Showing papers in "Acta Adriatica in 2012"

Seasonal changes in proximate composition of anchovy (Engraulis encrasicolus, L.) from the central Adriatic

Abstract: The chemical composition of fish varies greatly depending on the starvation and intensive food intake periods and other external factors such as sea temperature. The seasonal changes define the application of different technological processes and are an aspect of quality of raw material, sensory attributes and storage stability. The results of monthly proximate composition analysis of the edible portion of anchovy were investigated over a period of two years. The average proximate composition of anchovy caught in the Adriatic Sea was as follows: water content 76.52 ± 1.38 %, protein content 21.34 ± 0.29 %, fat content 2.27 ± 1.20 %, ash content 1.42 ± 0.08 %. Protein and ash content showed small annual variations and differences within months were mostly insignificant. The fat and water content showed significant seasonal changes and a very strong negative correlation between fat and water content was observed (r = - 0.947). The fat content varied from 0.86 to 4.47 %, with a minimum in February and maximum in October. There was a statistically significant relationship between fat and water content at the 99% confidence level, indicating that this relation could be used to estimate fat content based on the analytical determination of water content.

Environmental drivers of zooplankton variability in the coastal eastern Adriatic (Mediterranean Sea)

Abstract: The objectives of this paper were to determine the main environmental drivers of zooplankton variability in coastal waters adjacent to urban areas and to evaluate the differences in zooplankton abundance and population structure in relation to chemical and biological parameters in the water column Samples were collected seasonally from May 2006 to January 2009 at 8 sampling sites in the bays and channels along the eastern Adriatic coast Zooplankton population structure showed high similarity within the investigated region, especially evident in the homogeneity of copepod community composition, where relative importance of the individual species showed characteristic high ranking of small and medium-sized taxa Zooplankton numerical variability primarily responded to seasonal variation in water temperature and spatial variation in salinity, but spatial distribution of the collected data showed that abundances were also linked to chemical and biological parameters generally used as descriptors of water quality This indicates that zooplankton community size reflects the trophic status of an area and supports the use of zooplankton studies as an auxiliary method in the evaluation of the trophic state of coastal waters

Pelagic cnidarians in the Boka Kotorska Bay (Montenegro, South Adriatic)

Abstract: Planktonic cnidarians were investigated at six stations in the Boka Kotorska Bay from March 2009 to June 2010 by vertical hauls of a plankton net from bottom to surface. In total, 12 species of hydromedusae and six species of siphonophores were found. With the exception of the instant blooms of Obelia spp. (341 ind. m-3 in December), hydromedusae were generally less frequent and abundant: their average and median values rarely exceed 1 ind. m-3. On the contrary, siphonophores were both frequent and abundant. The most numerous were Muggiaea kochi, Muggiaea atlantica, and Sphaeronectes gracilis. Their total number was highest during the spring-summer period with a maximum of 38 ind. m-3 observed in May 2009 and April 2010. M. atlantica dominated in the more eutrophicated inner area, while M. kochi was more numerous in the outer area, highly influenced by open sea waters. This study confirms a shift of dominant species within the coastal calycophores in the Adriatic Sea observed from 1996: autochthonous M. kochi is progressively being replaced by allochthonous M. atlantica in the coastal waters, especially in the eutrophicated areas. This study provides a detailed report on the composition and abundance of the planktonic cnidarians community in this region, and should be considered as a baseline for future studies on gelatinous zooplankton.

Molecular identification of the brown algae, Cystoseira spp. (Phaeophycae, Fucales) from the Adriatic Sea – preliminary results

Abstract: In the attempt to identify an appropriate molecular marker which will enable genetic distinction between different Cystoseira species from the Adriatic Sea, two mitochondrial molecular markers were tested: the mt 23S rDNA and the mt23S-tRNAVal spacer. Two species were studied: Cystoseira spinosa and Cystoseira squarrosa. Sequence analyses showed no variation in the mt 23S rDNA among all individuals analyzed. But the analysis of the mt23S-tRNAVal spacer showed a differentiation between three haplotypes named A, B and C. The most abundant haplotype A was found in equal number in both species, while haplotype B was found only in C. spinosa and haplotype C was found in C. squarrosa only. However, when comparing to sequences available for several selected Mediterranean Cystoseira species, the mt23S-tRNAVal spacer failed to discriminate between species. Although these results indicate a limited use of the mitochondrial mt23S-tRNAVal intergenic spacer for discrimination among Adriatic Cystoseira species, they could also be interpreted as a sign of conspecificity of the investigated species or the reflection of a recent radiation. Further analysis will be necessary to improve molecular identification of these brown algae.

