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- The effects of stocking density on physiological traits in Holothuria forskali broodstockPublication . Sousa, João; Félix, Pedro M.; Brito, Ana C.; Venâncio, Eliana; Silva, Francisco Azevedo e; Simões, Tomás; Raposo, Andreia; Neves, Marta; Narciso, Luís; Melo, Ricardo; Pombo, AnaThe high demand of sea cucumbers in international markets, mostly based in Asia, has left a deep impact on the natural stock of many species, leading to an investment in aquaculture techniques in order to mitigate these impacts. This study aimed to determine the effects of stock density in rearing broodstock of Holothuria (Panningoturia) forskali Delle Chiaje, 1823, a common species in the Mediterranean Sea and eastern Atlantic with commercial value. To do so, two different density treatments were selected: 1 kg/m2 and 2 kg/m2. The trial took place over five months and individuals were fed a mixture of frozen microalgae (Tetraselmis sp. and Phaeodactylum tricornutum). At the end of the trial, the effects of stock density on the individuals’ condition were assessed by analysing different variables, namely their fresh and gutted weight, evisceration and mortality rates, gonadosomatic index and oocyte size and even biochemical content, such as protein and lipid content in muscle bands. No significant differences were found between density treatments regarding any of the parameters assessed, aside from mean oocyte diameter. Individuals from the lower-density treatment presented a smaller mean oocyte diameter, supplied with fewer oocytes, than individuals in both the higher-density treatment and the baseline group. Regardless of this one difference, all trial individuals were able to maintain their elevated gonadal developmental stage for a full period of five months past their reproductive peak, with female holothurians subjected to the higher-density treatment showing signs of increasing vitellogenic reserves, a considerable advantage in aquaculture broodstock rearing.
- Chemical composition and omega 3 human health benefits of two sea cucumber species of North AtlanticPublication . Sales, Sabrina; Lourenço, Maria Helena; Pessoa, Maria Fernanda; Pombo, Ana; Félix, Pedro Miguel; Bandarra, Narcisa MariaThe main goal of this study was to investigate the seasonal chemical changes of two sea cucumber species caught from Portugal. The potential contribution to human health of lipids was also evaluated. For this, the chemical composition (protein, ash, and fat) and lipids composition of Holothuria arguinensis and Holothuria forskali was followed in summer and winter. Both species presented adequate levels of protein and ash and low content of total lipids, although their lipid profile showed a high proportion of polyunsaturated fatty acid (PUFA). Eicosapentaenoic acid (EPA) was abundant in all samples, and a favorable and similar n-3/n-6 ratio was found for both species. The atherogenic and thrombogenicity indices and ypocholesterolaemic/hypercholesterolaemic ratio suggests a high-quality for H. arguinensis and H. forskali. In general, significant differences were observed between species but not between summer and winter. Some significant variations were observed between summer and winter in the lipid profile of both species and in the chemical composition of H. forskali. Results indicate that these species have adequate nutritional quality for human consumption and may be suitable for the development of reliable fatty acid guides in sea cucumbers.
