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Now showing 1 - 10 of 3229
  • Tagging mortality in acoustic telemetry studies: insights from a multispecies analysis
    Publication . Martínez Ramírez, Lucas; Bentes, Luis; Dias Almeida Cardoso, André Filipe; Erzini, Karim; Gandra, Miguel; Kraft, Sebastian; Winkler, Alexander; Abecasis, David
    The widespread adoption of acoustic telemetry has transformed our understanding of marine species' behavior and movement ecology. However, accurately interpreting telemetry data, especially concerning tagging mortality, is essential for drawing valid conclusions. In this study, we scrutinized tagging mortality in 223 individuals across 14 species and evaluated the impact of tagging methodologies, including capture method and size effects. Results reveal high tagging survival rates overall, attributable to the resiliency of the studied species and the rigorous animal welfare protocols followed during tagging procedures. Our results highlight the importance of tailoring array designs to the specific mobility patterns of the studied species for accurate survival assessments. This research contributes to generalizing mortality assessments and clearing the path for more precise and reliable telemetry studies in the future.
  • Redescription of the Chilean angel shark Squatina armata (Philippi, 1887) (Squatiniformes, Squatinidae)
    Publication . Kraft, Sebastian; Fernández-Cisternas, Ítalo; Araya, Miguel; Concha, Francisco J.
    Angel sharks ( Squatina spp. Dum & eacute;ril, 1805) are a group of coastal benthic sharks distributed worldwide, currently including threatened and understudied species. Two species are formally described along the East Pacific coast, the California angel shark S. californica Ayres, 1859 and the Chilean angel shark S. armata (Philippi, 1887). The latter species occurs in the southeastern Pacific and has historically been understudied. Additionally, the original description of S. armata lacks sufficient data to confidently identify individuals of this species compared to modern descriptions, and no type specimen is currently available to ensure specimen identification. Detailed morphological descriptions for identifying species are an essential resource for solving taxonomic issues in groups of morphologically similar species and to promote the conservation of critically endangered species. Therefore, a neotype from the type locality is here designated for S. armata , and a detailed and standardized morphological characterization based on modern taxonomic works is provided. This work contributes in improving the knowledge on the Chilean angel shark taxonomy and provides an improved frame of reference for identifying angel sharks in the East Pacific, especially in areas where species may occur in sympatry.
  • Structural enrichment promotes natural behaviour and welfare of captive gilthead seabream broodstock
    Publication . Oliveira, Ana Rita; Cabrera-Álvarez, María José; Soares, Florbela; Diáz-Gil, Carlos; Candeias-Mendes, Ana; Saraiva, João; Arechavala-Lopez, Pablo
    The intensification of aquaculture practices in the last decade can compromise the welfare of farmed fish. However, one strategy to be considered to improve the welfare of captive fish is the implementation of structural enrichment in the rearing environment. The behavioural and physiological effects of suspended ropes inside rearing tanks were experimentally assessed on gilthead seabream (Sparus aurata) breeders, evaluating the potential use of such structures in production units. Over the course of six months, 60 adult gilthead seabreams, were reared in cylindrical tanks with and without structural enrichment. Fish were video recorded regularly before, during and after feeding. Biometry and blood samples for biochemical analyses of plasma (cortisol, glucose and lactate) were taken throughout the experiment. Suspended ropes modified the horizontal distribution of fish after feeding, influencing the swimming activity and social interactions throughout the experimental period. In addition, structural enrichment promoted foraging and anticipatory behaviour of gilthead seabream. No effects of structural enrichment were detected on gilthead seabream condition or growth, although there was an apparent positive yet fading effect of enrichment on plasma cortisol and glucose. In general, structural enrichment had diverse positive effects on the behaviour diversity and natural repertoire of captive gilthead seabream, and therefore, on fish welfare. This type of structural environmental enrichment can be easily incorporated into land-based flow-through and recirculating aquaculture systems, both for experimentation and commercial purposes.
