Spat availability of commercial bivalve species recruited on artificial collectors from the northern Gulf of California. Seasonal changes in species composition

This study reports a year‐round recruitment of spat of four commercial bivalve species; Pteria sterna, Euvola vogdesi, Pinctada mazatlanica and Pinna rugosa collected in the region of Puerto Peñasco, north‐eastern coast of the Gulf of California. Bimonthly recruitment of commercial bivalve spat on netlon^® collectors was evaluated for six sites from June 2007 to August 2008. To describe spat recruitment abundances with environmental parameters, sea surface temperature (°C) and surface chlorophyll a concentration (mg m^?3) were characterized by means of monthly Aqua/MODIS satellite data. For each species a repeated measures anova was used to evaluate differences in the number of spat between months, sites and depths. Maximum sea surface temperature was recorded in August–September (~31.5°C) and the minimum in January–February (~15°C), while the minimum surface chlorophyll a was observed in June–September (mean range = 1.5–2 mg m^?3) and the maximum in January–March (mean range = 2–5 mg m^?3). Spat recruitment showed distinct patterns; P. sterna can be characterized as having a Winter–Spring pattern, E. vogdesi a winter pattern, while P. mazatlanica and P. rugosa a summer spat recruitment pattern. This information constitutes part of the fundamental data needed for the development of aquaculture and conservation initiatives in the region based on wild spat supply.     

Gonad development, larval settlement and growth of Mytilus edulis L. in a suspended population in Hvalfjördur, south-west Iceland

Annual cycles of gamete development in Mytilus edulis L. in south-west Iceland were investigated during 1986 to 1987. Histological preparations of the gonads showed that all individuals were fully mature in the beginning of June in both years and one spawning period was recorded each year at a sea temperature of 10-12^oC. The main spawning took place from the middle of July to the middle of August, and from the middle of June to the end of July in 1986 and 1987, respectively. Redevelopment of the gonads after spawning was observed in February when both food availability, measured as chlorophyll a concentration, and temperature were low. Rapid gonad maturation took place during the spring phytoplankton bloom in March-April. Larval settlement was heavy on the artificial collectors used. The length of the larval period was estimated as being 4-5 weeks and peak settlement occurred in the middle of September. The size of the early plantigrades settling on the collectors during the study period indicated direct settlement of mussel larvae from the plankton onto the collectors. One year after settlement the spat averaged 24.6 mm ± 6.0 (SD) shell length and two years after settlement a market size of 50.8 mm ± 5.7 (SD) was reached. Growth was correlated with food availability, measured as chlorophyll a concentration. The growth season lasted from March to October with the greatest shell growth in late summer. The results showed that the growth of M. edulis was markedly increased by suspending the animals in a more favourable environment than that found on the natural mussel beds.     

Contrasted optimal environmental windows for both sardinella species in Senegalese waters

We investigate Sardinella aurita and Sardinella maderensis recruitment success relative to the variability of oceanographic conditions in Senegalese waters using generalized additive models (GAM). Results show that recruitment of both species is marked by a strong intra‐annual (seasonal) variation with minimum and maximum in winter and summer, respectively. Their interannual variations are synchronous until 2006 (recruitment decreasing), while from 2007 there is no synchrony. The model developed shows that sardinella recruitment variability is closely related to the tested environmental variables in the study area. However, the key environmental variables influencing the recruitment success are different for both species: the Coastal Upwelling Index and the sea surface temperature for S. aurita and S. maderensis, respectively. We report that recruitment success of S. aurita and S. maderensis are associated with distinct ranges of sea surface temperature, upwelling intensity, wind‐induced turbulence, concentration of chlorophyll‐a and north Atlantic oscillation index. Considering food security and socio‐economic importance of both stocks, we recommend that consideration is given to the environmental variability in the small pelagic fish national management plans, particularly in the context of climate change.     

