Southwestern Mediterranean Sea Research Articles

Body morphometric and otolith shape analyses of anchovy (Engraulis encrasicolus (Linnaeus, 1758)) in the Algerian basin

Body morphometric characteristics and otolith shape described by elliptic Fourier descriptors analyses were carried out on European anchovy (Engraulis encrasicolus) samples collected from six locations in Algerian waters during the acoustic survey ALPEL2018 (south-western Mediterranean Sea, GFCM-GSA04). The discriminant analysis was applied over twelve morphometric body distances and 31 normalized elliptic Fourier descriptors. It highlighted significant difference between areas but with high overlapping. No significant difference was detected between males and females, or right and left otoliths. Hierarchical clustering analysis conducted on the mean form of body and otolith shape showed a clear geographical cline. The results indicate that the geographical trend is present with a high level of overlapping between the near areas, suggesting that European anchovies in Algerian waters are not completely isolated.

Review of the toxic trace elements arsenic, cadmium, lead and mercury in seafood species from Algeria and contiguous waters in the Southwestern Mediterranean Sea.

An assessment is made of published data on concentrations of four toxic trace elements arsenic (As), cadmium (Cd), lead (Pb), mercury (Hg), and methyl mercury (MeHg) in seafood species from Algerian coastal waters. The data relate mainly to fish and mollusks, with Pb and Cd being the most studied elements. In contrast, no studies were found for As and MeHg in mollusks and crustaceans, and none for total Hg in crustaceans. Data analysis has shown that the element concentrations depend on the element analyzed, in particular its chemical form, and they vary with the species studied and the area where the organisms were sampled. As concentrations in muscle of sardine (Sardina pilchardus) from the eastern zone (Bejaia) (2.98mgkg-1 wet weight), Pb in muscle of tuna (Euthynnus alletteratus) (0.49mgkg-1 wet weight) from the western region (Mostaganem) and in muscle tissue of the mussel (Mytilus galloprovincialis) (10.67mgkg-1 dry weight) from Oran all exceed the threshold risk limits set by national and international regulations. Given these findings, to guarantee seafood safety for the Algerian consumer, it is recommended to carry out monitoring of these trace elements in seafood species caught along the Algerian coast, particularly the most consumed fish, i.e., sardines, and predators such as swordfish and tuna which can accumulate high concentrations of toxic metals, particularly Hg. Obtaining a regional assessment based on similar analyses from Tunisia and Morocco was severely hampered since few similar species or taxonomic groups were analyzed in all three countries.

Multiple records and polymorphism of Parastichopus regalis (Cuvier, 1817) (Echinodermata: Holothuroidea: Stichopodidae) along the Algerian coast.

The family Stichopodidae is represented in the Mediterranean Sea by the genus Parastichopus which includes two non-endemic species; Parastichopus tremulus (Gunnerus, 1767) and Parastichopus regalis (Cuvier, 1817). On the Algerian coast (southwestern Mediterranean Sea), two morphotypes of P. regalis were observed, one with dark spots on the dorsal surface and the other non-spotted. In total, 65 individuals of P. regalis were recorded from 22 stations along the Algerian coast during an oceanographic campaign. Twelve individuals (6 of each morphotype) were used for a comparative study of the morphological (including endoskeletal) characteristics. Table ossicles, the only ossicles of the body wall of the two morphotypes of P. regalis, are here compared with regard to the disk diameter of the tables and the total area of the surface of the disc. Statistical analysis did not show any significant differences between the spotted and the non-spotted morphotypes.

On the Structure and Kinematics of an Algerian Eddy in the Southwestern Mediterranean Sea