  • Effects of dietary supplementation with macroalgae on sperm quality and antioxidant system in Senegalese sole
    Publication . Félix de Azeredo Pinto e Melo, Francisca; Oliveira, Catarina; Cabrita, Elsa; Gavaia, Paulo; Silva, Nádia
    Within the efforts in the search for novel feed ingredients in aquaculture, macroalgae are being widely explored due to their diversity of bioactive compounds with considerable prophylactic and therapeutic potential. Plocamium cartilagineum and Sargassum vulgare , have the potential to positively impact fish health, mainly due to their antioxidant properties. The production of Senegalese sole ( Solea senegalensis ) still faces some constraints due to the low sperm quantity and quality of males from captivity, which is highly affected by oxidative stress. We hypothesized that the scavenger ability of P. cartilagineum and S. vulgare could ameliorate the reproductive performance of Senegalese sole males, once incorporated in the broodstock feeds. In this experiment, broodstock groups were fed with three different formulated experimental diets for 60 days: Control (Ctrl), a diet supplemented with 5% P. cartilagineum ( Pc ), and a diet supplemented with 5% S. vulgare ( Sv ). Fish were sampled twice to evaluate sperm quality using different techniques: sperm motility by Computer Assisted Sperm Analysis (CASA) software, and cell viability and Reactive Oxygen Species (ROS) by flow cytometer. At the final sampling, 6 fish per treatment were sacrificed and gonads were extracted to determine the relative expression of anti- and pro-apoptotic genes ( bcl2b, bcl-x, mcl1b, badb, bax, boka ), and genes involved in fish antioxidant system ( sod3, cat, gpx, hsp70 ). Sex steroids were measured on blood plasma by ELISA. Specific growth rate (SGR) and feed efficiency were also evaluated at the end of the experiment. Senegalese sole breeders fed with Pc diet for 60 days showed enhanced sperm total motility and cell viability at the end of the experiment, when compared with the Ctrl diet. On the other hand, fish fed with Sv diet had lower spermatozoa intracellular ROS and upregulated gpx in the gonads. No differences were obtained in levels of sex steroids and gonadal apoptotic system after 60 days of feeding, however, the macroalgae species and the percentages of incorporation used proved to positively modulate different spermatozoa traits.
  • gys1 regulates maternal glycogen reserve essential for embryonic development in zebrafish
    Publication . Chen, Jie; Ji, Xiao; Gao, Jing; Huang, Jiao; Ren, Jianfeng
    The reserve of glycogen is essential for embryonic development. In oviparous fish, egg is an isolated system after egg laying with all the required energy deposits by their mothers. However, the key regulated factor mediates the storage of maternal glycogen reserve which support for embryogenesis in the offspring is largely unknown. Glycogen synthase (GYS) is a central enzyme for glycogen synthesis. In our previous study, we generated a gys1 knockout zebrafish line, showed an embryonic developmental defect in F3 generation. In this study, firstly we determined that the gys1 was maternal origin by backcrossing the F2 mutant with wildtype lines. PAS staining and glycogen content measurement showed that glycogen reserve was reduced both in ovaries and embryos in the mutant group compared to wildtypes. Free glucose measurement analysis showed a 50 % of reduction in gys1 mutant embryos compared to wildtype embryos at 24 hpf; showed an approximal 50 % of reduction in gys1 mutant adults compared to wildtypes. Microinjection of 2-NBDG in embryos and comparison of fluorescent signal demonstrated that glucose uptake ability was decreased in the mutant embryos, indicating an impaired glucose metabolism. Untargeted metabolomics analysis then was employed and revealed that key modified metabolites enriched into vitamin B pathway, carbohydrate and unsaturated fatty acid pathways. These results demonstrated that gys1 played a role on glycogen metabolism, involved into the maternal glycogen reserve which essentially contribute to embryonic development.
