Journal Article

Do environmental factors affect recruits per spawner anomalies of New England groundfish?

Jon Brodziak and Loretta O'Brien

in ICES Journal of Marine Science

Published on behalf of ICES/CIEM

Volume 62, issue 7, pages 1394-1407
Published in print January 2005 | ISSN: 1054-3139
Published online January 2005 | e-ISSN: 1095-9289 | DOI: http://dx.doi.org/10.1016/j.icesjms.2005.04.019
Do environmental factors affect recruits per spawner anomalies of New England groundfish?

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We evaluated the influence of environmental factors on recruits per spawner (RS) anomalies of 12 New England groundfish stocks. Nonparametric methods were used to analyse time-series of RS anomalies derived from stock-recruitment data in recent assessments. The 12 stocks occur in three geographic regions: the Gulf of Maine (cod Gadus morhua, redfish Sebastes fasciatus, winter flounder Pseudopleuronectes americanus, American plaice Hippoglossoides platessoides, witch flounder Glyptocephalus cynoglossus, and yellowtail flounder Limanda ferruginea), Georges Bank (cod, haddock Melanogrammus aeglefinus, and yellowtail flounder), and Southern New England (summer flounder Paralichthys dentatus, yellowtail flounder, and winter flounder). Randomization tests were applied to detect years when RS anomalies were unusually high or low for comparison with oceanographic conditions such as the 1998 intrusion of Labrador Subarctic Slope water into the Gulf of Maine region. Randomization methods were also used to evaluate the central tendency and dispersion of all RS anomalies across stocks. Average RS anomalies were significantly positive in 1987 across stocks and regions, indicating that environmental forcing was coherent and exceptional in that year. Responses of RS values of individual stocks to lagged and contemporaneous environmental variables such as the North Atlantic Oscillation (NAO) index, water temperature, windstress, and shelf water volume anomalies were evaluated using generalized additive models. Overall, the NAO forward-lagged by 2 years had the largest impact on RS anomalies. This apparent effect is notable because it could provide a leading indicator of RS anomalies for some commercially exploited stocks. In particular, the three primary groundfish stocks on Georges Bank (cod, haddock, and yellowtail flounder) all exhibited positive RS anomalies when the NAO2 variable was positive.

Keywords: environmental forcing; generalized additive models; New England groundfish; North Atlantic Oscillation; randomization test; recruits per spawner; shelf water volume; water temperature; windstress

Journal Article.  7808 words.  Illustrated.

Subjects: Environmental Science ; Marine and Estuarine Biology

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