Population structure of the protected fan musselPinna nobilisin the south Aegean Sea (eastern Mediterranean)

2014 ◽  
Vol 94 (4) ◽  
pp. 787-796 ◽  
Author(s):  
Dimitris Vafidis ◽  
Chryssanthi Antoniadou ◽  
Eleni Voultsiadou ◽  
Chariton Chintiroglou
Keyword(s):  
Size Structure ◽  
Habitat Degradation ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Current Status ◽  
Small Scale ◽  
The South ◽  
Depth Zone ◽  
Size Frequency Distribution ◽  
Temporal Sampling

Pinna nobilisis an endemic Mediterranean species of high economic and cultural importance. Nowadays, it is under strict protection as a dramatic decline in its populations has been recognized, assigned to the combined effect of fisheries and habitat degradation. This study attempts to evaluate, by non-destructive sampling, the current status ofP. nobilispopulations in the south Aegean Sea (Dodecanese island complex), where they have been affected for centuries by practically uncontrolled harvesting. Population density and total length of individuals was estimated by diving along strip transects at six islands. Two stations were randomly selected per island, and two depth zones were surveyed per station. Additionally, temporal sampling was carried out at Astypalaia Island from March 2004 to June 2006, to assess relevant trends in density of individuals and size structure of the population. In total 1372P. nobilisindividuals were measuredin situto estimate maximum shell length. The studied populations showed increased density in the shallower depth zone and sheltered sites; small-scale environmental regimes are proposed as shaping factors ofP. nobilisdistribution. Increased density was also detected during the cold period of the year, probably related to recruitment success. In the lower depth zone theP. nobilispopulation consisted of larger individuals. A significant decrease in size was detected temporally as mean length was smaller in December 2004; in the same month the presence of small-sized juveniles was depicted in a left-shift in size–frequency distribution. These observations are probably related to the reproductive biology of the species.

scholarly journals Key Environmental Factors Controlling Planktonic Foraminiferal and Pteropod Community’s Response to Late Quaternary Hydroclimate Changes in the South Aegean Sea (Eastern Mediterranean)

2020 ◽  
Vol 8 (9) ◽  
pp. 709
Author(s):  
Christina Giamali ◽  
George Kontakiotis ◽  
Efterpi Koskeridou ◽  
Chryssanthi Ioakim ◽  
Assimina Antonarakou
Keyword(s):  
Environmental Factors ◽  
Environmental Changes ◽  
Late Quaternary ◽  
Eastern Mediterranean ◽  
Planktonic Foraminifera ◽  
Explanatory Power ◽  
Principal Component ◽  
Aegean Sea ◽  
Late Glacial ◽  
The South

A multidisciplinary study was conducted in order to investigate the environmental factors affecting the planktonic foraminiferal and pteropod communities of the south Aegean Sea. Aspects of the Late Quaternary paleoceanographic evolution were revealed by means of quantitative analyses of planktonic foraminiferal and pteropod assemblages (including multivariate statistical approach; principal component analysis (PCA)), the oxygen (δ18O) and carbon (δ13C) isotopic composition of planktonic foraminifera and related paleoceanographic (planktonic paleoclimatic curve (PPC), productivity (E-index), stratification (S-index), seasonality) indices, extracted by the gravity core KIM-2A derived from the submarine area between Kimolos and Sifnos islands. Focusing on the last ~21 calibrated thousands of years before present (ka BP), cold and eutrophicated conditions were identified during the Late Glacial period (21.1–15.7 ka BP) and were followed by warmer and wetter conditions during the deglaciation phase. The beginning of the Holocene was marked by a climatic amelioration and increased seasonality. The more pronounced environmental changes were identified during the deposition of the sapropel sublayers S1a (9.4–7.7 ka BP) and S1b (6.9–6.4 ka BP), with extremely warm and stratified conditions. Pteropod fauna during the sapropel deposition were recorded for the first time in the south Aegean Sea, suggesting arid conditions towards the end of S1a. Besides sea surface temperature (SST), which shows the highest explanatory power for the distribution of the analyzed fauna, water column stratification, primary productivity, and seasonality also control their communities during the Late Quaternary.

