Dryad
Shapiera, Melanie;
Gregory, Robert S.;
Morris, Corey J.;
Pennell, Curtis J.;
Snelgrove, Paul V. R.;
Gregory, RS;
Morris, CJ;
Pennell, CJ;
Snelgrove, PVR
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2015-02-17
We used acoustic telemetry to track age 1 juvenile Greenland cod Gadus ogac in Newman Sound, Newfoundland, from October 2010 to November 2012, in 2 consecutive 1 yr experiments. Using single (Year 1) and reciprocal (Year 2) transplant study designs, we investigated seasonal dispersal, home range area, and potential homing behaviour between coves ~3.5 km apart. We tracked individuals moving at metre to kilometre scales, using a network of 26 to 32 hydrophones. We converted tag detections to position estimates in order to calculate seasonal home ranges and individual movement patterns. Home range increased significantly with season (pre-winter, winter, and post-winter) in both study years. Mean seasonal home range area ranged from 0.29 to 3.47 km2 in Year 1 and 0.43 to 1.72 km2 in Year 2. In contrast, fish size-at-capture, capture location, and release location had no significant effect on seasonal home range. Increased movement distance during the winter and post-winter season suggests a reduction in predation pressure on age 1 juveniles at these times, challenging previous assumptions about their vulnerability. We observed variable behaviour spanning residency to kilometre-scale dispersal movements, which represent greater distances than previously assumed. Similar proportions of control and transplant fish visited the other cove, indicating an absence of homing behaviour among dispersing individuals. Juveniles of marine fishes are often characterized as key life history transition stages between vulnerable larvae and older, larger individuals which are less susceptible to predators. Our results indicate that early juvenile life stages may be substantially more mobile than presupposed and contribute to population connectivity in temperate fishes in ways not well described previously.