New Aquaculture Species Research Articles

Breeding, larval development, and growth of juveniles of the edible sea urchin Tripneustes depressus: A new target species for aquaculture in Ecuador

Sea urchin fishery has gradually expanded in different countries and territories around the world, including South America, and the sea urchin Tripneustes depressus is a feasible candidate for aquaculture. The aim of this study was to prepare a biotechnical protocol for rearing larvae and production of juveniles. Large T. depressus were collected at monthly intervals at a subtidal rocky coast off Palmar, Santa Elena, Ecuador from January 2015 to December 2017. T. depressus spawns when exposed to thermal shock in low illumination room. Seven spawning events were recorded between March and May and between July and August. On average, females spawned approximately 3.60 ± 0.83 × 107 oocytes (mean diameter: 78.4 ± 2.1 μm) and males spawned approximately 5.60 ± 1.10 × 107 spermatozoa respectively). A cohort of May 13, 2017 was followed for 250 days. Embryo and larval stages were completed within 48 h and 21 days, respectively, at 26.5 ± 0.5 °C. Larvae were fed a mixed diet of Tysochrisis lutea, Chaetoceros gracilis and Rhodomonas sp. at concentrations ranging from 2.5 × 103 to 2.0 × 104 cells /ml as they increased in size. Larvae were measured considering: Total Length (TL), Medium Base Line (MBL) and Base Width (BW). On day 2 after fertilization (AF): 311.7 ± 2.0 μm, 158.9 ± 1.0 and 270.7 ± 3.4 (n = 10), respectively. On AF16: 544.7 ± 4.0 μm, 273.6 ± 6.9 and 355 ± 3.5 (n = 10). On AF21, larval rudiment size was equal in size to that of the stomach and larvae were competent. Their body measurements, and specifically total length at that food concentration, showed no phenotypic plasticity. Thirty two days post spawning (DPS) all juveniles had open mouths and a functional gut for feeding (size: 0.40 ± 0.01 mm DT), and at DPS98 three size categories were differentiated. Sea urchin sizes by categories at DPS98 and DPS152 were, respectively: small (2.20 ± 0.1 mm DT and 23.9 ± 0.45 mm TD), medium (4.90 ± 0.08 mm DT and 33.3 ± 0.3 mm TD); and large (7.20 ± 0.11 mm DT and 43.8 ± 0.5 mm DT) with zero mortality. T. depressus reach 4 cm diameter at 188 days after metamorphosis and can reproduce after six months of life, when it reach approximately 4.2 cm diameter), although the gonads are not yet commercial in size. This protocol is an initial perfectible protocol for sea urchin aquaculturing. However, we have made recommendations for consideration that include increasing survivorship and supplying post-larvae for juvenile production.

Broodstock development, induced breeding and larval rearing of Indian pompano, Trachinotus mookalee, (Cuvier, 1832) – A new candidate species for aquaculture

The present study describes the first trial on broodstock development, induced breeding and larval rearing of Indian pompano, Trachinotus mookalee. Indian pompano fingerlings were collected from wild and raised to adults having an average size of 2.84 ± 0.10 kg weight and 47.6 ± 1.43 cm length. These adult fishes were stocked in 125 t capacity circular tank having re-circulatory facility for broodstock development. The fishes were fed with squid along with clam meat and matured in four months. Mature females with >500 μm ova and oozing males were selected in the ratio of 1:2 (female:male) and were induced with single dose of hCG at the rate of 350 IU /kg body weight. Three trials with same sex ratio and hormonal doses were tried. The fish spawned after 36–38 h of induction at a temperature 29 ± 1 °C. Eggs were collected and treated with iodophore and stocked in 1 t FRP tank for hatching. The eggs hatched out after 18–20 h of incubation at a temperature of 29 ± 1 °C. The overall fertilization and hatching rate was found to be 69 ± 1.55% and 87.67 ± 0.81%, respectively. Larval rearing was carried out in 2 t capacity fibre reinforced plastic (FRP) tanks using green water system. The newly hatched larvae was 2.12 ± 0.02 mm in total length, with an oval shaped yolk sac of 0.55 mm2 and an oil droplet of 0.06 mm2 in area. The mouth opening was formed 40–46 h post hatch with mouth gape measuring 228.10 ± 1.31 μm. A systematic and overlapping regime of live feed beginning from copepod nauplii, rotifer, Artemia nauplii and artificial pellet were utilized during larval rearing. Weaning of larvae to inert diet was started from 15th day post hatching (DPH) onwards. Larvae started metamorphosis by 17th DPH onwards and was completed by 21st DPH, when the larvae reached 27.33 ± 0.10 mm. The larval rearing protocol resulted in an average survival rate of 21.53 ± 1.45% till complete metamorphosis. The present study showed T. mookalee to mature in captive conditions. The potential for induced spawning in captivity and larval rearing with a survival rate of 21.53% makes Indian pompano an excellent candidate for mariculture. This forms the first report of broodstock development, induced breeding and larval rearing of this species in captivity. The results of this study would facilitate mass scale seed production of Indian pompano in captivity, which is essential for its aquaculture.

