Seriolella Violacea Research Articles

Comparative analysis of hypoxia tolerance, growth performance, and locomotor activity of Seriola lalandi and Seriolella violacea juveniles

In the north of Chile, several projects propose to promote the diversification of national aquaculture with native fish species. However, one of the expected impacts of climate change on the Chilean coasts is an increase in the intensity and frequency of hypoxia events. Therefore, it can become one of the main problems for fish aquaculture in farming facilities. Two species of Chilean diversification programs are Seriola lalandi and Seriolella violacea, which have different habitats and may have different oxygen requirements. Thus, this work aimed to evaluate the variations in oxygen consumption rates in 10 month-old juveniles of both fish species and to determine the presence of tolerant and non-tolerant individuals at low dissolved oxygen (DO) availability. A simulation of an acute hypoxia event by loss-of-equilibrium (LOEhyp) experiments allowed us to classify tolerant and non-tolerant fish. Then, individual oxygen consumption rates were measured, and the resting metabolic rate (RMR) and the maximum metabolic rate (MMR) for hypoxia-tolerant and non-tolerant juveniles were obtained. The results reveal that S. lalandi juveniles have a higher oxygen demand than S. violacea, the first presenting a significantly higher metabolic rate and locomotor activity. Furthermore, the blood parameters suggest that triglyceride metabolism could be used as alternative energy sources by S. violacea during hypoxic-environments. The juveniles classified as tolerant from both species have a lower RMR than non-tolerant fish, which is associated with reduction in their locomotor activity evidenced by decreasing tail beat frequency. Furthermore, the hypoxia-tolerant juveniles also reached a significantly higher size than non-tolerant fish. This work provides valuable results for the future S. lalandi and S. violacea industries, considering the effects of low OD in the farms. Likewise, the first evidence of the hypoxia adaptive mechanism of native fish are presented, providing scientific support for their aquaculture in Chile.

Effect of Rigor Stage and Pressurisation on Lipid Damage, Total Volatile Amine Formation and Autolysis Development in Palm Ruff Stored on Ice

The effect of the rigor stage (pre or post) and previous high-pressure processing (HPP; 450 and 550 MPa for 3 min) was checked during the storage on ice of farmed palm ruff (Seriolella violacea). Fish processed in pre-rigor conditions led to higher and lower levels (p < 0.05) of moisture and lipid contents in chilled fish, respectively, when compared to their counterpart samples processed in the post-rigor stage. Pre-rigor fish showed a higher (p < 0.05) quality level than post-rigor samples according to the assessment of the K value (59.0-92.1 and 70.3-96.3 ranges, respectively), fluorescent compounds (0.29-1.11 and 0.37-1.90 ranges, respectively), free fatty acids (FFA) (15.1-188.0 and 33.8-232.5 g·kg-1 lipids ranges, respectively), and total volatile amines (216.3-387.6 and 217.7-412.2 g·kg-1 muscle ranges, respectively). Pressure-treated fish showed higher (p < 0.05) quality retention than non-treated samples according to the formation of fluorescent compounds (0.29-0.86 and 0.85-1.90 ranges, respectively), FFA (15.1-50.6 and 58.9-223.5 g·kg-1 lipids ranges, respectively), and total volatile amines (216.3-250.3 and 351.1-412.2 g·kg-1 muscle ranges, respectively) and the evolution of the K value (59.0-77.2 and 86.9-96.3 ranges, respectively). The use of pre-rigor fish and previous HPP is recommended for the commercialisation of the current species as a fresh product.

High Abundance of Candidatus Arthromitus in Intestinal Microbiota of Seriolella violacea (Palm Ruff) under Reared Conditions

Intestinal microbiota has been involved in several processes that benefit the host, such as digestion, nutrient metabolism, resistance to pathogens colonization and immune function. In this study, we investigated the diversity, composition and functional prediction of microbiota of reared Seriolella violacea (palm ruff) in the same cohort sampled at different times (7-, 8- and 9-month-old). Microbial community structure analyses, using 16S rRNA amplicon sequencing, revealed that the intestinal microbiota was dominated by the phyla Firmicutes, Proteobacteria, Fusobacteria and Tenericutes. At the genus level, Candidatus Arthromitus was the most abundant in all sampled timepoints, representing in average 78% of the bacterial community (ranging from 18 to 98%), corresponding to segmented filamentous bacteria, which are interesting because they have been associated with the maturation of immune responses in the gut and protecting the host from bacterial infections. The comparisons of the intestinal microbiota among the three groups showed differences in abundance of bacterial taxa and also in alpha diversity indexes (Shannon and Simpson), as well as beta diversity metrics (weighted and unweighted UniFrac). Potential functions of the intestinal microbiota of palm ruff were retrieved using Philipin and Tax4fun and these analyses revealed high levels of genes for sugar metabolism. To our knowledge, this study represents the first description of the intestinal microbiota of S. violacea.

Mercury in fish tissues from the Galapagos marine reserve: Toxic risk and health implications

Fishing is one of the most important economic and cultural activities in Galapagos and Hg presence in aquatic ecosystems is a serious problem for human health, so its concentrations should be studied. We sampled five demersal species (Caulolatilus princeps, Caulolatilus affinis, Mycteroperca olfax, Hyporthodus mystacinus and Pontinus clemensi) and four pelagic species (Coryphaena hippurus, Acanthocybium solandri, Thunnus albacares and Seriolella violacea) to evaluate Hg concentration in muscle, liver and gonads. Hg was analyzed by Cold Vapor Atomic Absorption Spectrophotometry with Flow Injection System (CV-AAS-FIAS). Demersal species had higher Estimated Weekly Intakes (EWI) of Hg than pelagic species. According to the Codex Alimentarius (1995), EFSA (2018), FDA (2021) regulations, and according to the regulations in Europe, A. solandri, P. clemensi, and H. mystacinus were found above the maximum allowed concentration (MAC) (0.65, 0.65 and 1.26 mg/kg wet weight, respectively) so they could not be ingested nor commercialized. The Margin of Safety (MoS) of these species was above 1, so they could pose a risk to human health. We hypothesize that the Hg concentrations found in the studied species could come from the volcanism of the archipelago, since no major sources of anthropogenic Hg contamination can be found in the islands.

Swimming performance and physiological responses of juvenile Cojinoba Seriolella violacea in hypoxic conditions

Understanding environmental constraints and associated physiological adaptations of culture organisms is key for the implementation of off-shore grow-out facilities. In the southeast Pacific Ocean along the coasts of Chile and Peru, seasonal upwelling events lead to hypoxic conditions, which are projected to increase in both frequency and intensity with climate change. Aquaculture operations must take into account the physiological adaptability of a species for environmental conditions. For Cojinoba (Seriolella violacea), a native target species for aquaculture diversification in northern Chile, little is known in regard to physiological capacity for hypoxia. Therefore, hypoxia tolerance studies were conducted followed by measurement of resting and active metabolism and associated energy facilitation in response to hypoxia in juvenile Cojinoba. Hypoxia tolerance studies found they were resilient to dissolved oxygen levels of 1.0 mg O2 Lˉ1 for 8 h. Swimming metabolism studies exposed Cojinoba to normoxia (7.5 mg O2 Lˉ1) or hypoxia (1.0 mg O2 Lˉ1), and quantified minimum metabolic rate (MO2 min), active metabolic rate (MO₂ max), critical swimming speed (Ucrit) and associated energetic metabolites and hematological variables. In hypoxia, there was a decrease in MO₂ max (34%) leading to a large (82%) decrease in aerobic metabolic scope. MO2 min decreased as well by 12%, with lactate increasing presumably to temporarily maintain basic metabolic function. In addition, Ucrit decreased by 53% in hypoxia, although tail beat frequency was similar in normoxia and hypoxia up to a velocity of 40 cm s−1. Moreover, although erythrocyte concentration increased in hypoxia, hemolysis was observed in exercised fish in this condition. There was a notable increase (5-fold compared to normoxia) in lactate levels of exercised fish in the hypoxia group, which suggests a quick conversion to anaerobic metabolic pathways to maintain energy balance when swimming in hypoxic environments. Therefore, Cojinoba have adaptive responses that may facilitate survival during severe hypoxic events although overall physiological performance is diminished.

Cultivable Yeast Microbiota from the Marine Fish Species Genypterus chilensis and Seriolella violacea.

Because of its outstanding biological and industrial importance, many efforts have been made to characterize the mycobiota of new environments and their biochemical and biotechnological potentials. Gut mycobiota can be a source of novel yeasts with the potential to be used as probiotics or have industrial applications. In this work, we characterized two as-yet unexplored yeast communities from the intestinal content of the cultured marine Chilean fishes Genypterus chilensis (G. chilensis) and Seriolella violacea (S. violacea). Yeasts were isolated through culture, identified by sequencing their ITS region, and characterized their enzymatic profile with API®ZYM. Rhodotorula mucilaginosa was identified in both fish species. For the first time, Candida palmioleophila, Candida pseudorugosa, Cystobasidium slooffiae, and a member of the Yamadazyma genus were also identified and described as part of the normal fish gut–microbiota. Furthermore, the diverse enzymatic profile exhibited by some of these isolates suggests that it may be possible to develop novel applications for them, such as new probiotics and other biotechnological applications.

Metals in commercial fish in the Galapagos Marine Reserve: Contribution to food security and toxic risk assessment

Metal pollution in the marine environment can damage places with exceptional biodiversity such as the Galapagos Islands. For this reason, it is important to evaluate the toxic risk from metals derived from fish consumption and to perform a nutritional assessment. We sampled 20 individuals of demersal (Caulolatilus princeps and Mycteroperca olfax) and pelagic (Thunnus albacares and Seriolella violacea) species.The levels of the toxic elements (Al, B, Ba, Cd, Ni, Pb and Sr), and the macroelements, microelements and trace elements (Ca, Cr, Fe, K, Li, Mn, Mo, Mg, Na, V and Zn) of species muscle tissue were analyzed by Inductively Coupled Plasma Optical Spectrometry (ICP-OES).Demersal species have higher concentrations of Cr, K, Mg and Mo; while pelagic species have higher levels of Zn. M. olfax could potentially cause Cd toxicity so it is recommended not to ingest more than 86 and 73 g of this species (i.e. roughly, one serving) per week for men and women, respectively. None of the species could be marketed in Europe and the USA due to Cd level exceed the allowed limits by EFSA and FAO. Furthermore, the dietary intake of C. princeps is recommended due to its high concentration of Ca, Na, K, Mg and Cr, while T. albacares is recommended for people with Zn deficiency. However, due to the Cd level in C. princeps it is not recommended to ingest more than five servings per week. We attribute the source of metals in the studied fish from the volcanic origin of the islands rather than from human pollution. This is the first study that thoroughly estimate concentration of metals in commercial fish species and its contribution to food security in the Galapagos.

Physiological insights for aquaculture diversification: Swimming capacity and efficiency, and metabolic scope for activity in cojinoba Seriolella violacea

Aquaculture diversification is important for providing sustainable sources of food fish amidst changing environments, pathogens, economies, and market demand. Particularly for newly cultured species where information may be limited, optimization of culture practices relies on an understanding of the physiology and ecology of a species. The cojinoba (Seriolella violacea; Centrolophidae), a coastal pelagic marine fish, is a species of growing importance for aquaculture production in South America. Although methods for breeding and larval to juvenile rearing have been established, little is known about the physiology of this species. Therefore, measures of metabolism, swimming capacity and efficiency, red:white (R:W) muscle ratios, and associated aerobic and anaerobic biochemical parameters, such as plasma glucose and lactate, and muscle enzyme activities (i.e., pyruvate kinase, citrate synthase, electron transport system [ETS]), were measured. For cojinoba at 15 °C with mean body length (BL; total length) of 22 cm, critical swimming velocity (Ucrit) was approximately 80 cm/s or 3.8 BL/s, and optimal swimming velocity (Uopt) was 50 cm/s or 2.3 BL/s. Aerobic scope for metabolism was approximately 300 mg O2/kg/h, with Mo2 max 3.4 fold greater than standard metabolic rate. Swimming was facilitated by linear increases in tail beat frequency until burst and glide swimming initiated near Ucrit. At low velocities, large (~20% BL) pectoral fins were used for propulsion and maneuverability/maintaining equilibrium; beat frequency diminished rapidly with increasing velocity. Red:white muscle ratios at 50% BL and 75% BL (caudal peduncle) were comparable to other ectothermic species, with a greater proportion of red muscle in the caudal peduncle presumably corresponding to facilitation of sustained pelagic swimming. Plasma glucose and lactate were elevated at Ucrit by 20% and 45% respectively, indicating mobilization of anaerobic energy sources at fatigue. Aerobic enzyme activities were much higher in red muscle, the ratio of anaerobic:aerobic enzyme activity was higher in white muscle, and ETS activities decreased at fatigue in both red and white muscle. The cojinoba has a moderate metabolic rate compared to other pelagic species, displays shoaling behavior, is maneuverable at low velocities due to pectoral fin use, but has optimal swimming efficiencies at higher velocities. These factors are beneficial for designing culture systems to promote exercise benefits for growth and welfare.

Cytogenetic characterization, rDNA mapping and quantification of the nuclear DNA content in Seriolella violacea Guichenot, 1848 (Perciformes, Centrolophidae).

Seriolella violacea Guichenot, 1848 is an important component of the fish fauna of the Chilean coast and is of great economic interest. Cytogenetic information for the family Centrolophidae is lacking and the genomic size of five of the twenty-eight species described for this family are is barely known. This study aimed to describe for the first time the karyotype structure via classical and molecular cytogenetics analysis with the goal of identifying the constitutive heterochromatin distribution, chromosome organization of rDNA sequences and quantification of nuclear DNA content. The karyotype of S. violacea is composed of 48 chromosomes, with the presence of conspicuous blocks of heterochromatin on chromosomal pairs one and two. FISH assay with a 5S rDNA probe, revealed the presence of fluorescent markings on the heterochromatic block of pair one. The 18S rDNA sites are located exclusively on pair two, characterizing this pair as the carrier of the NOR. Finally, the genomic size of S. violacea was estimated at 0.59 pg of DNA as C-value. This work represents the first effort to document the karyotype structure and physical organization of the rDNA sequences in the Seriolella genome, contributing with new information to improve our understanding of chromosomal evolution and genomic organization in marine perciforms.

Morphofunctional characterization of the digestive system in the palm ruff larvae, Seriolella violacea under culture conditions

In the present study, the histological changes and digestive enzymatic activity patterns are described during the larval development of palm ruff, Seriolella violacea from hatching up to 50 days after hatching (DAH). At hatching, the digestive tract consisted of an undifferentiated straight tube dorsal to the yolk-sac, which presented alkaline protease activity (trypsin and chymotrypsin) as well as amylase and lipase activities with similar patterns during larval development. At 20 and 23 DAH, histology of the stomach revealed a sac-like shaped organ, with an epithelium that began to differentiate in a cardiac and a pyloric region. Typical histological structures of a stomach were visible at 33 DAH with a concomitant pepsin activity. Gastric glands were clearly visible at 35 DAH, increasing in numbers up to 37 DAH, suggesting a functional stomach at this age. A significant increase in the specific activity of all enzymes including pepsin (except amylase) was observed between days 33–35 DAH, which suggests a complete maturation of the digestive system in S. violacea larvae. Total activity from all the different enzyme activities followed the same trend as the specific activity. Based on the results from this study it might be feasible to begin weaning this species at 35 DAH, thereby reducing the amount of live food in the current protocol used which initiates weaning 45 days.

Capture, swallowing, and egestion of microplastics by a planktivorous juvenile fish

Microplastics (<5 mm) have been found in many fish species, from most marine environments. However, the mechanisms underlying microplastic ingestion by fish are still unclear, although they are important to determine the pathway of microplastics along marine food webs. Here we conducted experiments in the laboratory to examine microplastic ingestion (capture and swallowing) and egestion by juveniles of the planktivorous palm ruff, Seriolella violacea (Centrolophidae). As expected, fish captured preferentially black microplastics, similar to food pellets, whereas microplastics of other colours (blue, translucent, and yellow) were mostly co-captured when floating close to food pellets. Microplastics captured without food were almost always spit out, and were only swallowed when they were mixed with food in the fish's mouth. Food probably produced a ‘gustatory trap’ that impeded the fish to discriminate and reject the microplastics. Most fish (93% of total) egested all the microplastics after 7 days, on average, and 49 days at most, substantially longer than food pellets (<2 days). No acute detrimental effects of microplastics on fish were observable, but potential sublethal effects of microplastics on the fish physiological and behavioural responses still need to be tested. This study highlights that visually-oriented planktivorous fish, many species of which are of commercial value and ecological importance within marine food webs, are susceptible to ingest microplastics resembling or floating close to their planktonic prey.

Effect of high hydrostatic pressure treatment on physical parameters, ultrastructure and shelf life of pre- and post-rigor mortis palm ruff (Seriolella violacea) under chilled storage

To identify processing conditions that better maintain palm ruff quality attributes, high hydrostatic pressure (HHP) was applied to pre- and post-rigor fillets. Physical parameters as whiteness index (WI), water holding capacity (WHC), texture and ultrastructure and shelf life were evaluated after the application of 450 and 550 MPa (3 and 4 min) and during cold storage. Pre-rigor fillets retained less water and were softer than post-rigor, although the onset of rigor increased palm ruff's WHC and firmness. Application of HHP whitened palm ruff's dark flesh; however, this effect reverted at the end of the storage. Pressurized post-rigor samples retained less water than the control and storage caused a WHC increase in samples pressurized at 550 MPa, independent on the rigor condition. Post-rigor fillets softened at pressures of 450–550 MPa appearing to have a lower threshold than beef or cod (above 600 MPa). Ultrastructural changes revealed a subtle contraction (7.4%) of the myofibrils in the unpressurized post-rigor muscle compared to pre-rigor; after 26 days' storage both samples presented extensive muscle degradation and sarcomere length was reduced in 30%. HHP induced pressure-dependent shortening of the sarcomere and modifications to the structure which after 550 MPa was hardly recognizable. After 26 days' storage, there was only slight degradation of the ultrastructure, showing that beyond the structural modifications caused by HHP, post-mortem deterioration is delayed in HHP-treated fillets. Furthermore, HHP extended palm ruff's shelf life to 14–23 days. Thus, HHP may be considered as a technology that maintains the textural quality and shelf life of fresh and stored fish.

Effects of High Pressure Treatment on Physicochemical Quality of Pre- and Post-Rigor Palm Ruff (Seriolella Violacea) Fillets

ABSTRACTFish and fish products are characterized for having a short shelf life. Nonthermal processing techniques such as high hydrostatic pressure (HHP) have increasingly been employed to extend shelf life of food products. The aim of this study was to evaluate changes on flesh physicochemical spoilage parameters (pH, total volatile bases (TVB-N), trimethylamine (TMA), thiobarbituric acid (TBA), and color) of palm ruff (Seriolella violacea) fillets in pre- and post-rigor conditions, subjected to two different HHP conditions: 450 MPa and 550 MPa, for 3 and 4 min each. Unpressurized and pressurized fillets were kept in chilled storage (4 ± 1°C) for 26 days to assess the effect of HHP on shelf life. pH and TBA values increased after HHP treatment and with storage time for both unpressurized and pressurized samples. This is attributable to pressure-induced lipid oxidation. Lightness (L*) values increased with pressure, where fish fillets had a cooked appearance. TMA and TVB-N values decreased after HHP treatment compared to the unpressurized samples, showing that HHP treatment is an efficient method to maintain the quality of palm ruff fillets. There was no clear difference between pre- and post-rigor in the parameters evaluated.

Survival and Growth Improvement of Palm Ruff, Seriolella violacea, Larvae Fed Artemia Nauplii Enriched with an Experimental Emulsion

AbstractThe palm ruff, Seriolella violacea (Cojinoba), is a potential new species for Chilean aquaculture. To approach Cojinoba larviculture, an experimental Artemia enrichment emulsion, containing docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) = 2.5, supplemented with vitamin E, astaxanthin, and β‐glucan, was evaluated in both Artemia and Cojinoba larvae, 30–50 d.a.h. This study tested an experimental enrichment emulsion versus a commercial emulsion, with an integral approach of multicompound emulsions. After 23 h enrichment, experimental emulsion (EE)‐enriched nauplii reached DHA and EPA concentrations of 23.8 and 18.7 mg/g dry weight (dwt), respectively, while in Cojinoba larvae they were 18.4 and 19.7 mg/g dwt. Control emulsion (CE)‐enriched nauplii exhibited lower DHA and EPA (6.1 and 7.7 mg/g dwt), while only DHA decreased in the control larvae (12.6 mg/g dwt). Vitamin E was higher in EE‐enriched nauplii (29.2 mg/100 g dwt) than in the control (8.4 mg/100 g dwt). Larvae fed EE‐enriched Artemia exhibited 8% increase in survival and 19% in growth compared with the control. Astaxanthin was detected only in larvae fed EE‐enriched nauplii. The tumor necrosis factor‐α concentration was not significantly different between larvae fed EE‐ and CE‐enriched nauplii. EE looks promising as an Artemia enrichment and experimental diet to assess palm ruff larval requirements, and has a positive impact on fish larvae performance.

Cranial osteological development and abnormalities in northern palm ruff, Seriolella violacea (Guichenot, 1848), larvae and juveniles

Seriolella violacea, a new species to be potentially farmed in Chile and Peru, has shown cranial malformations during farming that could adversely affect its commercial development. This study seeks to generate early knowledge of the osteological development and type of cranial abnormalities that this species presents under culture conditions. Larvae from wild caught broodstock were reared from 1 to 60 days post hatching (DPH) (4.8 ± 0.1 mm TL and 11.8 ± 1.0 mm TL respectively). Larvae samples were collected throughout the experimental trial for recording cranial osteological development and abnormalities in cartilage and bone. At 5.7 ± 0.1 mm TL, coraco-scapular, sclerotic, ethmoid plate and quadrate cartilages were present. At 8.0 ± 0.6 mm TL, early ossification was observed in the jaw, premaxilla and maxilla. At 11.8 ± 1.0 mm TL, the branchiostegal rays, jaw, maxilla and opercular complex were ossified. The first cartilaginous structures observed were the Meckel's cartilage, the branchial arches and the suspensory ligament. The first cranial malformations were detected at 5.7 ± 0.1 mm TL, coinciding with mouth opening. The most frequent malformations were a curvature of the lower jaw (23.1%), abnormal separation between branchial arches and the Meckel's cartilage (19.4%) and bulging jaws (15.7%).

Effect of two temperatures on yield and increase in cranial skeletal abnormalities during early development of palm ruff,Seriolella violacea(Guichenot 1848)

The present study evaluates the effect of two temperatures, 14°C (T14) and 18°C (T18), on yield and the presence of cranial abnormalities during early development in north palm ruff (Seriolella violacea). Different time indices – days post-hatching (DPH), degree-days (D°) and effective degree-days (D°eff) – were used to analyse growth during cultivation. Several ontogenetic events were achieved in less time during cultivation at 18°C. Additionally, a larger total length and final weight, as well as a higher survival rate, were achieved after 80 days of culture at higher temperatures (T18 = 55.5 ± 1.5 mm; 2.87 ± 0.21 g; 1.80 ± 0.18% and T14 = 24.3 ± 2.2 mm; 0.26 ± 0.08 g; 1.33 ± 0.12%). D° and D°eff were valid as independent temperature indices for predicting the growth response of S. violacea against thermal variations. The frequencies of cranial skeletal abnormalities (mouth and opercular complex) were evaluated in the pre-flexion, flexion, post-flexion and juvenile stages. However, the frequency of cranial skeletal abnormalities at the end of this study was not significantly influenced (P > 0.05) by temperature, and values below 21% were recorded in both treatments. These results can be of practical use for optimizing culture conditions to maximize the yield and quality of S. violacea juveniles.