Improvement in recruitment of Japanese sardine with delays of the spring phytoplankton bloom in the Sea of Japan

To evaluate the impact of temporal variation of primary productivity on the recruitment of Japanese sardine (Sardinops melanostictus) in the Sea of Japan, the phenology of sea surface phytoplankton abundance was estimated from 8 day multiple satellite (SeaWiFS, MODIS‐Aqua, MERIS, and VIIRS) derived sea surface chlorophyll (SSChl) a concentrations from January 1998 to December 2015. Because relationships between SSChl a and in situ chlorophyll a concentrations were significantly different among periods based on the satellite combinations used, maximum and minimum SSChl a concentrations of 1 year were relativized as 1 and 0, respectively. Spatio‐temporal variation of relativized SSChl a concentrations was determined by using empirical orthogonal function (EOF) analysis. Scores in the first EOF mode denoted the basin‐scale variations of SSChl a concentrations in the Sea of Japan, and the major peak from the end of February to the end of May displayed the spring bloom. The logarithm of recruitment per spawner (LNRPS) for sardine was positively affected by delays in the start and end dates of the spring phytoplankton bloom. The delay of the date of the lowest sea surface temperature contributed to the delay of the end of the spring bloom during the period 1998–2015 and elevated the LNRPS during the period 1982–2015. Sardine spawns in the southern Sea of Japan from April to May, hence, delays of the spring bloom prolonged its overlap with sardine larval periods, and thus improved the recruitment of Japanese sardine in the Sea of Japan.     

Settlement and growth of the mussels (Mytilusgalloprovincialis,Lamarck, 1819) on different collectors suspended from an offshore submerged longline system in the Black Sea

A study of spat settlement of a submerged longline mussel culture system was carried out in Sinop area, Black Sea, between May 2008 and May 2009. The effects of six different types of collectors on spat settlement and growth were investigated. Six different types of spat settlement rope were used as polypropylene ropes with 18 mm diameter, 18 mm diameter timeworn silk rope, 22 mm diameter rope made from old hawser (OSR), 22 mm diameter ropes made from old anchovy net without pegs, 18 mm diameter old used nylon ropes and 18 mm diameter tasselled polypropylene ropes. Monthly temperature, salinity, chlorophyll‐a, total suspended matter, inorganic matter and organic matter were determined during the experimental period. The best settlement was observed on the OSR type when measured per metre (3450.00 ± 125.83 ind m^?1). Consequently, the findings showed that settlement preference of spat occurred according to rope structure, and if ropes are designed to combine numerous well‐fixed tassels, spat settlement can increase. Spat growth was affected by environmental factors and rope structure. In addition, the study revealed a negative relationship between density and growth.     

Study of seasonal settlements of five scallop species in the western Mediterranean

Scallop settlements were examined over a 16 month period using collectors placed in the sea at 28 day intervals near Torre la Sal Beach, Castellón, Eastern Spain in the western Mediterranean. Collectors were set over depths of 20 m and five species, Flexopecten flexuosus, Chlamys varia, Aequipecten opercularis, Pecten jacobaeus and Palliolum incomparabile, were collected. The most frequent species, F. flexuosus, had peak settlements in August 1992 and in July 1993. C. varia had peaks in April and July 1992 and in June 1993. Both of these species settled throughout the year, except in winter. A. opercularis settled predominantly from February to June and in October, but with a few settlements during the rest of the year. Pecten jacobaeus had a small peak in February and another peak from April to July. P. incomparabile spat were rare. Settlements were studied in relation to chlorophyll a, suspended particulate and sea temperature data in the area of study.     

