Potential and limitations of applying the mean temperature approach to fossil otolith assemblages

Abstract

Evaluation of the impact of climatic changes on the composition of fish assemblages requires quantitative measures that can be compared across space and time. In this respect, the mean temperature of the catch (MTC) approach has been proven to be a very useful tool for monitoring the effect of climate change on fisheries catch. Lack of baseline data and deep-time analogues, however, prevent a more comprehensive evaluation. In this study, we explore the applicability of the mean temperature approach to fossil fish faunas by using otolith assemblage data from the eastern Mediterranean and the northern Adriatic coastal environments corresponding to the last 8000 years (Holocene) and the interval 2.58–1.80 Ma B. P. (Early Pleistocene). The calculated mean temperatures of the otolith assemblage (MTO) range from 13.5 to 17.3 °C. This case study shows that the MTO can successfully capture compositional shifts in marine fish faunas based on variations in their climatic affinity driven by regional climate differences. However, the index is sensitive to methodological choices and thus requires standardized sampling. Even though theoretical and methodological issues prevent direct comparisons between MTO and MTC values, the MTO offers a useful quantitative proxy for reconstructing spatial and temporal trends in the biogeographic affinity of fossil otolith assemblages.

Palaeontological evidence for community-level decrease in mesopelagic fish size during Pleistocene climate warming in the eastern Mediterranean

“…Overall, the fish in the three assemblages are small, with a median length of 3.22 cm (ranging from 0.82 to 10.07 cm) and a median weight of 0.27 g (ranging from 0.002 to 106.13 g) (figure 2 and electronic supplementary material, figure S3; electronic supplementary material, table S3; [60]). The small size of the fish is expected, given the nature of the otolith fossil record and the sampling method [68]. The transition from the MIS 20 glacial to the MIS 19 interglacial is associated with 36% decrease in the assemblage-level median fish weight (from 0.36 g to 0.23 g), followed by 73% increase in the subsequent MIS 18 glacial period (to 0.40 g), and these changes are statistically significant: Kruskal-Wallis test χ 2 = 65.104, d.f.…”

Palaeontological evidence for community-level decrease in mesopelagic fish size during Pleistocene climate warming in the eastern Mediterranean

“…Overall, the fish in the three assemblages are small, with a median length of 3.22 cm (ranging from 0.82 to 10.07 cm) and a median weight of 0.27 g (ranging from 0.002 to 106.13 g) (Figures 2 and S3; Table S3). The small size of the fish is expected, given the nature of the otolith fossil record and the sampling method (63). The transition from MIS 20 glacial to MIS 19 interglacial was associated with 36% decrease in the assemblage-level median fish weight (from 0.36 g to 0.23 g), followed by 73% increase in the subsequent MIS 18 glacial period (to 0.40 g; Kruskal-Wallis test χ 2 = 65.104, df = 2, p < 0.001; pairwise Wilcoxon test: p < 0.001 for both MIS 20-MIS 19 and MIS 19-MIS 18; Figure 2; Table S3).…”

Otolith atlas for marine fishes of the southwestern Atlantic occurring along southern Brazil (28° S-34° S)

“…In addition to their broad applicability in fisheries sciences due to their high fossilization potential, otoliths play an important role in identifying fossil fish remains in palaeo-ichthyological studies, for example, to identify fossil fish assemblages for phylogenetics (Nolf 1985;Lin et al 2019;Aguilera et al 2020) and reconstruct reef fish communities (Lin et al 2019). Archeologists and anthropologists may also use otoliths to reconstruct fishing and food habits of ancient populations and palaeoclimatologists to reconstruct climatological events (Reitz and Wing 2008;Bertucci et al 2018;Agiadi et al 2022;Milheira et al 2023).…”