scholarly journals Net Fisheries’ Métiers in the Eastern Mediterranean: Insights for Small-Scale Fishery Management on Kalymnos Island

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1509 ◽  
Author(s):  
Kyriakoula Roditi ◽  
Dimitris Vafidis
Keyword(s):  
Mediterranean Sea ◽  
Fishery Management ◽  
Eastern Mediterranean ◽  
Market Price ◽  
Aegean Sea ◽  
Small Scale ◽  
Target Species ◽  
Essential Information ◽  
Small Scale Fisheries ◽  
The Difference

Small-scale fisheries constitute an important component of coastal human societies. The present study describes the small-scale net fisheries on Kalymnos Island (south-east Aegean Sea) that harbors the largest small-scale fleet in the eastern Mediterranean Sea. In addition, this study aims to evaluate their characteristics and economics. Relevant métiers were identified through a multivariate analysis by inputting the main resources and fishing gear data that were recorded during landings. Four main practices were observed being used as fishing gears, gillnets and trammel nets, targeting the species Mullus barbatus, Boops boops, Mullus surmuletus, Scorpaena porcus, and Sepia officinalis. Further analysis, which incorporated data concerning the type of the gear used, revealed 11 distinct métiers. Most of these métiers are practiced by other Mediterranean small-scale fisheries as well, in terms of target species, gear and seasonality. However, the métier that had its target species as B.boops is not practiced in other Mediterranean small-scale fisheries. The seasonal rotation of métiers was determined by the availability of different species rather than their market price. The results revealed the difference in fishing practice used by the fishermen in the study area compared to other fishing practices in the Mediterranean Sea. In particular, the fishermen of this study area targeted more species (B.boops) with a very low market price. They also provided essential information for the development and implementation of management plans aiming at the sustainability of small-scale fisheries.

scholarly journals Assessment of the sardine (Sardina pilchardus Walbaum, 1792) fishery in the eastern Mediterranean basin (North Aegean Sea)

2011 ◽  
Vol 12 (2) ◽  
pp. 333 ◽  
Author(s):  
K. ANTONAKAKIS ◽  
M. GIANNOULAKI ◽  
A. MACHIAS ◽  
S. SOMARAKIS ◽  
S. SANCHEZ ◽  
...  
Keyword(s):  
Mediterranean Basin ◽  
Eastern Mediterranean ◽  
Population Analysis ◽  
Aegean Sea ◽  
Population Characteristics ◽  
Current Status ◽  
Sardina Pilchardus ◽  
North Aegean ◽  
North Aegean Sea ◽  
The Impact

The aim of this study was to describe the biometric characteristics of the European sardine (Sardina pilchardus) catches and assess the current status of sardine stock in North Aegean Sea based on population characteristics and abundance trends. The stock was dominated by age groups 1 and 2, not exceeding age group 4. The sardine stock in this area was assessed through an Integrated Catch-at-Age model which implements a separable Virtual Population Analysis on catch at age data with weighted tuning indices. Sardine landings data derived from the commercial purse seine fishery over the period 2000-2008 were combined with the age structure of the stock as resulted from fisheries independent acoustic surveys. Sensitivity analysis of the impact of natural mortality values on stock assessment results was applied. Additionally forecast of the sardine population parameters and catches under different exploitation scenarios was implemented in a medium term basis. Results indicated that the North Aegean Sea sardine stock is considered fully exploited with the fishery operating close but over the empirical exploitation level for sustainability. Finally, the status of the sardine stock in N. Aegean Sea is discussed in relation to the sardine stocks from the western and the central Mediterranean basin.

scholarly journals Abundance and population characteristics of the invasive sea urchin Diadema setosum (Leske, 1778) in the south Aegean Sea (eastern Mediterranean)