- Effect of rearing temperature in the growth of hatchery reared juveniles of the sea cucumber Holothuria arguinensis (Koehler & Vaney, 1906)Publication . Madruga, A.S.; Félix, P.M.; Sousa, J.; Silva, F. Azevedo e; Brito, A.C.; Mendes, S.; Pombo, A.Since the early 1980's there has been an increase in sea cucumber harvest and trade, mainly due to Asiatic market pressure. In the Indo-Pacific regions, the collapse of various stocks of these echinoderms has already occurred due to overfishing. In Europe, sea cucumber exportation depends exclusively on wild stock harvesting, which has demonstrated to be an unsustainable method to supply the markets, as these species are highly susceptible to overfishing. To enable a sustainable development of this emerging market in Europe the need to develop aquaculture techniques for these animals becomes of the utmost importance. At the current early stages of development, the viability of sea cucumber aquaculture for temperate species depends on the optimization of the rearing conditions. As ectotherms, temperature proves to be one of the most relevant parameters that affects the growth of sea cucumbers, as it influences metabolism and energy management and, in turn, future rearing methods and aquaculture sites. Therefore, this study aimed to determine the influence of temperature on the growth of H. arguinensis juveniles. A group of 168 juveniles (3.25 g ± 0.21; 3.81 cm ± 0.31) were placed under four different temperature treatments 18, 20, 22 and 24 ◦C for 4 months. The highest length (1.45 cm ± 0.16) and weight (2.79 g ± 0.14) gain were recorded at 20 ◦C. Similarly, the 20 ◦C treatment also produced the highest values for specific growth rate (0.50%/day) and the daily body length rate (0.30%cm/day). All allometric coefficients showed negative allometry (b < 3), a growth strategy that accentuates with increasing size. This lifehistory trait shows a higher distance from isometry the more distance the animals are from their optimum stocking temperature. Hence, metrics like the Fulton condition factor (K) show an inadequacy for the assessment of sea cucumber's condition, because a higher relative length decreases the value of K. A rearing temperature of 20 ◦C resulted in the best growth overall considering all increments in length and weight, pointing towards this as the best rearing temperature for the temperate species, H. arguinensis.
- Allometric relationships to assess ontogenetic adaptative changes in three NE Atlantic commercial sea cucumbers (Echinodermata, Holothuroidea)Publication . Silva, F. Azevedo e; Brito, A. C.; Simões, T.; Pombo, A.; Marques, T. A.; Rocha, C.; Sousa, J.; Venâncio, E.; Félix, P. M.Holothuria arguinensis, Holothuria mammata and Holothuria forskali are three common sea cucumber species found in the NE Atlantic, traded in international markets and susceptible to capture. Allometric relationships reveal if the scaling relationships between biometric characters are proportional with growth, being a useful tool to understand species growth strategies. Allometric relationships of the three species were estimated and compared between them and with populations from different regions. These allometric relationships revealed that the three species have negative allometric growth. However, they have different growth strategies between them and reveal different regional intra-specific growth strategies when compared to other populations, suggesting ontogenetic adaptation as a consequence of external factors.
- Do broodstock diets influence viability and larval development of Holothuria mammata?Publication . Venâncio, Eliana; Félix, Pedro M.; Brito, Ana C.; Sousa, João; Silva, Francisco Azevedo e; Simões, Tomás; Narciso, Luís; Amorim, Ana; Dâmaso, Luísa; Pombo, AnaThe intensive exploitation of sea cucumbers, mainly exported to Asian seafood markets, has contributed to deplete natural populations of several species. In Europe, the aquaculture production of these echinoderms is minimal, reflecting the low scientific production on the topic. In Portugal, like in Mediterranean countries, there are native species with high commercial value, which can be potential candidates for aquaculture. The control over the reproductive cycle is an important tool for rearing success, which, in turn, decreases the pressure over natural stocks. However, there are very few studies on the larval development of European species and none on the broodstock maturation in captivity. The present work studied the influence of three diets on the gonadal maturation and larval viability and development of Holothuria mammata. After 120-days of captivity the broodstock groups fed with a mixture of live microalgae (Diet 2) and a mixture of live microalgae and extruded dry food (Diet 3) reached the spawning stage, in contrast to the group fed with a mixture of frozen microalgae (Diet 1). Spawning was induced by thermal shock. Larval rearing from broodstock fed on Diet 2, total mortality was observed on the 12th day, after the onset of mid auricularia stage. The stocks of larvae from the broodstocks fed diets 1 and 3 reached the stage of pentactula on the 27th day. The success in spawning induction and embryonic development suggest that H. mammata may accept different types of diets as frozen microalgae mixes or live microalgae and dry feeds and still produce viable offspring. However, it is essential to develop more studies on the reproductive biology of H. mammata to optimize the hatcheries techniques to broodstock conditioning and larval rearing in captivity.
