Search

Mercury (Hg) is a dangerous and persistent trace element. Its organic and highly toxic form, methylmercury (MeHg), easily crosses biological membranes and accumulates in biota. Nevertheless, understanding the mechanisms of dietary MeHg toxicity in fish remains a challenge. A time-course experiment was conducted with juvenile white seabreams, Diplodus sargus (Linnaeus, 1758), exposed to realistic levels of MeHg in feed (8.7 μg g−1, dry weight), comprising exposure (E; 7 and 14 days) and post-exposure (PE; 28 days) periods. Total Hg levels increased with time in gills and liver during E and decreased significantly in PE (though levels of control fish were reached only for gills), with liver exhibiting higher levels (2.7 times) than gills. Nuclear magnetic resonance (NMR)-based metabolomics revealed multiple and often differential metabolic changes between fish organs. Gills exhibited protein catabolism, disturbances in cholinergic neurotransmission, and changes in osmoregulation and lipid and energy metabolism. However, dietary MeHg exposure provoked altered protein metabolism in the liver with decreased amino acids, likely for activation of defensive strategies. PE allowed for the partial recovery of both organs, even if with occurrence of oxidative stress and changes of energy metabolism. Overall, these findings support organ-specific responses according to their sensitivity to Hg exposure, pointing out that indications obtained in biomonitoring studies may depend also on the selected organ. [ABSTRACT FROM AUTHOR]

A single specimen white seabream, Diplodus sargus (Linnaeus, 1758), was recorded on 11 November 2019 from the coast of Konacık (Arsuz) in the Iskenderun Bay (North-eastern Mediterranean, Turkey). This specimen was identified as a specimen of Diplodus sargus. Known as Xanthochromism, abnormal skin coloration is an unusually yellow pigmentation in fishes. It is often associated with the lack of usual red pigmentation and its replacement with yellow. The present paper reported the first occurrence of the xanthochromic specimen of Diplodus sargus from Turkey's Mediterranean coast. [ABSTRACT FROM AUTHOR]

One of the most visible features of fish reproduction is seasonality; however, daily rhythmicity is present in most species and should not be disregarded. This study investigated the seasonal and daily spawning rhythms of the white seabream (Diplodus sargus) in captivity, and a possible endogenous control of the daily rhythm. Spawns were monitored daily, during an entire reproductive season by using an automatic and programmable egg collector. The spawning season lasted 5 months, from January until June, when temperatures oscillated between 11.5 and 24.4°C. Female fecundity was higher between 17.5 and 20.4°C, suggesting a temperature influence in spawning. This species showed a very clear daily spawning rhythm (Cosinor analysis, p < 0.001), strongly related with photoperiod. Eggs started to be released at sunset and peaked around 21:00 h. Egg quality parameters also changed along the spawning period, with viability and hatching rates, increasing towards the end of the night period. The spawning rhythm persisted (Cosinor analysis, p < 0.001) for 5 days under constant light conditions, suggesting the presence of an endogenous clock mechanism which controlled this circadian pattern. The present results represent an advantage for the optimization of egg production protocols in this species, and an added value to the current knowledge of marine fish physiology. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is a dangerous and persistent trace element. Its organic and highly toxic form, methylmercury (MeHg), easily crosses biological membranes and accumulates in biota. Nevertheless, understanding the mechanisms of dietary MeHg toxicity in fish remains a challenge. A time-course experiment was conducted with juvenile white seabreams, Diplodus sargus (Linnaeus, 1758), exposed to realistic levels of MeHg in feed (8.7 μg g−1, dry weight), comprising exposure (E; 7 and 14 days) and post-exposure (PE; 28 days) periods. Total Hg levels increased with time in gills and liver during E and decreased significantly in PE (though levels of control fish were reached only for gills), with liver exhibiting higher levels (2.7 times) than gills. Nuclear magnetic resonance (NMR)-based metabolomics revealed multiple and often differential metabolic changes between fish organs. Gills exhibited protein catabolism, disturbances in cholinergic neurotransmission, and changes in osmoregulation and lipid and energy metabolism. However, dietary MeHg exposure provoked altered protein metabolism in the liver with decreased amino acids, likely for activation of defensive strategies. PE allowed for the partial recovery of both organs, even if with occurrence of oxidative stress and changes of energy metabolism. Overall, these findings support organ-specific responses according to their sensitivity to Hg exposure, pointing out that indications obtained in biomonitoring studies may depend also on the selected organ.