  • Impact of persistently high sea surface temperatures on the rhizobiomes of Zostera marina in a Baltic Sea benthocosms
    Publication . Cúcio, Catarina; Brakel, Janina; Weinberger, Florian; Wahl, Martin; Teles, Ana; Muyzer, Gerard; Aires, Tania; Engelen, Aschwin
    Persistently high marine temperatures are escalating and threating marine biodiversity. The Baltic Sea, warming faster than other seas, is a good model to study the impact of increasing sea surface temperatures. Zostera marina, a key player in the Baltic ecosystem, faces susceptibility to disturbances, especially under chronic high temperatures. Despite the increasing number of studies on the impact of global warming on seagrasses, little attention has been paid to the role of the holobiont. Using an outdoor benthocosm to replicate near-natural conditions, this study explores the repercussions of persistent warming on the microbiome of Z. marina and its implications for holobiont function. Results show that both seasonal warming and chronic warming, impact Z. marina roots and sediment microbiome. Compared with roots, sediments demonstrate higher diversity and stability throughout the study, but temperature effects manifest earlier in both compartments, possibly linked to premature Z. marina die-offs under chronic warming. Shifts in microbial composition, such as an increase in organic matter-degrading and sulfur-related bacteria, accompany chronic warming. A higher ratio of sulfate-reducing bacteria compared to sulfide oxidizers was found in the warming treatment which may result in the collapse of the seagrasses, due to toxic levels of sulfide. Differentiating predicted pathways for warmest temperatures were related to sulfur and nitrogen cycles, suggest an increase of the microbial metabolism, and possible seagrass protection strategies through the production of isoprene. These structural and compositional variations in the associated microbiome offer early insights into the ecological status of seagrasses. Certain taxa/genes/pathways may serve as markers for specific stresses. Monitoring programs should integrate this aspect to identify early indicators of seagrass health. Understanding microbiome changes under stress is crucial for the use of potential probiotic taxa to mitigate climate change effects. Broader-scale examination of seagrass-microorganism interactions is needed to leverage knowledge on host-microbe interactions in seagrasses.
  • Characterising different artisanal fishing gears catches that operate in distinct habitats to assess ichthyofauna assemblages in Bons Sinais estuary, Mozambique
    Publication . Jeremias J. Mocuba; Eudriano F.S. Costa; Daniel Oliveira Mualeque; Maria Alexandra Teodósio; Francisco Leitão; Mocuba, Jeremias; Florêncio dos Santos Costa, Eudriano; Teodosio, Maria; Leitão, Francisco
    Monitoring the ichthyofauna is crucial to detect changes in aquatic communities for fisheries management and conservation. This study aimed to identify the most effective gear for ichthyofauna studies in the estuary. Thus, the performance of the beach seine (active gear) and chicocota (fixed gear), common fishing gears used by artisanal fishers in the Bons Sinais estuary (BSE), were used to characterise fish assemblage structure. Monthly surveys were conducted at two fixed sample points of the BSE to assess the composition of the fish assemblage. The analysis revealed statistical differences in abundance, biomass, and the presence/absence of different species between gears regardless sampling months. At ecological level, differences among gears were explained by different modus operandi, technological features and also different sampling habitats where gears operate; beach seine is catching bottom-bound and littoral fish while Chicocota is sampling the pelagic assemblage of the mid-channels. The frequency of occurrence of the 13 most abundant species differed between gears. Both gears showed little size-selectivity, with the mean total length and mean body height of these species statistically differing between gears. A total of 92 fish species were identified. No statistical differences were observed among gears for species richness, diversity and evenness. Both fishing gears captured several local socio-economically important species in the BSE. In particular, 13 of the most important species accounted for more than 54% and 60% of the total abundance and biomass in beach seine and chicocota, respectively. The complementary use of fixed and active fishing gears for studying fish community structure in estuaries is recommended. This multi-gear sampling approach enhances the capacity to detect changes in fish communities and provides valuable data for fisheries management and conservation efforts.
  • Reducing invertebrate by-catch in a coastal fishery using a raised monofilament trammel net
    Publication . Monika Jadwiga Szynaka; Pedro Monteiro; Karim Erzini; Jorge M.S. Gonçalves; Aida Campos; Szynaka, Monika Jadwiga; Monteiro, Pedro; Erzini, Karim; Gonçalves, Jorge Manuel Santos; Campos, Aida
    Trammel nets are one of the least selective fishing gears and are known to catch a variety of species, many of which are discarded, including important invertebrates that are considered habitat-forming species. Although there are few studies focusing on this type of by-catch, these habitat-forming species include corals and sponges that are vulnerable to disturbances from fishing activities using bottom contact gear. Experimental fishing was conducted off the port of Portimao (southern Portugal) from November 2021 to April 2022 using standard and modified trammel nets rigged to be lifted off the bottom with the objective of reducing invertebrate by-catch and impacts on the bottom habitat. The modified lifted net caught 36% less by-catch of invertebrates in numbers than the standard net, with no significant decrease of biomass and value of target species. The results obtained with the two net types are discussed, as well as the necessity for good video recording equipment that can improve sampling accuracy, and the usefulness of interviewing the fishers on net performance after experimental fishing was conducted.
