Adnan Çağlar Oruç

The family Callionymidae comprises a taxonomically challenging group of benthic marine fishes, mainly due to pronounced sexual dimorphism, ontogenetic variation, and the limited reliability of some diagnostic morphological characters. In the present study, six dragonet species occurring along the Turkish coasts, Callionymus filamentosus, C. lyra, C. pusillus, C. risso, Synchiropus phaeton, and S. sechellensis, were examined using morphological and molecular approaches. Specimens were collected from the Black Sea, Sea of Marmara, Aegean Sea, and Levantine Basin. Morphometric and meristic characters, coloration patterns, sexual dimorphism, and preopercular spine morphology were evaluated. In order to complete morphological identification and provide an independent molecular assessment of species differentiation, mitochondrial COI sequences were analysed using DNA barcoding and phylogenetic approaches. A Principal Component Analysis (PCA) based on 14 morphometric ratios from all 35 individual specimens was used to evaluate morphological variation among the examined taxa. The first two principal components accounted for 55.0% of the total variation, with the two Synchiropus species showing comparatively distinct distributions in morphometric space, whereas greater overlap was observed among the four Callionymus species. COI sequences were obtained from 22 individuals. Intraspecific genetic divergence ranged from 0 to 1.1%, whereas interspecific distances ranged from 11.9% to 24.7%. Maximum Likelihood analysis recovered distinct clusters corresponding to the morphologically identified species, while the position of C. filamentosus sequences indicated that phylogenetic relationships within the examined callionymids warrant further investigation. Overall, the combined morphological and molecular results support the complementary use of traditional diagnostic characters and DNA barcoding for the identification of Mediterranean dragonets. The present study also contributes additional COI barcode data for poorly represented Mediterranean Callionymidae and provides baseline information for future systematic and phylogenetic studies.

Artificial wrecks (AWs), which are intentionally submerged structures to promote marine biodiversity and support recreational diving, have gained increasing prominence on a global scale. Nevertheless, concerns regarding their environmental safety persist, especially in regions where regulatory oversight is limited. This study examines the ecological and human health risks posed by two artificial wrecks (“Alaybey” and “9 Eylül”) deployed in the Karaburun Peninsula, Northeast Mediterranean, Türkiye, compared to a no-wreck site (Aslan Kayası). Despite rigorous pre-sinking protocols to remove fuels and oils, critical pollutants—such as antifouling paint residues containing Cu, Zn, Pb, and PCBs—persist due to incomplete cleaning. Over two years, seasonal sampling of sediments, mussels (Mytilus galloprovincialis), and fish (Diplodus vulgaris) revealed alarming trends. Sediments near AWs showed enrichment of Pb (EF: 37.2–92.1) and Cd (EF: 9.3–16.0) from significant to extremely high enrichment. The Potential Ecological Risk Index (PERI) reached > 1,000 at the “9 Eylül” wreck, classifying it as "extremely high risk." Mussels on AWs bioaccumulated Cd and Pb above EU safety thresholds, while fish on AWs exhibited Pb levels of 236–340 fold over limits. Notably, Hg contamination in fish samples obtained from the no-wreck site (1.2 mg kg⁻¹) was traced to historic mining activities, underscoring region-wide pollution. These findings challenge the assumption that "cleaned" AWs are environmentally benign and highlight systemic gaps in pollutant mitigation, particularly for toxic coatings. The study advocates for stringent pre-deployment protocols, including paint stripping and PCB screening, to align AWs projects with global sustainability goals.

This study examines the feeding ecology and reproductive biology of the invasive pufferfish Torquigener hypselogeneion along the Levantine coast of Türkiye. A total of 400 specimens were sampled (2018–2019), with a length-weight relationship of W = 0.0198L3.0144 (r = 0.983). Stomach content analysis identified 24 prey groups, with crustaceans, gastropods, and bivalves being the most significant. T. hypselogeneion exhibits fully opportunistic feeding behavior. The reproductive period spans July to October, peaking in September (GSI values). Relative fecundity averaged 29046 ± 1525 eggs. During the field surveys, it was determined that T. hypselogeneion was one of the most abundant invasive fish species in the coastal ecosystem in the study area. These findings provide key bio-ecological insights into T. hypselogeneion in the eastern Mediterranean.