A worrying phenomenon has been affecting the common white seabream (Diplodus sargus) for near 40 years. Professional and recreational fishers from the Mediterranean coasts and the Atlantic coasts of Europe and Macaronesia have reported individuals of white seabream that became “like a tire” after cooking, and consequently inedible. The phenomenon was related neither to the freshness of the fish nor to the way it had been preserved or cooked. According to recreational fishers, this Abnormally Tough Specimen (ATS) phenomenon appeared singularly in time, in different places and to different extents. This singular, scattered appearance, with no area of origin from which to spread, de facto excluded any process of contagion. In order to compensate for the lack of knowledge and understanding related to this issue, we undertook a first study that aimed at addressing the extent of the white seabream anomaly in the western Mediterranean. To reach this objective, we carried out surveys on voluntary basis among fishers (both professional and recreational) and researchers throughout the western Mediterranean. Data from the surveys (n = 270) were then analyzed to evaluate the distribution of ATS and its possible relationship with human activities. Results showed that the anomaly affected the white seabream and very occasionally some other species, mainly of the same family Sparidae. In addition, the phenomenon did not occur simultaneously in the different areas surveyed over the last years and in some places it seems to have disappeared. We highlighted a possible link between ATS occurrence and the presence of human activities in adjacent areas. We hypothesized pollution – including by copper – could be a possible driver of ATS. Results suggested a tendency of ATS to cluster around fish farms and commercial and industrial ports, although we are aware other human factors might also influence the phenomenon. To conclude, the present study gives an overview of the importance of the white seabream anomaly in the Mediterranean and encourages further research to disentangle the exact mechanisms behind this phenomenon.

Abstract This study assessed the effect of supplementation of low-fishmeal (FM) diets with taurine in white seabream (Diplodus sargus) juveniles. Four isoproteic (36% CP) and isolipidic (18% CL) diets were formulated to include 15%FM or 5%FM, supplemented or not with 1% of Taurine (TAU). Twelve groups of 15 fish (IBW = 58 g) were fed each diet to near satiation for 10 weeks. Growth performance, feed intake, and feed efficiency were not affected by dietary FM level. Nevertheless, dietary TAU supplementation increased growth performance and feed efficiency. Nitrogen and energy retention were improved by both dietary FM level and TAU supplementation. Plasma cholesterol, lactate, and bilirubin did not differ among dietary treatments, but dietary TAU supplementation decreased plasma glucose and triglycerides levels. Decrease of FM level reduced total bile salts while TAU supplementation had the opposite effect. No differences were noticed in innate immune parameters assessed. Overall, results indicate that white seabream can be fed with diets almost devoid of FM, and that dietary TAU supplementation increases growth performance and feed efficiency. Moreover, results suggest that dietary TAU was limiting both in 15% and 5% FM diets. [ABSTRACT FROM AUTHOR]

Despite the relatively high number of spearfishing practitioners in Portugal, scientific information on spearfishing is limited. A web‐based survey was conducted to obtain socio‐economic information on Portuguese spearfishers, identify the most common fishing habitats, target species, fishing effort, and evaluate their perceptions towards management and conservation measures. Results suggest that spearfishing is essentially seen as promoting well‐being, escaping the daily routine and outdoor enjoyment. Favourable environmental conditions and habitat availability seem to play an important role in the fishing effort, with warmer, less exposed rocky bottoms covered with algae being the most appreciated for spearfishing. Spearfishers reported targeting mostly two species: European seabass Dicentrarchus labrax and the white seabream Diplodus sargus. The added fishing mortality caused by spearfishers should be included in stock assessment of these species. Most respondents felt that the management measures in place were inappropriate and unfair for the spearfishing activity. [ABSTRACT FROM AUTHOR]

