The diet of Weddell seals (Leptonychotes weddellii) in Terra Nova Bay using stable isotope analysis

Stable isotope analyses were used to investigate the diet of Weddell seals in Terra Nova Bay (Ross Sea) and the potential variation of their foraging behaviour with age, sex and body mass. For this purpose, skin samples were collected from adult breeding seals and pups, together with muscle samples of their potential prey. Our results showed variation in foraging behavior between age classes, with pups reporting lower δ13C values than adults, while no significant differences in δ15N were recorded. In addition, contrary to expectations, a mixing model analysis showed that adult seals foraged mainly on shallow benthic prey, such as Trematomus spp. (34.1%) and Dissostichus mawsoni (21.1%), rather than on pelagic fish, such as Pleuragramma antarcticum (9.8%). Overall, with this paper we provide novel diet information on a seal colony not previously sampled, adding new insight into the feeding ecology of a top Antarctic predator

Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farms

Filter-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

Evaluating sea cucumbers as extractive species for benthic bioremediation in mussel farms

Filter-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 pilotscale 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

Artificial reproduction of Holothuria polii: A new candidate for aquaculture

Holothuria polii (Delle Chiaje, 1823) is a common Mediterranean sea cucumber and has recently become a highly exploited target species destined mainly to the Asian markets. Unregulated harvesting is putting the natural stocks at risk, with potential consequences for the benthic communities to which these organisms belong. In response aquaculture, sea ranching and restocking could become solutions to this issue in the Mediterranean region. In this study, we present the first results on artificial breeding of H. polii, describing the spawning induction, larval development and early juvenile growth in hatchery cultures, our goal is to develop a rearing protocol for this species. The trials were conducted between July and September 2016. Holothuria polii was induced to spawn by testing two different methods. The thermal shock proved a simple and effective method for obtaining healthy gametes from this species. Larval development in H. polii progressed through five stages, reaching the pentactula stage in 10 days. Three different microalgal feeding regimens were tested for larval breeding; the higher feeding concentration 20,000-40,000 cells mL(-1) proved to be the best, with 14% of the larvae metamorphosed into settled juveniles by adhering to the artificial substrates at 15 days. Our results indicate that H. polii performs very well in the hatchery rearing during the larval and juvenile phases; this indicates that this species could be a valuable new candidate for aquaculture in the Mediterranean region both for production and for restocking purposes

Genetic identification of native populations of Mediterranean brown trout Salmo trutta L. complex (Osteichthyes: Salmonidae) in central Italy

Italian native populations of Mediterranean brown trout belong to the Salmo trutta complex. This species complex includes many mitochondrial lineages and phenotypes that have caused taxonomic controversies over time. The spatial distribution and the genetic diversity of these fishes are threatened by habitat destruction, global warming and, mainly, by the introduction of domestic trout of Atlantic origin. Indeed allochthonous trouts were massively restocked in Italian rivers for a century and they admixed with native populations. In order to identify residual native populations of Mediterranean brown trout, a genetic analysis of specimens collected within Latium region, on the Tyrrhenian slope of central Italy, was undertaken. To this purpose, 210 trout specimens were collected from six different rivers and analyzed for the identification of their nuclear (LDH-C1*RFLP) and mitochondrial (Control Region sequences) genotypes. Genetic characterization with these molecular markers allowed a quantitative estimate of allochthonous genotypes, which are present in all brown trout populations of the six sites, even if not equally distributed across the sampling area. At least three populations, inhabiting diverse lotic ecosystems(mountain, hilly and coastal streams respectively), are characterized by a high percentage of native nuclear allele*100atlocusLDH-C1*and typical Mediterranean haplotypes (of AD and ME lineages), which can be considered as different management units (MUs). This finding highlighted the aquatic ecosystems of the Latium Region as an important hot spot of salmonid biodiversity within the Italian peninsula, with important implications from a conservation perspectiv

Spawning and rearing of Holothuria tubulosa: A new candidate for aquaculture in the Mediterranean region

Holothuria tubulosa (Gmelin, 1788) has recently shown an increased demand in Asian markets, becoming one of the intensively exploited holothurian species in the Mediterranean Sea. A risk is that over-harvesting is likely affecting both the species' natural stocks and the benthic communities. In this scenario, sea ranching and restocking through aquaculture could assist in mitigating its overexploitation. This study is the first to demonstrate the successful artificial breeding and rearing of H.tubulosa, and its consequent potential as a new species for the Mediterranean aquaculture industry. Here we describe the spawning induction, larval development and early juvenile growth in hatchery cultures, aimed at developing a spawning and rearing protocol for this species. The trials were conducted from July to October in both 2014 and 2015. Holothuria tubulosa was induced to spawn by testing four different methods. Thermal stimulation plus thermal shock emerged as the most efficient method to obtain active and healthy gametes. Larval development in H.tubulosa progressed through five stages, reaching the juvenile stage in 27days. Two different microalgal feeding regimens were tested for larval breeding. Under the best feeding conditions, 7% of the larvae metamorphosed into settled juveniles, adhering to artificial substrates previously conditioned with benthic biofilm. Our results indicate that H.tubulosa shows good performance in hatchery rearing during the larval phases, indicating that this species could be a new candidate for aquaculture in the Mediterranean region, both for production and restocking proposes

