S. Somarakis

S. Somarakis
Hellenic Centre for Marine Research | hcmr · Institute of Marine Biological Resources and Inland Waters

Biology

About

181
Publications
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Publications

Publications (181)
Article
Full-text available
Otolith morphological variability is used as a reliable indicator to discriminate fish that experience different environmental conditions during their lifetimes. The present study examined the effects of developmental temperature (DT) during the egg and yolk-sac larval period on the otolith shape and asymmetry of Gilthead seabream in the later meta...
Article
Special Issue for 2021 dedicated to papers produced within the MEDIAS project. Guest editors: Marianna Giannoulaki, Juan Zwolinski, Ali Cemal Gucu, Andrea De Felice, and Stylianos Somarakis.
Article
Full-text available
The study of small pelagic fish by hydroacoustic methods in the Mediterranean Sea began in the Adriatic in the 1950’s. Since 2009, internationally coordinated, extensive, regular surveys have been conducted in the framework of the MEDIAS - Mediterranean International Acoustic Surveys – action, under the EU Data Collection Framework, to provide inpu...
Article
In this study, we consider the applicability of Bergmann’s rule to the populations of small pelagic fish species in the Mediterranean Sea. Under Bergmann’s rule, body size increases with decreasing temperature and increasing latitude. Although this macroecological pattern in body sizes is well established for many taxa of endotherms and ectotherms,...
Article
Full-text available
The invasion of the tetrodotoxin (TTX)-bearing silver-cheeked toadfish and potential poisoning due to its consumption (tetrodotoxication) threatens public safety in the Mediterranean Sea. In this study, TTX and TTX analogues of Lagocephalus sceleratus (Gmelin, 1789) were measured using liquid chromatography tandem mass spectrometry (LC-MS/MS) in fi...
Research Proposal
Full-text available
Deadline approaching! https://www.frontiersin.org/research-topics/20490/impacts-of-environmental-variability-related-to-climate-change-on-biological-resources-in-the-medite Current estimates of the trend in Sea Surface Temperature (SST) from satellite-based remote sensing represent the main evidence of Mediterranean Climate change. The reported d...
Article
Full-text available
We present the development of a 3D full-lifecycle, individual-based model (IBM) for anchovy and sardine, online coupled to an existing hydrodynamic/biogeochemical low-trophic level (LTL) model for the North Aegean Sea. It was built upon an existing 1D model for the same species and area, with the addition of a horizontal movement scheme. In the mod...
Article
Full-text available
The Golani’s round herring Etrumeus golanii is an Erythraean small pelagic fish (lessepsian migrant) that entered into the Mediterranean Sea through the Suez Canal. It has expanded its distribution from the east to the western Mediterranean with well-established local populations. We investigated basic aspects of its reproductive biology off the is...
Presentation
Full-text available
Mesopelagic fish are consisted of small species, which inhabit the mesopelagic zone and constitute the most abundant vertebrate group in the marine environment. Together with other organisms they form Deep Scattering Layers (DSLs) detected by echo-sounders, while several species perform diel vertical migrations. The aim of this study was to describ...
Article
The high frequency of regenerated scales degree of scale regeneration (SRD) in reared fish has been used in the past for the identification of aquaculture escapees in the wild stocks. In the present study, we examined the evolution of the SRD in Gilthead seabream (Sparus aurata) throughout the entire rearing process (hatchery and on‐growing, 2.0–21...
Article
Full-text available
A Wisconsin type bioenergetics model was developed to investigate the growth and reproduction of the Mediterranean swordfish Xiphias gladius L., 1758. Reproduction was simulated using an energy allocation algorithm with a fixed part of assimilated energy stored for egg production. Stomach contents were used to estimate the daily ration of swordfish...
Article
Hypoxia is a major stressor on biological communities in many oceanic and coastal ecosystems. Various size-dependent processes (e.g. growth and reproduction rates, predator-prey interactions) are adversely affected by hypoxia. We hypothesized that the impacts of hypoxia on planktonic communities would also be reflected in their Normalized Biomass S...
Article
Otolith structure is a useful tool in the discrimination among fish populations, as it is a permanent record of the influence of endogenous and exogenous factors. In the present study we examined otolith morphology and fluctuating asymmetry (FA) for differences between wild‐caught (by bottom trawl) and reared specimens of Gilthead seabream (Sparus...
Technical Report
Full-text available
Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4-10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, a...
Conference Paper
Full-text available
Zacharias Kapelonis, Apostolos Siapatis, Athanassios Machias, Stylianos Somarakis, Konstantinos Markakis, Marianna Giannoulaki, Maria Myrto Pyrounaki, Stavroula Tsoukali, Konstantinos Tsagarakis: Distribution and vertical migration of mesopelagic fish in Korinthiakos Gulf Mesopelagic fish, small species which inhabit the mesopelagic zone, constitut...
Article
Full-text available
A 1-D full-life-cycle, Individual-based model (IBM), two-way coupled with a hydrodynamic/biogeochemical model, is demonstrated for anchovy and sardine in the N. Aegean Sea (Eastern Mediterranean). The model is stage-specific and includes a 'Wisconsin' type bioenergetics, a diel vertical migration and a population dynamics module, with the incorpora...