Invasive species can cause severe economic damages, ecosystem alterations, and can even threat human health. In the global warming scenario, which can act as a driving force for the expansion of thermophilic species, we investigated for the first time the economic damage caused by the invasive bearded fireworm, Hermodice carunculata , to artisanal longline fishery in the Mediterranean Sea. We focused on bottom longline fishery targeting the highly prized white seabream Diplodus sargus , investigating catch composition of the fishing gear and Catch Per Unit Effort (CPUE) of species caught, with particular emphasis on the economic damage caused by the bearded fireworm, H. carunculata , in relation to water temperature. Our results clearly indicated direct and indirect economic damage to fishing activities practiced in the southeastern coast of Sicily (Ionian Sea). Type and extent of the damage caused by the invasive worm (H. carunculata) were discussed in relation to temporal scale and overall yields obtained by this traditional artisanal fishery, and some solutions are proposed. However, the actual situation requires special attention because it is expected to worsen in the context of the global warming future scenarios, such that further studies are urgently needed. • Our results indicated both direct and indirect economic damage caused by Hermodice carunculata to the investigated fishing activities. • The rise in economic damage caused by H. carunculata is likely associated with an increase in water temperature. • Worms that scavenged directly the bait remained frequently hooked as a very undesirable by-catch, thus reducing catch potential of the gear. • The three most abundant commercial species targeted with longlines were Diplodus sargus , Diplodus vulgaris , and Pagrus pagrus. [ABSTRACT FROM AUTHOR]

Background. Life stage transitions (e.g., settlement and recruitment), characterized by high mortality rates, act as selective bottlenecks for fishes with a bipartite life cycle. Mortality at these stages is usually selective and potentially affected by larval history. This process is reflected in an inconsistency in larval traits’ distribution between subsequent life stages (e.g., settlers and recruits) originating from the same reproductive season. Despite the importance of this issue only very scarce information is available about this aspect of Mediterranean fishes life histories. Materials and methods. Here we described settlement and investigated the match/mismatch of larval traits between settlers and recruits coming from the same reproductive season, using the white seabream, Diplodus sargus sargus (Linnaeus, 1758), as a model species along ~ 200 km of the Apulian Adriatic coast (south-western Adriatic Sea, Italy). Both microstructure and chemistry analyses were carried out on otoliths of settlers (n = 140) and recruits (n = 113). Results. We highlighted a mismatch in two life traits, i.e., PLD (pelagic larval duration) and natal origin, between settlers and recruits. Recruits showed PLD longer than the maximum recorded for settlers, and a higher number of natal sources compared to settlers. Mismatch in PLD could suggest selective juvenile mortality related to PLD, and recruits with higher PLD potentially originated from the settlement tail (i.e., settled after the settlement peak). Conclusion. Our findings can support hypotheses suggesting that 1) a fraction of juveniles are selectively eliminated; 2) settlement tail could play a relevant role in replenishing local populations of white seabream.

Abstract The presence of toxic elements in fish represents a hazard for human health, especially in Mediterranean countries and other regions with high per-capita fish consumption. The present research, carried out along the northern Catalan coast (NW Mediterranean), aimed to determine the levels of trace metals and arsenic in the muscle of white seabream Diplodus sargus (L.), a common demersal species of growing interest for fisheries and aquaculture. Average mercury concentrations widely exceeded the limits imposed by EU despite the low contamination levels previously reported for the study area, stressing the potential risk associated to the consumption of medium-sized, non-predatory fishes. The other analyzed elements fell within the recommended limits. Preliminary results about the feeding habits of D. sargus are reported, in order to determine feeding habitat and items of the analyzed specimens. Highlights • Risky levels of Hg were found in D. sargus muscle from a low-contaminated zone. • Trace-element concentrations varied with fish size and sampling site. • Ontogenic habitat and diet shift may explain part of the observed variability. • Non-predatory fishes from "clean" areas are also cause for concern. [ABSTRACT FROM AUTHOR]

