Shark Lasers Could Help Save Vulnerable Species

Why It Matters

Accurate age data are essential for assessing recruitment and setting protection measures for the roughly 2,500 remaining speartooth sharks, making this technique a potential game‑changer for marine conservation.

Key Takeaways

• Laser ablation ICP-MS yields precise speartooth shark ages
• Traditional vertebrae band counts overestimate ages for this species
• Strontium fingerprints reveal sharks' seasonal habitat changes
• Only ~2,500 adult speartooth sharks remain in Australia/PNG
• Method could extend to other vulnerable marine species

Pulse Analysis

Accurately determining the age of long‑lived sharks has long been a bottleneck for fisheries science and conservation. Researchers have relied on counting growth bands in thin sections of vertebrae, a method borrowed from dendrochronology that assumes one band equals one year. In practice, band visibility varies with species, diet and preservation, leading to systematic errors—especially for cryptic, river‑dwelling sharks such as the speartooth (Glyphis glyphis). Mis‑aged individuals skew population models, making it difficult to assess recruitment rates or the impact of fishing pressure.

The University of Melbourne team introduced laser ablation inductively coupled plasma mass spectrometry (LA‑MC‑ICP‑MS) to bypass visual band counting. A focused laser vaporizes microscopic sections of a vertebra, creating an aerosol that a mass spectrometer analyzes for elemental concentrations, notably strontium. Because strontium incorporation mirrors ambient water chemistry, the resulting geochemical fingerprint tracks seasonal shifts in salinity and precipitation. The study showed that speartooth sharks’ vertebrae recorded distinct wet‑ and dry‑season signatures, allowing researchers to assign ages with a precision unattainable by traditional microscopy.

These refined age estimates have immediate conservation value for a species estimated at only 2,500 mature individuals across Australian and Papua New Guinean river systems. Reliable age structure informs stock assessments, helps set protective catch limits, and guides habitat restoration priorities. Moreover, the laser‑based workflow is transferable to other data‑deficient taxa, from elasmobranchs to freshwater fish, where age validation remains elusive. As the technique becomes more accessible, it could become a standard tool in marine ecology, sharpening our ability to monitor vulnerable populations before they slip toward extinction.