previously identified as poor single-algal diets for juvenile geoduck clams, Panopea generosa, were selected to mix with two comparatively better food-value microalgae [Isochrysis sp. (TISO), Chaetoceros muelleri (CM)] to estimate synergistic or non-additive effects of mixed microalgae on the growth/survival of young juveniles of P. generosa. In addition, the effects of different TISO/CM proportions [75/25, 50/50, 25/75; ash-free dry weight (AFDW) basis] on growth/survival were assessed. Shell length, wet weight, dry weight, AFDW and organic matter content were significantly increased when using mixed TISO diets compared with TISO alone. In contrast, there were no significant differences with these variables when comparing mixed CM diets with CM alone. Ultimately, the best diet in terms of length and weight enhancement was a previously identified optimal one of TISO/CM (50/50). Survival on day 23 (60.7–79.3%) was not significantly different among any of the 11 diets tested. There were no significant differences in shell length, wet weight, dry weight, AFDW and organic matter content among the three TISO/CM ratios tested, but these diets gave superior results to TISO and CM fed alone. Survival (60.7–74.7%) on day 23 in the three TISO/CM ratios tested did not vary significantly.

Filter-feeding shellfish could act as biological agents in the control of parasitic sea lice (Caligidae) at salmon farms as a benefit of integrated multi-trophic aquaculture. Determining the extent to which various bivalve species ingest sea lice (Lepeophtheirus salmonis) larvae under controlled laboratory conditions was an important first step towards understanding the potential for shellfish to reduce the number of these copepod larvae in the water column at net pens. A series of laboratory experiments examined the effects of temperature (~ 5, 10, and 15 °C), diet (larvae alone or with phytoplankton), and bivalve size (small, medium, and large) on the amount of L. salmonis larvae ingested by basket cockles (Clinocardium nuttallii), Pacific oysters (Crassostrea gigas), mussels (Mytilus spp.), and Pacific scallops (unconfirmed hybrid: Mizuhopecten yessoensis x Patinopecten caurinus). Feeding rate was assessed by placing bivalves individually in 2-l containers holding approximately 450 larvae in 750 ml of filtered seawater. Results of the temperature/diet experiments indicated that all four species of bivalves ingested sea lice larvae, regardless of phytoplankton presence or absence, and that temperature had no significant effect on the proportion of larvae ingested. All three sizes of oysters and scallops ingested sea lice larvae, with large shellfish consuming a significantly greater proportion of the larvae than small individuals. Future research, examining the role of bivalves in the control of sea lice, should be continued at a commercial scale at a salmon farm.

The Canadian Integrated Multi-Trophic Aquaculture Network (CIMTAN) is a Natural Sciences and Engineering Research Council strategic network that was initiated in 2010. It was triggered by the fact that aquaculture, though the world fastest growing food production sector, is associated with environmental, economic, and societal issues. Integrated multi-trophic aquaculture (IMTA) offers an innovative solution for the environmental sustainability, economic stability, and societal acceptability of aquaculture by taking an ecosystem-based management approach. IMTA is the farming, in proximity, of aquaculture species from different trophic levels, and with complementary ecosystem functions, so that one species’ excess nutrients are recaptured by the other crops and synergistic interactions among species occur. CIMTAN is providing the interdisciplinary research and development and highly qualified personnel training in the following linked areas: (1) ecological design, ecosystem interactions, and biomit...

Aquatic invasive species in biofouling communities continue to cause ecological and economic impacts globally. Didemnum vexillum , an aggressive invasive tunicate, can have detrimental impacts on the shellfish aquaculture industry and a reliable method of control is required. In this study, cultured Pacific oysters ( Crassostrea gigas ) fouled with D. vexillum were treated with various concentrations of brine, freshwater, hydrated lime, and acetic acid at four exposure times (0.5, 1, 5, and 10 min). Results demonstrated that only lime and acetic acid significantly reduced total biofouling and D. vexillum coverage. Lime concentrations of 1 and 2% at 5 and 10 min exposures and 4% at 5 min exposure successfully removed up to 92.3% of D. vexillum fouling while maintaining high (≥ 80%) oyster survival. This led to the testing of 1, 2, 3, and 4% lime at 1 and 5 min exposures on C. gigas in a laboratory setting to determine potential impacts of these treatments on oyster survival, growth, and condition. The same treatments were also repeated on the mottled sea star, Evasterias troschellii , a major predator of Pacific oysters, to ascertain effects on sea star mortality. Combined, the results of field and laboratory experiments demonstrated that exposure to 3 and 4% hydrated lime for 5 min was effective in removing total biofouling, D. vexillum fouling, and predatory sea stars without causing significant adverse effects on oyster survival, growth, or condition. This study provides insights to assist the shellfish aquaculture industry with possible solutions to control invasive tunicates and predatory sea stars.

The basket cockle (Clinocardium nuttallii) is a candidate species for aquaculture in the northeast Pacific. The aim of the current research was to assess the feasibility of C. nuttallii grow-out, with an emphasis on growth performance and qualities affecting product marketability. In this article, we investigated the combined effects of culture mode (intertidal and off-bottom suspended culture) and initial stocking density (1500, 3000, 10 500 and 21 000 ind m−2) on C. nuttallii survival and growth during the first year of grow-out (May through October). In intertidal culture, cockles exhibited low survival and poor growth rates. In suspended culture, survival was consistently high (>96%) at all stocking densities tested; growth and condition parameters had the highest values at 1500 and 3000 ind m−2. The edible portion (meat yield) exceeded 40% of the whole wet weight at all stocking densities, occurrences of fouled and deformed cockles were

We investigated the effects of culture mode (intertidal and off-bottom suspended culture) and initial stocking density (5%, 10%, 35% and 70% bottom cover) on survival, growth and condition indices of three size cohorts (16, 22 and 32 mm initial shell length) of the basket cockle, Clinocardium nuttallii, during a second year of grow-out. In addition, we evaluated the effects of depth (2, 4 and 6 m) in suspended culture. All size cohorts demonstrated significantly higher growth rates, soft-tissue biomass and condition indices in the off-bottom suspended system compared to the intertidal one. In suspended culture, however, C. nuttallii exhibited sub-optimal survival, shell deformities and heavy fouling. For all size cohorts, stocking density had a significant effect on most growth and condition parameters, except meat yield indices, in both culture modes. An initial maximum stocking density of 10% cover is recommended for all size cohorts. Culture depth did not have a consistent statistically significant effect on any of the growth or condition parameters. Depending on the grow-out scenario, stocking density and harvestable size chosen, the cumulative harvestable proportion after the second year of grow-out constituted 15.5–63.1% of the seed planted. Our results could be used to develop and improve culture techniques for C. nuttallii and other cockle species.

Temperature is well known to be a significant factor influencing bivalve gonad development and has major implications for the success of broodstock conditioning in a hatchery setting. Little is known, however, about how temperature affects the reproductive development of the Pacific geoduck clam, Panopea generosa, despite it being a major commercial species. To determine the appropriate broodstock conditioning temperatures for this species, adults were held in the laboratory for 155 days at fixed temperatures of 7, 11, 15, and 19 °C. Clams held at the two lower temperatures (7 and 11 °C) displayed a more advanced state of reproductive development than those at the two higher temperatures (15 and 19 °C). Significantly higher percentages of individuals with mature gonads were noted at 7 and 11 °C than at 19 °C and significantly more oocytes follicle− 1 were evident at 7 and 11 °C than at 15 and 19 °C. Clams in the 7 °C treatment had a significantly higher gonadosomatic index than those in the 11 °C one (which were not significantly different from clams held at 15 or 19 °C), but that was likely because there was a significantly lower incidence of spawning activity at 7 than at 11 °C. The 11 °C treatment had a significantly higher overall percentage of individuals spawning between weeks 15 and 17 of the experiment than any of the three other temperature treatments. Gonads of individuals in the 19 °C treatment degenerated, with 0 oocytes follicle− 1 and 90% of the gonad occupied by connective tissue after 113 days. In a hatchery setting, P. generosa should be held at a temperature of 11 °C if reproductive output is to be maximized. Lower temperatures (e.g. 7 °C), however, could be used to hold ripe broodstock for extended periods.

