The influence of spatial and temporal scale in detecting offshore recruitment signals of Atlantic cod (Gadus morhua) based on coastal juvenile surveys

• Main Author: Cooke, Emma L. L.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2019
• Subjects: atlantic cod; Gadus morhua; Newfoundland
• Online Access: https://research.library.mun.ca/13728/; https://research.library.mun.ca/13728/1/thesis.pdf

The moratorium on the Newfoundland Atlantic cod (Gadus morhua) fishery in 1992 motivated studies on the factors influencing population stability and tools to forecast future cod abundance. Unfortunately, short-duration time series compromised most efforts to link life stages. I used coastal seine surveys of juveniles (age-0 and -1) to predict offshore pre-adult (age-3) cod abundance at multiple spatial scales (individual bays to offshore regions), temporal scales (short and long-term time series from 7 to 18 years in length) and environmental and biological factors influencing recruitment signal strength. These analyses detected strong recruitment signals among all early age classes from the Newman Sound Survey (1995 – 2013) and demonstrated interactions between juvenile abundance and environmental variables. In contrast, a strong recruitment signal was only detectable from a single bay using the shorter Fleming Survey (1992 – 1997, 2001). For both surveys, recruitment signal strength varied with distance from the index sites, among management zones, and between areas of known ecological and biological significance. Studies evaluating year-class strength often overlook the value of coastal juvenile surveys. These results demonstrate the utility of using information from long-duration coastal seine surveys when forecasting adult population strength. The implications of my results could help stakeholders prepare for socio-economic implications of poor recruitment years, and can be used in management decision-making.