An Algerian Eddy, anticyclonic vortex generated by the instability of the Algerian Current in the southwestern Mediterranean Sea, is studied using data provided by drifters (surface currents), Argo floats (temperature and salinity profiles), environmental satellites (absolute dynamic topography maps and ocean color images) and operational oceanography products. The eddy was generated in May 2018 and lasted as an isolated vortex until November 2018. Its morphology and kinematics are described in June–July 2018 when drifters were trapped in its core. During that period, the eddy was slowly moving to the NE (~2 km/day), with an overall diameter of about 200 km (slowly growing with time) and maximal surface swirl velocity of ~50 cm/s at a radius of ~50 km. Geostrophic currents derived from satellite altimetry data compare well with low-pass filtered drifter velocities, with only a slight overestimation, which is expected as its maximum vorticity corresponds to a small Rossby number of ~0.6. Satellite ocean color images and some drifters show that the eddy has an elliptical spiral structure. The looping tracks of the drifters trapped in the eddy were analyzed using two statistical methods: least-squares ellipse fitting and wavelet ridge analysis, revealing a typical eccentricity of about 0.5, a wide range of inclination and a rotation period between 3 and 10 days. Clusters of drifters on the northeastern limb of the eddy were also considered to estimate divergence and vorticity. The results indicate convergence (divergence) and downwelling (upwelling) at scales of 20–50 km near the northeastern (northwestern) edge of the eddy, in agreement with the quasi-geostrophic theory. Vertically, the eddy extends mostly down to 250 m depth, with a warm, low-salinity and low-density signature and with geostrophic currents near 50 cm/s in the top layer (down to ~80 m) reducing to less than 10 cm/s near 250 m. Near the surface, colder water is advected into it.

Contamination level and ecological risk assessment of particulate trace metals in Southwestern Mediterranean Sea

In an effort to assess the coastal water quality in an Algerian Bay, suspended particulate matter (SPM) was analyzed for trace metals and various environmental parameters in Bou Ismail Bay. The trace metal concentrations analyzed by absorption atomic spectrometry followed the decreasing order Al > Fe > Zn > Mn > Ni > Cu > Pb > Co > Cr > Cd > Hg > As (p<0.001). To assess risk, a multiple risk assessment approach was used. The enrichment of particulate metals followed a descending order of Cd > Zn > Ni > Fe > Cu > Co > Hg > Pb > Cr > As. Cadmium and nickel, may enter the bay from anthropogenic non-point sources, had the highest potential ecological risk and biological effect. Nickel contributes 46% to the potential acute toxicity (ΣTUi) of the SPM. The combined metals Pb, Cd, Cu, Zn, Cr, Ni, Hg and As had 25%–30% probability of biotoxicity but did not indicate a likelihood of any significant toxic effects based on results from previous amphipod toxicity tests. Generally, the SPM was categorized as being slightly toxic (ΣTUi<4).

Dynamics of the genus Ostreopsis (Gonyaulacales, Dinophyceae) in a Mediterranean fish farm.

This study revealed the dynamics of the genus Ostreopsis in the south-western Mediterranean Sea fish farm during the 2016 and 2017 summers. This phytoplankton is known to produce palytoxin-like compounds, listed among the most potent marine toxins known, and can pose a serious concern for humans in the Mediterranean area. Principal component analysis (PCA) explained the significance of temperature, salinity, and dissolved inorganic nitrogen in the proliferation of this toxic dinoflagellate. The peak of the Ostreopsis sp. (6.34 × 103 cells L-1) was recorded at 28.4°C, at a salinity of 38.3 PSU, and the dissolved inorganic nitrogen had a value of 0.60μmolL-1. Our results highlight the importance of monitoring the proliferation of this harmful dinoflagellate in southern Mediterranean waters.

Seasonal variation of microplastics density in Algerian surface waters (South-Western Mediterranean Sea)

Coastal waters worldwide are widely contaminated with various-size plastics, whose presence in aquatic ecosystems has been shown to produce a wide range of economic and social impacts and harmful effects on marine ecosystems. While microplastics have been reported from many regions of the Mediterranean Sea, very few data exist regarding microplastics concentration in Algerian waters. In this study, we used a Manta trawl (330 µm) at six sampling stations in Bou-Ismail Bay, Algeria (South-West Mediterranean Sea) in order to provide novel information about the occurrence and composition of microplastics along the Algerian coast. Sampling was performed seasonally at six different sampling stations in 2018, providing additional information about the spatio-temporal variability of microplastics concentrations at the sea surface. Microplastics were found in all collected samples, with highly variable concentrations of 0.95, 0.88, 1.26, and 0.36 items/m3 in Autumn, Winter, Spring and Summer, respectively, and an overall mean concentration of 0.86 ± 0.35 items/m3. A classification based on the shape and appearance of microplastics indicated the predominance of fibers (32%), followed by fragments (27%), films (16%), foams (13%), and granules (12%). A qualitative microplastics analysis through Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) revealed that microplastics were mainly composed of polyethylene (68.2%), polypropylene (24.7%), polystyrene (4.1%) and other polymers (3%). These data provide an initial overview of the quantity, characteristics, and spatio-temporal distribution of floating microplastics in Bou-Ismail Bay (Algeria).

