ANCHOR TAGS AFFECT SWIMMING PERFORMANCE AND GROWTH OF JUVENILE RED DRUM (SCIAENOPS-OCELLATUS)

Swimming efficiency and growth of anchor-tagged red drum (Sciaenops oc ellatus)juveniles were compared with untagged controls. The OZ consump tion of fish swimming at different speeds was measured in a Blazka-typ e respirometer. Daily growth rates of tagged and untagged red drum wer e compared over 42 d of feeding fixed rations of live mosquitofish (Ga mbusia affinis) to siblings held individually in 380 L tanks. At swimm ing speeds of less than or equal to 1.0 body lengths per second (bl s( -1)), no differences in O-2 consumption were found. However, at speeds of 1.5-2.5 bl s(-1), tagged red drum O-2 consumption was significantl y greater (by 36-39%) than that of untagged fish (ANOVA, P < 0.05), in dicating a substantially impaired swimming efficiency. Daily growth ra tes of tagged and untagged fish also differed significantly (P < 0.02) . Tagged fish grew at a mean rate of 0.95 mm d(-1) and 1.45 g d(-1), w hile untagged fish (controls) grew at 1.14 mm d(-1) and 1.62 g d(-1). Results suggest that internal anchor tags, which weighed less than 1% of fish body weight, represented a hydrodynamic drag burden that reduc ed swimming performance and growth. These effects may decrease growth and/or survival in the wild and thus bias estimates of biological para meters in stock assessment and enhancement studies.