Reproductive performance of asian catfish ( Hemibagrus wyckii Bleeker, 1858), a candidate species for aquaculture

Background: Hemibagrus wyckii Bagridae is one of the important economic fish species that lives in the rivers and reservoir in Riau Province, Indonesia. The present study aimed to determine the reproductive performance of H.wyckii under culture conditions. Method s: A total of 10 female and 10 male fish were selected, and weight, length, characteristics of egg and sperm, and hatchery performance were measured. Eggs were fertilized using the dry method. Egg weight and egg diameters were measured for 50 eggs per female. Egg size (50 eggs for each fish) was measured using Labo microscope model L-711 using software camera 3. Then, saline solution was added over the eggs, followed by the addition of pooled sperm from 10 males. Results: Average relative fecundity, egg weight and egg diameter were 2060±512 eggs/kg fish, 29.86±1.21 mg and 2.67±0.26 mm, respectively. The fertilization rate and hatching rate were 60.91±4.68% and 42.91±2.92% respectively. Sperm characteristics such as volume per fish (mL), pH, concentration (per mL), motility (%) and duration of motility (second) were 0.82±0.20, 7.15±0.12, 3.68±0.15, 72.77±1.46 and 47.5±4.84, respectively. Conclusion: The study results and scientific observations regarding reproductive performance suggest that H. wyckii can be considered a new candidate species for aquaculture.

Reproductive performance of asian catfish (Hemibagrus wyckii Bagridae), a candidate species for aquaculture

Background: Hemibagrus wyckii Bagridae is one of the most important economic fish species that lives in the rivers and reservoir in Riau Province, Indonesia. The present study aimed to determine the reproductive performance of H.wyckii under culture conditions. Methods: A total of 10 female and 10 male fish were selected, and weight, length, characteristics of egg and sperm, and hatchery performance were measured. Eggs were fertilized using the dry method. Egg weight and egg diameters were measured for 50 eggs per female. Egg size (50 eggs for each fish) was measured using an Olympus microscope (CX40). Then, saline solution was added over the eggs, followed by the addition of pooled sperm from 10 males. Results: Average relative fecundity, egg weight and egg diameter were 2060±512 eggs/kg fish, 29.86±1.21 mg and 2.67±0.26 mm, respectively. The fertilization rate and hatching rate were 60.91±4.68% and 42.91±2.92% respectively. Sperm characteristics such as volume per fish (mL), pH, concentration (per mL), motility (%) and duration of motility (second) were 0.82±0.20, 7.15±0.12, 3.68±0.15, 72.77±1.46 and 47.5±4.84, respectively. Conclusion: The study results and scientific observations regarding reproductive performance suggest that H. wyckii can be considered a new candidate species for aquaculture.

