Intraspecific density effect on growth of Marphysa “sp.” Juveniles

There is growing demand for the territorial tube-building genus Marphysa (Eunicidae: Polychaete), commonly known in Portugal as “goose”, for use as fishing bait, and it is being harvested all around the world for that purpose. Effects of intraspecific density on juvenile growth were studied over a four-month period in laboratory facilities. Three polychaete densities (low, 50 worms; medium, 150 worms; and high, 250 worms) were used in a 0.25 m2 aquarium containing sandy sediment and recirculating water. Total length, dry weight and number of segments were recorded for 60% of the initial population. All polychaetes were also counted to determine mortality rate and territorial behaviour through the existence of body lesions and broken and regenerating posterior segments. The results obtained in this study showed that density had a significant effect (p<0.001) on growth rates in any of the densities studied and that growth was significantly higher at lower densities (p<0.001). For all density levels, estimated daily growth was higher in the first month, decreasing progressively over time. The high aggressiveness and territorial behaviour of Marphysa “sp.” juveniles, well evidenced by the highest mortality (35%) under high density and by the presence of worms with lesions under low density (30%) observed in the first month, suggests that territoriality is probably the main factor involved in the organization and spatial arrangements of individuals within a population. Marphysa juveniles probably compete for burrow space. The results reveal that Marphysa juveniles have a very territorial and aggressive behaviour that should be considered if the species is used for aquaculture production. Additional studies are required to determine the density effects for different developmental stages

Paralytic shellfish toxins and ocean warming: bioaccumulation and ecotoxicological responses in jujvenile Gilthead Seabream (Sparus aurata)

Warmer seawater temperatures are expected to increase harmful algal blooms (HABs) occurrence, intensity, and distribution. Yet, the potential interactions between abiotic stressors and HABs are still poorly understood from ecological and seafood safety perspectives. The present study aimed to investigate, for the first time, the bioaccumulation/depuration mechanisms and ecotoxicological responses of juvenile gilthead seabream (Sparus aurata) exposed to paralytic shellfish toxins (PST) under different temperatures (18, 21, 24 °C). PST were detected in fish at the peak of the exposure period (day five, 0.22 µg g-1 N-sulfocarbamoylGonyautoxin-1-2 (C1 and C2), 0.08 µg g-1 Decarbamoylsaxitoxin (dcSTX) and 0.18 µg g-1 Gonyautoxin-5 (B1)), being rapidly eliminated (within the first 24 h of depuration), regardless of exposure temperature. Increased temperatures led to significantly higher PST contamination (275 µg STX eq. kg-1). During the trial, fish antioxidant enzyme activities (superoxide dismutase, SOD; catalase, CAT; glutathione S-transferase, GST) in both muscle and viscera were affected by temperature, whereas a significant induction of heat shock proteins (HSP70), Ubiquitin (Ub) activity (viscera), and lipid peroxidation (LPO; muscle) was observed under the combination of warming and PST exposure. The differential bioaccumulation and biomarker responses observed highlight the need to further understand the interactive effects between PST and abiotic stressors, to better estimate climate change impacts on HABs events, and to develop mitigation strategies to overcome the potential risks associated with seafood consumption.Agência financiadora European Union (EU) 678193 Portuguese Foundation for Science and Technology (FCT) IF/00253/2014 CEECIND/01739/2017 UID/Multi/04326/2019info:eu-repo/semantics/publishedVersio

