Swimming performance and associated ionic disturbance of juvenile pink salmon Oncorhynchus gorbuscha determined using different acceleration profiles.

ABSTRACT

Swimming performance was assessed in juvenile pink salmon Oncorhynchus gorbuscha (body mass<5.0 g) using five different protocols four constant acceleration tests each with a different acceleration profile (rates of 0.005, 0.011, 0.021 and 0.053 cm s(-2)) and a repeated ramped-critical swimming speed test. Regardless of the swim protocol, the final swimming speeds did not differ significantly (P>0.05) among swim tests and ranged from 4.54 to 5.20 body lengths s(-1). This result supports the hypothesis that at an early life stage, O. gorbuscha display the same fatigue speeds independent of the swimming test utilized. Whole body and plasma [Na+] and [Cl-] measured at the conclusion of these tests were significantly elevated when compared with control values (P<0.05) and appear to be predominantly associated with dehydration rather than net ion gain. Given this finding for a small salmonid, estimates of swim performance can be accurately measured with acceleration tests lasting<10 min, allowing a more rapid processing than is possible with a longer critical swim speed test.