Climate change and chemical contamination are global environmental threats of growing concern for the scientific community and regulatory authorities. Yet, the impacts and interactions of both stressors (particularly ocean warming and emerging chemical contaminants) on physiological responses of marine organisms remain unclear and still require further understanding. Within this context, the main goal of this study was to assess, for the first time, the effects of warming (+ 5 °C) and accumulation of a polybrominated diphenyl ether congener (BDE-209, brominated flame retardant) through dietary exposure on energy budget of the juvenile white seabream ( Diplodus sargus ). Specifically, growth (G), routine metabolism (R), excretion (faecal, F and nitrogenous losses, U) and food consumption (C) were calculated to obtain the energy budget. The results demonstrated that the energy proportion spent for G dominated the mode of the energy allocation of juvenile white seabream (56.0–67.8%), especially under the combined effect of warming plus BDE-209 exposure. Under all treatments, the energy channelled for R varied around 26% and a much smaller percentage was channelled for excretion (F: 4.3–16.0% and U: 2.3–3.3%). An opposite trend to G was observed to F, where the highest percentage (16.0 ± 0.9%) was found under control temperature and BDE-209 exposure via diet. In general, the parameters were significantly affected by increased temperature and flame retardant exposure, where higher levels occurred for: i) wet weight, relative growth rate, protein and ash contents under warming conditions, ii) only for O:N ratio under BDE-209 exposure via diet, and iii) for feed efficiency, ammonia excretion rate, routine metabolic rate and assimilation efficiency under the combination of both stressors. On the other hand, decreased viscerosomatic index was observed under warming and lower fat content was observed under the combined effect of both stressors. Overall, under future warming and chemical contamination conditions, fish energy budget was greatly affected, which may dictate negative cascading impacts at population and community levels. Further research combining other climate change stressors (e.g. acidification and hypoxia) and emerging chemical contaminants are needed to better understand and forecast such biological effects in a changing ocean. [ABSTRACT FROM AUTHOR]

Background. Life stage transitions (e.g., settlement and recruitment), characterized by high mortality rates, act as selective bottlenecks for fi shes with a bipartite life cycle. Mortality at these stages is usually selective and potentially affected by larval history. This process is reflected in an inconsistency in larval traits' distribution between subsequent life stages (e.g., settlers and recruits) originating from the same reproductive season. Despite the importance of this issue only very scarce information is available about this aspect of Mediterranean fi shes life histories. Material and methods. Here we described settlement and investigated the match/mismatch of larval traits between settlers and recruits coming from the same reproductive season, using the white seabream, Diplodus sargus sargus (Linnaeus, 1758), as a model species along ~ 200 km of the Apulian Adriatic coast (south-western Adriatic Sea, Italy). Both microstructure and chemistry analyses were carried out on otoliths of settlers (n = 140) and recruits (n = 113). Results. We highlighted a mismatch in two life traits, i.e., PLD (pelagic larval duration) and natal origin, between settlers and recruits. Recruits showed PLD longer than the maximum recorded for settlers, and a higher number of natal sources compared to settlers. Mismatch in PLD could suggest selective juvenile mortality related to PLD, and recruits with higher PLD potentially originated from the settlement tail (i.e., settled after the settlement peak). Conclusion. Our fi ndings can support hypotheses suggesting that 1) a fraction of juveniles are selectively eliminated; 2) settlement tail could play a relevant role in replenishing local populations of white seabream. [ABSTRACT FROM AUTHOR]

Several studies have reported the existence of ectoparasites in the stomach contents ofDiplodus sargus. The cleaning behaviour has, however, never been previously observed for this species. In this short study, we report the first observations of the cleaning behaviour ofD.sargus. These observations were in two yachting marinas, located in the Portuguese western coast between the months of April and August. The cleaning behaviour was only observed towards two Mugilidae species,Chelon labrosusandMugil cephalus. [ABSTRACT FROM AUTHOR]

This paper presents the results of an application of ultrasonic telemetry on white seabream, Diplodus sargus inhabiting an artificial reef (AR) in NW Sicily (western Mediterranean Sea). The objective of the study was to investigate the movement pattern of seabreams, verify their homing behaviour and site fidelity, determine their home range and describe their use of the habitat. Four seabreams were tagged and released, and their movements were recorded with automated and manual acoustic receivers. The spatial and temporal distribution of positional data suggest that the tagged seabreams hide inside the AR during the day, staying out of their shelter at night. The nocturnal movements of the tagged fishes are suggested to be a search for food in the seagrass patches surrounding the ARs. The monitored seabreams showed clear homing behaviour and strong site fidelity. Their home range extended from 0.01 to 0.17 km and included the AR and the surrounding sandy area with seagrass patches. Home range areas increased proportionally to the distance between the refuge on AR and the foraging areas on seagrass patches. The higher activity of seabreams during the night was interpreted as a result of a trade-off between predation risk and foraging needs. [ABSTRACT FROM AUTHOR]