Management of the fishery for California sea cucumbers Parastichopus californicus in the Pacific Northwest is limited by a lack of natural growth rate estimates. Growth rates of caged juvenile California sea cucumbers (from Departure Bay, British Columbia) consuming a natural diet for 12 months (September 2008–September 2009) were examined. Growth was low between September and March but significantly increased thereafter, appearing to follow seasonal physiological processes, temperature, and natural sedimentation rates. Over the 12-month period, whole wet weight in air (WWA) increased by an average of 164%, immersed whole weight (IWW) increased by 251%, and the size index (SI) increased by 85%. Average standard growth rates were 0.267%/d for WWA, 0.346%/d for IWW, and 0.169%/d for SI. Measurement accuracy, effects of body content, and relationships between size and weight metrics are discussed. These findings are an important addition to the knowledge of California sea cucumber biology and are va...

Unfortunately for all articles of Vol. 35 No. 1 the future journal title “Journal of Oceanology and Limnology” was used instead of the current journal title “Chinese Journal of Oceanology and Limnology”. All articles in the issue are affected. Please make sure to cite the articles with the following Vol. and No. info: Chinese Journal of Oceanology and Limnology, Vol. 35 No. 1, [page range].

This study evaluated the effect of diet and ration on the growth and survival of larvae of the purple sea urchin, Strongylocentrotus purpuratus . Larval total length, mid-line body length, body width, post-oral arm length, time to reach metamorphic competency, and survival rate were assessed during the experimental period (28 days). In the first experiment, seven algal diets [ i.e. Dunaliella tertiolecta , Chaetoceros muelleri , Isochrysis sp. (Tahitian strain) and all possible binary and tertiary combinations] were assessed, along with a control treatment of no food. Larvae reared on the bi-algal diet of D. tertiolecta / Isochrysis sp. and the uni-algal diet of D. tertiolecta provided significantly better growth than all other treatments. Larvae were successfully raised to metamorphic competency with both the binary combination of D. tertiolecta / Isochrysis sp. and the single species D. tertiolecta within 28 days of culture, whereas larvae in all other dietary treatments failed to reach competence within 28 days. In the second experiment, a bi-algal diet ( D. tertiolecta and Isochrysis sp. at equal biovolumes) was evaluated using five rations: (1) low ration: 1.25 × 10 3 cells ml − 1 ; (2) normal ration: 2.5 × 10 3 cells ml − 1 ; (3) standardized ration: 2.5 × 10 3 to 10.0 × 10 3 cells ml − 1 , with increasing ration according to developmental stage; (4) medium ration: 5.0 × 10 3 cells ml − 1 ; and (5) high ration: 10.0 × 10 3 cells ml − 1 . Typical echinoid larval development in all body dimensions was only achieved for larvae offered the standardized ration. Larvae reared on this ration attained metamorphic competency within 28 days, whereas larvae fed the fixed rations (lower or higher concentrations) failed to attain competency by the end of the experiment. In general, in comparison to larvae fed the standardized ration, larvae on the low ration showed longer post-oral arm length and narrower body width whereas larvae on the high ration showed shorter post-oral arm length and body width in relation to their total length. Overall survival (from prism stage to metamorphic competency) for the best treatments in both experiments was 44.4 ± 2.9 and 53.3 ± 1.9% (mean ± SE) for the binary diet of D. tertiolecta / Isochrysis sp. and standardized ration treatments, respectively. Based on these results, larvae fed a binary combination of D. tertiolecta and Isochrysis sp. or D. tertiolecta alone with a ration increasing with developmental stage is recommended for hatchery production of S. purpuratus .

The effects of stocking density, ration, and temperature on seed growth – from early post-settlement to a size suitable for out-planting ( i.e. ~ 4 mm shell length) – and the effect of stocking density on metamorphic rates were examined for the basket cockle, Clinocardium nuttallii , to determine optimal hatchery rearing conditions for this species. The effect of stocking density on seed growth depended on sampling time. A significant finding of the research was that optimal seed growth can be maintained when less than ~ 100% of the rearing unit's bottom area is covered, regardless of seed size. Metamorphic rates were high (88.2–91.0%) and not significantly affected by stocking density in the tested range (20–320 ind cm −2 ). Optimal rations were determined for five different size classes of seed fed a bi-algal diet of Chaetoceros muelleri and Isochrysis sp. (Tahitian strain, TISO) and these were, respectively, 3.2, 6.4, 6.4, 12.8, and 25.6 × 10 6 equivalent-TISO cells ind − 1 d − 1 for size classes 1 (initial mean shell length: 0.74 mm), 2 (1.59 mm), 3 (2.10 mm), 4 (2.60 mm), and 5 (3.00 mm). Whilst optimal rations generally increased with an increase in seed shell length, the opposite trend was observed for weight-specific rations. Faster-growing seed built up higher organic matter content in their body than slower-growing individuals, suggesting that satiation feeding for maximum growth should be preferred during hatchery rearing. Due to the rapid growth of seed over a short period of time, frequent adjustments of both stocking density and ration are necessary in order to best utilise available resources ( i.e. space and food) and to maintain maximum growth over time. Seed were grown at various temperatures (range of means: 5.9–26.4 °C) with optimal growth occurring at 18.3 °C.

