Tagging is usually intended to measure or
determine something, e.g. population size,
migration routes, stock definition, exploitation
rates, or comparisons such as growth and
survival effects of two hatchery treatments.
Learning whether a lake contains several
separate stocks of a species or instead has a
single intermixing group is much simpler than
determining survival and exploitation rates for
wide-ranging anadromous fish. Experimental
designs and requirements regarding issues such
as tag retention and growth effects can be quite
different depending upon the goals of a study.
Thus it is critical to begin by clearly defining
what you are trying to accomplish.