2021 ◽  
Vol 28 (1) ◽  
Author(s):  
Dimitris Vafidis ◽  
Chryssanthi Antoniadou ◽  
Konstantinos Voulgaris ◽  
Anastasios Varkoulis ◽  
Chrysoula Apostologamvrou
Keyword(s):  
Population Density ◽  
Sea Urchin ◽  
Benthic Communities ◽  
Aegean Sea ◽  
Population Characteristics ◽  
Native Range ◽  
The South ◽  
Test Diameter ◽  
Size Frequency Distribution ◽  
Diadema Setosum

Abstract Background The Indo-Pacific sea urchin Diadema setosum has invaded the Mediterranean Sea and has spread along many locations in the southeastern part of the basin, where established populations exist on the shallow subtidal rocky shore. Diadema setosum is a ubiquitous species, of particular ecological importance due to the high levels of grazing pressure it imposes on benthic communities. Its biology, however, is not adequately studied, especially along its introduced range of distribution. The present study examines the population status of D. setosum outside its native range, in the Dodecanese island complex, south Aegean Sea. Thirty-four stations located across 16 islands were surveyed by scientific SCUBA-diving (up to a depth of 10 m) in December 2019 and June-July 2020. Samplings included: (i) visual census along transects to estimate relative abundance and population density, and (ii) random collection of specimens from densely populated stations to assess biometry and reproductive condition (histological examination of gonads) of D. setosum. Results Diadema setosum was found in 21 out of the 34 surveyed stations. The species had sparse populations of well-hidden individuals in rocky crevices, but with dense localized patches in Agathonisi, Leros, Kalymnos, Pserimos, Symi, Alimia and Chalki islands. In those seven islands, mean population density was 2.5 ± 1.48 individuals m−2. Diadema setosum had denser populations in shallower depths but larger dimensions in deeper; these results suggest segregated density and size patterns along a depth gradient. The size structure, according to the size frequency distribution of the test diameter, was unimodal with a fitted mode at 4.0–4.5 and 6.5–7.0 cm in shallow and deep populations, respectively. The examined morphometric relationships followed negative allometry, as previously suggested for the species within its native range of distribution, and test diameter appeared to be a good predictor of biomass. Diadema setosum specimens had immature gonads in winter and mature in summer, suggesting a synchronous reproductive pattern. These results conform to previous data from temperate populations of the species. Conclusions Differences in local environmental conditions, e.g. hydrodynamics and habitat type, together with biotic interactions, e.g. recruitment and competition, probably shape D. setosum population in the south Aegean distributional range. The establishment of D. setosum has severe implications on benthic communities and local sea urchin populations demanding management measures to prevent the forecasted further expansion of this invasive species.

Natatolana neglecta (Isopoda, Cirolanidae): an increasing threat for artisanal fishing in the Turkish Aegean Sea

Crustaceana ◽  
2019 ◽  
Vol 92 (7) ◽  
pp. 881-887
Author(s):  
Fevzi Kirkim ◽  
Tammy Horton ◽  
Okan Akyol ◽  
Tevfik Ceyhan
Keyword(s):  
Aegean Sea ◽  
Small Scale ◽  
Artisanal Fishing ◽  
The South ◽  
First Report ◽  
South Eastern ◽  
Short Period ◽  
Eastern Aegean ◽  
Eastern Aegean Sea

Abstract Samples of the isopod Natatolana neglecta (Hansen, 1890) are reported herein from Güllük Bay, south-eastern Aegean Sea. In the last decade, the abundance of this species has been increasing in the area, and this has led to attacks on fishes captured with gillnets, at night. The small-scale fishermen now are forced to restrict their catch to a short period daily, and are showing concerns regarding the continuation of their fishing practice. Here, we present the first report on the occurrence of N. neglecta in the Bay of Güllük, and provide information on the threat of this species for coastal fishermen in the south-eastern Aegean Sea.

