Servet Ahmet Doğdu

This study aims to identify the non-indigenous fish species for which significant knowledge gaps persist by evaluating the existing scientific literature on their fundamental biology (age-growth and length-weight relationships). Data were synthesized descriptively following PRISMA 2020 guidelines. In the study, a list of 177 non-indigenous fish species recorded in the Mediterranean was compiled, and a systematic literature survey was conducted to identify scientific publications containing length-weight relationship (LWR) and age-growth (AG) parameters for these species. Studies outside the Mediterranean or on non-fish taxa were excluded. Databases were searched up to November 2025. Data were synthesized descriptively by species, country, and study type. Risk of bias was not formally assessed in this review. A total of 143 studies were identified. The analyses revealed an uneven geographical distribution of research, with Türkiye leading by a wide margin with 84 (58.86%) studies. Lagocephalus sceleratus with 25 studies for LWR, and Saurida lessepsianus with 11 studies for AG, stood out as the most researched species. However, it was determined that fundamental biological data are still unavailable for many non-indigenous species. These findings reveal critical knowledge gaps that need to be urgently addressed for the sustainable management of increasing non-indigenous fish populations and highlight the urgency of expanded scientific research on these species.

The Indo-Pacific lizardfish Synodus randalli has entered the Mediterranean Sea via the Suez Canal and has rapidly expanded its range since it was first recorded in 2023. In this study, ten S. randalli specimens collected from the Iskenderun Bay (Türkiye) were genetically characterized using the COI barcode region. Phylogenetic analyses revealed that all Mediterranean S. randalli sequences form a highly supported monophyletic clade, clearly distinct from S. synodus and other species. Pairwise K2P distances indicated a distinct barcoding difference between S. randalli and S. synodus. Density plots, histograms, and box plots confirmed that intra- and inter-species variation ranges did not completely overlap. ASAP species delimitation analysis yielded two well-defined clusters corresponding to the two species. Overall, our results provide the first robust COI reference sequences for Mediterranean S. randalli, confirm its genetic distinctiveness, and demonstrate the reliability of COI barcodes for tracking non-native Synodontidae in the rapidly warming Mediterranean Sea.

This study reports the flat needlefish Ablennes hians on the coasts of Türkiye for only the second time. mtDNA COI gene region was used for molecular identification of the species. On 21 December 2024, fishermen caught the specimens used in the study at a depth of 24 m in Iskenderun Bay. The COI sequences obtained in this study matched A. hians reference sequences with 100% identity in BLAST searches of the BOLD and NCBI databases. Genetic distance results indicate that the Turkish population is extremely close to the Israel population (0.0085) this Mediterranean group is genetically distinct from the closest Red Sea (Egypt) population (0.0563) and other Indo-Pacific populations. This verified that A. hians may have entered the Mediterranean via the Red Sea. On the other hand, more specimens from the Mediterranean, Red Sea and Atlantic Ocean should be studied to determine the true route of the species.

In this study, we aimed to clarify the taxonomic status of Belonidae species distributed in the Mediterranean Sea and the Black Sea by conducting detailed genetic and morphological markers. A total of 550 needlefish samples were caught between January 2022 and January 2024. The data set used in the study contains a total of 171 sequences for the COI gene and 120 sequences for the 12s rRNA gene from different Belonidae species, including data from GenBank. Systematic analysis of needlefish species was investigated by using sequencing of mtDNA COI and 12s rRNA gene regions and morphological characters in the Turkish Marine Waters. A separate analysis of the two mitochondrial genes supported by morphological characters revealed that each species is grouped within itself. The genetic and morphological analyses showed that Belone belone acus and Belone belone euxini which are considered as the subspecies of Belone belone are not subspecies of the genus Belone and should be considered at the species level, Belone belone. Belone svetovidovi is also considerably different from Belone belone and should be considered as a different species. T. acus imperialis, which is thought to be distributed in the Mediterranean Sea, is not a subspecies of Tylosorus acus and should be revised as Tylosorus imperialis which genetically differs from Tylosorus acus and also other Tylosorus species at the species level.