Influence of age on stress responses of White Seabream to Amyloodiniosis

Amyloodiniosis is a disease that represents a major bottleneck for semi-intensive aquaculture, especially in Southern Europe. The inefficacy of many of the treatments for this disease on marine fish produced in semi-intensive aquaculture has led to a new welfare approach to amyloodiniosis. There is already some knowledge of several welfare issues that lead to amyloodiniosis as well as the stress, physiological, and immunological responses to the parasite by the host, but no work is available about the influence of fish age on the progression of amyloodiniosis. The objective of this work was to determine if stress, hematological, and histopathological responses are age dependent. For that purpose, we determined the mortality rate, histopathological lesions, hematological indexes, and stress responses (cortisol, glucose, lactate, and total protein) in “Small” (total weight: 50 ± 5.1 g, age: 273 days after eclosion (DAE)) and “Big” (total weight: 101.3 ± 10.4 g, age: 571 DAE) white seabream (Diplodus sargus) subjected to an Amyloodinium ocellatum infestation (8000 dinospores mL−1) during a 24-h period. The results demonstrated a strong stress response to A. ocellatum, with marked differences in histopathological alterations, glucose levels, and some hematological indexes between the fish of the two treatments. This work elucidates the need to take in account the size and age of the fish in the development and establishment of adequate mitigating measures and treatment protocols for amyloodiniosis.Funding: This study was funded by Projects DIVERSIAQUA (Mar2020 16-02-01-FMP-0066) and SAUDE&AQUA (Mar2020 02.05.01-FEAMP-0009). This study also received Portuguese national funds from FCT—Foundation for Science and Technology through project UID/Multi/04326/2019. Acknowledgments: Márcio Moreira has a PhD grant from FCT (SFRH/BD/118601/2016).info:eu-repo/semantics/publishedVersio

Response of Marine Plankton Communities in Ponds to the Presence of Vertical Structures

The effects of bottom vertical structures like AquaMats® in enhancing plankton productivity was evaluated. One experimental earthen pond of 500 m2 was provided with AquaMats® increasing the surface substrate area 12 times and water quality, phytoplankton and zooplankton populations developed during almost 100 days was compared with a pond without AquaMats®. Their presence favored the development of Dinoflagellates (Miozoa, Dinophyceae), mostly Gymnodiniales, which may be of some concern since some species of this group have been associated with toxic algal blooms while in the ponds without AquaMats® Diatoms (Bacillariophyta) predominate. In both ponds plankton production was very much sculptured by external nutrients added to the systems. The balance between different nutrients is extremely important to regulate the phytoplankton populations with Diatoms blooming at silicate concentrations higher than 2 μM and below this level and at low nitrate and high ammonium being more appropriate for Dinoflagellates. The linkage between phytoplankton and zooplankton population in ponds is strong with zooplankton exerting control over the phytoplankton population and vice-versa. The use of vertical substrates enhances plankton productivity by increasing the substrate area for periphyton fixation. The main zooplankton taxonomic groups associated with the presence of AquaMats® were Calanoid and Harpacticoid copepodites and nauplii, veligers of gastropods and trochophore of polychaets, larval stages of organisms that except for calanoid copepods are benthic and correspond to the meroplanktonic phase in the life cycle of those organisms

Sound production in the Meagre, Argyrosomus regius (Asso, 1801): intraspecific variability associated with size, sex and context

Many fish taxa produce sound in voluntary and in disturbance contexts but information on the full acoustic repertoire is lacking for most species. Yet, this knowledge is critical to enable monitoring fish populations in nature through acoustic monitoring.Portuguese Foundation for Science and Technology: PTDC/BIA-BMA/30517/2017; SFRH/BD/115562/2016; UID/MAR/04292/2019; UID/BIA/00329/2019; PTDC/BIA-BMA/29662/2017.info:eu-repo/semantics/publishedVersio

Swimming abilities of temperate pelagic fish larvae prove that they may control their dispersion in coastal areas