scholarly journals Reproductive biology of Plesionika narval in the SE Aegean Sea (Eastern Mediterranean)

2017 ◽  
pp. 454 ◽  
Author(s):  
AIKATERINI ANASTASOPOULOU ◽  
PANAGIOTA MAKANTASI ◽  
KOSTAS KAPIRIS ◽  
CHRIS J. SMITH ◽  
CHRISTOS MARAVELIAS ◽  
...  
Keyword(s):  
Reproductive Biology ◽  
Carapace Length ◽  
Gonadosomatic Index ◽  
Aegean Sea ◽  
Reproductive Period ◽  
Small Scale ◽  
Female Size ◽  
Depth Range ◽  
Depth Zone ◽  
Widespread Species

Plesionika narval is a widespread species of the Pandalidae family, of particular high economic importance for small-scale shrimp trap fisheries in the Dodecanese Islands (SE Aegean Sea). Understanding its biology and reproduction are crucial for stock management. Reproductive biology aspects were studied through data collected during monthly experimental surveys with baited shrimps traps from November 2014 to October 2015 at a depth range of 10 - 150m. A total of 3436 individuals within the size range of 6.46 to 20.20 mm carapace length (CL) was analyzed. Overall, mean female size was significantly higher than mean male size, while the mean size of ovigerous females was higher than that of non-ovigerous females. Mean carapace length of ovigerous and non-ovigerous females was significantly correlated to depth. Ovigerous females were observed throughout the study period; however, monthly proportions revealed April to October as the main reproductive period of the species in the area. The sex ratio showed a clear predominance of females in the shallow depth zone (10-25 m) and was found to be affected by sampling area and depth zone. Immature females were found from November to March. Mature females were found all year round, exhibiting higher percentages in March, June, July and September, coinciding with the main reproductive period. P. narval seemed to spawn more than one time within the annual reproductive cycle. Gonadosomatic index obtained its highest mean values in May, June and September, thus revealing the main reproductive period. Size at first maturity for females was estimated at CL50=11.7 mm.

scholarly journals Nesting operational forecasting models in the Eastern Mediterranean: active and slave mode

2006 ◽  
Vol 3 (4) ◽  
pp. 1225-1254 ◽  
Author(s):  
S.S. Sofianos ◽  
N. Skliris ◽  
A. Mantziafou ◽  
A. Lascaratos ◽  
G. Zodiatis ◽  
...  
Keyword(s):  
Sea Water ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Circulation Pattern ◽  
Horizontal Resolution ◽  
The Black Sea ◽  
Small Scale ◽  
Active Mode ◽  
Operational Systems ◽  
Slave Mode

Abstract. Modern ocean operational systems involve different groups and tools, in different regions and scales. Blending all these in a unique system with reliable forecasting capabilities is an important task. The efficiency of nesting procedures between different scale and resolution models are crucial in determining whether the dynamics at the different scales are well represented at each level or the nesting technique suppresses the dynamical features emerging from individual modelling components. In the present work, we investigate the role of the initialization of telescopically nested and with double horizontal resolution forecasting systems in the Eastern Mediterranean, comparing the results between weekly initialized experiments ("slave'' mode) and "free'' runs ("active'' mode) at the regional (Aegean-Levantine area) and shelf (Cyprus) scale. It is found that, although the main circulation pattern remains similar, the differences in the domain mean kinetic energy between the "slave'' and the "active'' experiments in the Aegean-Levantine region are large in both September 2004 and January 2005, with the "active'' being much more energetic, while in the Cyprus area differences are significantly smaller. The most pronounced differences in the circulation and sea surface temperature and salinity fields are observed in the Aegean Sea, during September 2004, related to the inflow and spreading of the Black Sea Water, and the Rhodes Gyre, during January 2005, related to small-scale eddy activity developed and surviving in the "active'' mode experiment that decreases the area of the gyre.