The potential of non-destructive sampling methods such as a baited remote underwater video system (BRUVS) for fish monitoring is immense. This potential is demonstrated in our study, which examined three sites with different habitats (rocky, wreck, seagrass) in the Karaburun- Ildır Bay Special Environmental Protection Area (SEPA) in the Aegean Sea. From 60 hours of video recordings, we identified 3771 individuals from 24 fish species belonging to 10 families. The rocky habitat had the highest total abundance (44.9%), with a statistical difference. The result of Shannon-Wiener`s index specified the highest value in the wreck (H`WR=1.73), although the rocky had greater fish diversity (H`RR=1.54). It is clear that there is a lack of studies, especially in the Eastern Mediterranean, and the benefits of long-term periodic monitoring studies using BRUVS should not be ignored.

In this study, a total of 80 specimens belonging to long-snouted seahorse populations distributed in the Black and Aegean Seas were collected from fishermen and analysed. As a result of the analyses, it was determined that there was a statistically significant difference between the populations in terms of total lengths, eye diameters, dorsal fin lengths and body heights values, and in the SIMPER analysis, based on metric measurements and meristic counts, it was calculated that the total difference between the populations was 3.13%.

Deployment of artificial wreck reefs (AWRs) near natural reefs can influence fish assemblages on both reefs. Here, we assessed fish attitudes (abundances, biomass and species richness) according to different level complexity areas of wrecks, feeding guilds of fish and body size of fish of two identical AWRs deployed at the same depth (36.6 m) and different distances from natural reefs. Scuba divers used visual census method to sample fish communities at wrecks for two years. An average of 2346 individuals per dive belonging to 52 species were observed on wrecks combined. Both mean fish abundance and mean biomass did not differ significantly between wrecks. Mean species richness was significantly greater at9 EylülthanAlaybey. Planktivore was the most abundant feeding guild on wrecks, and its abundance statistically differed between AWRs. The comparisons of fish assemblages at the different level complexity areas of the wrecks show differences, the highest mean abundances were recorded at the areas of low complexity of the wrecks. The results of this study show that although deploying artificial wreck reefs near to natural rocky reefs catalyses fish colonization, it does not present an exact influence on the fish communities of AWRs. We have not known yet how creating an artificial wreck reef affects fish community of natural reefs. With giving extra importance to the choice of deployment area, AWR applications may transform to win-win projects for both the marine environment and recreational users, such as divers and anglers.

The stress on the marine environment caused by industrialization in developing economies is indisputable. The Aliağa region, which has unique features such as being heavily influenced by industrialization and having different types of marine habitats was preferred as a monitoring point. By determining the current status of fish density and diversity, the focus was on obtaining data that could allow future comparisons. Without the seasonal variability, 39 fish species representing 14 families were identified, with two abundant families: ten species in both Sparidae and Labridae. The greatest fish diversity was recorded respectively in the spring, summer and autumn. Abundant species were Boops boops with 19.3%, Chromis chromis (17.4%), Spicara smaris (15.0%) and Atherina boyeri (12.5%) in total abundance. A total of 1.89 individuals/m2 that weighed 20.43 g/m2 were identified in the study period.

Pterois miles (Bennett, 1828) is an aquatic invader and disruptive predator for marine ecosystems. A single lionfish was photographed and sampled in March 2021 during a scientific survey at 36 m depth in Karaburun/İzmir Bay. In this study presents an update on the lionfish's northward progression in the Aegean Sea.

As the Black Sea and Marmara Sea population of the Broadnosed Pipefish Syngnathus cf. argentatus show some morphological differences from the Mediterranean Sea populations, some authors regard it as an endemic species Syngnathus argentatus Pallas, 1814, while others consider it as a synonym of S. typhle Linnaeus, 1758. The aim of this study is to compare the populations of the Black Sea and Sea of Marmara with the Aegean Sea population, using a combination of morphological and molecular characters, in order to clarify their taxonomic status. Sampling was carried out at three stations in the Black Sea, two in the Sea of Marmara and three in the Aegean Sea, and a total of 24 morphometric and 6 meristic characters were examined. Metric data were analysed by Principal Component Analysis (PCA) and phylogenetic relationships between the populations were analysed using both cytochrome oxidase subunit 1 (COI) gene and cytochrome b (cyt-b) gene sequences. Although constant differences were observed in snout depths between the Black Sea/Marmara Sea and the Aegean Sea populations, other morphological features and genetic analysis did not enable these populations to be differentiated. These findings indicate that S. argentatus is a synonym of S. typhle.