February 15-18, 2009 Washington State Convention Center Seattle ...

110
AN IMPLANTED MINITATURE ACOUSTIC TAG EVALUATION ON SUB-YEARLING FALL
CHINOOK SALMON Oncorhynchus tshawytscha
Deborah Frost*, R. Lynn McComas and B. Sandford
NOAA Fisheries
Northwest Fisheries Science Center
Manchester Research Station
7305 Beach Drive E.
Port Orchard, Washington 98366 USA
Debbie.Frost@noaa.gov
Implantable acoustic tags are often used to assess salmonid smolt behavior, survival, habitat use and predation risk. However,
the relatively large size of some acoustic tags limits their use in juvenile fish. A miniature implantable acoustic tag prototype
(21 mm by 7 mm by 6 mm and 0.9 g in air) was evaluated in three separate groups of Chinook salmon Oncorhynchus tshawytscha
smolts for impacts on 1) growth and survival, 2) predation risk and 3) behavioral differences. Growth rate over a 30-day
period was significantly affected by the tag (P = 0.003 for length and 0.000 for weight, Table 1). Tag to body weight ratio
ranged from 2.6 to 5.9% at tagging. Survival was not affected, however, partial to complete tag expulsion was noted in 37% of
the tagged fish in the growth evaluation group. Implantation of an active miniature prototype acoustic tag did not significantly
affect predation risk (P = 0.255). Non-significant differences in behavior involving activity level (P = 0.467) and position in
the water column (P = 0.298) (Figure 1) were also seen, however the small sample sizes in both the predation and behavior
evaluations suggested trends toward an affect by either the tag or the surgical procedure. These evaluations showed a tendency
for growth and tag retention to affect the overall successful use of this size of tag in this size of fish by impeding growth and
potentially contributing to false mortality with expulsed tags. The study emphasizes the need for careful evaluation for longterm
effects prior to field use.