Metals are environmentally ubiquitous and can be found at high concentrations in seawater and subsequently in marine organisms. Metals with high redox potential can trigger oxidative stress mechanisms with damaging effects in biological tissues. In aquatic species, oxidative stress has been evaluated by assessing antioxidant enzymes activities and oxidative damages in tissues. The purpose of this study was to evaluate oxidative stress biomarkers and metal residues in white seabream (Diplodus sargus), a species entering aquaculture production in Portugal. Metal residues (Cu, Cd, As and Pb), in liver and muscle, as well as oxidative stress biomarkers were assessed at different stages in the life cycle of white seabream under culture conditions and in wild specimens, of a marketable size. Metal concentrations in tissues were low, and below the established limits. However, wild white seabream showed higher accumulation than cultured ones. Antioxidant enzymes, namely catalase (CAT) and superoxide dismutase (SOD), were correlated with metal accumulation. Oxidative damages to tissues were low, with wild white seabream showing lower levels than cultured fish. This study showed that white seabream has a good antioxidant defense system, capable of reducing oxidative damages in tissues resulting from the presence of metals. [Copyright &y& Elsevier]

The knowledge of geochemical processes in fishponds is important in defining farming strategies and the carrying capacity of these systems, and is therefore essential for the management and sustainability of semi-intensive aquaculture in earth ponds. The main purpose of the present work, developed in the Aquaculture Research Station located in Ria Formosa, was to study the geochemical changes in semi-intensive earth ponds of white seabream Diplodus sargus L. during a production cycle, and relate it to farming conditions (fish biomass and feeding rate). Settled material and sediment samples were collected in a fish production pond and in a non-fish production pond during 2 years. The results obtained showed that particle-settling rates ( S, g m−2 day−1) increased linearly with time ( t, days): S=0.7 t–34, in the fishpond. Increasing deposition of particulate material increased the organic matter content of bottom sediments, particularly during the second production year. Organic matter mineralization, during periods of high temperatures, led to high nutrient concentrations in porewater (NH4+, 965 μM; NO3−, 40 μM; HPO42−, 39 μM) and subsequently to an increase in benthic primary production in the fishpond. The geochemical similarities between fishpond sediments and shallow coastal system's sediments, along with the high fish survival rate (94%), suggest that for the assayed farming conditions there were no environmental constraints within the pond. However, some impact on bottom sediments, namely, an increase in settled material, organic matter deposition, nutrients in porewater and microphytobentos production, was evident above a fish biomass of 500 g m−3 and a feeding rate of 150 kg month−1, indicating that pond environmental conditions should be carefully monitored from this point on. [ABSTRACT FROM AUTHOR]

Abstract: The lipid and fatty acid content of the gonads, liver and muscle of wild white seabream males and females was studied at different stages of the reproductive cycle. Samples were taken from mature white seabream at pre-spawning (November), mid-spawning (March) and post-spawning (June) stages. The results showed that lipid accumulates in gonads and muscle from November to March. The gonadosomatic index (GSI) was also increased during this period. Male gonads showed a greater increase in polar lipid (PL) than neutral (NL), while female gonads displayed the reverse. The increase in both neutral and polar lipid was higher in the muscle of males than in females. In the same period, male livers showed no changes either in lipid content or the hepatosomatic index (HSI), while female livers registered an increase in both lipid content and HSI. Between March and June, in both males and females, total, neutral and polar lipid decreased sharply in the gonads and muscle. Muscular lipid content reduction was more pronounced in males than females. On the other hand, the lipid content of the liver in males and females remained relatively constant. In general terms, the amounts of major fatty acids (16:0, 18:1n-9, 20:5n-3 and 22:6n-3) in gonadal and muscular polar and neutral lipid in both males and females increased from November to March and declined thereafter. Variations of the liver fatty acid content were less extreme. In the period from mid-spawning to post-spawning, the presence of 20:4n-6 in polar and neutral lipid increased to a notable extent in all organs studied. [Copyright &y& Elsevier]