Preprint
Full-text available
the site-attachment behaviour of O. melanura settlers was examined in an estuarine area of western Greece. the approach that was followed included underwater assignments of shoal identities and continuous recording of specific behavioural traits. Variations between ontogenetic stages with respect to the pattern of residence at the sites were quanti...
Article
Full-text available
Anchovy Engraulis encrasicolus distribution in European waters spans from the Mediterranean Sea to the North Sea, and is expected to expand further north with global warming. Observations from the eastern Mediterranean (North Aegean Sea), the Bay of Biscay and the North Sea reveal latitudinal differences in growth, maximum size, fecundity and timin...
Article
Full-text available
Multispecies ichthyoplankton associations are believed to be adaptive and their objective definition can be useful in designating species with similar or contrasting spawning strategies. In this case study, a suite of indicators, recently developed to characterize the spatial patterns of animal populations, are applied on egg abundance data of summ...
Article
Marine litter is a threat to marine life and an economic burden for coastal communities, but efforts to address the issue are hampered by the lack of data for many countries. We performed the first harmonized assessment of seafloor litter (trawl and visual surveys) in six countries of the Adriatic-Ionian macroregion. Seafloor litter showed an uneve...
Article
Under the general framework of existing recruitment hypotheses, knowledge on the drivers and mechanisms involved in the determination of the year class strength of small pelagic fish (SPF) is briefly reviewed with focus on selected aspects of the adult and larval stages, related to breeding patterns, egg production, spawning habitats, reproductive...
Article
Morphometric characters have traditionally been used to describe the population structure of fishes. Body shape variation, which is often environmentally induced, may provide a good record of short-term population structuring. However, factors unrelated to environmental or genetic influences on body morphology may complicate sampling and the use of...
Article
Full-text available
We combined generalised additive models and GIS to model and map anchovy potential spawning habitat using anchovy egg and adult presence/absence data from the North Aegean Sea along with in situ environmental information, collected during the beginning / peak of the spawning period. First, we compared the spawning habitat models constructed using d...
Article
Small pelagic fish are among the most ecologically and economically important marine fish species and are characterized by large fluctuations all over the world. In the Mediterranean Sea, low catches and biomass of anchovies and sardines have been described in some areas during the last decade, resulting in important fisheries crises. Therefore, we...
Article
Full-text available
Identification of fishing grounds is crucial for a good understanding of fisheries practices and for proposing effective management measures. A methodology to map fishing grounds and analyze their spatial patterns was developed. The proposed approach combines VMS (Vessel Monitoring System) data, used for estimation of fishing effort, and catch data...
Technical Report
Full-text available
Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, a...
Technical Report
Full-text available
In 2014, the EU fishing fleet numbered 81 500 vessels with a combined gross tonnage (GT) of 1.6 million tonnes and engine power of 6.4 million kilowatts (kW). EU fleet capacity has continued to decrease steadily, at an average annual rate of 2% in terms of vessel numbers and engine power (kW) and 3% in terms of gross tonnage (GT). Based on data sub...
Technical Report
Commission Decision of 25 February 2016 setting up a Scientific, Technical and Economic Committee for Fisheries, C(2016) 1084, OJ C 74, 26.2.2016, p. 4–10. The Commission may consult the group on any matter relating to marine and fisheries biology, fishing gear technology, fisheries economics, fisheries governance, ecosystem effects of fisheries, a...
Article
We studied the otolith microstructure and growth of sardine, Sardina pilchardus, in the North Aegean Sea (eastern Mediterranean Sea), using samples of larvae and juveniles that had hatched in winter (November-January) and winter-spring (February-May), respectively. The juveniles had developed during an extended period coinciding with marked pelagic...
Article
This Theme Section consists of 11 essays aiming to explore diverse issues related to academic freedom and tenure, presenting the views and thoughts of 15 scholars from different disciplines. Historical, legal, theoretical, philosophical, political and educational aspects of academic freedom and tenure are addressed; the decline in productivity of t...
Article
Full-text available
The introduction of market forces into higher education (i.e. marketization) in recent decades goes along with a sharp decline in tenured positions offered, accompanied by polemic voices against tenure. The main claim, that tenure reduces the productivity of senior faculty, has not been thoroughly tested, with existing scarce evidence being controv...
Article
Full-text available
In this essay we briefly describe climate change in the Mediterranean Sea Large Marine Ecosystem (LME) using different indices. We further describe the evolution of yearly catches and species composition of the catches in the West (W), Central (C), and East (E) Mediterranean LME during 1970-2010 and the exploitation status of the fisheries resource...
