Dispersal and home range of age 1 Greenland cod (Gadus ogac) in Newman Sound, Newfoundland

Shapiera, Melanie B. (2013) Dispersal and home range of age 1 Greenland cod (Gadus ogac) in Newman Sound, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The stability of a population is largely dependent on the dispersal dynamics of the juvenile cohort. In the marine environment, dispersal range, mortality during dispersal, and site fidelity of juveniles contribute to the resilience and connectivity among populations. However, juvenile dispersal parameters are rarely investigated and quantified, even among species or populations of concern. I determined dispersal distances, site fidelity, and home range areas of 1 year old Greenland cod (Gadus ogac) in Newman Sound, a coastal fjord of Newfoundland, through the use of passive acoustic telemetry. A network of 26-32 fixed hydrophone listening stations monitored movements of 82 out of 84 juveniles surgically implemented with coded acoustic transmitters. Single and reciprocal transplant experiments between two coves approximately 3.5 km apart were carried out during October 2010 and November 2011, respectively. A behavioural dichotomy between resident" and "disperser" fish was seen during both experiments. Individual dispersers moved on the km scale, associated with the timing of the onset and disappearance of the seasonal thermocline, and in the month of July during both years. Similar proportions of control and transplant fish visited opposite source coves, suggesting low site fidelity and/or low homing initiative in both sample populations. ANOVA analyses of the tagging periods identified season as the only significant predictor of home range size, with a general increase in home range from pre-winter to post-winter seasons, and no effect of fish capture or release location. Mean seasonal home range areas during both tagging periods exceed those documented for age 2-3 Atlantic cod in other studies, suggesting a less established residency in age 1 Greenland cod. High individuality in movement patterns and area usage indicate that factors affecting dispersal, such as temperature, predation, and age, likely differ in importance across individuals in the age class.

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