The verification of authenticity and detection of food mislabeling are elements that have been of high importance for centuries. During the last few decades there has been an increasing consumer demand for the verification of food identity and the implementation of stricter controls around these matters. Fish and seafood are among the most easily adulterated foodstuffs mainly due to the significant alterations of the species' morphological characteristics that occur during the different types of processing, which render the visual identification of the animals impossible. Even simple processes, such as filleting remove very important morphological elements and suffice to prevent the visual identification of species in marketed products. Novel techniques have therefore been developed that allow identification of species, the differentiation between species and also the differentiation of individuals that belong to the same species but grow in different populations and regions. Molecular markers have been used during the last few decades to fulfill this purpose and several improvements have been implemented rendering their use applicable to a commercial scale. The reliability, accuracy, reproducibility, and time‐and cost‐effectiveness of these techniques allowed them to be established as routine methods in the industry and research institutes. This review article aims at presenting the most important molecular markers used for the authentication of fish and seafood. The most important techniques are described, and the results of numerous studies are outlined and discussed, allowing interested parties to easily access and compare information about several techniques and fish/seafood species.

Monitoring of Delphinidae species population patterns in the Mediterranean Sea was carried out in a sequence of surveys employing different approaches. Data from seven-year surveys with small catamaran sailing boats were analyzed under model-based approaches. Density Surface Models were used to produce spatial distribution prediction of three Delphinidae species (Stenella coeruleoalba, Tursiops truncatus, and Delphinus delphis) in an extended study area covering much of the Mediterranean Sea. A classical distance sampling protocol was applied in order to calculate the detection probability of clusters. Static (depth, slope, distance from the coast, and distance from isobaths of 200 m) and nonstatic (sea surface temperature and chlorophyll) variables were used to predict the species distribution/abundance in a generalized additive model context. Stenella coeruleoalba was found to be the dominant species, with an extended distribution in the study area; its abundance was significantly affected by both depth and distance. Tursiops truncatus and Delphinus delphis illustrated a significant abundance correlation with depth and chlorophyll, respectively, while both species showed a robust longitude correlation. Our model pinpoints the significance of nondesigned transect line surveys, suggesting the importance of specific habitat areas for future monitoring and conservation aspects of marine mammals.

The rainbow trout, Oncorhynchus mykiss, comprises a non-indigenous species of the European freshwater ecosystem. Due to its remarkable advantages of fast-growing and facultative adaptability in various habitats under different conditions, it has become the most dominant commercially reared species of freshwater aquaculture in Greece. Despite its economic importance, there is a dearth of population genetic studies regarding the origin of any posterior introduction by the private aquaculture sector. In this study, a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was used, in order to assess variation in five mitochondrial DNA protein-encoding regions and the control region, covering more than 5,500 bp of the 16,600 bp total mitochondrial genome size. The samples derived from 10 rainbow trout farms throughout Greece representative of the freshwater aquaculture sector. The conducted population structure analysis revealed two major clusters among the farmed-rainbow trout populations. Moreover, the overall genetic diversity was substantially attributed to the diversity within populations rather than among them. In any case, both factors obtained from AMOVA analysis were statistically significant. The obtained haplotype network reinforced the existence of two central haplotype clusters among the farmed-rainbow trout populations in the Greek freshwater aquaculture sector.

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