Contamination and Sources Identification of Polycyclic Aromatic Hydrocarbons in Water and Sediments of Annaba Bay Basin, Algeria

Annaba gulf is a coastal area (southwestern Mediterranean Sea) that receives large diffuse inputs from Fertial plant, Seybouse wadi and Boujemaâ wadi, which are influenced by anthropogenic activities. Wastewaters and surface waters and sediments from these sites were analyzed for Polycyclic Aromatic Hydrocarbons (16 PAHs) by using gas chromatography system operating with the flame ionizing detector (FID). Total PAHs ranged from 0.033 to 0.503 µg L–1 in water, and from 32.44 to 509.58 µg kg–1dw in sediments. In order to identify pollution emission sources of PAHs, three source identification techniques were used, including diagnostic ratios, Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA). The results show that the pollution originated mainly from pyrogenic inputs in water and sediments. Annaba Bay basin is contaminated mainly by heavy PAHs discards originated from domestic and industrial wastewaters and traffic emissions.

Saharan Dust Pulse and High Ultraviolet Radiation Alter Microbial Carbon Fluxes in the South-Western Mediterranean Sea

Saharan Dust Pulse and High Ultraviolet Radiation Alter Microbial Carbon Fluxes in the South-Western Mediterranean Sea

Young-of-the-Year Yellowmouth Barracuda Sphyraena viridensis (Cuvier, 1829) Growth in Eastern Algeria Based on Otolith Microstructure Analysis

Age estimates were made on otoliths of 32 young-of-the-year (YOY) Barracuda, Sphyraena viridensis Cuvier (1829), captured in the south-western Mediterranean Sea. Increments were observed in Barracuda sagittae sectioned in a transverse plane and viewed with light microscopy. Increment counts were made for age estimation. Estimated ages ranged from 27 to 299 days of fish ranging in size from 15.9 to 38.9 cm total length (TL). The observed mean growth rate is 3.487 mm.day−1. Decreasing growth performance is evidenced according to age: 3.822 mm.day−1 between 159 and 302 mm (27–139 days), 1.596 mm.day−1 between 352 and 389 mm (172–299 days).

Foraging Far from Home: Gps-Tracking of Mediterranean Storm-Petrels Hydrobates pelagicus melitensis Reveals Long-Distance Foraging Movements

Identifying important foraging areas is fundamental to detecting the demographic drivers of a species and ultimately to plan conservation measures. For some species, such as small pelagic seabirds, foraging grounds are difficult to locate and remain largely unknown. We used miniaturised GPS devices (∼0.95g) to study foraging movements of Mediterranean Storm-petrels Hydrobates pelagicus melitensis during the incubation period. A total of 43 individuals at Benidorm colony (southwestern Mediterranean Sea) were tracked during a single foraging trip. We first assessed potential negative effects of the tracking devices. We recorded 22 complete foraging trips and measured home-range, foraging areas and the degree of overlap among individuals. We used first passage time analyses (FPT) to differentiate foraging/resting from flying/travelling activities and to infer potential foraging areas. All tracked birds returned to the colony. On average, individual body weight slightly decreased after foraging trips, suggesting a small immediate negative effect of the device. Tracked birds had high breeding success (0.71). Foraging trips lasted between 1 and 4.5 days with the total distance travelled ranging between 303.14 and 1,726.53km. The visited areas covered the whole south-western part of the Mediterranean Sea. Tracked individuals shared more than 50% of their home-range areas. Foraging areas were located further from the colony than previously thought (from 240 to 469km away) on deep sea areas of the Alboran Sea and Cartagena Canyons. Further studies are needed to locate foraging grounds during other life-cycle periods and to evaluate repeatability yearly, in order to determine the important marine areas for the species.—Rotger, A., Sola, A., Tavecchia, G. & Sanz-Aguilar, A. (2021). Foraging far from home: GPS-tracking of Mediterranean Storm-petrels Hydrobates pelagicus melitensis reveals long-distance foraging movements. Ardeola, 68: 3-16.