Use of satellite data to identify critical periods for early life survival of northern shrimp in the Gulf of Maine

The northern shrimp Pandalus borealis is at its southern limit in the Gulf of Maine (GOM), and recruitment success is higher in years with relatively cool water temperature. However, the mechanisms for the temperature effect are not clear. We used rolling window analysis of daily satellite data to identify critical periods for early life survival of the 1998–2012 northern shrimp year‐classes and to investigate the importance of the phenology of the hatch and bloom. Survival was negatively correlated with sea surface temperature (SST) during a 6‐week period around the time of larval emergence (late winter) and during a 4‐week period in late summer when SST and stratification reached annual maxima. Survival was negatively correlated with chlorophyll‐a concentration (chl‐a) during two 5‐week periods centered approximately a month before the hatch midpoint and around the time of settlement to the benthos. A small‐magnitude winter bloom occurred around the time of the hatch in many years, but our results did not reveal a link between survival and bloom‐hatch phenology. The timing of winter and spring blooms were correlated with SST during the preceding 10 months. A survival model including SST and chl‐a during the critical periods explained 73% of the variance in survival. Summer SST increased significantly during the study period; the other critical variables showed no trend. The rolling windows approach revealed sensitive periods in early life history that may not have otherwise been hypothesized, providing a foundation for research towards a greater understanding of processes affecting recruitment.     

Comparative growth and survival of spat of the Caribbean pearl oyster,Pinctada imbricata cultivated 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.     

Reproductive cycle of the rock oyster,Striostrea prismatica (Gray, 1825) from two locations on the southern coast of Ecuador

The reproductive cycle of the rock oyster Striostrea prismatica was determined at two fishing areas, General Villamil and Ayangue (located on the southern coast of Ecuador), between May 2012 and April 2013. Monthly sampling campaigns were performed at both locations. The tissues were histologically examined to determine gonadal index (GI), oocyte development, follicular area coverage and sex ratio. Surface seawater temperature, salinity and chlorophyll a concentration were measured during samplings. Our results show a similar annual reproductive pattern at both locations. The GI reached maximum values during the summer. Oysters reached highest ripeness in January and February, while spawning occurred in February–March. Gametogenesis was linked to a consistently increasing follicular area (from 1.3 ± 0.7% to 85.8 ± 7.8%) and associated to surface seawater temperature. Spawning coincided with warm water temperature fluctuations and a seawater salinity decrease. No correlation was found with Chlorophyll a concentration. The sex ratio of sampled populations was 1:1, suggesting that oysters sizing more than 10 cm in shell length present a stable sex proportion in the population. The diameter of mature oocytes was significantly reduced (32.7%) during histologically preparations in comparison to fresh oocytes. Our study provides useful information of environmental factors that may control the observed gametogenesis and spawning activity of S. prismatica.     

Changes in the spawning habitat of two small pelagic fish in the Northwestern Mediterranean

We investigated the effects of three sea surface oceanographic variables (temperature, salinity, and chlorophyll a) on the abundance of eggs and larvae of two summer‐spawning species in the NW Mediterranean Sea, the anchovy Engraulis encrasicolus and the round sardinella Sardinella aurita, based on data from ichthyoplankton surveys carried out in the 1980s, 2000s, and 2010s. The environmental data showed an increase in seawater temperature and salinity along time, coupled with a decrease in chlorophyll a (proxy for primary production). These long‐term directional changes in environmental conditions helped explain the important reduction observed in the abundance of eggs and larvae of anchovy, as well as shrinking of spawning habitat in this species. At the same time, the probability of occurrence of round sardinella has increased from practically zero in the 1980s to probabilities near 1 along the coastal area of the study region in the two decades of the 21st century. Given that the trends observed in the environmental variables along the three decades of study are expected to continue during the 21st century, as a consequence of climate change, the spawning habitat of anchovy is expected to continue decreasing, while round sardinella habitat can expand. Considering that anchovy is of high commercial importance in NW Mediterranean fisheries, while round sardinella has very low commercial interest, our results show that the viability of small pelagic fisheries in the area may be compromised.     

