| Summary: | 5th International Otolith Symposium (IOS2014), 20-24 October 2014, Mallorca, Balearic Islands Spain.-- 1 page The growth and age of the lanternfish Ceratoscopelus maderensis from the western Mediterranean Sea (December 2009) was estimated throughout its entire lifespan, using otoliths (sagitta) of 59 individuals, from 3.5 mm (larva) to 64 mm (mature adult) standard length (SL). Sagittal otoliths were analyzed by means of light microscope in larvae. The examination of several sagitta from transforming and juvenile-adult stages was also accomplished by means of scanning electron microscopy (SEM) to determine otolith microstructure in those zones that were under the light microscopic resolution threshold. Serial photographs of each sagitta were mounted to count increment rings over the entire development of the specimens, and subsequently, estimate individual ages, under the assumption that the microincrements are formed by daily deposition (proven in other studies on myctophids). Maximum radius followed a significantly positive linear regression with body length. Three characteristic zones were identified in the otoliths apart from the central core: larval, transitional and post-metamorphic zones. The central core and hatched ring were determined on the basis of 30 larvae. In larvae ≤12 mm notochord length (NL), the microincrements ranged between 0.8 and 1.4 μm, accordingly with between-rings widths reported for lanternfishes from other regions. Distances between presumably daily rings increased progressively across larval development. A variable and characteristic band pattern was found in transforming (>16 mm SL) and adult stages, reflecting the ontogenetic shift experienced during the metamorphosis, coinciding with a habitat change from the epipelagic zone to deeper waters and the onset of diel vertical migrations. The transitional zone around the central core was rather variable and dim among individuals. In the largest adults, “daily-based rings” decreased towards the otolith edge with frequent changes in the deposition rate. The number of microincrements ranged from 7 to 332 in the analysed individuals, and it has been adjusted by von Bertalanffy’s model as a function of the NL/SL (r2=0.955, IC=95%). Growth patterns deduced from otolith microstructure observations coincided with those reported for the same species in North Atlantic waters (Linkowski et al. 1992). Despite there were non-significant differences between the two regions, growth patterns suggested faster growth in the Mediterranean, where the species may reach 60 mm SL in 350 days, whilst in the Atlantic individuals may reach the same length in 400 days. A likely explanation for “faster growth” in the Mediterranean could be due to its warmer temperature regime with respect the Atlantic region Peer Reviewed
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