We evaluated the effect of four densities (940, 1880, 3760, 7520 eggs cm−2 and 0.5, 1, 2, 4 ind mL−1 of embryos and larvae, respectively) and four temperatures (8, 11, 14, 17°C) on early growth and survival of the sea urchin Strongylocentrotus purpuratus. Prism-stage length was significantly greater in embryos initially held at 940 and 1880 eggs cm−2 than in those held at 3760 and 7520 eggs cm−2. Larvae grew significantly faster and had significantly greater survival when reared at 0.5 or 1 ind mL−1 than when held at 2 or 4 ind mL−1. Embryos had greater survival at 11 and 14°C than at 8 and 17°C, whereas embryo length was significantly smaller at 8°C than at 11, 14 or 17°C. Larvae grew significantly slower at 8°C than at 11, 14 or 17°C, whereas survival was significantly reduced at 8 and 17°C compared with 11 and 14°C. Per cent survival from prism to metamorphic competency in the best treatments was 48.9 ± 2.2% and 50.0 ± 3.6% (mean ± SE) for the 1 ind mL−1 and 11°C treatments, respectively. On the basis of these results, for rearing of S. purpuratus under static conditions, we recommend that fertilized eggs and larvae be held at ≤1880 eggs cm−2 and ≤1 ind mL−1, respectively, and at 11–14°C.

We previously identified dissolved cadmium (Cd(diss)) as the main source of this metal in cultured Pacific oysters, Crassostrea gigas, in Deep Bay, British Columbia, Canada (Lekhi et al., 2008). Total suspended particulate Cd (Cd(part)) was not found to be a significant source of oyster Cd (Cd(oys)), with Cd(part)20 μm negatively correlated with Cd(oys) concentration. High phytoplankton abundance in spring and summer was hypothesized to reduce Cd(oys) indirectly by drawing down Cd(diss) and increasing oyster growth. In the present study we expanded on these results by examining specifically how the phytoplankton community composition modulates both Cd(diss) and Cd(oys) concentrations in Deep Bay. Based on calculations of nutrients and Cd(diss) drawdown, phytoplankton accounted for approximately 90% of the overall summer reduction in Cd(diss) in the bay. Diatoms were the dominant phytoplankton group, being correlated negatively with Cd(oys) and positively with Cd(part). This suggests that diatom growth mediates the transfer of Cd from the dissolved to the particulate phase, resulting in lower Cd(oys). Spring blooms and sporadic harmful algal blooms may mediate a large flux of Cd(part) to the sediments. Thus, phytoplankton act as a sink, rather than a source, of Cd to oysters in Deep Bay and have a crucial role in the seasonality of Cd(oys) by reducing the concentration of Cd(diss) during the summer. Based on environmental variables, two descriptive models for annual Cd(oys) concentrations were developed using multiple linear regression. The first model (R(2)=0.870) was created to explain the maximum variability in Cd(oys) concentrations throughout the year, while the second (R(2)=0.806) was based on parameters that could be measured easily under farm conditions. Oyster age heavily affected both models, with the first model being secondarily affected by temperature and the second one being more sensitive to changes in salinity.