Collagen, one of the most important biopolymers, is widely used in the food and pharmaceutical industries due to its functional and technological properties. Alien species, especially of Indo-Pacific origin, entering Mediterranean waters can exert pressure on native species and cause ecological and economic effects. In this study, we produced collagen from the scale of Sargocentum rubrum to bring this species to the economy and to reduce the pressure on our infested marine ecosystem as a surplus value. Acid-soluble collagen was extracted; a characteristic sodium dodecyl SDS-PAGE gel electrophoresis profile for type I collagen was obtained from the S. rubrum scales. The yield of collagen extracted from the scales of S. rubrum by the ASC method was calculated as 11.2%. The results of the analyses show that the collagen obtained from S. rubrum scales was Type I collagen with high yields. It has been proved that non-economic alien species as S. rubrum used in our study can be used as an alternative source instead of terrestrial animal collagen. The results obtained show that collagen obtained from S. rubrum scales can be a good alternative source for biomedical and other cosmetic industries.

The length-weight relationship data is important basic information that helps to compare species between populations and habitats. In this study, we provide detailed information on the length-weight relationships and condition factors of Lagocephalus guentheri from the Iskenderun Bay, northeastern Mediterranean Sea. A total of 408 (262 Female, 146 Male) specimens were collected on commercial trawlers by local fishermen caught between December 2022 to December 2023 from Iskenderun Bay. The total length range was 11.0-36.9 cm and 11.2-36.7 cm for females and males, respectively. The total weight values of females and males ranged from 20.30-1080.50 g and 20.50-1012.36 g, respectively. The length-weight relationship of L. guentheri was calculated as W = 0.0098 × L3.2145 (R2 = 0.9960) for females, W = 0.009 × L3.2399 (R2 = 0.9963) for males, and W = 0.0095 × L3.2243 (R2 = 0.9962) both sexes. The Fulton’s condition factor was observed as 1.2384 for females, 1.2504 for males, and 1.2335 for both sexes. This study is the most recent reference on length-weight relationships and condition factors for L. guentheri after correction of species identification. It is very important to determine the population parameters of pufferfish species to shed light on the studies to be carried out to restore the ecological balance in the Mediterranean ecosystem. This study will provide basic information that will be useful for fisheries scientists and managers in the Mediterranean Sea.

Stomach content analysis of fish not only helps document their food spectrum but also provides an overview of the food network they are involved in. In this study, we aimed to investigate the food composition of L. guentheri from the Iskenderun Bay, northeastern Mediterranean Sea. Specimens were collected from between January 2022 and August 2022. A total of 215 L. guentheri specimens stomachs were examined during the study for stomach content analysis. About 215 stomachs analysed, 60 (27.9%) stomachs were empty and 155 (72.1%) stomachs contained food items. Analysis of the diet composition showed that the fish are carnivorous and prey on pisces, crustacea, bivalves and cephalopoda. Based on the index of relative importance, pisces were identified as the most important prey (68%), followed by crustaceans (14%), bivalves (5%), cephalopoda (0.5%) and digested materials (12.5%). The results show that L. guentheri has a high feeding tendency to fish. This study increases the knowledge of the feeding preferences of L. guentheri. The present paper is also the first document on the diamondback puffer Lagocephalus guentheri food composition in the Mediterranean Sea.

The records of the striper eel catfish Plotosus lineatus have been assigned based on morphological characters in the Mediterranean Sea. However, molecular and genetic analyses are needed to confirm the morphological taxonomic determination and avoid misidentification. In this study, the mitochondrial cytochrome c oxidase subunit I (COI) gene region was used for genetic confirmation of Plotosus lineatus in the Mediterranean Sea. The obtained P. lineatus sequences were found to have a 100% identity match with the Red Sea and Mediterranean records. The present molecular genetic study confirms the presence of P. lineatus in Turkish marine waters. Also, this study is the first genetic confirmation of P. lineatus on the coast of Türkiye and in the Mediterranean Sea.