  • Comparative transcriptome analysis reveals molecular damage associated with cryopreservation in Crassostrea angulata D-larvae rather than to cryoprotectant exposure
    Publication . Anjos, Catarina; Duarte, Daniel Filipe Correia; Fatsini Fernández, Elvira; Domitília Matias; Cabrita, Elsa
    Background The Portuguese oyster Crassostrea angulata, a bivalve of significant economic and ecological importance, has faced a decline in both production and natural populations due to pathologies, climate change, and anthropogenic factors. To safeguard its genetic diversity and improve reproductive management, cryopreservation emerges as a valuable strategy. However, the cryopreservation methodologies lead to some damage in structures and functions of the cells and tissues that can affect post-thaw quality. Transcriptomics may help to understand the molecular consequences related to cryopreservation steps and therefore to identify different freezability biomarkers. This study investigates the molecular damage induced by cryopreservation in C. angulata D-larvae, focusing on two critical steps: exposure to cryoprotectant solution and the freezing/thawing process. Results Expression analysis revealed 3 differentially expressed genes between larvae exposed to cryoprotectant solution and fresh larvae and 611 differentially expressed genes in cryopreserved larvae against fresh larvae. The most significantly enriched gene ontology terms were "carbohydrate metabolic process", "integral component of membrane" and "chitin binding" for biological processes, cellular components and molecular functions, respectively. Kyoto Encyclopedia of Genes and Genomes enrichment analysis identified the "neuroactive ligand receptor interaction", "endocytosis" and "spliceosome" as the most enriched pathways. RNA sequencing results were validate by quantitative RT-PCR, once both techniques presented the same gene expression tendency and a group of 11 genes were considered important molecular biomarkers to be used in further studies for the evaluation of cryodamage. Conclusions The current work provided valuable insights into the molecular repercussions of cryopreservation on D-larvae of Crassostrea angulata, revealing that the freezing process had a more pronounced impact on larval quality compared to any potential cryoprotectant-induced toxicity. Additionally, was identify 11 genes serving as biomarkers of freezability for D-larvae quality assessment. This research contributes to the development of more effective cryopreservation protocols and detection methods for cryodamage in this species.
  • Examination of the effects of excess microalgae availability on the disruption of mussel byssus secretion
    Publication . Ji-Yue Ni; Yan Zhou; Yu-Qing Wang; Shi-Hui Huang; Qian-Wen Cui; Wen-Yi Wang; Xiao-Ying Yang; Power, Deborah Mary; Yi-Feng Li
    The present study evaluated the effects of food availability on byssus secretion in the hard-shelled mussel Mytilus coruscus. Byssus production was evaluated, and foot tissue transcriptomes, the site of byssus production, were generated. The results showed that byssus secretion was disrupted in mussels fed high levels of microalgae (HFL, 88.8 mg/L day−1), compared to the control group (p < 0.05), and that more byssus production occurred in the HFL group during the recovery period. Byssus secretion was not affected in mussels fed low levels of microalgae (8.88 × 10−3 mg/L day−1), but the shedding of byssus filaments was significantly increased compared to the control mussels (p < 0.05). Transcriptome data of the foot tissue revealed that lysosome, FoxO signaling, and autophagy pathways involved in autophagic cell death and apoptosis were significantly affected (p < 0.05) and may explain differences in byssus growth under modified food availability in M. coruscus. High feed levels modified metabolic pathways, such as sphingolipid, tyrosine, and phenylalanine, and downregulated genes coding for mussel foot proteins, which may explain reduced byssus production. The study found that contrary to expectation increased food availability reduced mussel byssus production by altering foot metabolism and promoting autophagy of foot tissue.