Integrated Multi-Trophic Aquaculture (IMTA) system combining the sea urchin Paracentrotus lividus, as primary species, and the sea cucumber Holothuria tubulosa as extractive species

Sea cucumbers and sea urchins are promising candidates for aquaculture since they are high market value and low-trophic organisms. However, although they often co-exist in many marine habitats showing feeding interactions, there is currently a lack of investigations available regarding the co-culture of these organisms in Integrated Multi-Trophic Aquaculture (IMTA). The present study investigated, for the first time, the laboratory-scale feasibility of an integrated aquaculture between P. lividus and H. tubulosa, two of the most valuable Mediterranean echinoderms, through a four-month experiment.More specifically, three food sources with different fish meal concentrations were tested separately to sustain the integrated production in a land-based RAS (Recycling aquaculture system) of both co-cultured species: 1) completely vegetable diet (D-0), 2) vegetable diet with 20% of fish meal (D-20) and 3) vegetable diet with 40% of fish meal (D-40). Among these experimental diets D-20 (with 20% of fish meal supplement) was consumed more efficiently and sustained high growth rates for both co-cultured species. However, significant growth was detected with all experimental diets, indicating successful integrated aquaculture between sea urchins and sea cucumbers. The present study, therefore, suggested the existence of substantial benefits of an integrated aqua culture between these echinoderm species, that could promote the environmental and economic sustainability of their production on a large-scale. Our results showed, in fact, that less than 24% of the organic matter administered with the food remained as waste in our IMTA system after being ingested by the two trophic levels. The sea urchins ingested 87% of the food administered, absorbing 64% of the organic matter, whilst in the second step, the sea cucumbers consumed 54% of organic matter present in the sea urchin feces. Hence the aquaculture model investigated here was highly effective in reducing the total waste, at the same time providing added value in the form of sea cucumber biomass

Phylogeography of Sarmarutilus rubilio (Cypriniformes: Leuciscidae): Complex Genetic Structure, Clues to a New Cryptic Species and Further Insights into Roaches Phylogeny

Italy hosts a large number of endemic freshwater fish species due to complex geological events which promoted genetic differentiation and allopatric speciation. Among them, the South European roach Sarmarutilus rubilio inhabits various freshwater environments in three different ichthyogeographic districts. We investigated the genetic diversity of S. rubilio using two different mitochondrial markers (COI and CR), aiming to define its relationship with other similar taxa from the Balkan area and, from a phylogeographic perspective, test the effects of past hydrogeological dynamics of Italian river basins on its genetic structure and demographic history. Our analysis highlighted a marked genetic divergence between S. rubilio and all other roach species and, among Italian samples, revealed the existence of three deeply divergent geographic haplogroups, named A, B and C. Haplogroup C likely corresponds to a new putative cryptic species and is located at the northern border of the South European roach range; haplogroup B is restricted to Southern Italy; and haplogroup A is widespread across the entire range and in some sites it is in co-occurrence with C or B. Their origin is probably related to the tectonic uplifting of the Apuan Alps in the north and of the Colli Albani Volcano in the south during the Pleistocene, which promoted isolation and vicariance followed by secondary contacts

Integrated Multi-Trophic Aquaculture (IMTA) system combining the sea urchin Paracentrotus lividus, as primary species, and the sea cucumber Holothuria tubulosa as extractive species

Sea cucumbers and sea urchins are promising candidates for aquaculture since they are high market value and low-trophic organisms. However, although they often co-exist in many marine habitats showing feeding interactions, there is currently a lack of investigations available regarding the co-culture of these organisms in Integrated Multi-Trophic Aquaculture (IMTA). The present study investigated, for the first time, the laboratory-scale feasibility of an integrated aquaculture between P. lividus and H. tubulosa, two of the most valuable Mediterranean echinoderms, through a four-month experiment.More specifically, three food sources with different fish meal concentrations were tested separately to sustain the integrated production in a land-based RAS (Recycling aquaculture system) of both co-cultured species: 1) completely vegetable diet (D-0), 2) vegetable diet with 20% of fish meal (D-20) and 3) vegetable diet with 40% of fish meal (D-40). Among these experimental diets D-20 (with 20% of fish meal supplement) was consumed more efficiently and sustained high growth rates for both co-cultured species. However, significant growth was detected with all experimental diets, indicating successful integrated aquaculture between sea urchins and sea cucumbers. The present study, therefore, suggested the existence of substantial benefits of an integrated aqua culture between these echinoderm species, that could promote the environmental and economic sustainability of their production on a large-scale. Our results showed, in fact, that less than 24% of the organic matter administered with the food remained as waste in our IMTA system after being ingested by the two trophic levels. The sea urchins ingested 87% of the food administered, absorbing 64% of the organic matter, whilst in the second step, the sea cucumbers consumed 54% of organic matter present in the sea urchin feces. Hence the aquaculture model investigated here was highly effective in reducing the total waste, at the same time providing added value in the form of sea cucumber biomass