Lasers Determine Shark Age and Aid Conservation Efforts

Scientists are using lasers to determine the age of sharks. This new method combines geochemistry and marine ecology. It provides a novel approach to refining conservation practices for these vulnerable species.

Researchers analyze the chemical composition of shark vertebrae. They link these measurements to the chemistry of the land and water systems the sharks inhabit. This technique challenges conventional age analysis methods and assumptions about shark ecology.

Two analytical geochemistry techniques are used. Micro-X-ray fluorescence (micro-XRF) uses X-rays. Laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) uses laser beams. A focused laser beam removes material from the vertebrae sample. The resulting aerosol then goes into a mass spectrometer for ionization and element detection.

Shark vertebrae grow concentrically, similar to tree rings. They incorporate elements and isotopes from their environment as they grow. The analyzed elements include potassium, calcium, and strontium. Isotopes are atoms with the same number of protons but different numbers of neutrons. These are used as natural tracers to identify sources, track pollution, and determine the age of various materials.

This technology helps determine the age of organisms in ecosystems. Traditional methods rely on transmitted light optical microscopy. This involves counting light and dark bands in thin slices of vertebrae. Each band is assumed to represent one year of growth.

The study focused on the Speartooth Shark, a vulnerable river shark species. Fewer than 2,500 mature individuals remain in the wild. The research confirms that shark vertebrae record geochemical fingerprints of their environment. Strontium, for example, is incorporated into the vertebrae from the environment as sharks grow. Its concentration in the vertebrae depends on environmental strontium concentrations.