The recruitment of scallops (and beyond) by two different artificial collectors (Gulf of Taranto,Mediterranean Sea)

This study provides for the first time an evaluation of the natural availability of scallop seeds along the coastal area of Taranto (Mediterranean Sea, Southern Italy). To select the best artificial collectors to harvest scallop seeds in this area, cylindrical collectors (Cyl) were compared to traditional ‘Japanese‐style onion bags’ (Bag) across three sites. Scallops represented 26.6% of total bivalve recruitment among all collectors (782 ± 331 ind. m^?2). The most recruited scallops were Flexopecten glaber and Mimachlamys varia. The white (F. glaber) and black scallops (M. varia) were abundant at all three sites, while the queen scallop, Aequipecten opercularis, was only found at one site. Beyond the recruitment of scallops, numerous other potential commercial bivalve species were collected, including Limaria tuberculata, which was the most abundant bivalve species (33.3% of total recruitment). At all sites, Bag collectors had higher recruitment than Cyl collectors. Scallops recruited in artificial collectors exhibited a multicohort size distribution at most sites, suggesting potentially continuous reproductive activity in the scallop populations. F. glaber, M. varia and L. tuberculata could be good candidates to diversify the aquaculture production because of the availability of seed and their growth rate. Moreover, the farming of these bivalves integrates well with other forms of aquaculture (e.g. mussels), thus potentially offering farmers an additional source of income.     

Growth of the oyster Crassostrea corteziensis (Hertlein, 1951) in Sonora, Mexico

This is the first evaluation of growth and survival of spat of the Cortez oyster Crassostrea corteziensis (Hertlein) produced under controlled conditions in a coastal area in the state of Sonora, Mexico for aquaculture purposes. A suspended culture technique, used for the Pacific oyster C. gigas, was used. The Cortez oyster has an isometric shell growth during the first 13 months, reaching 71.3±1.9 mm length, 52.6±1.3 mm thickness and 25.1±0.8 mm width. Allometric growth was found between total weight and length, thickness and width (survival was 70%). The relationships between particulate organic, inorganic material, chlorophyll a and environmental parameters with growth are described. Growth rates of C. corteziensis were affected by temperature with retardation at less than 18°C. For aquaculture purposes, it is recommended that spat be sowed after winter, and oyster harvest occur at the end of autumn. According to the von Bertalanffy equation, Cortez oysters would reach the traditional exploitation size of 65 mm (mean length) at harvest. Finally, the results of this study have shown that C. corteziensis is a good candidate for aquaculture projects in this region.     

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.     

Habitat differentiation between sei (Balaenoptera borealis) and Bryde's whales (B. brydei) in the western North Pacific

Two closely related baleen whale species, sei and Bryde's whales, in the western North Pacific were studied to identify differences in habitat use. Data were obtained from May to August 2004 and 2005. This study examined the relationship between oceanographic features derived from satellite data and the distribution of sei and Bryde's whales using basic statistics. We investigated oceanographic features including sea surface temperature (SST), sea surface chlorophyll a (Chl‐a), sea surface height anomalies (SSHAs), and depth of the habitat. These two whale species used habitats with different SST, Chl‐a, and SSHA ranges. The 0.25 mg m^?3 Chl‐a contour (similar to the definition of the Transition Zone Chlorophyll Front) was a good indicator that separated the habitats of sei and Bryde's whales. Then generalized linear models were used to model the probabilities that the whale species would be present in a habitat and to estimate their habitat distribution throughout the study area as a function of environmental variables. The potential habitats of the two species were clearly divided, and the boundary moved north with seasonal progression. The habitat partitioning results indicated that SST contributed to the patterns of habitat‐use and might reflect differences in prey species between the two whales. This study showed that the habitats of the sei and Bryde's whales were clearly divided and their potential habitat‐use changed seasonally.     