The Sense Acuity and Behavioral (SAAB) Hypothesis proposes that the swimming capabilities and sensorial acuity of temperate fish larvae allows them to find and swim towards coastal nursery areas, which are crucial for their recruitment. To gather further evidence to support this theory, it is necessary to understand how horizontal swimming capability varies along fish larvae ontogeny. Therefore, we studied the swimming capability of white seabream Diplodus sargus (Linnaeus, 1758) larvae along ontogeny, and their relationship with physiological condition. Thus, critical swimming speed (U-crit) and the distance swam (km) during endurance tests were determined for fish larvae from 15 to 55 days post-hatching (DPH), and their physiological condition (RNA, DNA and protein contents) was assessed. The critical swimming speed of white seabream larvae increased along ontogeny from 1.1 cm s(-1) (15 DPH) to 23 cm s(-1) (50 and 55 DPH), and the distance swam by larvae in the endurance experiments increased from 0.01 km (15 DPH) to 86.5 km (45 DPH). This finding supports one of the premises of the SAAB hypothesis, which proposes that fish larvae can influence their transport and distribution in coastal areas due to their swimming capabilities. The relationship between larvae's physiological condition and swimming capabilities were not evident in this study. Overall, this study provides critical information for understanding the link between population dynamics and connectivity with the management and conservation of fish stocks.Funding Agency Portuguese Foundation for Science and Technology SFRH/BD/104209/2014 Portuguese Foundation for Science and Technology UID/Multi/04326/2019 FCT, under the Transitional Norm DL57/2016/CP[1361]/CT[CT0008 CLIMFISH project-A framework for assess vulnerability of coastal fisheries to climate change in Portuguese coast n2/SAICT/2017-SAICTinfo:eu-repo/semantics/publishedVersio

Cytotoxic and hemolytic activities of extracts of the fish parasite dinoflagellate amyloodinium ocellatum

The dinoflagellate Amyloodinium ocellatum is the etiological agent of a parasitic disease named amyloodiniosis. Mortalities of diseased fish are usually attributed to anoxia, osmoregulatory impairment, or opportunistic bacterial infections. Nevertheless, the phylogenetic proximity of A. ocellatum to a group of toxin-producing dinoflagellates from Pfiesteria, Parvodinium and Paulsenella genera suggests that it may produce toxin-like compounds, adding a new dimension to the possible cause of mortalities in A. ocellatum outbreaks. To address this question, extracts prepared from different life stages of the parasite were tested in vitro for cytotoxic effects using two cell lines derived from branchial arches (ABSa15) and the caudal fin (CFSa1) of the gilthead seabream (Sparus aurata), and for hemolytic effects using erythrocytes purified from the blood of gilthead seabream juveniles. Cytotoxicity and a strong hemolytic effect, similar to those observed for Karlodinium toxins, were observed for the less polar extracts of the parasitic stage (trophont). A similar trend was observed for the less polar extracts of the infective stage (dinospores), although cell viability was only affected in the ABSa15 line. These results suggest that A. ocellatum produces tissue-specific toxic compounds that may have a role in the attachment of the dinospores’ and trophonts’ feeding process.info:eu-repo/semantics/publishedVersio

Methodology for assessing the individual role of fish, oyster, phytoplankton and macroalgae in the ecology of integrated production in earthen ponds

Production costs in extensive and semi-intensive fish culture in earthen ponds are often too high to offer sustainable economic activity due to the low productivity of these systems. The right combination of commercial finfish species with inorganic (primary producers) and organic extractive (bivalves) species in Integrated MultiTrophic Aquaculture (IMTA) create a balanced system with higher profitability and risk reduction. To achieve this, it is crucial to understand the role of each functional groups within the system what we did by comparing three different IMTA production three different IMTA production treatments with distinct combinations of trophic levels: •fish, filter feeders, phytoplankton and macroalgae,•fish, filter feeders and phytoplankton•fish, phytoplankton and macroalgae Each treatment was carried out in two similar ponds under semi-intensive conditions and flow through system, in a total of 6 earthen ponds of 500 m2 surface and depth of 1.5 m. Results showed that the presence of oysters in the ponds enhanced water quality by decreasing turbidity and by controlling phytoplankton which led to regulation of dissolved oxygen levels. The enhanced water quality in these systems lead to improved fish performance and higher biomass production contributing to greater profitability. The combination of fish, oyster, phytoplankton and macroalgae was particularly good providing much more fish supply compared with the other two treatments. •Oysters enhanced water quality in the ponds by decreasing turbidity and controlling phytoplankton which regulated the dissolved oxygen levels.•The enhanced water quality in systems with oysters improve fish performance resulting in higher biomass production and greater profitability.•The combination of fish, oyster, phytoplankton and macroalgae was particularly good providing much more fish supply compared with the other two treatments.Funding Agency Fundacao para a Ciencia e a Tecnologia (FCT) COFASP/0003/2015 SFRH/BD/118601/2016 Project DIVERSIAQUA Mar2020 16-02-01-FMP-0066 project Algared+ Poctep 0055_ALGARED_PLUS_5_E UID/Multi/04326/2019info:eu-repo/semantics/publishedVersio

