Many tagging and marking methods have been studied on Delta Smelt and Longfin Smelt at the FCCL. Floy tags (external tags applied on the dorsal fin) have been evaluated for Delta Smelt and Longfin Smelt, showing good survival and tag retention, but the epidermis of Delta Smelt is thin and caused the knot to get pulled into the skin. Longfin Smelt had less tag shedding than Delta Smelt. T-bar anchor tags (external tags that are pieces of flexible T-shaped plastic) were tried on adult Delta Smelt, but the process of injecting the T-bar anchor tag through the skin of the Delta Smelt caused substantial damage to the fish by ripping a large hole in their body.
Evaluation of natural marks for Delta Smelt showed chromatophore patterns which can provide reliable individual identification (Castillo et al. 2018). Images were evaluated using visual (naked eye) and automated image recognition (TinEye Match Engine’s Application Programming Interface, API; https://www.tineye.com). Lindberg et al. (2013) clipped the adipose fin and also inserted VIA tags (polyester pieces imprinted with alphanumeric codes that are externally visible when implanted into transparent tissue) under the skin near the dorsal fin on Delta Smelt. Wilder et al. (2016) looked at the feasibility of tagging cultured adult Delta Smelt as a potential surrogate for wild fish in field experiments and intracoelomically implanted Delta Smelt with PIT tags (glass-encapsulated microchips) and found cultured adult Delta Smelt can be successfully implanted with PIT tags. Wilder et al. (2016) also used JSATS tags (acoustic transmitters) on adult Delta Smelt and found that survival of Delta Smelt implanted with acoustic tags via injection needle or surgery was substantially lower than in those implanted with PIT tags.
Castillo et al. (2012) reported calcein marked (a fluorescent dye that binds to calcium and brands all calcified tissues) Delta Smelt had 100% mark retention for at least 30 days (juveniles) and 90 days (adults). Castillo et al. (2012) also conducted experiments to assess entrainment losses of Delta Smelt using photonic marks (fluorescent pigments injected into the dorsal, caudal, and anal fins of fish using a pressurized CO2 gun) on adults. Photonic marking was found unfeasible for juvenile Delta Smelt due to low mark retention, longer marking times (Castillo et al. 2012; 2014) and lower survival (G. Tigan, pers. comm., 2018, FCCL). Hobbs et al. (2012) validated tagging offspring through peritoneal injection of ripe female delta smelt using two concentrations of strontium chloride hexahydrate. This study provides evidence for the efficacy of tagging offspring via injection of strontium into ripe females. The most effective methods have been visible implant alphanumeric (VIA) tagging and adipose fin clips for sub-adult to adult fish; and calcein and photonic marks for young life stages. Among these methods only VIA tagging and Floy tags are currently applied at the FCCL for individual organism identification.
Sandford M, Castillo G, Hung TC (2019) A review of fish identification methods applied on small fishes, Reviews in Aquaculture, accepted.
Castillo GC, Sandford ME, Hung TC, Yang WR, Tigan G, Ellison L, Lindberg JC, Van Nieuwenhuyse EE (2019) Evaluation of chromatophores as natural marks for delta smelt: the effects of life-stage and light intensity, Environmental Biology of Fishes 102(9), 1137-1147.
Castillo GC, Sandford ME, Hung TC, Tigan G, Lindberg JC, Yang WR, Nieuwenhuyse EE (2018) Using natural marks to identify individual cultured adult delta smelt, North American Journal of Fisheries Management 38(3), 698-705
Wilder RM, Hassrick JL, Grimaldo LF, Greenwood MFD, Acuña S, Burns JM, Maniscalco DM, Crain PK, Hung TC (2016) Feasibility of passive integrated transponder and acoustic tagging for endangered adult Delta Smelt, North American Journal of Fisheries Management 36(5), 1167-1177
Castillo G, Morinaka J, Fujimura R, DuBois J, Baskerville-Bridges B, Lindberg J, Tigan G, Ellison L, Hobbs J (2014) Evaluation of calcein and photonic marking for cultured delta smelt, North American Journal of Fisheries Management 34(1), 30-38
Hobbs JA, Castillo G, Tigan G, Lindberg J, Ikemiyagi N, Ramos G (2012) Tagging the next generation: validation of trans-generational chemical tagging for an endangered fish, Environmental Biology of Fishes 95(4), 463-468