Laboratory of Sclerochronology and Stomach Contents of Marine Organisms
In this lab, hard parts of fish commercial species are prepared and examined for age estimation. The study of growth is essential for assessing the productivity of commercial stocks and suggesting appropriate management measures. Species with fast growth, early breeding age and low longevity tolerate fishing pressures better than those with slow growth, late breeding age and high longevity. Specifically, age estimation is done through microscopic analysis of the following hard parts including otoliths (sagitte, and/or lapillus, and/or asteriscus) and other bony parts and scales in bony fishes, vertebrae and spines in cartilaginous fishes, and statoliths and beaks in cephalopods. Microscopic observation of otoliths makes it possible to highlight the different stages of growth, which may be annualgrowth (annual growth) in adult specimens, or dailyrings (daily rings) in juvenile individuals and in any case less than one year old. Sometimes sagittas must be prepared by grinding, sanding, sectioning, and fixing on slides using glues for subsequent sanding and fixing in balsam. The sectioning of strong and large sagittas is then done by means of a micro-sectioning machine with diamond blades, after embedding in resins under a hood. As part of the ecosystem approach to fisheries management, gastric contents (stomachs previously extracted and prepared in the wet laboratory) of commercial species are also analyzed to study their nutrition and trophic relationship with various organisms in demersal communities. Diets are analyzed by microscopic observation of prey and/or portions thereof, previously fixed in alcohol, to allow taxonomic identification.