The influence of temperature and presence of predators on growth,survival and energy allocation for reproduction in the Catarina scallop Argopecten ventricosus

Environmental factors are known to modify the life history of marine ectotherms. In a 16‐month laboratory experiment, we investigated the influence of temperature and presence of predators on life‐history parameters including shell growth, survival and the energy investment in reproduction and body mass of the short‐lived (2–3 years) scallop Argopecten ventricosus. In parallel, A. ventricosus was maintained in the field at the Pacific coast of Baja California, México, to compare growth, survival and reproductive effort under natural conditions. For the laboratory treatments, scallops were reared at simulated field temperatures (SFT), 5 °C above SFT and in the presence of predators. Elevated water temperatures caused higher growth and gonad production, although at the cost of increased mortality. Presence of predators induced energy allocation to muscle rather than gonad growth, deferred spawning and extended survival. Field scallops exhibited higher growth, higher reproductive investment and were able to reproduce twice, whereas all laboratory scallops died after the first spawning. The natural variability of environmental parameters such as food and temperature may thus support optimal growth in the field, and when animals are protected from predators, reproduction in the second year of life.     

Spat Collection and Growth to Commercial Size of the Tehuelche Scallop Aequipecten tehuelchus (D'Orb.) in the San Matias Gulf, Patagonia, Argentina

Studies on larval settlement and growth of the commercial scallop Aequipecten tehuelchus were carried out over a 2-yr period in San Matias Gulf, Argentina. Gonadal index was used to indicate spawning and spat collectors were deployed when spawning began. Artificial spat collectors (mono-filament bags filled with thin shrub branches) were placed at a depth of 25 m in two areas of the Gulf during two seasons (1989–1990 and 1991–1992). Maximum settlement occurred by mid-February during the first season and by mid-January in the second season. Larger numbers of spat were found in collectors placed near the sea bottom. After settlement, spat were removed and placed in cages for growout. Scallops reached the average commercial size (60 mm shell height) 16 mo later. Mortality rate during the entire period was 10%.     

Effects of water depth on survival and growth of <Emphasis Type="Italic">Argopecten purpuratus</Emphasis> (Lamarck, 1819) spat in northern Chile

Collection and suspended culture of Argopecten purpuratus spat in Japanese-type collectors was undertaken in the Rinconada Marine Reserve (Antofagasta, Chile) to determine growth variations between surface and bottom waters. Scallop spat was collected at 16-m depth and grown at 1- and 16-m depths. An initial settlement of ca. 13,000 post-larvae per bottom collector (2 cohorts) was observed on 3 February 2001. Two new cohorts settled in bottom collectors on 3 March, while no spat settlement occurred in surface collectors. The four cohorts exhibited substantial and different mortality rates over the study period, depending on the cohort and on-growing depth. The first and second cohorts exhibited mortality rates of 80.3 and 53.1% in bottom collectors, respectively, versus 29 and 43.6% in surface structures. The third and fourth cohorts exhibited mortality rates of 21.4 and 59.7% in bottom collectors, respectively. Mean shell height of scallop spat after 88 days of culture was 6.46 mm for the first cohort and 4.37 mm for the second cohort in bottom collectors, versus 10.33 and 7.31 mm in surface collectors, respectively. Mean post-larval growth rate in bottom collectors (86 μm day⁻¹) was significantly lower than growth rate in surface collectors (146 μm day⁻¹). Factors explaining the depth-related mortality and growth rates are discussed to improve scallop culture in the Reserve. It was concluded from the results that culture improvement in Antofagasta Bay would require collecting spat in bottom waters and raising it near the surface during initial cultivation stages.     

