Recruitment of Atlantic cod to Newfoundland coastal waters at daily and seasonal scales

• Main Author: Ings, Danny William
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2005
• Subjects: Greenland; Hake; atlantic cod; Gadus morhua; Gadus ogac; Greenland cod; Newfoundland
• Online Access: https://research.library.mun.ca/15910/; https://research.library.mun.ca/15910/1/20050501%20Ings_DannyWilliam_masters.pdf

Recruitment of marine fish is influenced by abiotic and biotic processes operating at many spatial and temporal scales. Recruitment level was thought to be set during the larval stages but recent evidence suggests that year-class strength can be modified during the early juvenile stages. Annual recruitment has received much attention but variation at finer temporal scales may affect biological processes that influence year-class success. I tested the hypothesis that timing of recruitment of fish from the plankton to nearshore benthic areas is determined by water mass movements. I also tested whether seasonal recruitment of fish to near shore bottom habitats was associated with prey availability and growth rates of post-recruited fish. Seining was conducted daily at one location during 2002 and biweekly at 12 sites during 1998-2002 to monitor fish densities and arrival times nearshore. I found that daily recruitment of Atlantic cod (Gadus morhua ), Greenland cod (Gadus ogac) and hake (Urophycis tenuis) to sites on the northeast coast of Newfoundland was associated with onshore winds following upwelling. Results were consistent with larval transport onshore during downwelling. Recruitment of Atlantic cod, Greenland cod and hake to the nearshore was not associated with tidal stage. The phenology of Atlantic cod recruitment to near shore benthic habitats appears simple but seasonal growth rates are more complex. During July to November of2000 to 2002, the monthly pattern of abundance of newly-recruited Atlantic cod near shore was similar to seasonal patterns of zooplankton abundance that I observed near shore. Seasonal zooplankton abundances near shore were similar to those previously reported offshore . Newly-recruited Atlantic cod were relatively abundant during September and October of 2000-2002. During these months, growth rates of post-recruited fish were also relatively high. However, I found growth rates of post-recruitment fish were comparatively high twice annually with highest growth occurring during June ...