Innoculation / Tattoo / Photonic
(Panjet, Dermojet, Med-e-jet)A photonic marking gun uses a spring-loaded trigger system or CO2 canister to force a pigmented solution from a nozzle at high pressure through cell membranes. The hand-held injector is portable and useful for field studies for both individual and batch marks. Marks vary in size and longevity, where retention rate is dependent upon mark location, water temperature and growth rate.
Advantages:
- Photonic marking works well to produce batch marks on dorsal caudal and pectoral fins
- Cheap and often fast to apply, which makes the use of external marking popular for many types of studies
- Ideal to identify separate populations and has little or no effect on fish growth, health and behavior
- Suitable for a range of sizes, since the fish do not have to carry a tag and marks may have long duration
- Numbered tags enable the identification of individual fish
- Method is applicable to large numbers of fish and to many species
Disadvantages:
- When marking small fish, the high pressure may incur tissue damage
- Marks can be difficult to see on species with heavily pigmented skin
- There are a limited number of mark combinations to identify individuals
- In most cases, researchers or surveyors have to recover the marked fish themselves
- Possible recognition errors, due to confusion between marks and mark deterioration with time