PNNL

Abstract

Recently, a micro acoustic tag was developed for use in juvenile American Eels Anguilla rostrate and Pacific Lamprey Entosphenus tridentatus, called the Eel/Lamprey Acoustic Tag (ELAT). The ELAT (12.0 mm × 2.0 mm, 0.088 g in air) has the potential to be used to study other small-bodied fishes. In this pilot study, juvenile Chinook Salmon O. tshawytscha 50–100 mm fork length (FL) were surgically tagged with an ELAT (n = 99) or remained untagged (control; n = 101). Fish were held for 30 days to evaluate survival, tag retention, and growth. Mortality did not differ significantly between control (n = 3, or 3.0%) and tagged ?sh (n = 4, or 4.1%; H = 0.18, df = 1, p = 0.67). Logistic regression analysis showed survival was influenced by initial FL (p = 0.04) and tag burden (p = 0.01). Mortalities only occurred in tagged ?sh with initial FLs of = 65 mm (FL range 57–65; tag burdens 3.8–5.9%). However, a tagged fish with an initial FL of 62 mm or an initial tag burden of 4.1% (FL range 58–64 mm) was predicted to have a 90% chance of survival, and the smallest fish that survived the study was 54 mm FL (1.8 g; tag burden 4.9%). Tag retention was high (99%) with only one fish expelling an ELAT during the study. Control fish grew slightly larger than the tagged individuals, but differences in final pooled FLs were not significant (H = 1.24, df = 1, p = 0.27). Differences in final pooled weight gains were also not significant (H = 0.39, df = 1, p = 0.53). Although this was a pilot study, our results demonstrated the successful surgical implantation of the ELAT into Chinook Salmon as small as 54 mm FL (1.8 g).