Differences in susceptibility to the skin fluke Benedenia epinepheli between Epinephelus bruneus, E. septemfasciatus, and a new hybrid grouper Kue-Tama, E. bruneus × E. lanceolatus

Interspecific hybrids of marine fish are becoming popular for aquaculture. The advantageous characteristics of hybrid fish include high growth rates, enhanced feed conversion rates, better appearance, high tolerance to environmental stress, and increased resistance to certain diseases. A new hybrid grouper Kue-Tama, female Epinephelus bruneus × male E. lanceolatus has recently been established. This hybrid showed significantly higher growth than that by E. bruneus and is considered a promising new species for aquaculture, especially in temperate areas where the slow growth of E. bruneus has prevented stable farming practices. The present study compared the resistance of Kue-Tama, its maternal parent E. bruneus and E. septemfasciatus, another popular grouper for farming, against the skin fluke, Benedenia epinepheli, which is a problematic parasite in grouper farming. The result of the cohabitation experimental infection showed that E. septemfasciatus was the most resistant to the skin fluke, followed by Kue-Tama and then E. bruneus. There appeared to be a negative relationship between the amount of mucus produced and the parasite intensity suggesting a resistance to skin flukes though the dry-weight of mucus collected from a given skin surface area did not differ between the three groupers. These results demonstrated that Kue-Tama has another favorable characteristic for aquaculture, in addition to their higher growth rate.

Effect of three triploidy induction methods on the growth and survival of larvae and post-larvae of the Caribbean scallopArgopecten nucleus

Argopecten nucleus is a small scallop from the Caribbean Sea and a relatively new species for aquaculture. One of the key challenges to develop the farming operations for this species from the current pilot scale to commercial level is to improve its harvest size. In this study, we tested three different methods for triploidy induction. Additionally, the effect of these protocols on survival, developmental rate and size of larvae and post-larvae were assessed. Three different mechanisms to stimulate the inhibition of the release of the second polar body were tested; (1) cold shock (18°C); (2) 6-dimethylaminopurine (6-DMAP); (3) cytochalasin B (CB) and (4) dimethylsulphoxide (DMSO). The treatment with 6-DMAP yielded the highest percentage of triploid larvae (39%). The survival and development rate, however, were higher in non-treated larvae (control) than in the treatment groups. Interestingly, larvae from CB and the DMSO control groups exhibited lower growth rates in length than those from control and the other two treatments. No influence of the triploidy induction treatments was observed on post-larvae survival, but the size of post-larvae was larger for the cold shock treatment and DMSO control group. Our results indicate that the use of 6-DMAP has the greatest potential to produce triploid larvae of A. nucleus without affecting negatively growth and survival of post-larvae.

Nutrient Requirement of African Sneakhead Fish (<i>Parachanna obscura</i>, Gunther 1861): a Review

The domestication of new species in aquaculture, strongly contributed to the promotion of the aquaculture in the recent years. Fish need lipids, energy, protein vitamins and minerals in their feed for to insure growth, reproduction, and other physiological functions. Several studies have been made on P. obscura in sight of its domestication. Dietary protein requirement, dietary lipid requirement and dietary carbohydrate requirement of P. obscura were previously studied. The aim of this study is to make a bibliographical on the nutrient requirements of the African snakehead fish ( P. obscura ) in order to promote P. obscura rearing. Protein requirements of P. obscura larvae are between 45 and 55.5% whereas for fingerlings are 42.5 and 53.5% of the diet. The optimal carbohydrate requirement of P. obscura fingerlings is 12% of diet and maximum crude lipid is 7% of the diet.

Effect of different salinities on gene expression and activity of digestive enzymes in the thick-lipped grey mullet (Chelon labrosus).

The effects of different environmental salinities (0, 12, 40, and 55ppt) on pepsinogen 2 (pga2), trypsinogen 2 (try2), chymotrypsinogen (ctr), and pancreatic alpha-amylase (amy2a) gene expression, and on the total activities of their corresponding enzymes, were assessed in Chelon labrosus juveniles, after their corresponding full-complementary DNA sequences were cloned. Furthermore, the quantitative effect of different salinities on the hydrolysis of feed protein by fish digestive enzymes was evaluated using an in vitro system. Relative pga2 expression levels were significantly higher in animals maintained at 12ppt, while a significantly higher gene expression level for ctr and try2 was observed at 40ppt. amy2a gene expression showed its maximum level at 40ppt and the lowest at 55ppt. A significant reduction in the activity of amylase with the increase in salinity was observed, whereas the maximum activity for alkaline proteases was observed in individuals maintained at 40ppt. A negative effect of high salinity on the action of proteases was confirmed by the in vitro assay, indicating a decreased efficiency in the digestive function in C. labrosus when maintained at high environmental salinities. Nevertheless, individuals can live under different environmental salinities, even though gene expression is different and the enzymatic activities are not maintained at the highest studied salinity. Therefore, compensatory mechanisms should be in place. Results are discussed on the light of the importance as a new species for aquaculture.

