Until present, bio-optical characteristics and their variations in the eastern Mediterranean and Black Sea have rarely been studied. In order to characterize the basic features of bio-optical ...variables found in the seas surrounding Turkey, remotely sensed data sets covering the period between September 1997 and March 2017 were studied for the purpose of this research. Chlorophyll-a concentration (CHL), absorption coefficient by colored dissolved organic matter (CDOM) and particulate backscattering coefficient (BBP) were both evaluated to describe their recent linear and non-linear inter-annual patterns in the sub regions of the northern Levantine Sea (LS), the eastern Aegean Sea (AS), the Marmara Sea (MS) and the southern Black Sea (BS). The results determined a highly significant and decreasing trend of CHL in the Black Sea, whilst most other regions from the seas around Turkey displayed non-significant trends. The analysis indicated that the seas around Turkey can be clustered into two regions based on their bio-optical properties; one being the Black Sea and Marmara Sea, and the second cluster being the Aegean Sea and Levantine Sea.
Though guitarfish are common bycatch and have an economical value in the Mediterranean Sea, there is still limited knowledge on blackchin guitarfish’s, Glaucostegus cemiculus, their presence or any ...biological feature, with specific regard to those that inhabit the eastern Mediterranean coasts of Turkey. To explore this information gap, bio-ecological features, which are investigated in terms of stomach contents and reproduction, were examined from individuals obtained from Izmir Bay. A total of 122 individuals caught as by-catch were collected monthly between: July 2015–June 2016. Crustaceans were found to be the main prey item in their diets. Maturity stages were mainly immature, with the exception of two individuals: an immature 2-developing female and mature 3b-active male. Knowledge retrieved from present studies on bio-ecological features contributes to closing the current information gap on endangered blackchin guitarfish in the eastern Aegean Sea. Such studies also provide a platform for essential discussion on the various ways in which effective r monitoring strategies for the species could be implemented and managed; particularly in the Turkish coast of the eastern Mediterranean.
Groupers are important components of coastal ecosystems as well as a valuable resource for fisheries. Their populations are known to be decreasing throughout the world primarily due to ...over-exploitation. However, even the basic data for an effective management strategy is lacking. Interviews of a representative sample of 113 fishers in Turkey in the northeastern Mediterranean were conducted with specific questions regarding fishing gears, periods and areas as well as best day's catch and the sizes of fishes caught. Fishermen recognized Epinephelus marginatus, E. aeneus, E. costae, Hyporthodus haifensis, Mycteroperca rubra and Polyprion americanus distributed in the area. “Endangered” E. marginatus and “Near Threatened” E. aeneus were the dominant species of the grouper fishery. Based on best days’ catch values and reported lengths of fish caught, the northern coasts of Iskenderun Bay were found to be important for both species. Demersal longliners, spearguns, traps, anglers and demersal trawlers were reported catching groupers in the study area. Artisanal fishermen, especially demersal longliners contributed the most to the grouper fishery. Fishing pressure were subject to seasonal fluctuations, with decreasing reported catches during summer when threatened groupers spawn. Finally, some critical aspects of fishery pressure were related to the removal of juveniles which may lead to reproduction loss.
•E. aeneus and E. marginatus were reported as dominant in the Gulf of Iskenderun and Mersin.•Demersal longliners are responsible of the most of grouper catches.•Fishery pressure follows seasonal trends, with decreasing efforts during summer.•Captures of juvenile and big ones may contribute to vulnerability of populations.•Fisherman knowledge can help developing effective conservation and management plans.
The fish assemblages of the Eastern Mediterranean are highly variable owing to the Lessepsian migration. So far, there has been limited discussion about the temporal variation of Lessepsian ...populations, which may be a key to better understanding the establishment, persistence and spreading dynamics of these species. The objective of this study was, therefore, to develop an understanding of inter‐annual variations of Lessepsian fish populations through investigating the effects of climate conditions. For this purpose, we evaluated the data obtained from the seasonal bottom trawl surveys conducted over the course of 12 years, from 2004 to 2015, at the infra‐littoral zone of Iskenderun Bay. Our results indicated that Lessepsians constituted 27%, 62% and 85% of total teleost fishes in the number of species (LS‐%), biomass (LW‐%) and abundance (LN‐%), respectively. The linear trends showed that the dominance of Lessepsian fishes increased with annual rates of 1.9 (p < .01, LS‐%), 2.77 (p < .01, LW‐%) and 1.43% (p < .05, LN‐%) per year during the study period. In contrast, seasonal trend decomposition based on GAMMs revealed that the true shape of trends was non‐linear. The majority of the new Lessepsians entered the study area after 2009 when warmer conditions prevailed. Those new invaders such as Nemipterus randalli, Pomadasys stridens and Apogon smithi successfully settled in a short time and remarkably altered the composition of fish assemblages after 2010. We found that variations of lessepsian fish assemblages were correlated with the increase of annual minima and average values of sea surface temperature.
