Check out my recent #JFB Editor's Choice: "Uncovering the lazybones of the shark world": https://doi.org/10.1111/jfb.70230. Stable isotopes, going beyond identifying where a fish has come from, or where it has been, and instead providing data on key life-history traits! Paper by Delgado et al https://doi.org/10.1111/jfb.70109