6. Marking and Tagging
Tagged and marked animals have been studied to obtain information on their behavior, population dynamics, and ecology, all of which are essential for developing conservation and management strategies. Identification of fishes by using naturally occurring or artificial tags or marks is often required for studies on age and growth, mortality rates (including natural and fishing-induced mortality), abundance, angler catch or harvest rates, habitat use and movement/migration, stock recognition, or stocking success (Pine et al., 2012). Investigators can use both intrinsic and extrinsic identification systems, allowing the nature of the study to dictate the type of tag or mark employed. Integrated use of more than one tagging or marking technique helps ensure fish identification and is helpful in estimating tag loss rates.
Basic considerations for selecting a particular type of tag or mark in the context of the study objectives include potential effects on animal survival, behavior, and growth; tag permanency and recognition; number and size of the animals; stress of capture, handling, and marking; total costs; recovery of the marked fishes; and any required coordination among agencies, states, provinces, or countries (Pine et al. 2012). Investigators should also determine if the animal will be at greater than normal risk to predation, if its desirability as a mate will be reduced, and if a risk of infection is increased substantially, as well as other potential impacts (ASIH et al. 1987, 1988). Because techniques for tagging and marking fishes have been extensively reviewed and are constantly evolving, literature reviews should inform the researcher (McFarlane et al. 1990; Parker et al. 1990; Nielsen 1992; Hammerschlag et al. 2011; Wagner et al. 2011; McKenzie et al. 2012; Pine et al. 2012).
The effects of marking on fishes depend on the physical condition of the fish at the time of release. Occurrence of injury is species and size specific, and smaller fishes may be more susceptible. Minor wounds caused by most tagging and marking procedures typically heal satisfactorily without treatment with antibiotics. All sedatives or antibiotics administered must be used in a manner consistent with regulatory requirements.