Efeito a longo termo da temperatura do cultivo larvar no crescimento e fibras musculares de corvinas, Argyrosomus regius / Long-term effect of larval rearing water temperature on meagre, Argyrosomus regius, growth and muscle cellularity

A temperatura de cultivo desempenha um papel fundamental no desenvolvimento dos peixes. Neste estudo foram testadas duas temperaturas durante a ontogenia larvar da corvina. Após este período, os alevins foram transferidos para tanques maiores, todos à temperatura ambiente, onde permaneceram até atingirem os 12 meses de idade. O crescimento e a área e densidade das fibras musculares foram analisados quando o peixe atingiu 1, 2, 4, 6 e 12 meses. Os resultados mostram que os alevins de 1 mês sujeitos a uma temperatura mais elevada (1.5º superior) apresentaram um maior comprimento, um maior peso seco (11 mg versus 7 mg) e uma maior frequência de fibras com uma área compreendida entre os 100 e os 200 µm2. Por outro lado, os alevins sujeitos a uma temperatura inferior apresentaram maior densidade de fibras (13493 mm2 versus 5689 mm2) e um maior recrutamento de novas fibras. A partir do momento em que todos os alevins passaram a estar à mesma temperatura (ao fim de 30 dias), as diferenças foram-se desvanecendo. O ponto de viragem parece ter sido aos quatro meses de idade, quando a média da área das fibras era superior no controlo (704 µm2 versus 540 µm2). De um modo geral, o recrutamento das fibras musculares diminuiu com a idade do peixe enquanto a engrossamento das fibras permaneceu constante. Este estudo mostra que o uso de diferentes temperaturas durante a ontogenia larvar pode provocar diferenças no crescimento assim como afetar a área e densidade das fibras musculares. No entanto, estas diferenças parecem ser mitigadas quando os peixes passam a estar à mesma temperatura

Variações na textura, conteúdo lipídico e fibras musculares de corvinas de três tamanhos comerciais diferentes, capturadas no inverno e no verão / Seasonal variations in texture, fat content and muscle cellularity in meagre, Argyrosomus regius, of three different commercial sizes

A corvina é uma espécie com elevado potencial para aquacultura intensiva na região do Mediterrâneo. O consumo de alimento desta espécie é extremamente afetado pela temperatura da água e diminui nos meses de inverno. Neste estudo foi analisada a qualidade de corvinas com três tamanhos diferentes: 800, 1500 e 2500 g, capturadas no inverno e no verão. Os resultados obtidos indicam que a estação do ano afeta as caraterísticas morfométricas, conteúdo lipídico (2.5 para 4.3 % e 3.1 para 4.5 % em corvinas de 1500 e 2500 g, respetivamente, no inverno e no verão) e índice hepatossomático (1.3 para 2.8 % e 1.6 to 2.6 % em corvinas de 1500 e 2500 g, respetivamente, no inverno e no verão). As propriedades texturais do filete não foram afetadas mas foi encontrada uma correlação negativa entre a coesividade e o conteúdo de gordura do filete de corvinas de 1500 g. As fibras musculares também foram avaliadas e não foram encontradas diferenças na área das fibras embora a densidade de fibras tenha sido maior no verão do que no inverno (400 para 598 fibras/mm2 e 287 para 413 fibras/mm2 em corvinas de 1500 e 2500 g, respetivamente, no inverno e no verão). Esta diferença poderá estar associada a um aumento do recrutamento das fibras musculares durante o período de inverno, o que é sugerido pela distribuição das áreas das fibras medidas na corvina de 1500 g. Em conclusão, este estudo mostra que a época da captura da corvina pode afetar os diferentes atributos da qualidade do filete deste peixe