Sea-urchin ingestion rate, absorption, gonad yield, and gonad quality can be influenced by a variety of factors, including food quantity, food quality, and various environmental conditions. We examined the combined effects of two factors (diet and temperature) on ingestion rate, absorption, assimilation efficiency, and gonad enhancement of the purple sea urchin, Strongylocentrotus purpuratus , over a 12-week period. Four diets [three kelp species ( Macrocystis integrifolia , Nereocystis luetkeana , and Saccharina latissima ) and one prepared feed] and three temperatures (8.0 ± 0.4, 12.3 ± 0.3, and 16.2 ± 0.4 °C: mean ± SD) were tested in a completely crossed factorial design. Ingestion rate, gravimetric absorption, and assimilation efficiency of urchins fed the various diets were calculated at weeks 6 and 12. In addition, a number of gonad attributes were quantified at the beginning and end of the experiment including wet weight, percent water content, gonad index, texture, firmness, colour, and flavour. Ingestion rate, gravimetric absorption, and assimilation efficiency were generally significantly affected by both temperature and diet. Wet-weight ingestion rates were significantly higher with the three kelp treatments than with the prepared diet at both weeks 6 and 12. This particular dietary difference was not apparent, however, when ingestion rates were expressed on a dry-weight basis. The highest ingestion rates were recorded for animals held at 12 °C at week 6 and at 16 °C at week 12. Absorption rates and assimilation efficiencies were significantly higher at 16 °C than at 8 °C at week 6 and significantly higher at 16 °C than at the other two temperatures at week 12. Final gonad weight and gonad index were significantly greater in urchins fed the prepared diet than in those fed any of the three kelp species, with little difference among the kelp treatments. Final gonad weight was significantly affected by temperature, but this effect was dependent on diet; temperature had little impact on gonad weight (and index) in the three kelp treatments, but 12 and 16 °C produced significantly heavier gonads than 8 °C for urchins fed the prepared diet. Gonads of urchins fed kelps had more (significantly more in the case of M. integrifolia and N. luetkeana ) water than those fed the prepared diet. Gonad colour, texture, and firmness were generally not significantly affected by temperature, diet, or the interaction of these two factors. Gonad flavour was generally (sometimes significantly) better in urchins fed the prepared diet than in those fed the three kelp species. Taking all the measured variables into consideration, we recommend that culture operations utilise a prepared diet at 12 °C to optimise gonad production of S. purpuratus .

Globally, invasive tunicates continue to plague shellfish aquaculture operations by fouling both cultured bivalves and cultivation gear. Recently, in British Columbia, Canada the colonial tunicate Didemnum vexillum has become established at various oyster aquaculture sites and on some tenures it is the dominant fouling species. In the present study we examined potential chemical, mechanical, and biological treatments to control D. vexillum and botryllid tunicates (Botrylloides violaceus and Botryllus schlosseri) fouling Pacific oysters (Crassostrea gigas) grown in suspended tray culture. Fouled oysters were deployed from July to November 2009 with chemical (4% hydrated lime exposure) and mechanical (manual removal via scrubbing) treatments applied in July prior to deployment and in September following sampling, and a biological treatment (10 green sea urchins, Strongylocentrotus droebachiensis, per tray) applied in August. Oysters were measured and photographed monthly to determine changes in oyster shell growth and percent coverage by D. vexillum and the two botryllid tunicates. Both chemical and mechanical treatments reduced D. vexillum fouling on oysters by 85 to 96%, however, the reduction in D. vexillum fouling created free space that allowed botryllid fouling to increase. The sea urchin S. droebachiensis was not successful as a biological treatment at controlling tunicate fouling. Our results suggest that both lime and mechanical treatments may be viable options for controlling D. vexillum fouling Pacific oysters, although a decrease in percent survival was observed for lime-treated oysters, suggesting that the concentration and duration of exposure should be investigated further.

The effects of environmental variables, culture depth, and phytoplankton abundance and composition on juvenile Pacific oyster Crassostrea gigas growth and mortality were studied be - tween June and October of 2008 at 4 sites in the Strait of Georgia, British Columbia, Canada. In addi- tion, the effects of temperature-triggered depth manipulation on growth and mortality of oysters were examined in order to assess potential control measures for mitigating high summer mortalities associated with high temperature, harmful algal blooms (HABs), and other environmental stressors. Control oysters were held at constant depths of 3, 10, and 15 m, while experimental oysters were kept at 3 m depth and lowered to 10 or 15 m when the surface water temperature reached 14, 16, or 18°C. Site and Depth significantly affected the growth and mortality of control oysters. At the site with the best growth, cumulative mortality was low (range: 6.4 to 19%) and negatively correlated with tempe- rature and positively with transparency. At the high-mortality site (range: 64 to 98%), mortality was positively correlated with temperature, chlorophyll concentration, and the biomass of diatoms and potentially harmful algae. Cumulative mortality was generally higher at 3 m than at 15 m depth. Sig- nificantly larger oyster volume was obtained with the oyster controls at 3 m than with those held at 10 or 15 m at most sites. Temperature-trigger treatments did not significantly affect oyster volume or cumulative mortality, and oysters moved to 10 and 15 m had final volumes similar to the 10 and 15 m controls, independent of trigger temperature. Oyster growers could select their sites for maximal growth and minimal mortality based on temperature profile, freshwater input, and phytoplankton abundance and composition.

