Boxplots showing levels of explanatory variables determined to significantly explain survival to 28 d for fish that survived 7 d and had recorded metrics on surgical wounds.

Results are for estimated fitted values from a linear mixed effects model evaluated by AIC. Boxplots of the fitted estimated survival values show median values surrounded by a box of the 25th to 75th percentiles (i.e. interquartile range) with whiskers at the outlying values, which are 1.5 times the interquartile range extended from the median.</p

Average survival for subyearling Chinook salmon (<i>Oncorhynchus tshawytscha</i>) held at Bonneville Dam by treatment (all replicates combined) at 7, 14, 21, and 28 d.

Average survival for subyearling Chinook salmon (Oncorhynchus tshawytscha) held at Bonneville Dam by treatment (all replicates combined) at 7, 14, 21, and 28 d.</p

Pushing the envelope: Micro-transmitter effects on small juvenile Chinook salmon (Oncorhynchus tshawytscha).

Significant effort has been invested in downsizing telemetry transmitters so they can be used to monitor survival and behavior in a variety of fish species and life stages. Commercially available "micro" transmitters in particular have presented researchers with the opportunity to tag very small fish (< 250 mm fork length). We conducted a release/recapture study in tandem with a laboratory study of tag effects on juvenile yearling spring and subyearling fall Chinook salmon (Oncorhynchus tshawytscha). Fish surgically implanted with both a micro-acoustic transmitter and passive integrated transponder (PIT) tags were compared with fish injected with only a PIT tag. Detections from both tag types showed that during the downstream migration, fish surgically implanted with both a micro-acoustic transmitter and PIT tag did not survive at the same rate or behave in the same manner as those injected with only a PIT tag. Differences in survival were more pronounced in subyearlings than in yearlings. This was likely due to warmer temperatures experienced by migrating subyearlings, their higher metabolic rate, and their smaller size and consequently higher tag-burden. To identify the mechanisms driving these differences, we necropsied migrating study fish recaptured at locations 225-460 km downstream from the release site. Results revealed that compared with PIT-tagged fish, micro-acoustic-tagged fish had heightened inflammatory responses within the body cavity, delayed healing of surgical incision sites, and poor body-condition. For study fish tagged along with those released to the river but held in the laboratory for observation, outcomes revealed that tag effects were similar in direction, but not as pronounced under artificial conditions

Rank among surgeons based on percentage mortality for study replicates 1–8.

Mean and overall rank scores are also listed; a lower ranking corresponds with higher mortality. (DOCX)</p

Nonparametric Kaplan-Meier estimated mortality for treatments pooled across replicates 1–8.

The mortality curves for the three peroxide treatments were very similar, therefore they were pooled for this analysis. The two salt treatments were also pooled due to having very similar mortality curves.</p

Number of subyearling Chinook salmon (<i>Oncorhynchus tshawytscha</i>) surgically PIT-tagged by replicate and date along with average fork length and temperature at tagging.

Table also shows the number of fish that survived transport to the Bonneville Juvenile Fish Facility (Ponded at Bonneville) and the temperature on holding day 28 corresponding to each replicate group.</p

Nonparametric Kaplan‑Meier estimated mortality for replicates 1–8 pooled across treatments.

Nonparametric Kaplan‑Meier estimated mortality for replicates 1–8 pooled across treatments.</p

S1 Fig -

Examples of select metrics used to evaluate progression of healing including a.) suture tearing b.) presence of foreign material c.) inflammation associated with suture entrance/exit sites d.) ulceration at suture entrance/exit sites e.) incision apposition 50% of incision length. (TIF)</p