An 83-day feeding trial was carried out to determine the effect of different dietary protein and lipid levels on the growth performances and carcass composition of white seabream. Juveniles (10.7±0.2 g) were fed to satiation on four diets, varying in protein (15% and 28%) and lipid (12% and 16%) levels. The best growth performance was observed in fish fed on diets with higher protein level. Dietary lipids did not affect growth performance. Voluntary feed intake decreased with a increasing dietary protein level at both dietary lipid levels. Feed conversion ratio improved with the increase in dietary protein and lipid levels. Carcass composition remained unaltered by dietary protein levels ( P>0.05). Carcass protein content tended to decrease, while lipid content tended to increase in groups fed on 16% lipid, compared with the 12% lipid groups. Additionally, protein retention was higher in fish fed on low-protein and low-lipid levels, compared with the high-protein and high-lipid group (29% vs. 19%). Lipid retention increased significantly with dietary protein level ( P<0.001). Energy retention improved with dietary protein, but was not affected by dietary lipid levels. On the basis of our results, feeding white seabream on 15% dietary protein had a negative effect on growth and feed utilization. Dietary lipid did not induce a protein-sparing action in Diplodus sargus juveniles. [ABSTRACT FROM AUTHOR]

Abstract: To make a first approach in the assessment of the sea urchin predators in the Azores, the diet of white seabream (Diplodus sargus) and ballan wrasse (Labrus bergylta), were studied by the analyses of their stomach contents. The white seabream is a diurnal omnivore, feeding on algae, sea-urchins, worms, gastropods and amphipods, while ballan wrasse fed mainly on echinoderms (sea-urchins), gastropods and decapods. Both species tended to feed on harder prey, such as echinoderms and gastropods, as they grew. Although both species feed upon similar resources, the diet overlap was low. This study shows that the white seabream and the ballan wrasse are important predators of sea-urchins in Azorean coastal habitats. Furthermore, larger fish account for most of the predation on sea-urchins. Thus, a reduction in the abundance and mean size of fishes, which is a typical consequence of fishing, may significantly decrease predation on sea-urchins and could thus facilitate their proliferation. [Copyright &y& Elsevier]

To establish the changes which occur during embryogenesis and early larvae development, eggs, yolk-sac larvae (one day old larvae) and absorbed yolk-sac larvae (three day old larvae) of white sea bream were examined for lipid class and fatty acid composition. The development was characterized by a decrease in all lipid classes with the exception of phosphatidylserine (PS) and fatty free acids (FFA) which increased, and sphingomyelin (SM) which remained unchanged. The changes observed in lipid class content and the decrease in fatty acids in total lipid (TL) reflect the utilization and mobilization of lipids during both embryogenesis and early larvae development. Fluctuations in the relative composition of fatty acids in phosphatidylcholine (PC) during development suggest a selective bulk uptake and catabolism of fatty acids in this lipid class. Unlike PC, catabolism of triacylglycerol (TG) fatty acid appears to be non-selective. During development, the decrease in levels of polyunsaturated fatty acids (PUFA) eicosapentaenoic (20:5n−3, EPA) and docosahexaenoic (22:6n−3, DHA) in total lipid denotes their utilization as energy substrate by Diplodus sargus larvae. [Copyright &y& Elsevier]

Total lipids (TL), lipid classes, and their associated fatty acids from muscle and liver of captive and wild mature female broodstocks were investigated in order to estimate the fatty acid requirements of white seabream (Diplodus sargus). The results showed that the percentage of triacylglycerol was higher in liver and muscle of captive fish than in wild fish. The distribution of phospholipid classes in liver and muscle of both fish groups was similar, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol being the predominant lipid classes. The general pattern of fatty acid distribution in total lipid of liver and muscle from captive and wild fish was similar. However, the relative percentage of specific fatty acids differed in captive and wild fish. The most noteworthy difference was the lower proportion of arachidonic acid (20:4n-6, AA) and the higher proportion of eicosapentaenoic acid (20:5n-3, EPA) in liver and muscle of captive fish with respect to those of wild fish. The proportion of docosahexaenoic acid (22:6n-3, DHA) did not differ between the two fish groups. The differences in EPA and AA proportions between captive and wild fish implied that captive fish presented a higher EPA/AA ratio and a lower DHA/EPA ratio than wild fish. In general terms, in both liver and muscle, the differences in fatty acid composition observed for TL were extended to all lipid classes. The results suggest that the different AA, EPA and DHA proportions in liver and muscle between captive and wild broodstocks are attributed to different levels of these fatty acids in broodstock diets. [Copyright &y& Elsevier]

