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Over the past two decades, the field of sclerochronology has been rapidly developing, with scientists devoting significant efforts to studying the physical and chemical variations in hard tissues of aquatic organisms. Most of this research has been limited to certain taxa and geographic areas. Although growth increments in fish otoliths are used for sclerochronology purposes, relatively little has been done in the Mediterranean Sea. According to the literature, the chemical composition of otoliths from Mediterranean fish species has primarily been used for analyzing migration patterns, habitat use, and population structure of commercially important fish species. To the best of our knowledge, there are no studies on fish growth chronology construction conducted in the Mediterranean Sea. In order to identify the opportunities for sclerochronology research on fish from the Mediterranean, we used FishBase to identify potential candidate species with a sufficiently long lifespan and clearly defined growth increments for growth chronology construction and otolith chemistry research. We also present the challenges and limitations for sclerochronology research, including: (i) very few fish species in the Mediterranean Sea have a longevity of several decades; (ii) issues associated with reliable age determination for certain long-lived fish species; (iii) a general lack of understanding and effort to constructed and manage otolith collections; and (iv) limitations imposed by the availability of funding, expertise, and instrumentation. Despite these challenges, fish sclerochronology research has strong potential in the Mediterranean and adjacent seas. Recent studies in the Adriatic Sea have resulted in the construction of bivalve chronologies and the geochemical analysis of shells, providing important time-series data for comparative analysis and a multispecies approach. Furthermore, studies conducted in other parts of the world have demonstrated great potential for the use of fish otoliths in monitoring environmental variability and the effects of pollutants and disturbance.

The growth of age-1 Pacific saury Cololabis saira was compared based on an analysis of the body-length frequency distributions, radius of the annual ring (otolith hyaline zones; ROH), and growth patterns in otolith increments. Fish were sampled at various locations between off the Japanese coast (144°E) and in the Central Pacific (160°W) in June and July 2006, and the measurements were compared among the stations ranging over six longitudinal areas, each with a longitudinal area of 10°. The mode of body-length frequency distributions of age-1 fish was larger in fish sampled west of 160°E (size class modes of 32.0-32.5 and 31.5-32.0 cm, respectively, in each 10° longitude area) than in those sampled east of 170°E (28.5-29.0 or 29.0-29.5 cm in 3 areas). The ROH was also larger in the former group (west of 160°E) than in the latter group (east of 170°E), but hatch periods of these two groups and age in days when the hyaline zones form in August or September did not differ based on the analysis of otolith growth increments. The growth difference occurred in the period between when the fish started their northward migration and when the hyaline zone was formed. These results indicate that the habitats of the two groups were separate until at least June or July of their second year of life. [ABSTRACT FROM AUTHOR]

Abstract: Topographical relationships between the mineral and organic components are important to understand the process involved in biomineralisation. We examined nanostructural features of cod (Gadus morhua) otoliths using atomic force microscope (AFM). Acicular aragonitic fibres that form primary increments observed in scanning electron or light microscopy were composed of lamellae, themselves being composite arrangements of round granules (diameter<50nm) surrounded by an organic (?) cortex. The lamellae presented a banding pattern, which might correspond to a growth period of about 15min. Cod otolith granules were similar in size, shape and arrangement to that previously reported for another fish species. The existence of smallest otolith organization units is suggested since granules are themselves composite. Finally, the intra-daily growth rhythm makes it possible to consider very high-resolution biological and environmental reconstructions in the future. [Copyright &y& Elsevier]

Age and growth of alfonsinoBeryx splendens(Lowe) were studied using counts of presumed daily incremental growth rings on the transverse section of otoliths of fish collected from the Kanto District, central Japan. Microstructural growth increments were observed from the core to the outermost margin of the broadest of approximately 50 branches formed on the surface of an otolith. Of 98 otoliths examined, 46 were readable. The number of increments and fish lengths ranged from 448 (218 mm fork length[FL]) to 3701 (411 mm FL). The ages of these fish were estimated to be 1 year, 2 months and 10 years, 2 months, respectively, assuming that an increment was formed daily. The von Bertalanffy growth equation combined for males and females was expressed as follows:L t = 542{1 − exp [−0.133(t + 2.00)]}, whereL t is fork length (mm) at yearly aget. The results of the present study were compared with those of other researchers who had studied alfonsino from central Japan. [ABSTRACT FROM AUTHOR]

The otolith microstructure and microchemistry of a tropical eel, Anguilla marmorata , were examined in glass eels collected from Taiwanese and Japanese coasts. Ages at metamorphosis (onset of metamorphosis) and recruitment, respectively, were 114 ± 13.8 (mean ± SD) days and 144 ± 15.7 days in Taiwanese stock, and 123 ± 13.9 days and 154 ± 17.3 days in Japanese stock. No significant differences were found in ages between the two stocks. The duration of metamorphosis estimated from otolith microstructure was 10–24 days, which is the same in the different stocks. For both stocks examined, close linear relationships were found between ages at metamorphosis and recruitment, suggesting that individuals that metamorphosed earlier were recruited to the coasts at a younger age. [ABSTRACT FROM AUTHOR]