Çandarlı Bay is a marine environment at risk of heavy pollution because of industrial facilities including the only ship recycling zone of Turkey, and intense marine traffic related to the raw ...materials needs of a dense industrial zone. These risk factors make the development of practical environmental management strategies increasingly necessary. Oil spills from the heavy ship traffic, one of the major risks, can be detected by satellite remote sensing technologies. In this study, it is aimed to show spatial characteristics of oil spills as well as its dynamics in the time domain of the bay. Results from a three year period of the study show that as a main environmental problem, oil pollution has a relatively high percentage of spatial distribution in the bay. It is therefore concluded that regular monitoring of the intense oil pollution in the bay is required with an agile and low-cost method of satellite monitoring to intervene in good time and to minimize its impacts. The study provided an extensive understanding of spatio-temporal dynamics of oil pollution in the bay. The approach used will also provide a baseline for decision-makers to develop environmental management plans for other coastal zones with similar sensitivities.
•Çandarlı Bay (Turkey), as a sensitive marine environment, is under the severe oil pollution impact due the activities of the petrochemical and shipping industries including ship recycling.•To monitor the oil pollution sources and their effects to the marine environment, the Synthetic Aperture Radar (SAR) has been proposed as a tool.•Time series of SAR images data were used to evaluate spatial and temporarily changes of oil pollution in the bay.
Optical closure using radiative transfer simulations can be used to determine the consistency of in situ measurements of inherent optical properties (IOPs) and radiometry. Three scattering ...corrections are applied to in situ absorption and attenuation profile data for a range of coastal and oceanic waters, but are found to have only very limited impact on subsequent closure attempts for these stations. Best-fit regressions on log-transformed measured and modelled downwards irradiance, Ed, and upwards radiance, Lu, profiles have median slopes between 0.92 - 1.24, revealing a tendency to underestimate Ed and Lu with depth. This is only partly explained by non-inclusion of fluorescence emission from CDOM and chlorophyll in the simulations. There are several stations where multiple volume scattering function related data processing steps perform poorly which suggests the potential existence of unresolved features in the modelling of the angular distribution of scattered photons. General optical closure therefore remains problematic, even though there are many cases in the data set where the match between measured and modelled radiometric data is within 25% RMS%E. These results are significant for applications that rely on optical closure e.g. assimilating ocean colour data into coupled physical-ecosystem models.
To date, little is known about the larval‐fish assemblages (LFAs) in the eastern Mediterranean. The purpose of this study is to investigate the intra‐annual variations of LFAs with an emphasis on the ...effects of physical, chemical, biological and meteorological conditions in the gulf of Iskenderun, which is a shallow (100 m maximum depth), semi‐enclosed bay located in the northeastern corner of the Mediterranean. The gulf is under the influence of offshore waters throughout the year. The study was based on an ichthyoplankton survey program performed at 28 stations over 12 months, between November 2009 and October 2010. During the study, a total of 11,411 larval individuals belonging to 177 taxa were sampled. The jackknife estimate of maximum species richness was 225 ± 19 for the study area. The maximum larval richness (84 species) and abundance (827 larvae/10 m2) values coincided with spring bloom in April. Gobiids dominated the ichthyoplankton of Iskenderun Bay by constituting 9% of species richness and 42% of total individuals. Four LFAs were identified which were in early winter (November to January), late winter (February and March), spring (April to June) and summer (July to October). The intra‐annual variations of richness, abundance and composition of ichthyoplankton were significantly correlated with the temperature and mesozooplankton biomass. The wind conditions and thermal stratification were also significantly correlated with the composition of LFAs. In conclusion, phenology of LFAs were formed under the influence of physical and tropho‐dynamic conditions in Iskenderun Bay, Northeastern Mediterranean.
A bio-optical model has been developed for the Ligurian Sea which encompasses both deep, oceanic Case 1 waters and shallow, coastal Case 2 waters. The model builds on earlier Case 1 models for the ...region and uses field data collected on the BP09 research cruise to establish new relationships for non-biogenic particles and CDOM. The bio-optical model reproduces in situ IOPs accurately and is used to parameterize radiative transfer simulations which demonstrate its utility for modeling underwater light levels and above surface remote sensing reflectance. Prediction of euphotic depth is found to be accurate to within ∼3.2m (RMSE). Previously published light field models work well for deep oceanic parts of the Ligurian Sea that fit the Case 1 classification. However, they are found to significantly over-estimate euphotic depth in optically complex coastal waters where the influence of non-biogenic materials is strongest. For these coastal waters, the combination of the bio-optical model proposed here and full radiative transfer simulations provides significantly more accurate predictions of euphotic depth.
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