Spectral reflectance profile of Caulerpa racemosa var. cylindracea and Caulerpa taxifolia in the Adriatic Sea

Abstract: The invasive algae in the Mediterranean Caulerpa taxifolia and Caulerpa racemosa var. cylindracea have gained much interest in the Adriatic Sea due to their fast spread and negative impacts on native seaweed species. Lack of accurate mapping and its overall high costs present some of the major difficulties for successful detection and subsequent environmental management. Remote sensing techniques could provide a quicker, more accurate and more cost efficient approach to mapping these invasive species. In order to allow for classification of remotely sensed data, we have collected and analyzed hyperspectral reflectance profiles of both invasive Caulerpa species in the Adriatic and the native Caulerpa cf. laetevirens species from the southeastern Atlantic coast of the United States. We have measured distinctive spectral features for spectroscopically distinguishing between these species, which is particularly interesting in the areas where these native and invasive species coexist. The initial results suggest that it might be possible to distinguish between the species based on their spectral reflectance profile. These results would have to be verified with samples taken from more populations in different phenological phases of the seaweed growth and other environmental conditions.

Zooplankton composition and distribution across coastal and offshore waters off Albania (Southern Adriatic) in late spring

Abstract: We present for the first time composition, numerical abundance and vertical structure of micro- and mesozooplankton in the Albanian coastal and open sea region. Zooplankton was sampled at six stations on the 75-km long continental shelf slope transect in May 2009. The most numerous microzooplankton were copepod nauplii (maximum: 39 ind. L-1), followed by calonoid and cyclopoid copepodites (maxima: 5 and 4 ind. L-1, respectively). The most abundant of fourteen tintinnid species was Tintinnopsis radix, found in the surface to 50 m layer. The species composition of the coastal and open sea mesozooplankton was similar to that previously reported for the south Adriatic Sea. The copepod Oithona similis was the dominant species at all stations, followed by Oithona plumifera, Acartia clausi, Paracalanus parvus, Oithona nana and Cyclopoida-oncaeids at the shallower coastal stations, and Clausocalanus pergens, Oithona plumifera and Oithona nana offshore. Mesozooplankton diversity rose considerably from the coast to the open sea. Mesozooplankton abundance exhibited the opposite trend, with the maximum (2286 ind. m-3) noted at the shallowest station. Findings of typically open sea tintinnid and copepod species at the coastal station indicate the high influence of currents from the open sea area during our investigation. Our results suggest the low influence of fresh water on zooplankton population densities, even at the shallow stations where penetration of fresh water in the surface layers was notable.

Inshore versus offshore length distribution of round sardinella (Sardinella aurita) in the middle eastern Adriatic Sea

Abstract: Round sardinella, Sardinella aurita specimens (N= 2, 033) were caught in inshore (Virsko more) and offshore waters (Dugi otok) of the eastern middle Adriatic Sea by commercial purse seine, monthly from November 2007 to January 2009. Out of all specimens, 983 were male (48.4%), 1, 021 were female (50.2%) and 29 (1.4%) were undetermined specimens, giving an overall sex ratio of m/f=0.96. Round sardinella specimens from inshore waters (N=526) and offshore waters (N=1, 507) showed total length (LT) range 13.0-32.5 cm and 10.0-30.0 cm, respectively. In total, they showed positive allometry (b=3.2266). Fulton’s mean condition factor for round sardinella from inshore waters was =0.76 ± 0.23, and for samples from offshore waters, it was =0.73 ± 0.05. Females indicated better condition ( =0.75 ± 0.05) in both analyzed areas than males ( =0.74 ± 0.05).