Temperatures experienced during early ontogeny significantly influence fish phenotypes, with clear consequences for the wild and reared stocks. We examined the effect of temperature (17, 20, or 23 °C) during the short embryonic and yolk-sac larval period, on the swimming performance and skeleton of metamorphosing Gilthead seabream larvae. In the following ontogenetic period, all fish were subjected to common temperature (20 °C). The critical swimming speed of metamorphosing larvae was significantly decreased from 9.7 ± 0.6 TL/s (total length per second) at 17 °C developmental temperature (DT) to 8.7 ± 0.6 and 8.8 ± 0.7 TL/s at 20 and 23 °C DT respectively (p < 0.05). Swimming performance was significantly correlated with fish body shape (p < 0.05). Compared with the rest groups, fish of 17 °C DT presented a slender body shape, longer caudal peduncle, terminal mouth and ventrally transposed pectoral fins. Moreover, DT significantly affected the relative depth of heart ventricle (VD/TL_,p < 0.05), which was comparatively increased at 17 °C DT. Finally, the incidence of caudal-fin abnormalities significantly decreased (p < 0.05) with the increase of DT. To our knowledge, this is the first evidence for the significant effect of DT during the short embryonic and yolk-sac larval period on the swimming performance of the later stages.

Environmental pollution is a growing threat to natural ecosystems and one of the world’s most pressing concerns. The increasing worldwide use of pharmaceuticals has elevated their status as significant emerging contaminants. Pharmaceuticals enter aquatic environments through multiple pathways related to anthropogenic activity. Their high consumption, insufficient waste treatment, and the incapacity of organisms to completely metabolize them contribute to their accumulation in aquatic environments, posing a threat to all life forms. Various analytical methods have been used to quantify pharmaceuticals. Biotechnology advancements based on next-generation sequencing (NGS) techniques, like eDNA metabarcoding, have enabled the development of new methods for assessing and monitoring the ecotoxicological effects of pharmaceuticals. eDNA metabarcoding is a valuable biomonitoring tool for pharmaceutical pollution because it (a) provides an efficient method to assess and predict pollution status, (b) identifies pollution sources, (c) tracks changes in pharmaceutical pollution levels over time, (d) assesses the ecological impact of pharmaceutical pollution, (e) helps prioritize cleanup and mitigation efforts, and (f) offers insights into the diversity and composition of microbial and other bioindicator communities. This review highlights the issue of aquatic pharmaceutical pollution while emphasizing the importance of using modern NGS-based biomonitoring actions to assess its environmental effects more consistently and effectively.

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 morphometric features for stock discrimination. In the present study, we used geometric morphometric variables to compare the European sardine Sardina pilchardus putative stocks of the Aegean and Ionian Seas (eastern Mediterranean). Landmark data of fish collected at seven different sites were subjected to canonical analysis of principal coordinates (CAP). The average body condition of sardines from these sites was strongly and linearly related to corresponding scores along CAP1, the axis exhibiting the highest correlation with the morphometric data cloud. The average scores along CAP2 and CAP3 appeared to be linked to morphological differentiation related to temperature effects and prey availability (mesozooplankton biomass). Despite the primary and confounding effect of body condition, discrimination of different morphotypes corresponding to the Aegean and the Ionian Sea stocks was highly significant with 81% correct reallocations for the respective CAP model.

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 metamorphosis (56–58 days post-hatching, dph) and the early juvenile stage (93–95 dph). The experimental populations were reared at different water temperatures (17, 20, or 23 °C DT) from epiboly onset to the end of the yolk-sac larval stage (5–7 days post-fertilization, dpf) and then at a common rearing temperature (20 °C), up to the end of the trials (93–95 dph). Otolith shape and bilateral asymmetry were analyzed at metamorphosis (20–21 mm standard length, SL) and the early juvenile stage (31–32 mm SL). The results of elliptic Fourier analysis showed that DT significantly affected the otolith shape at both stages examined. Furthermore, elevated DT significantly increased the asymmetry levels of seabream otoliths in the early juvenile stage. The results are discussed in terms of the thermally induced long-term changes of seabream otolith morphology and the potential effects of the raised otolith asymmetry on wild seabream juveniles.