Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea
Abstract Maturity, sex ratio (proportion female by number) and length-at-age of cod in the Irish Sea were examined using data collected during groundfish surveys in spring 1992–2002. Skewed sex ratios with a predominance of males were observed in the survey catches of 2- and 3-year-old cod taken on...
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croxfordunivpr:10.1016/j.icesjms.2003.10.005 2024-04-28T08:19:36+00:00 Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea Armstrong, M.J Gerritsen, H.D Allen, M McCurdy, W.J Peel, J.A.D 2004 http://dx.doi.org/10.1016/j.icesjms.2003.10.005 http://academic.oup.com/icesjms/article-pdf/61/1/98/29121488/61-1-98.pdf en eng Oxford University Press (OUP) ICES Journal of Marine Science volume 61, issue 1, page 98-112 ISSN 1095-9289 1054-3139 Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography journal-article 2004 croxfordunivpr https://doi.org/10.1016/j.icesjms.2003.10.005 2024-04-02T08:07:30Z Abstract Maturity, sex ratio (proportion female by number) and length-at-age of cod in the Irish Sea were examined using data collected during groundfish surveys in spring 1992–2002. Skewed sex ratios with a predominance of males were observed in the survey catches of 2- and 3-year-old cod taken on the spawning grounds. In contrast, commercial midwater trawl catches of cod in the same area had consistently higher sex ratios, suggesting that mature males and females have different vertical migration behaviour. Estimates of proportion mature were not affected by method of capture. In a GLM analysis, the factor age explained most of the variation in maturity in each sex, whilst length, although a significant factor, explained less variation than year and region (spawning and non-spawning grounds). Maturity was observed in a variable proportion of 2-year-olds, whilst virtually no 1-year-olds and all 3-year-olds and older were mature irrespective of area or year of capture. Population estimates of proportion mature in 2-year-olds, from all years' data combined, were 0.87 in males and 0.45 in females. Estimates were higher in spawning areas than in non-spawning areas, and showed a general increase over time throughout the survey area. However, in any year, the proportion mature at age 2 varied little with length and was reduced only in the smallest fish (<40 cm) at this age in some years. The increase over time in proportion mature coincided with rising sea surface temperature (SST) and a decline in recruitment and stock biomass at high rates of fishing mortality. Mean length-at-age differed consistently between year classes, the differences being largely established in the first year of life. The fastest growth rates were apparent in very weak year classes produced in the late 1990s when SST was relatively high. The interrelationships between growth, maturity, SST and abundance are examined, and changes in growth and maturity since earlier studies in the 1970s are investigated. Article in Journal/Newspaper Gadus morhua Oxford University Press ICES Journal of Marine Science 61 1 98 112 |
institution |
Open Polar |
collection |
Oxford University Press |
op_collection_id |
croxfordunivpr |
language |
English |
topic |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography |
spellingShingle |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography Armstrong, M.J Gerritsen, H.D Allen, M McCurdy, W.J Peel, J.A.D Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea |
topic_facet |
Ecology Aquatic Science Ecology, Evolution, Behavior and Systematics Oceanography |
description |
Abstract Maturity, sex ratio (proportion female by number) and length-at-age of cod in the Irish Sea were examined using data collected during groundfish surveys in spring 1992–2002. Skewed sex ratios with a predominance of males were observed in the survey catches of 2- and 3-year-old cod taken on the spawning grounds. In contrast, commercial midwater trawl catches of cod in the same area had consistently higher sex ratios, suggesting that mature males and females have different vertical migration behaviour. Estimates of proportion mature were not affected by method of capture. In a GLM analysis, the factor age explained most of the variation in maturity in each sex, whilst length, although a significant factor, explained less variation than year and region (spawning and non-spawning grounds). Maturity was observed in a variable proportion of 2-year-olds, whilst virtually no 1-year-olds and all 3-year-olds and older were mature irrespective of area or year of capture. Population estimates of proportion mature in 2-year-olds, from all years' data combined, were 0.87 in males and 0.45 in females. Estimates were higher in spawning areas than in non-spawning areas, and showed a general increase over time throughout the survey area. However, in any year, the proportion mature at age 2 varied little with length and was reduced only in the smallest fish (<40 cm) at this age in some years. The increase over time in proportion mature coincided with rising sea surface temperature (SST) and a decline in recruitment and stock biomass at high rates of fishing mortality. Mean length-at-age differed consistently between year classes, the differences being largely established in the first year of life. The fastest growth rates were apparent in very weak year classes produced in the late 1990s when SST was relatively high. The interrelationships between growth, maturity, SST and abundance are examined, and changes in growth and maturity since earlier studies in the 1970s are investigated. |
format |
Article in Journal/Newspaper |
author |
Armstrong, M.J Gerritsen, H.D Allen, M McCurdy, W.J Peel, J.A.D |
author_facet |
Armstrong, M.J Gerritsen, H.D Allen, M McCurdy, W.J Peel, J.A.D |
author_sort |
Armstrong, M.J |
title |
Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea |
title_short |
Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea |
title_full |
Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea |
title_fullStr |
Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea |
title_full_unstemmed |
Variability in maturity and growth in a heavily exploited stock: cod (Gadus morhua L.) in the Irish Sea |
title_sort |
variability in maturity and growth in a heavily exploited stock: cod (gadus morhua l.) in the irish sea |
publisher |
Oxford University Press (OUP) |
publishDate |
2004 |
url |
http://dx.doi.org/10.1016/j.icesjms.2003.10.005 http://academic.oup.com/icesjms/article-pdf/61/1/98/29121488/61-1-98.pdf |
genre |
Gadus morhua |
genre_facet |
Gadus morhua |
op_source |
ICES Journal of Marine Science volume 61, issue 1, page 98-112 ISSN 1095-9289 1054-3139 |
op_doi |
https://doi.org/10.1016/j.icesjms.2003.10.005 |
container_title |
ICES Journal of Marine Science |
container_volume |
61 |
container_issue |
1 |
container_start_page |
98 |
op_container_end_page |
112 |
_version_ |
1797583018828759040 |