The basket cockle, Clinocardium nuttallii, is a candidate species for aquaculture in British Columbia, Canada. Previous research on broodstock conditioning, embryonic development and larval rearing of C. nuttallii demonstrated the potential for reliable hatchery production of cockle seed. In this paper, we investigated the effects of culture density (50% and 150% bottom cover in a monolayer) and substratum (none and fine sand) on cockle seed survival, growth, behaviour and shell morphology to improve the efficiency of the nursery production phase. Low stocking density (50% cover) yielded a shell length increase from 3 to 7 mm over a 4-week period. High stocking density (150% cover) negatively impacted some of the growth and condition parameters studied, but did not have a statistically significant effect on seed survival. Growing seed without substratum did not significantly affect seed survival or growth, but led to shell deformities (at shell length >15 mm) and lower burrowing rates when cockles were subsequently placed on sand. We recommend planting seed for grow-out at a shell length not exceeding 15 mm. Acclimating seed to the substratum before planting may increase the burrowing rates, thereby reducing the risks of seed dislocation and mortality. Additional studies are required to determine optimal substratum acclimation times and techniques.

Many factors can influence the growth and survival of larval and juvenile echinoids (e.g. diet type, food ration, stocking density, temperature, salinity, dissolved oxygen, water chemistry and settlement cues), but most of these factors have not been studied in detail with regard to most species targeted for commercial aquaculture production. This review summarizes the state of knowledge on factors influencing the growth and survival of larval and juvenile echinoids. Sea-urchin larvae are typically reared with either Dunaliella tertiolecta Butcher or Chaetoceros spp. The optimum food ration is in the range of 3000–9000 cells mL−1 and 20 000–60 000 cells mL−1 for D. tertiolecta and Chaetoceros spp., respectively, the concentration depending on larval stage and stocking density. Larvae have been successfully cultured at densities of 0.25–5.00 individuals mL−1, but the optimum level appears to be 1–2 individuals mL−1. A variety of benthic diatom species, particularly Navicula spp., can serve as the initial food source for young juveniles. Older juveniles may be fed with various species of foliose macroalgae and/or prepared diets. Most research on larval and juvenile echinoids has been done using ambient salinity and temperature, but some work has shown the importance of temperature on growth rate.

Harvested for their gonads, sea urchin populations are declining worldwide primarily as a result of overfishing. Consequently, research is now focusing on full life cycle aquaculture of these organisms. If juvenile or adult sea urchins are to be fed macroalgae (a preferred food of echinoids) in commercial-scale operations, suitable methods for storing large amounts of algae will be required. In this study, the effect of various storage methods for the kelp Saccharina latissima on somatic growth of juvenile green sea urchins, Strongylocentrotus droebachiensis, was evaluated. Juvenile S. droebachiensis (initial test diameter, 4.5–10.7 mm) were held in laboratory tanks, supplied with flow-through seawater, and fed ad libitum one of the following S. latissima treatments: (1) frozen long term (>2 mo), (2) frozen short term (1 wk), (3) air-dried, or (4) fresh. Measurements of test diameter and whole wet weight of the sea urchins were taken monthly for 16 mo. Mean (±SE) final sizes in the treatments ran...

This review examines the nutritional factors that influence the growth and survival of larval bivalves. Factors considered include feed form (live phytoplankton, preserved phytoplankton and artificial feeds) and feed biochemical composition (protein, lipid, carbohydrate and essential fatty acids). These factors, as they relate to larval production, are discussed in terms of growth and survival rates. To facilitate comparisons among larval studies, growth rates and feeding rates are standardized to common units. In addition, the standardized results for larvae of the Pacific oyster (Crassostrea gigas Thunberg) are analysed using linear regression techniques to determine the strength of the correlations between daily doses of biochemical feed components and daily growth rates. Piecewise linear spline modelling is used to determine maximum effective dose response, the point where feeding additional biochemical components to the larvae yields no significant improvements in growth. Derived from these analyses are suggested daily rations of lipid, protein, carbohydrate, eicosapentanoic acid, docosahexanoic acid and energy for larvae of C. gigas.