Research Document - 2004/124
Relative Strength of the 2001 and 2002 Year-Classes, From Nearshore Surveys Of Demersal Age 0 and 1 Atlantic Cod (Gadus morhua) in NAFO Division 3KL and in Newman Sound, Bonavista Bay
By Gregory, R.S., B.J. Laurel, J.E. Linehan, D.W. Ings, D.C. Schneider
Abstract
From 1959-64 and 1992-97 (i.e. 1990s), and again in 2001, demersal age 0 Atlantic cod (Gadus morhua) in the nearshore (<10 m deep) were surveyed by seine from St. Mary's Bay to Notre Dame Bay, Newfoundland during the Fleming survey, conducted annually in September and October. In the absence of a regular coastwide Fleming survey since 1997, we have conducted a qualitative assessment of the strength of six 1997-2002 year-classes of Atlantic cod. Our assessment was based on abundance of demersal age 0 and age 1 Atlantic cod sampled at 6-13 nearshore sites in Newman Sound, Bonavista Bay in five summer-autumn periods during 1995-2002. Sampling techniques and collection dates for the Fleming survey and Newman Sound study were similar. Therefore, cod abundances in the two studies were comparable, albeit at different geographic scales. Abundance trends of age 0 and 1 cod covaried between the studies in 1995, 1996, and 2001, when both were conducted concurrently, suggesting that abundances of juvenile cod in Newman Sound mirrored those observed in the spatially broader Fleming survey. In 1997, age 0 abundance in the Fleming survey was the highest observed in the 1990s, leading to the prediction that age 1 cod would be high the following year. High age 1 abundance in 1998 compared to 1995 and 1996 in Newman Sound supported this prediction. Compared with the historical low in 1996 observed in both studies, age 0 abundance was 10 times higher in 1998 and 40 times higher in 1999. These results suggest that the 1997, 1998, and 1999 year-classes should be strong compared to those in 1995 and 1996. Analysis of length frequency data collected from July to November in Newman Sound indicated that age 0 Atlantic cod settled in the nearshore in two distinct recruitment pulses in "good years" - i.e. 1998 and 1999 - the first pulse arriving in early August, the second in late September. In "bad years" - i.e. 1995 and 1996 – the first pulse has been weak and late to recruit to the nearshore. The length frequency data also suggest that the pulse structure may remain intact through the first winter and appears to be detectable in age 1 cod the subsequent year. In 2001, Gregory et al. 2002 predicted that the 2000 year-class of Atlantic cod will prove to be weak relative to the strong 1998 and 1999 year-classes which preceeded it. Catches of the 2000 year-class throughout 2001 as age 1 fish, and in 2002 as age 2 fish support this prediction. In contrast to 1997 99, densities of age 0 Atlantic cod have been consistently low throughout much of the season in the past three years (2000-02), and were comparable to 1996, the poorest year-class on record in three independent surveys of age 0 abundance off northeastern Newfoundland.
Accessibility Notice
This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.
- Date modified: