Eduardo Esteves

Status of the Guadiana Estuary (south Portugal) during 1996-1998: An ecohydrological approach

The aims of this study were to monitor basic hydrological and ecological characteristics of the Guadiana Estuary (1996-1998) before the construction of the Alqueva dam. This work was carried out to determine how environmental factors affect seasonal and tidal variations of plankton populations in the estuary. The available information on the subcatchment of the estuary (e.g., urban, agricultural and forested areas) was integrated into a geographic information system-based software program. Mean monthly river flow varied markedly on a seasonal and yearly basis. River flow near Mértola (ca 50 km upstream from the mouth) reached 3400 2 10 6 m 3 in winter and decreased to 42 2 10 6 m 3 in summer. With respect to nutrients, nitrogen to phosphorus ratios indicated some limitation by phosphorus, except at the end of summer, when nitrogen limitation appeared. During this period, cyanobacterial blooms usually occurred in the upper/middle estuary. Estuarine Turbidity Maximum may significantly influence the retention of zooplankton in the estuary. The fish larval life cycle, especially sensitive to environmental alterations, showed high ratios of ribonucleic to desoxyribonucleic acids indicating good physiological condition. It was concluded that an ecohydrological approach, allowing integration of different elements from the cellular to the habitat level into a geographic information system, can contribute to a better understanding of the processes that influence the aquatic biota of the estuary. The approach will be a useful assessment tool for monitoring the estuary following dam completion.

The distribution of estuarine fish larvae : Nutritional condition and co-occurrence with predators and prey

Fish larvae were collected monthly between March and September 1997 in the Mira and Guadiana estuaries (southern Portugal). Hydrological parameters were registered and zooplankton samples were obtained simultaneously. Densities of fish larvae (ind·100 m -3 ) were calculated from 211 samples and larval nutritional condition measured as RNA/DNA ratios were obtained for 346 individuals, using a fluorimetric method for nucleic acid quantification. Correlating variables were further studied using multiple regression analysis in order to assess the relative importance of abiotic and biotic factors affecting within-year trends in abundance and nutritional condition of estuarine fish larvae. Results indicated that: 1) the abundance of fish larvae seems conditioned by temperature and predation; and 2) their nutritional condition is dependent on temperature and prey availability. Temperature is an important variable structuring estuaries and therefore conditions the behaviour and physiology of fish larvae. Furthermore, the co-occurrence of predators and larvae might be related to similar feeding patterns or comensalism. Whenever feeding conditions are suitable, they usually determine enhanced growth and nutritional condition. However, predation seems to control this latter relationship through its effect on larval mortality.

Comparison of RNA/DNA ratios obtained with two methods for nucleic acid quantification in gobiid larvae

In this paper, RNA and DNA contents and RNA/DNA ratios obtained with two fluorometric methods for the extraction and quantification of nucleic acids in individual estuarine gobiid larvae are compared. A total of 141 gobiid larvae, collected in the Mira and Guadiana estuaries (Portugal), were analysed. This study indicated that the nucleic acids content and RNA/DNA ratios of individual larvae varied with the procedure used. The two methods yielded similar log DNA values but different log RNA and log (RNA/DNA). The differences could be due to a number of factors related to specific steps of tested protocols. Comparison of nucleic acids contents and calibration of the two methods by regression analysis provided a reasonable basis for comparison although differences between estimates were evident.

Seasonal Variations in Gross Biochemical Composition, Percent Edibility, and Condition Index of the Clam Ruditapes decussatus Cultivated in the Ria Formosa (South Portugal)

ABSTRACT The grooved carpet shell clam Ruditapes decussatus (L. 1758) is one of the most popular and profitable molluscs exploited in rearing plots in the Mediterranean. However, annual catch has been declining steadily since the early 1990s. To understand the seasonality of its nutritional value, thus providing an improved basis for economic valuation of the resource, gross biochemical composition, percent edibility, and condition index were investigated during a year with monthly periodicity in a commercially exploited population of the clam R. decussatus in the Ria Formosa, a temperate mesotidal coastal lagoon located in the south of Portugal. Our results show that total and nonprotein nitrogen covaried during the year, resulting in a protein content that peaked in the warmest months. Although complementary in summer, carbohydrate and lipid contents showed irregular annual trends. The observed seasonality was comparable with that shown by studies elsewhere at similar latitudes, and is underpinned by the reproductive cycle of the species. Our results show the clams to be at their prime nutritional value at the beginning of summer, when protein content peaks.

Age and growth in the Alfonsino, Beryx splendens (Berycidae) from the Azores (central eastern Atlantic)

Abstract Age was determined in the Alfonsino, Beryx splendens, by counting the opaque rings on the anti‐sulcal surface of left sagittae obtained from specimens, 15–43.5 cm fork length (FL), caught off the Azores. Females were from 1 to 12 years old and males were 1 to 9 years old. Von Bertalanffy (VB) growth equations were fitted to data obtained from age‐length keys, back calculation, and length‐frequency analyses. Growth was compared between sexes and among methods. Growth was similar in males, whereas in females the equations derived from length‐frequency analysis overestimated length‐at‐age relative to other methods. Sex specific growth could not be confirmed.

Portable Device for Touch, Taste and Smell Sensations in Augmented Reality Experiences

The purpose of this work is to present a portable hardware device that can provide touch, taste and smell sensations to an augmented reality experience. The proposed hardware is part of a mobile five senses augmented reality system for Museums, to improve and augment, as much as possible, the visiting of a museum, i.e., see, ear, touch, feel and experience all its interesting objects. The existing solutions related to the augment of sensing experiences consist of big hardware systems and they are far from being portable. In this work, a new small and portable device is presented, to integrate and connect with the user’s smartphone to provide the complete five-sense experience. The implemented device adds to the complete augmented system, the touch, smell and taste experiences. Moreover, the device is flexible enough to adapt itself to different sizes of the user’s smartphone or tablet. It is powered by a rechargeable battery, which gives the module the ability to keep the system running during the visit of the museum. The core unit is a microcontroller, it receives instructions from the mobile application in the user’s smartphone and acts accordingly, controlling the remaining hardware of the portable device to deliver the five-sense experience to the user. The communication between the device and the mobile application is possible through wireless communication, using a Bluetooth interface. The communication with the remaining module, denoted here as physical interfaces, will be wired. Preliminary results of device’s first prototype are also presented in this paper.

A sensory and nutritional comparison of mussels (Mytilus sp.) produced in NW Iberia and in the Armona offshore production area (Algarve, Portugal)

A biometric, nutritional and sensory analysis of raw and cooked mussels comparing Mytilus sp. from the north-west coast of Portugal and Spain (Minho and Galicia, respectively) and the new offshore production site of Armona (Algarve, south Portugal) was carried out. In addition, multiple factorial analysis was performed to explore potential relationships between sensory attributes and nutritional content properties between the different mussels. Results showed that, at similar times of sale, biometrics of mussels from Armona and Vigo were similar and bigger than the remaining. Nonetheless, despite some similarities in proximate composition, mussels presented differences in lipid classes, fatty acid content and free amino acids profiles. These differences were not fully reflected in the sensory assessment by the panel, which were able to distinguish different production sites in raw specimens but displayed problems in discrimination these in cooked mussels. Some nutritional components were related to specific sensory sensations.

Physicochemical and Microbiological Changes in Dried Small-Spotted Catshark (Scyliorhynus canicula): Contributing to the Developing an Alternative Shark-Based Salted-Dried Seafood Product

ABSTRACT Our aim is to contribute to the valorization and optimization of a salted-dried seafood product prepared from small-spotted catshark (Scyliorhynus canicula) akin to “litão seco,” the high-priced, traditional dried blackmouth catshark (Galeus melastomus). This work focused on studying the changes in physicochemical and microbiological parameters of S. canicula salted (for 3 h or 24 h) and dried (convection oven for 24 h or tray drier for 3 h). As expected, salting and drying reduced the water content and water activity, while chloride content in fillets increased. Also, significant but distinct changes in color, namely CIE L* and b*, were observed. Total viable counts were significantly reduced in the salted-dried shark, but the later still presented Staphylococcus aureus, though at marginally acceptable, non-hazardous levels. The abundance of yeasts was reduced by 3 log(cfu/g) in samples oven-dried for 24 h but only by 0.8 log after 3 h in the tray-drier. From our results, salted-dried S. canicula has the required physicochemical characteristics and microbiological quality to be apt for human consumption and is a suitable candidate for becoming a traditional seafood product comparable to “litão seco.”

Freshness and Nutritional Composition of Several Species of Chilled Seafood Marketed in Luanda (Angola) and in Faro (Portugal)

Given that the chemical composition of seafood species reflects the conditions characterizing their geographic area of origin, this study aims to describe and compare the nutritional composition of several seafood species marketed in Luanda (Angola) and in Faro (Portugal), namely octopus (Octopus sp.), large-eye dentex (Dentex macrophthalmus), hake (Merluccius sp.) and barracuda (Sphyraena guachancho). In addition, a sensory-based methodology (the Quality Index Method, QIM) was carried out and a set of physicochemical parameters (pH, total volatile basic nitrogen (TVBN) and thiobarbituric acid reactive substances (TBARS)) were determined to assess the degree of freshness and quality of the different species. The results showed that location significantly (t-test, p < 0.05) influences some parameters of the nutritional composition, viz. moisture, protein content and lipid content. Quality indexes (QI) resulting from sensory analyses using QIM schemes were less than five (out of a maximum of 16–19 demerit points) indicating seafood’s high quality. In terms of physicochemical quality parameters, the values of pH varied between 6.11 for octopus and 6.78 for large-eye dentex, TVBN content ranged from 5.4 mg N/100 g for octopus and 9.6 mg N/100 g for barracuda in Luanda, and TBARS concentrations varied between 0.43 mg MDA/kg for large-eye dentex in Faro and 2.09 mg MDA/kg for hake in Faro. For every species studied the values were well below acceptable limits for consumption considering EU regulations (25–35 mg N/100 g for TVBN) and literature (7-8 µg MDA/g for TBARS), both in Luanda and in Faro. This study provides original results about nutritional composition and sensory and physicochemical indicators of seafood freshness and quality for the studied species in Luanda.

Effects of Spoilage on Nitrogen and Carbon Stable Isotopes Signatures of the Clam Ruditapes decussatus

Fish and seafood products are highly susceptible to post-mortem spoilage due to autolytic reactions at start, then microbiological activity and eventually oxidative reactions. Chemical and microbiological parameters are usually used to assess quality and make decisions for protecting public health, but they lack precision in defining which spoilage pathway is occurring at each moment. The objective of this work was to assess the effects of spoilage reactions on nitrogen and carbon stable isotopes in the grooved carpet shell clam, Ruditapes decussatus, and compare them to biochemical indicators of seafood deterioration, in order to better understand the relations between the different spoilage pathways during commercial storage conditions. Clams were kept in a refrigerator at 5 °C, to simulate normal commercial storage conditions, and sampled in the beginning of the experiment, and after eight, ten and twelve days. Moisture, condition index, percentage edibility, total volatile basic nitrogen (TVB-N), pH, nitrogen and carbon percentages and stable isotopes were determined for each sampling moment. Stable isotope analyses were performed using a Costech Elemental Analyzer (ECS 4010) coupled to a Thermo Finnigan Delta V Advantage. Stable isotopes analysis, especially for nitrogen, proved to be a good tool for the study of clam deterioration. Nitrogen stable isotopes results showed a relation with other spoilage indicators, such as pH and TVB-N, and allowed identifying spoilage specific pathways, such as amino acids decarboxylation and production of volatile nitrogen compounds.