Article
Full-text available
Geostatistical techniques were applied and a series of spatial indicators were calculated (occupation, aggregation, location, dispersion, spatial autocorrelation and overlap) to characterize the spatial distributions of European anchovy and sardine during summer. Two ecosystems were compared for this purpose, both located in the Mediterranean Sea:...
Article
Full-text available
Otolith increment widths have often been used to infer somatic growth history when studying the influence of temperature and food supply. However, there is no functional relationship between otolith accretion rate ('inherent otolith growth') and somatic growth rate; although both may be mediated by temperature and food, the uncoupling of these rate...
Chapter
Full-text available
The present chapter deals with the estimation of female fecundity in fishes, mostly teleosts. The chapter is organized in three main blocks. The first block is devoted to technical issues of fish fecundity measurements from fixation, preservation and treatment of ovarian material to automatic oocyte counts. The use of certain staining protocols for...
Conference Paper
Fish spawning frequency varies from daily to once in a lifetime. Some species spawn and feed in separate areas, during different seasons, by storing energy and drawing on it later for reproduction (i.e. capital breeding). Other species spawn using energy acquired locally, throughout a prolonged spawning season, allocating energy directly to reprodu...
Article
Full-text available
Understanding critical ontogenetic transitions in the life of fish, such as metamorphosis, is of prime importance for determining the factors that affect survival probabilities and control recruitment levels. Metamorphosis involves a plethora of changing characters and its definition requires a multi-parametric approach. In the present study, mean...
Article
Full-text available
A number of scientific papers in the last few years singled out the influence of environmental conditions on the spatial distribution of fish species, highlighting the need for the fisheries scientific community to investigate, besides biomass estimates, also the habitat selection of commercially important fish species. The Mediterranean Sea, altho...
Technical Report
Full-text available
STECF acknowledges the intensive and thorough work performed by EWG 14-07. All three Terms of Reference have been fully addressed. The Annual Rep orts 2013 of 22 MS, excluding the Bulgarian Annual Report (withdrawn from evaluation),were revi ewed in relation to MS National Programme proposals for 2011-2013 or updates for 2013. As in previous years,...
Article
Full-text available
Two different stock assessment models were applied to the North Aegean Sea anchovy stock (Eastern Mediterranean Sea): an Integrated Catch at age Analysis and a Bayesian two-stage biomass based model. Commercial catch data over the period 2000-2008 as well as acoustics and Daily Egg Production Method estimates over the period 2003-2008 were used. Th...
Article
Full-text available
Anchovies and sardines hold a very important position in pelagic ecosystems and are usually found in species pairs, exhibiting fluctuations in abundance. In upwelling systems, alternations in small pelagic fish have been hypothesized to be, at least partly, trophically mediated. In non-upwelling areas, direct comparisons of sardine and anchovy trop...
Chapter
Full-text available
Apart from being commercially and socially significant, anchovies and sardines populations occupy crucial positions in the oceans’ ecosystems. Low in the food chain, clupeoids tend towards abundance, as if their purpose in life was to be eaten and fuel the upper levels of marine trophic chains. The present book covers a broad spectrum of topics on...
Article
Full-text available
Using the Food and Agriculture Organization’s (FAO) Mediterranean capture fisheries production dataset in conjunction with global and Mediterranean sea surface temperatures, we investigated trends in fisheries landings and landings per unit of effort of commercially important marine organisms, in relation to temperature oscillations. In addition to...
Chapter
Full-text available
The present chapter deals with the estimation of female fecundity in fishes, mostly teleosts. The chapter is organized in three main blocks. The first block is devoted to technical issues of fish fecundity measurements from fixation, preservation and treatment of ovarian material to automatic oocyte counts. The use of certain staining protocols for...
Technical Report
Full-text available
Data collection currently occurs under the Data Collection Framework (DCF) 1 and the multi-annual Union programme for data collection established there under. 2 The Second Financial Instrument for the CFP funds the DCF. 3 Member States establish DCF National Programmes in accordance with pr ovisions of the multi-annual Union programme for data coll...
Technical Report
Full-text available
STECF reviewed the report of the EWG 13-12 and note d the progress made regarding the assessment of Bla ck Sea stocks. STECF acknowledges the considerable eff orts of the WG participants in undertaking its work . The EWG 13-12 attempted to develop quantitative sto ck assessments for nine species but only five of th e assessments (sprat, turbot, whi...
Article
A new type of vertebral malformation is described, consisting of deformed cartilaginous neural and haemal processes and the compression and fusion of vertebral bodies. The malformation is designated as haemal vertebral compression and fusion (haemal VCF). We studied the aetiology of the malformations and described microanatomical histopathological...