Protein Changes Caused by High Hydrostatic Pressure (HHP): A Study Using Differential Scanning Calorimetry (DSC) and Fourier Transform Infrared (FTIR) Spectroscopy

The aim of this study was to evaluate the effect of HHP and rigor state on palm ruff (Seriolella violacea) muscle proteins. HHP treatments were performed at 450–550 MPa for 3 and 4 min at 15 °C. Protein secondary structure was evaluated by using Fourier transform infrared spectroscopy, and the thermal behavior was evaluated by using differential scanning calorimetry. The results showed that HHP treatments reduced α-helix and increased β-sheet in fish protein structures. Throughout the 35-d storage period, secondary structures in HHP samples changed depending on pressure intensity, holding time, and rigor state. The thermograms of palm ruff muscles showed four endothermic transitions in prerigor state and three in postrigor state. The HHP treatment affected thermal stability of myosin protein, which is reflected in the change of denaturation temperature (Td) and a decrease in denaturation enthalpy (ΔHd) with respect to the native protein; actin was denatured by the pressure treatments. In conclusion, rigor state and HHP affected protein structure of fish proteins.

The role of hyperiid parasites as a trophic link between jellyfish and fishes

The trophic interactions between the scyphozoan medusa Chrysaora plocamia and the palm ruff Seriolella violacea were investigated off northern Chile and showed that large numbers of hyperiid amphipods parasitizing the medusa may channel energy back to the fishes, which feed on the parasites. The biomass of hyperiids eaten by the fish was a function of the biomass of hyperiids parasitizing the medusa. This temporally available food supply may enhance fish recruitment. The large number of hyperiids parasitizing diverse jellyfish species represents a missing trophic link in current efforts to understand the effects of jellyfish blooms on marine food webs.

Effects of two temperatures on the oxygen consumption rates of Seriolella violacea (palm fish) juveniles under rearing conditions

Oxygen consumption rates (mg O2/kg fish/min; OC) of juvenile palm fish (average weight 420g) were determined for temperatures of 14 and 18°C. Three replicates of two tanks rearing fish at a density of 24kg/m3 were used to measure OC at 34ppt working as open respirometers in a recirculating system under farm-like conditions. The fish were fed commercial dry pelleted feeds at a ratio of 1% of total biomass. Oxygen consumption rates were determined by mass balance calculations. The OC increased from 1.6 to 2.4g O2/kg fish/day as temperature increased from 14 to 18°C. The determination of oxygen consumption by palm fish in farm-like conditions provides valuable information on the oxygen requirement of these fish in an aquacultural setting. This bioengineering information can be used for designing and sizing a rearing facility for the intensive culture of palm fish.

Effect of two temperatures on ammonia excretion rates of Seriolella violacea (Palm fish) juveniles under rearing conditions

Nitrogenous compounds can be toxic to aquatic animals, especially when they are reared for production purposes at high stocking densities. Seriolella violacea is a pelagic fish, native from the easterly South Pacific Ocean. This species has shown desirable behavioral and metabolic characteristics under captivity conditions, which leaded the Marine Fish Laboratory from the UCN to increase its efforts on the research and development to validate S. violacea as a new aquaculture option. Therefore, the objective of this study is to determine the excretion rates of palm fish juveniles weighing 300–500 g at two different temperatures: 14 °C and 18 °C. Total ammonia as nitrogen (TAN) excreted was 4.4 ± 0.9 and 7.1 ± 1.9 mg TAN/kg fish/h for 14 °C and 18 °C respectively. The experiments were carried out in a recirculating system operating as a farm-like situation. Tests were performed in 1000 L rearing tanks operating as open respirometers. The results of the present study indicate that TAN excretion rates on S. violacea juveniles, is temperature dependent. Data obtained in these experiments are valuable information for the engineering design of land based aquaculture systems for palm fish.