Cartography of littoral rocky-shore communities to assess the ecological status of water bodies through the application of CARLIT method in Algeria (South-Western Mediterranean Sea)

The cartography of shallow water macroalgal assemblages allows the assessment of water quality in coastal water bodies through the application of CARLIT. In this study, we have applied CARLIT to assess the ecological status of Algerian coastal water bodies for the first time. The surveyed zone is still in a good ecological status since 52% have a good to a high ecological Status. CARLIT index is well correlated with anthropogenic pressures and has proved suitable for the evaluation of the ecological status of coastal waters. Comparison between EQR values and EEI-c shows a similar pattern of change. CARLIT method allowed the collection of accurate information on the distribution and abundance of shallow-water communities. We also provide a cartographic baseline of the coastal assemblages useful for further evaluations on their geographic extension and for the implementation of a monitoring project on water quality in Algerian coast.

Morphohistology and histopathology of the digestive organs of the deep-water fish greater forkbeard, Phycis blennoides

Abstract The aim of this paper was to report on an examination of the digestive organs in the deep-water fish Phycis blennoides (Brünnich) from Algerian coastal waters. A total of 1,019 specimens (5.7–62.7 cm in total length) obtained from commercial fisheries were examined between December 2013 and May 2017. The anatomical study was conducted using morphometric measurements of different sections of the digestive tract of P. blennoides. The histological features of the digestive tract were examined in the esophagus, stomach, intestine, and pyloric cecum. They were compatible with carnivorous feeding behavior and confirmed by a low intestinal quotient (IQ = 0.72 ± 0.13). The histopathological assessment highlighted the hepatic steatosis and parasitic infestation in its intestine from Anisakis simplex, which also occurs in Algerian coastal waters. According to our knowledge, this paper reports for the first time the morphohistological analysis of the digestive tract of a Phycidae species in Africa and provides the first histopathological assessment of the digestive organs of the greater forkbeard in the southwestern Mediterranean Sea.

Population dynamics and predatory impact of the alien jellyfish Aurelia solida (Cnidaria, Scyphozoa) in the Bizerte Lagoon (southwestern Mediterranean Sea)

Understanding the life cycle strategies and predatory impact of alien jellyfish species is critical to mitigate the impact these organisms may have on local populations, biodiversity, and ultimately on the functioning of food webs. In the Mediterranean Sea, little is known about the dynamics of alien jellyfish, although this area is a biodiversity hotspot and one of the most threatened by an increasing number of alien jellyfish. Here, we investigated the population dynamics and predatory impact of a non-indigenous scyphomedusa, Aurelia solida Browne 1905, in the Bizerte Lagoon, Tunisia. The study was based on a bimonthly survey performed over two consecutive years, from November 2012 to August 2014. Field observations showed that the planktonic phase of A. solida occurs from winter to early summer. Prey composition was investigated by means of gut content and field zooplankton analyses. Calanoid copepods, mollusc larvae and larvaceans represented the main food items of A. solida. To determine the jellyfish feeding rate and their predatory impact on zooplankton populations, the digestion time for zooplankton prey was assessed at three different temperatures: 13, 18 and 23 °C in laboratory conditions, corresponding to the average range of temperatures encountered by A. solida in the Bizerte Lagoon. We found that A. solida consumed 0.5–22.5% and 0.02–37.3% of the daily zooplankton standing stock in 2013 and 2014, respectively. These results indicate a non-negligible but restricted seasonal grazing impact on some mesozooplankton groups, explained by the relatively short lifespan of the medusa stage (5–6 months).

Phytoplankton size changes and diversity loss in the southwestern Mediterranean Sea in relation to long-term hydrographic variability

Structural changes in plankton primary producers have large implications for food web dynamics, energy fluxes and the vertical export of biogenic particulate carbon. Here we examine phytoplankton data spanning the period 1993–2008 from the Bay of Tunis, southwestern Mediterranean Sea, in relation to long term hydroclimate variability. We show a conspicuous shift in the structure of the phytoplankton community characterized by an increase of small-sized species and diversity loss, revealing a dominance of smaller blooming diatoms and cyanobacteria. Such changes were concurrent with marked modifications in hydroclimatic patterns experienced in the Bay of Tunis consisting of a shift towards enhanced winter precipitation together with rising temperatures. This novel study shows an overall rise in the proportion of small phytoplankton cells and a decreasing trend in phytoplankton diversity in the southern Mediterranean area. These findings warn of a potential decline of trophic efficiency and lesser food web stability resulting from mean size reduction and the diversity loss.

Comparison of isotopic niches of four sea cucumbers species (Holothuroidea: Echinodermata) inhabiting two seagrass meadows in the southwestern Mediterranean Sea (Mostaganem, Algeria)

Among the fauna inhabiting the Posidonia oceanica seagrass meadow, holothurians are particularly abundant and provide essential ecological roles, including organic matter recycling within seagrass sediments. This study aimed to investigate the trophic niche of four holothurians of the order Holothuriida [Holothuria poli (Delle Chiaje, 1824), Holothuria tubulosa (Gmelin, 1791), Holothuria sanctori (Delle Chiaje, 1823) and Holothuria forskali (Delle Chiaje, 1823)] inhabiting P. oceanica meadows, through the measurement of nitrogen and carbon stable isotope ratios. Two shallow and contrasting sites of the littoral region of Mostaganem (North West Algeria) were chosen. The first site, located in Stidia, is weakly impacted by human activities. The second site, located in Salamandre, is highly impacted by human activities (industries, harbor facilities). High values of δ15N in holothurians and their food sources were observed at both sites. The δ13C values showed a lower contribution from detritic Posidonia than in other areas. This could be a consequence of P. oceanica bed degradation in the studied area. The stable isotope approach did not reveal dietary differences between species, and the four holothurians species exhibited significant isotopic niche overlap. However, niche sizes differed between species showing more variable individual trophic diversity in some species (H. tubulosa and H. sanctori in Salamandre; H. forskali in Stidia). If niche segregation does occur, it is not in terms of general resource use. More likely, it would be the abundance of food sources, the different life habits and their micro-habitats that may explain their co-existence in the P. oceanica seagrass meadow.

Conservation status of Paramuricea clavata (Risso, 1826) (Anthozoa, Alcyonacea) in the Chafarinas Islands (Mediterranean Sea)

The red gorgonian Paramuricea clavata (Risso, 1826) is affected by the combined effects of environmental stress factors and diseases in the Mediterranean area. Samplings at different depths in two sites of Chafarinas Islands (South–Western Mediterranean Sea) were carried out to quantify the degree of injuries on red gorgonian colonies. The results showed that shallow colonies displayed a higher rate of injuries than deep colonies. Overall, the conservation status of the population was worse than previously considered in this area.

Population fecundity of seven fishes from Algerian coastal waters (South-Western Mediterranean Sea)