- Spatiotemporal distribution patterns of the sea cucumber Holothuria arguinensis on a rocky‑reef coast (Northeast Atlantic)Publication . Silva, F. Azevedo e; Brito, A.C.; Pombo, A.; Simões, T.; Marques, T.A.; Rocha, C.; Madruga, A.S.; Sousa, J.; Venâncio, E.; Félix, P.M.The demand for sea cucumbers from the NE-Atlantic is increasing as a consequence of the depletion of stocks that historically supplied Asian markets. Some species from the NE-Atlantic are already showing overfishing signs due to either inefficient policies or their total absence, and they do not offer any margins of sustainability to sea cucumber fisheries. The current lack of knowledge of biological and ecological traits has led to ineffective protection of those species. Holothuria arguinensis is a good example of a temperate sea cucumber species suffering from the effects of unregulated and illegal harvest. This study aims to determine the temporal and spatial distribution patterns of H. arguinensis, assessing density and size-class structure in a NE-Atlantic population, in SW Portugal, as a function of environmental conditions. Sampling was done every 1.5 months at 6 stations defined according to habitat heterogeneity, following the coastline from the mouth of the Sado estuary to marine coastal areas. At each station, there were two habitats (rocky substrate and sandy areas) sampled through SCUBA diving along 30-m random transects, each with three replicates. Individuals were counted and measured (total length) and individual behavioural parameters, such as sheltering and settlement surface, were recorded. Water column parameters, sediment composition, and substrate cover were also recorded. Generalised Linear Models were fit to the data, modelling density and size distribution of the species with respect to environmental conditions. The results indicate that the distribution of H. arguinensis was mainly determined by its ability to deal with physical environmental stressors (current), rather than the chemical properties of the water column or sediment composition. The hydrodynamic features of the region exert the greatest impact on this species’ distribution and help shape habitat usage by different size class groups.
- Modelling the distribution of a commercial NE-Atlantic Sea Cucumber, Holothuria mammata: demographic and abundance spatio-temporal patternsPublication . Félix, Pedro M.; Pombo, Ana; Silva, Francisco Azevedo e; Simões, Tomás; Marques, Tiago A.; Melo, Ricardo; Rocha, Cristina; Sousa, João; Venâncio, Eliana; Costa, José L.; Brito, Ana C.There is an increasing demand for sea cucumbers, for human consumption, mainly from Asian markets and, as a consequence, NE-Atlantic species are now new targets for exploitation and exportation. Holothuria mammata is one of the most valuable species in Europe. However, the lack of historical economic interest in this species in most European countries has also led to a lack of studies concerning biological and ecological aspects on wild populations and this is a major issue for stock management. This study aims to determine the temporal and spatial patterns of distribution of H. mammata, considering its abundance and demographic structure in a NE-Atlantic area, SW Portugal, as a function of environmental conditions. For that, a population from a marine protected area was followed for 1 year at 1.5-month intervals. Throughout the coastal area, six sites were selected and at each sampling campaign three random transects per site and substrate (rock and sand) in which all H. mammata individuals were counted and measured. For each site and survey several environmental parameters of interest, from the water column, the sediment and substrate cover, were also measured. Generalized Linear Models were used to model the spatial and temporal distribution of the species according to environmental conditions, to determine the species’ habitat preferences. The distribution models indicate that abiotic and biotic parameters of the water column are not the main drivers shaping the distribution of H. mammata. The species has a patchy distribution, and its habitat preferences depend on environmental stability, the presence of shelter and habitat complexity, which is more important for smaller, more vulnerable, individuals, while bigger size classes tend to venture more into less stable environments in an opportunistic fashion. The knowledge of these population traits is determinant to develop stock management measures, which are now urgent to prevent the depletion of commercial sea cucumber populations in the NE-Atlantic. Sustainable fisheries policies should be developed and start by considering to delimit fishing areas and periods, considering the species spatial and temporal distribution patterns.