In order to demonstrate that IMTA can be profitable and a good alternative to regular semi-intensive fish mariculture production in earthen ponds three different production treatments with distinct combinations of trophic levels were designed: (i) a combination of fish, filter feeders, phytoplankton and macroalgae, (ii) fish, filter feeders and phytoplankton and (iii) fish, phytoplankton and macroalgae, to evaluate the role of each trophic level within an Integrated Multi-Trophic Aquaculture system (IMTA). Each treatment was carried out under semi-intensive conditions with two replicates, in a total of 6 earthen ponds of 500 m2 surface and depth of 1.5 m. The results showed that fish, oyster, phytoplankton and macroalgae integrated aquaculture is a healthy sustainable production system for mariculture in earthen ponds, providing much more fish supply compared with the other two treatments. Ponds with filter feeders had significantly lower turbidity (Nephelometric Formazin unit (FNU) of 13 in the morning and 17 in the afternoon) when compared to ponds without filter feeders (16 FNU in the morning and 20 FNU in the afternoon) with increased light penetration throughout water column (61 and 55 cm transparency in ponds with filter feeders compared to 51 cm in ponds without filter feeders) and consequently higher photosynthetic activity with significantly higher dissolved oxygen (5.4 mg L−1 in the morning and 6.7 mg L−1 in the afternoon in ponds with filter feeders compared to 5.3 mg L−1 in the morning and 6.4 mg L−1 in the afternoon in ponds without filter feeders) and carbon sequestration (0.50 and 0.53 mg L−1 8 h−1 in ponds with filter feeders and 0.43 mg L−1 8 h−1 in ponds without filter feeders). In the fish, filter feeder, phytoplanton and macroalgae IMTA treatment, phytoplankton played a crucial role because they increased DO levels, removed the excess of nutrients from animal excretion, and was used as food by the filter feeders. Almost as important is the presence of filter feeders since they control the density of the microalgae and particulate matter in the ponds contributing to a more constant level of DO and higher transparency of the water column. The increased transparency and pond fertilization by oyster excretion, resulted in higher proliferation of phytoplankton (chlorophyll a concentrations of 16.5 μg L−1 and 20.2 μg L−1 in ponds with filter feeder and 13.3 μg L−1 in ponds without filter feeder) with benefits not only for filter feeders themselves but also for the macroalgae. At the end there was higher water quality and higher savings (14% day−1) in the energy costs for pond aeration. Meagre, white seabream and flathead grey mullet enhance their performance in IMTA systems with the presence of filter feeders with food conversion rates (FCR) of 1.52 when compared with 2.46 in the regular semi-intensive system composed by fish, phytoplankton and macroalgae. Meagre grew significantly more in IMTA systems with controlled macroalgae while white seabream and flathead grey mullet enhance their performance in the presence of macroalgae. The results show that the fish, oyster, phytoplankton and macroalgae integrated production in earthen ponds is an improved system compared to the regular semi-intensive fish production. The enhanced water quality in these systems leads to improved fish performance and higher biomass production, and to reduction in the energy power used, contributing to greater profitability. • IMTA production in earthen ponds is an improved system comparatively to regular semi-intensive fish production. • The phytoplankton that develop in the ponds increase DO, capture excess nutrients and can be used to feedfilter feeders. • Filter feeders control microalgae density and particulate matter allowing for a more constant DO and higher transparency. • There is better water quality in IMTA with filter feeders and higher savings in the energy costs for water aeration. • Meagre, white seabream and flathead grey mullet performed better in IMTA systems with the presence of filter feeders. [ABSTRACT FROM AUTHOR]

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 m 2 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., (© 2019 The Authors.)