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.
Data from: Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod (Gadus ogac) in a Newfoundland fjord. A Canadian Healthy Oceans Network Population Connectivity, PC-03
Acoustic telemetry data was collected from October 2010 - October 2011 for 42 individual age 1+ Gadus ogac individuals tagged with Vemco Ltd™ V7-4L coded acoustic tags, programmed to emit a signal at a randomized average delay of every 240 ± 70 s, and a nominal tag life of 415 days. A receiver network comprised of 26 Vemco™ VR2W and VR2 hydrophones allowed for continual detection throughout Newman Sound over a full year. The data presented have been filtered to eliminate spurious detections using both a single detection filter (eliminating lone detections for a single fish over 24 hours) and a conservative speed filter (eliminating detections > 2 body lengths/second apart which could indicate ingestion by a predator). Using known positions of the acoustic receivers, we calculated position estimates in hourly time intervals using a weighted arithmetic mean to increase precision from a presence/absence dataset to a position-based dataset. Therefore the beginning of each hour time interval is indicated in the "Date" and "Time" field. Positions are indicated in decimal degrees in the "COA_Lat" and "COA_Lon" fields of the CSV files. Also included are the ArcGIS defined "POINT_X" and "POINT_Y" fields using a NAD_1983_UTM_Zone_21N projection. Individual fish IDs are included in the "Tag" field. The "Transplant" field indicates whether the individual was in the control group (site of capture = site of release) or the transplant group (site of capture ≠ site of release). Site of capture is indicated by the "Cove" field (HC = Heffern's Cove; BC= Buckley's Cove).
Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod (Gadus ogac) in a Newfoundland fjord_year1.csv
Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod (Gadus ogac) in a Newfoundland fjord (Year 2). A Canadian Healthy Oceans Network Population Connectivity, PC-03
Acoustic telemetry data was collected from November 2011 - November 2012 for 42 individual age 1+ Gadus ogac individuals tagged with Vemco Ltd™ V7-4L coded acoustic tags, programmed to emit a signal at a randomized average delay of every 240 ± 70 s, and a nominal tag life of 415 days. A receiver network comprised of 32 Vemco™ VR2W and VR2 hydrophones allowed for continual detection throughout Newman Sound over a full year. The data presented have been filtered to eliminate spurious detections using both a single detection filter (eliminating lone detections for a single fish over 24 hours) and a conservative speed filter (eliminating detections > 2 body lengths/second apart which could indicate ingestion by a predator). Using known positions of the acoustic receivers, we calculated position estimates in hourly time intervals using a weighted arithmetic mean to increase precision from a presence/absence dataset to a position-based dataset. Therefore the beginning of each hour time interval is indicated in the "Date" and "Time" field. Positions are indicated in decimal degrees in the "COA_Lat" and "COA_Lon" fields of the CSV files. Also included are the ArcGIS defined "POINT_X" and "POINT_Y" fields using a NAD_1983_UTM_Zone_21N projection. Individual fish IDs are included in the "Tag" field. The "Transplant" field indicates whether the individual was in the control group (site of capture = site of release) or the transplant group (site of capture ≠ site of release). Site of capture is indicated by the "Cove" field (HC = Heffern's Cove; BC= Buckley's Cove).
Season and site fidelity determine home range of dispersing and resident juvenile Greenland cod (Gadus ogac) in a Newfoundland fjord_year2.csv