Life-history traits of the striped red mullet Mullus surmuletus (Linnaeus, 1758) in the south Aegean Sea (eastern Mediterranean)

2019 ◽  
Vol 99 (06) ◽  
pp. 1417-1427 ◽  
Author(s):  
Vasiliki Kousteni ◽  
Aikaterini Anastasopoulou ◽  
Chryssi Mytilineou
Keyword(s):  
Stock Assessment ◽  
Eastern Mediterranean ◽  
Gonadosomatic Index ◽  
Aegean Sea ◽  
Growth Function ◽  
Reproductive Period ◽  
The South ◽  
Striped Mullet ◽  
Mullus Surmuletus ◽  
Marginal Increment

AbstractAlthough the red striped mullet is one of the main target fish of the Hellenic demersal fisheries, information about its biology is limited. The aim of this study was to describe the reproductive biology and growth of the species in the south Aegean Sea based on 1032 individuals sampled under the Data Collection Framework Program in 2016. According to the monthly variation of the maturity stages and the gonadosomatic index, spawning activity took place from March to July, although it appeared to occur throughout the year. Length at 50% maturity (L50) was 153.3 and 139.2 mm in females and males, respectively. Individual ages were determined by counting the annuli of otoliths macroscopically. Marginal increment analysis (MIA) combined with complementary information derived from otolith edge analysis, the assessment of the reproductive period and the length–frequency distribution modes of the population showed that annulus formation occurs between February and April. The length–weight relationship revealed a significant sex effect and was described by the parameters α = 0.0155 and b = 2.915 in females, and α = 0.0032 and b = 2.976 in males. The von Bertalanffy growth function (VBGF) parameters for sexes combined were Linf = 346.1 mm, k = 0.299 year−1 and t0 = −0.984 years. Longevity (tmax) was estimated at 11.75 years. This study provides valuable data for the stock assessment of M. surmuletus in one of the major Hellenic fishing grounds located in the south Aegean Sea.

scholarly journals Setting an ecological baseline prior to the bottom-up establishment of a marine protected area in Santorini island, Aegean Sea

2016 ◽  
Vol 17 (3) ◽  
pp. 720 ◽  
Author(s):  
M. SALOMIDI ◽  
S. GIAKOUMI ◽  
V. GERAKARIS ◽  
Y. ISSARIS ◽  
M. SINI ◽  
...  
Keyword(s):  
Protected Area ◽  
Fish Assemblages ◽  
Marine Protected Area ◽  
Eastern Mediterranean ◽  
Aegean Sea ◽  
Small Scale ◽  
Anthropogenic Pressures ◽  
Bottom Up ◽  
Rich Diversity ◽  
Functional Features

Since 2010, a bottom-up initiative has been launched in Santorini Island (Aegean Sea, Eastern Mediterranean) for the establishment of the first fully-protected marine protected area in the Cyclades, aiming at improving fisheries and enhancing responsible recreational uses at sea. Following discussions with local small-scale fishers and divers, two sites along the southern and southeastern coasts of the island were suggested as suitable to this end. In 2012, a baseline study was conducted at these areas to assess their state and provide an ecological snapshot that would enable sound designation and monitoring. Several ad hoc indices and metrics were applied, taking into account structural and functional features of the upper infralittoral algae and Posidonia oceanica beds. An integrated assessment of the infralittoral fish assemblages and their associated benthic communities was also performed. Our most important findings were: (i) the low total fish biomass and the absence of adult top predators, indicating overfishing; (ii) the overgrazing effects of the overabundant alien herbivore spinefoot fishes (Siganus spp.), as reflected by the abnormal structure of the algal communities; (iii) the scarcity of signs of pollution or other direct anthropogenic pressures, as indicated by the good environmental status of the P. oceanica meadows and the upper infralittoral vegetation; and (iv) the presence of a rich diversity of species and habitats, especially along the Akrotiri Peninsula and the wider volcanic Caldera. These findings provide useful insights on strengths and weaknesses of the study area and are discussed together with their implications for protection and management.

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