Masculinization of the Native Bay Snook, Petenia splendida, Using Oral Administration of the Synthetic Steroid 17α‐methyltestosterone

AbstractThe possibility of inducing sex reversal in bay snook, Petenia splendida, was evaluated to generate a protocol aimed at producing single‐sex populations (100% males) and improving farming conditions for this species. This popular staple food is a cichlid fish native to Central America, with aquaculture potential. We evaluated oral administration of the synthetic steroid 17α‐methyltestosterone (MT) to determine optimal dosage (30, 45, and 60 mg/kg of food) and days of feeding (30, 45, and 60) to attain efficient masculinization. The statistical analysis indicates a highly significant effect of both factors as well as for the interaction (P < 0.01). We registered significant differences in growth at the end of the experiment; fish fed with 60 mg of MT for 60 d reached the largest size, while fish fed with no MT were smaller. No significant differences were observed for survival (P > 0.05), ranging from 55.7 to 75.3% in the treatments. We recommend the use of 60 mg/kg of MT for 30 d for achieving successful sex reversal. This study provides valuable information supporting the inclusion of new species in aquaculture, reducing time and costs associated with sex reversal previously proposed for the species.

Wild and farmed meagre, Argyrosomus regius: A nutritional, sensory and histological assessment of quality differences

Meagre, Argyrosomus regius, is a promising new species for aquaculture due to its flesh quality, taste and growth performance in captivity. This study evaluated the quality of wild and farmed meagre in terms of flesh texture and nutritional profile. Texture traits were characterized using sensory analysis and instrumental measurements. Furthermore, muscle cellularity was analysed to determine potential relationships with flesh texture. Nutritional profile was evaluated focusing on protein and fat contents, as well as on fatty acid and amino acid profiles. Results showed that the most pronounced difference between wild and farmed meagre was the fat content, which was six times higher in the latter (3.93% versus 0.64%). This was reflected in a higher contribution of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), fulfilling completely the European Food Safety Authority (EFSA) recommendations in the case of farmed fish fillets (125% compared to 45% in farmed and wild meagre, respectively). Protein content was also higher in farmed fish (19.74% versus 17.18%) and amino acids scores were above 100% when compared to FAO/WHO amino acid standard. Raw fillet hardness was higher in wild meagre (96.05N versus 60.35N), but sensory analysis showed higher scores for firmness and oiliness in farmed fish. Muscle fibre density and area were similar in both wild and farmed meagre and therefore could not have been responsible for the differences found in fillet texture traits. In conclusion, this study shows that farmed meagre flesh may have some higher quality aspects in comparison to wild meagre and its overall attribute profile makes it an attractive food, thereby justifying its farming.

Structure and ultrastructure of oogenic stage in short mackerel Rastrelliger brachysoma (Teleostei: Scombidae)

Abstract Introduction: Structure, ultrastructural features and degeneration of oogenesis were first investigated in female Rastrelliger brachysoma as new candidate species for aquaculture by transmission electron microscopy. Materials and Methods: Specimens were naturally collected during the breeding season from Samut Songkhram Province, Thailand. Results: The ultrastructure of female oogenesis was principally divided into five stages based on the nuclear characterization and cytoplasmic organelles; (i) oogonium; (ii) previtellogenic; (iii) lipid and cortical alveolar; (iv) early and (v) late vitellogenic stages. Initially, oogonium was present within cell nest in the epithelial compartment. Its cell was supported by prefollicular cells. The multiple nucleoli in previtellogenic stage, referring to primary growth stage were the first to appear and they were scattered around the peripheral of nuclear membrane with the increasing number of cytoplasmic organelles. Some microvilli of granulosa cell initially protruded into the vitelline envelope. A simple layer of flattened granulosa and theca cells was also observed. The lipid and cortical alveolar stage under secondary growth oocyte was accumulated with two inclusions; the lipid droplets and cortical alveoli in the ooplasm. Another characterization, the increasing of numerous microvilli was also detected in the vitelline envelope. Finally, in the vitellogenic stage, a massive uptake and processing of proteins into yolk platelets due to embedding of the numerous microvilli in the largest vitelline envelope was observed. Oocyte degeneration in R. brachysoma was novel found especially oogonial and previtellogenic stages. Conclusion: Five oogenic stages of this fish are found with the changing of the arrangement of nucleus, cytoplasmic organelles and follicular complex, which will be applied to further studies.