Event Abstract Back to Event Population fecundity of seven fishes from Algerian coastal waters (South-Western Mediterranean Sea) SAMIRA BOUFERSAOUI1* and HOURIA HANDJAR2 1 École Nationale Supérieure des Sciences de la Mer et de l'Aménagement du Littoral, Algeria 2 University of Khemis Miliana, Algeria Population fecundity is the total number of eggs spawned during the spawning season of a given year. The aim of the current study is to estimate this parameter of seven marine fish species from the south-western Mediterranean in coastal waters of Algeria. A total of 450 females belonging to 7 species were sampled between 2013 and 2018 during their spawning seasons: Boops boops, Pagellus acarne, Lithognathus mormyrus, Trachurus trachurus, Sardina pilchardus, Dicologlossa cuneata and Microchirus azevia. These last two species are flat fishes, the others are round fishes. To determine the type of a spawner, oocyte diameter was measured by digital image analysis using TsView software. Fecundity of D. cuneate and M. azevia was determined by the gravimetric method without filtration of reserve oocytes. For the other species volumetric method was used after elimination of non-matures oocytes. The relationships between fecundity and total length (TL), body weight (BW) and gonad weight (GW) were tested with linear, exponential, logarithmic, polynomial and power regression models.Oocytes diameter study showed a unimodal distribution in D. cuneata and M. azevia. This result indicates that these two flat fishes had an ovary with all eggs at the same stage of maturity, so they belong to total spawners. All other species are partial spawners for which frequency distribution of oocytes diameters in mature ovaries showed five separate modes representing mature and immature stages. Eggs were at very different stages of development before and during spawning. Mean annual population fecundity changed widely between species, ranging from 5926 to 164,690 oocytes. The species and their respective ranges of fecundity (oocytes) were: B. boops 1107–139887, D. cuneate 8800–42467, L. mormyrus 25900–415200, M. azevia 213–154321, P. acarne 14500–182300, S. pilchardus 421–11405, T. trachurus 2544–136812. The relative fecundity ranged between 19–1262, 220–981,88–1235, 3–944, 96–1321, 14–440 and 16–479 eggs per gram of female in B. boops, D. cuneate, L. mormyrus, M. azevia, P. acarne, S. pilchardus and T. trachurus respectively. In all species, fecundity was positively related to total length (TL), ovary weight (OW) and body weight (BW), but ovary weight was the best predictor of fecundity. The relationship between fecundity and total length was non-linear, it was polynomial of second degree, except for M. azevia and T. trachurus.In fecundity/body weight and fecundity/ovary weight relations, the best relationship was adjusted by a power function. In all other relations, a secondary polynomial model was the best to be used to fit observed data. This study provides an insight of baseline knowledge of fecundity of seven fishes belonging to total and partial spawners, this information is important for studies on the reproductive capacity of fish populations, and it constitutes an important element to assess fishing pressure on these populations. Keywords: fecundity, spawner, oocyte, Ovary, Algerian coast Conference: XVI European Congress of Ichthyology, Lausanne, Switzerland, 2 Sep - 6 Sep, 2019. Presentation Type: Poster Topic: ECOLOGY AND LIFE CYCLES Citation: BOUFERSAOUI S and HANDJAR H (2019). Population fecundity of seven fishes from Algerian coastal waters (South-Western Mediterranean Sea). Front. Mar. Sci. Conference Abstract: XVI European Congress of Ichthyology. doi: 10.3389/conf.fmars.2019.07.00013 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 25 May 2019; Published Online: 14 Aug 2019. * Correspondence: Mx. SAMIRA BOUFERSAOUI, École Nationale Supérieure des Sciences de la Mer et de l'Aménagement du Littoral, Algiers, Algeria, samira.boufersaoui@gmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers SAMIRA BOUFERSAOUI HOURIA HANDJAR Google SAMIRA BOUFERSAOUI HOURIA HANDJAR Google Scholar SAMIRA BOUFERSAOUI HOURIA HANDJAR PubMed SAMIRA BOUFERSAOUI HOURIA HANDJAR Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Maiden voyage into death: are fisheries affecting seabird juvenile survival during the first days at sea?

The study of juvenile migration behaviour of seabird species has been limited so far by the inability to track their movements during long time periods. Foraging and flying skills of young individuals are assumed to be inferior to those of adults, making them more vulnerable during long-distance migrations. In addition to natural oceanographic effects and intrinsic conditions, incidental seabird harvest by human fisheries is one of the main causes of worldwide seabird population declines, and it has been hypothesized that juveniles are particularly vulnerable to bycatch during their first weeks at sea after leaving the nest. We used solar-powered satellite tags to track the at-sea movements of adults and juveniles of Scopoli's shearwater (Calonectris diomedea) after the autumn departure from their breeding colony in Chafarinas Islands (southwestern Mediterranean Sea). Eighty per cent of juvenile tags stopped transmitting during the first week at sea, within 50 km of their natal colony, in an area with one of the highest concentrations of fishing activities in the Mediterranean Sea. All adult birds tagged and only 20% of juveniles migrated into the Atlantic and southwards along the coast of West Africa. The two age groups showed different habitat preferences, with juveniles travelling farther from the coast, in windier and less productive waters than adults. We conclude that Scopoli's shearwater juveniles are particularly vulnerable to mortality events, and we highlight that fisheries, along with differential age-related behaviour skills between adults and juveniles, are likely causes of this mortality. Overall, our study highlights the importance of conducting tracking studies during the first stages of juvenile migration.

Age and growth of the axillary seabream (Pagellus acarne, Sparidae), in the central coast of Algeria, Mediterranean Sea

Age and growth of the axillary seabream (Pagellus acarne, Sparidae), in the central coast of Algeria, Mediterranean Sea