An example of otoliths removed from an adult carp.
An example of a cross section under a microscope. Notice the evident layers that correspond to years of growth in this otolith.
Because carp are long-lived (often few decades) one can learn a lot about their history and what makes them successful in particular lakes by conducting ageing analyses. The main information we are looking for is how many age classes are present in the population. Populations comprised of numerous year classes are more difficult to manage because their young can survive during most years. However, populations comprised of only 2-3 year classes spaced several years apart are much easier to manage because natural processes limit their reproduction in most years.
We age the carp under a microscope using their otoliths (inner-ear bones), which accrue growth rings much like trees.