Effect of stocking density on growth performance of juvenile sea cucumber Holothuria tubulosa (Gmelin, 1788)

Stock density is one among the most important factors in aquaculture that directly influences the growth of organisms; however, there is limited information about the effects of stocking density on growth performance of sea cucumber Holothuria tubulosa (Gmelin, 1788) that has a commercial potential and represents a new species for aquaculture. In this study, we investigated the effect of stocking densities on the growth performance of juvenile H. tubulosa (40.3 ± 3.34 g) in laboratory conditions. Stocking densities were selected as 6, 15 and 30 ind m−2 with total biomass 253.3 ± 0.18, 601.2 ± 0.11 and 1201.4 ± 0.15 g m−2 respectively. We monitored the growth by wet weights and calculated the growth performance through weight gain, growth rate, specific growth rate, relative weight gain, coefficients of variation and survival rate during 8 weeks of research period. We found that individual mean weight gain in 6 ind m−2 group was approximately 29.53 g while it was 3.03 g and −4.36 g for 15 ind and 30 ind m−2 groups respectively. Results have shown that the specific growth rate tends to decrease as the number of individuals in unit area increases. The final mean weight, growth rate, specific growth rate, relative weight gain and coefficients of variation were significantly different among treatment groups. In conclusion, a density of 6 ind m−2 is recommended for stocking juvenile H. tubulosa under rearing conditions. Stocking density of 15 ind m−2 is not favourable for long term as the growth rate is negligible where 30 ind m−2 should be avoided in tank-based rearing units.

Selection of reliable reference genes for RT-qPCR studies in Octopus vulgaris paralarvae during development and immune-stimulation

The common octopus, Octopus vulgaris is a new candidate species for aquaculture. However, rearing of octopus paralarvae is hampered by high mortality and poor growth rates that impede its entire culture. The study of genes involved in the octopus development and immune response capability could help to understand the key of paralarvae survival and thus, to complete the octopus life cycle. Quantitative real-time PCR (RT-qPCR) is the most frequently tool used to quantify the gene expression because of specificity and sensitivity. However, reliability of RT-qPCR requires the selection of appropriate normalization genes whose expression must be stable across the different experimental conditions of the study. Hence, the aim of the present work is to evaluate the stability of six candidate genes: β-actin (ACT), elongation factor 1-α (EF), ubiquitin (UBI), β-tubulin (TUB), glyceraldehyde 3-phosphate dehydrogenase (GADPH) and ribosomal RNA 18 (18S) in order to select the best reference gene. The stability of gene expression was analyzed using geNorm, NormFinder and Bestkeeper, in octopus paralarvae of seven developmental stages (embryo, paralarvae of 0, 10, 15, 20, 30 and 34days) and paralarvae of 20days after challenge with Vibrio lentus and Vibrio splendidus. The results were validated by measuring the expression of PGRP, a stimuli-specific gene. Our results showed UBI, EF and 18S as the most suitable reference genes during development of octopus paralarvae, and UBI, ACT and 18S for bacterial infection. These results provide a basis for further studies exploring molecular mechanism of their development and innate immune defense.

Two seas, two lineages: How genetic diversity is structured in Atlantic and Mediterranean greater amberjack Seriola dumerili Risso, 1810 (Perciformes, Carangidae)

The vastness of the ocean and our limited ability to observe and monitor the organisms therein make molecular markers particularly useful tools in the investigation of the ecology and evolutionary biology of fish. Nowadays, due to increased demand of fish foods, genetic researches are focused on new candidate species for aquaculture, such as Seriola species. Here, the analyses of eight polymorphic nuclear microsatellites loci and three mitochondrial (mt) DNA genes (16S-rRNA, Cyt-b, and D-Loop) in the greater amberjack, Seriola dumerili, detected breakpoint between Atlantic and Mediterranean populations, presumably arisen by the oceanographic features of the Almeria-Oran Front opposed to the gene flow of the species. Still, an absence of heterogeneity between the sampling locations within the Mediterranean Sea was noted, although an observed dichotomous structure of the phylogenetic mtDNA tree revealed two clades, with no spatial division within the basin. The origin of these two clades likely predates the late Pleistocene or Holocene colonization of the species from the Atlantic Ocean into the Mediterranean Sea. In addition, some preliminary genetic information are provided for Seriola rivoliana, the species that has been recently recognized as an Atlantic migrant in the Mediterranean.

Monitoring of trace metals, biochemical composition and growth of Axillary seabream (Pagellus acarne Risso, 1827) in offshore Copper alloy net cage

The study was conducted to assess trace metal contents, biochemical composition and growth performance of axillary seabream (Pagellus acarne Risso, 1827) cultured in a copper alloy mesh cage. A total of 400 axillary seabream (initial mean weight: 176.0±14.0 g), a new candidate species for the Mediterranean aquaculture, were stocked into a high-density polyethylene frame gravity cage and fed a commercial seabream diet for a period of 6 months. At the end of the feeding trial, fish reached a final weight of 264.8±16.8 g with a weight increase of 88.8 g and a feed conversion rate of 2.51. Overall, relative growth rate, specific growth rate and feed conversion ratio were satisfactory and comparable to the pelagic fishes such as gilthead seabream or European seabass, which are presently the main fish species for the Mediterranean aquaculture industry. Trace elements in fish grown in copper alloy net cages over a 6-month period showed satisfactory results, as the metal concentrations in fish tissues such as liver, skin, muscle and gills were below the reported upper limits for human consumption, indicating that copper alloy net is an acceptable and safe material for finfish cage aquaculture. Furthermore, from the growth performance data obtained in the present study, it can be concluded that axillary seabream showed potential for cage farming, and thus is a promising new candidate for the Mediterranean aquaculture industry.

Profitability of the new target sea cucumber species from Mediterranean and NE Atlantic: Holothuria polii, H. mammata, H. tubulosa and H. arguinensis

Profitability of the new target sea cucumber species from Mediterranean and NE Atlantic: Holothuria polii, H. mammata, H. tubulosa and H. arguinensis

Assessment of the in vitro barrier integrity by in vitro TEER measurement for toxicology screening

Cod is a relatively new species in intensive aquaculture. The aim of this study was to compare the nutritional composition and bioactive properties of wild and farmed cod as well as investigate how cooking influenced these parameters. Wild cod contained significantly more docosahexaenoic acid, whereas the levels of linoleic acid, eicosapentaenoic acid, and docosapentaenoic acid were lower than in farmed cod. Only minor difference in amino acid profile were found between wild and farmed cod but protein content was higher in the latter. Baking resulted in lower loss of moisture and a corresponding lower loss of taurine compared to poaching. The angiotensin converting enzyme (ACE) inhibitory capacity did not differ between wild and farmed cod (IC50 values of 0.06 mg/mL) nor was it significantly affected by cooking. From this study, it is evident that intake of wild and farmed cod provides similar health-promoting effects that are maintained during cooking.