Reproductive success of the Argentine anchovy,Engraulis anchoita,in relation to environmental variability at a mid‐shelf front (Southwestern Atlantic Ocean)

The mid‐shelf front (MSF) of the Buenos Aires province continental shelf in the Southwestern Atlantic Ocean plays a central role in the pelagic ecosystem of the region acting as the main spring reproductive area for the northern population of the Argentine anchovy Engraulis anchoita and supporting high concentrations of chlorophyll as well as zooplankton, the main food of anchovy. To investigate the influence of environmental variability on the reproductive success of E. anchoita, we analyzed a 13‐yr time series (1997–2009) of environmental data at MSF including chlorophyll dynamics, as well as zooplankton composition and abundance, ichthyoplankton distributions, and recruitment of E. anchoita. Spring chlorophyll concentrations showed high interannual variability and were mainly influenced by changes in water temperature and vertical stratification, which in turn control nutrient supply to the surface. Chlorophyll dynamics (magnitude, timing, and duration of the spring bloom) explained most of the variability observed in E. anchoita recruitment, most likely via fluctuations in the availability of adequate food for the larvae. Our results suggest that satellite ocean color products can be valuable tools for understanding variability in ecosystem dynamics and its effects on the recruitment of fish.     

Assessment of spat collector ropes in Galician mussel farming

The large amount of mussel seed required to support the present mussel farming production levels in Galicia (NW Spain) forces the development of new designs in artificial spat collectors for continual improvement of mussel seed gathering. In the present study, we have assessed both settlement and recruitment of Mytilus galloprovincialis on four different collector ropes in the Ría de Ares-Betanzos (Galicia). Besides the traditional collector ropes (lacing without loops and non-filamentous structure; NF-NL), three new rope designs with different lacing and structures were evaluated; ropes with a filamentous loop complement (F-L), ropes with a non-filamentous loop complement (NF-L) and filamentous ropes without loops (F-NL). Ropes with loops showed higher settlement densities (53,925 ± 4625 and 42,433 ± 5525 indiv./m for F-L and NF-L, respectively) than ropes without loops (26,475 ± 3875 and 13,033 ± 1136 indiv./m for F-NL and NF-NL, respectively). This may be explained by the increase in available surface area provided by the loops. Several studies recognized the importance of filamentous substrata for mussel spat settlement, which may help to explain greater settlement densities on filamentous structures between ropes with the same lacing. In recruitment evaluation, ropes with filamentous loops showed the highest densities expressed in indiv./m (5493 ± 587) as was the case of settlement. However, when density was expressed in kg/m, the ropes with non-filamentous loops had a higher yield (8.48 ± 0.22 kg/m), that could be a result of differences in adjusted shell length between ropes. Intra-specific competition and predation were identified as important factors affecting post-settlement mortality. The latter factors could also influence population length distribution. Ropes with rigid loops (NF-L) may supply refuges for spat from predators and therefore, enhance the recruitment of larger individuals, although other factors like size selective settlement could play a significant role in this result.     

Larval rearing of the giant Azorean barnacle,Megabalanus azoricus (Pilsbry, 1916): feeding trials,larval development and settlement on artificial substrata

A series of experiments were conducted to obtain an efficient larval rearing protocol for Megabalanus azoricus. The first part of this study investigates the effect of microalgae‐based diets on survival and larval development. Mono and mixed‐diets were tested at 20 ± 1°C, in a sequence of 11‐day feeding experiments. The second part presents a preliminary study on the influence of a biofilm on recruitment and use of oyster spat collectors in a mass rearing system. A photographic record of larval development and a brief reference to the diagnostic features that enable quick larval staging are also presented, along with morphometric measurements. Of the microalgae tested (Chaetoceros sp., Chloromonas sp., Dunaliella sp., T‐Isochrysis sp. and Skeletonema sp.) the mixed‐diet Skeletonema sp. with T‐Isocrysis sp. showed the highest survival percentages: total survival ranged from 79.7 to 85.7% and 69.7–80.0% of nauplii were in stage VI after 11 days of rearing. Cypris were also present, but only represented 5.3% of the survivors at most. In the mass rearing system juveniles were found settled in the collectors after 25 days, at 20 ± 1°C. However recruitment was less than 1%. Preliminary results showed no settlement preference towards collectors with biofilm. Nevertheless, this study provides the first record of M. azoricus settlement under laboratorial conditions and represent a starting point for future larval rearing studies.