- Effect of enriched substrate on the growth of the sea cucumber Holothuria arguinensis Koehler and Vaney, 1906 juvenilesPublication . Rodrigues, Tiago; Silva, Francisco Azevedo e; Sousa, João; Félix, Pedro M.; Pombo, AnaThe sea cucumber Holothuria arguinensis (Koehler and Vaney, 1906) presents an increasing commercial value in Asian markets and its exportation depends exclusively on wild stock harvesting. Production through aquaculture has been acknowledged as an alternative to supply demand and reduce pressure on natural stocks, but there are still bottlenecks to overcome, such as low growth rate and survival. This study focuses on the evaluation of the growth of juveniles of H. arguinensis through substrate enrichment—direct mixing of Sargassum vulgare with sediment—in recirculating aquaculture systems (RAS), for 4 months, with a baseline diet of Saccorhiza polyschides. Compared to the control (no enrichment), sea cucumbers fed with enriched sediment showed the highest specific growth rate (SGR), the highest growth rate (GR) and the lowest size heterogeneity. The results obtained in this study showed a favorable growth of sea cucumbers when in the presence of a substrate enriched with Sargassum vulgare, representing an important step towards the viability of large-scale sea cucumber rearing in Europe.
- Reproductive biology of the sea cucumber Holothuria mammata (Echinodermata: Holothuroidea)Publication . Venâncio, Eliana; Félix, Pedro M.; Brito, Ana C.; Silva, Francisco Azevedo e; Simões, Tomás; Sousa, João; Mendes, Susana; Pombo, AnaHolothuria mammata is one of the most valuable species of sea cucumber, as well as one of the main target species harvested in the Mediterranean and NE-Atlantic regions. This study aims to describe the reproductive cycle of H. mammata in a coastal area of southwest Portugal. Monthly samplings were carried out for 19 months, with the concomitant collection of environmental data and biometric data. H. mammata had a sex ratio of 1:1.2 (male:female) and a size at first maturity of 142 mm for males and 167 mm for females. The gonadosomatic index (GI) peaked between April and May for both sexes. Gonad development started when days had a shorter photoperiod (9 to 13 h of sunlight) and lower seawater temperature (<15ºC), and spawning occurred later, with longer photoperiod (13 to 15 h of sunlight) and higher seawater temperature (>15ºC) and chlorophyll-a concentrations. The development of new studies to increase the biological and ecological knowledge of the populations of H. mammata is essential to create conditions for the domestication of broodstock in captivity, to allow the development of fishing regulations based on informed decisions and to create precise measures for the conservation of ecosystems.
- Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farmsPublication . Grosso, Luca; Rampacci, Massimo; Pensa, Davide; Fianchini, Alessandra; Batir, Esin; Aydin, Ilhan; Ciriminna, Laura; Félix, Pedro M.; Pombo, Ana; Lovatelli, Alessandro; Vizzini, Salvatrice; Scardi, Michele; Rakaj, ArnoldFilter-feeding mussels blend suspended particles into faeces and pseudo-faeces enhancing organic matter flows between the water column and the bottom, and strengthening benthic-pelagic coupling. Inside operating farms, high bivalve densities in relatively confined areas result in an elevated rate of organic sinking to the seabed, which may cause a localized impact in the immediate surrounding. Deposit-feeding sea cucumbers are potentially optimal candidates to bioremediate mussel organic waste, due to their ability to process organic-enriched sediments impacted by aquaculture waste. However, although the feasibility of this polyculture has been investigated for a few Indo-Pacific species, little is known about Atlanto-Mediterranean species. Hence, for the first time, in the present study, we conducted a comparative investigation on the suitability of different Mediterranean sea cucumber species, to be reared in Integrated Multitrophic Aquaculture (IMTA) with mussels. A pilot-scale experiment was accomplished operating within a mussel farm where two sea cucumbers species, Holothuria tubulosa and Holothuria polii, were caged beneath the long-line mussel farm of Mytilus galloprovincialis. After four months, H. tubulosa showed high survivorship (94%) and positive somatic growth (6.07%); conversely H. polii showed negative growth (− 25.37%), although 92% of specimens survived. Furthermore, sea cucumber growth was size-dependent. In fact, smaller individuals, independently from the species, grew significantly faster than larger ones. These results evidenced a clear difference in the suitability of the two sea cucumber species for IMTA with M. galloprovincialis, probably due to their different trophic ecology (feeding specialization on different microhabitats, i.e. different sediment layers). Specifically, H. tubulosa seems to be an optimal candidate as extractive species both for polycultures production and waste bioremediation in M. galloprovincialis operating farms.