Performance of raw material thermal treatment on formulated feeds for common octopus (Octopus vulgaris) ongrowing

The common octopus (Octopus vulgaris) has aroused great interest in recent years as a new species for aquaculture. However, the inexistence of feeds with an adequate and balanced nutritional profile for all life stages has hampered O. vulgaris aquaculture development. In the present study, O. vulgaris juveniles were fed with one of two different diets, based on dried raw materials (22% gelatine, 10% egg yolk, 10% Boops boops, 5% Todarodes sagittatus, 5% Carcinus mediterraneus, 2% fish oil, 3% glucose, 3% starch and 40% water) and differing only on bogue (B. boops) thermal processing (either freeze-dried — FDb or bogue meal prepared with temperature below 60 °C — Mb). Growth, feed efficiency, digestibility and condition were assessed after 56 days of rearing. Data were used to determine growth, weight gain (Wg), absolute growth rate (AGR), specific growth rate (SGR), absolute feeding rate, absolute protein feeding rate (APFR), absolute lipid feeding rate (ALFR), specific feeding rate (SFR), feed efficiency (FE), feed conversion ratio (FCR), protein productive value (PPV), lipid productive value (LPV), digestive gland index (DGI) and apparent digestibility coefficients (ADC). Both diets were accepted, promoted growth and faeces production with 100% of survival. No significant differences were found in growth (SGR of 0.78 ± 0.19%BW·day− 1 for FDb and 0.85 ± 0.09%BW·day− 1 for Mb), feed efficiency (48.31 ± 9.70% and 39.22 ± 2.92% for FDb and Mb, respectively), PPV and LPV. Despite the similarity on FCR (P > 0.05), a higher ingestion was found on Mb group regarding AFR (P 0.05). The results revealed that dehydration of raw materials, performed under 60 °C (bogue-meal), had no effect on ingestion, digestibility, growth and survival when compared with the use of freeze-drying, which points out to the possible suitability of this thermal treatment for O. vulgaris feeds.

A new species for sea cucumber ranching and aquaculture: Breeding and rearing of Holothuria arguinensis

Abstract Multi-species sea cucumber fisheries, including the species Holothuria arguinensis , have developed recently in the North-eastern Atlantic and Mediterranean Sea. In this context, the current study evaluated the potential use of H. arguinensis in aquaculture and to enhance natural populations, describing the embryonic and larval development for a better understanding and application in marine conservation and population genetics. Wild broodstock collected in Ria Formosa (37°0′33.92″N, 7°59′44.99″W; Faro, South Portugal) was induced to spawn using established methodology of thermal stimulation from June to August. The larval development under controlled conditions exhibited the classic five stages described for most aspidochirote holothurians, reaching the juvenile stage after 18 days post-spawning. Low mortality was registered during the pelagic larval stage, however high mortality (85–95%) was registered at doliolaria and juvenile stages. Results indicate that H. arguinensis is suited to hatchery rearing for aquaculture and enhancement of natural populations. Nevertheless, as this is the first European sea cucumber species reproduced in a hatchery, further research is required to improve the survival of post-settlement stages and optimize the rearing of juveniles.

Effects of sex and season in haematological parameters and cellular composition of spleen and head kidney of pejerrey (Odontesthes bonariensis)

Phylogenetic diversity in fish determines high interspecific variability in morphology as well as in physiological parameters. Moreover, several haematological variables and the organ composition of haemolymphopoietic sites may vary according to sex or season. The aim of this study was to establish the haematological parameters and the cellular composition of haemolymphopoietic organs in Odontesthes bonariensis, a commercially valuable fish species in Argentina, and also to determine gender or seasonal variations. Haematocrit exhibited the highest value in summer, while haemoglobin concentration was greater in summer and autumn. Erythrocyte count was higher in spring than autumn and winter, but did not differ with summer. The increase in these variables in seasons with higher water temperatures might be a compensatory mechanism to compensate the lower level of oxygen in the environment. Leucocyte formula and blast haemolymphopoietic cells in spleen and head kidney also showed annual variations since cells related to specific immune response, i.e., lymphocytes and thrombocytes, decrease in winter, whereas cells of the non-specific immune pathways, such as granulocyte, rise. The elevation of a particular type of circulating leucocyte was preceded by an increase in values of its precursor in blood in the previous season. Both, spleen and head kidney were active in haemolymphopoiesis, although with some differences in their activity during different seasons. Males showed higher values of circulating lymphoblasts and granulocytes than females, whereas females exhibited higher values of thrombocytes. This study corroborates the high interspecific variations in haematological parameters in fish that underlines the needing of basic studies in order to assess fish health status in new promising species for aquaculture.