Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat

Gwladys Lambert, J. Rasmus Nielsen, Lena I. Larsen, Henrik Sparholt

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50%-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20% of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50%-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.
Original languageEnglish
JournalICES Journal of Marine Science
Volume66
Issue number9
Pages (from-to)1899-1914
ISSN1054-3139
DOIs
Publication statusPublished - 2009

Cite this

@article{96d4d937fb0c419bac39c34d3f6a5017,
title = "Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat",
abstract = "The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50{\%}-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20{\%} of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50{\%}-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.",
author = "Gwladys Lambert and Nielsen, {J. Rasmus} and Larsen, {Lena I.} and Henrik Sparholt",
year = "2009",
doi = "10.1093/icesjms/fsp153",
language = "English",
volume = "66",
pages = "1899--1914",
journal = "I C E S Journal of Marine Science",
issn = "1054-3139",
publisher = "Oxford University Press",
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}

Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat. / Lambert, Gwladys; Nielsen, J. Rasmus; Larsen, Lena I.; Sparholt, Henrik.

In: ICES Journal of Marine Science, Vol. 66, No. 9, 2009, p. 1899-1914.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Maturity and growth population dynamics of Norway pout (Trisopterus esmarkii) in the North Sea, Skagerrak, and Kattegat

AU - Lambert, Gwladys

AU - Nielsen, J. Rasmus

AU - Larsen, Lena I.

AU - Sparholt, Henrik

PY - 2009

Y1 - 2009

N2 - The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50%-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20% of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50%-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.

AB - The population dynamics of the Norway pout stock in the North Sea are investigated by statistical analyses, and GIS of ICES International Bottom Trawl Surveys (IBTS) and Danish commercial catch data from 1983 to 2006. The stock spawns mainly around mid-February along the northeastern English and Scottish coasts and between Shetland and Norway. Sex ratios indicate that males, which mature younger than females (age-at-50%-maturity, respectively, 1.2 and 1.5 years), migrate out of the Skagerrak–Kattegat to the spawning grounds before females. There is a decrease in the 2+-group maturity ratios as well as in weight and female length from before to after spawning. The results indicate spawning mortality. Only some 20% of the 1-group reaches maturity in the first quarter, which is higher than assumed in the stock assessment. Although the maturity ogives are variable over time, this difference should be taken into account when estimating spawning-stock biomass in routine assessments. Growth is also variable, with a tendency for male maximum length to be smaller than that of females, and immature fish to be smaller than mature ones in each age group. The juvenile growth rate is higher when the stock density is low and results in a reduced age-at-50%-maturity. Besides these intraspecific patterns, the growth rates show interspecific links to stock sizes of the important predators: cod, haddock, and whiting.

U2 - 10.1093/icesjms/fsp153

DO - 10.1093/icesjms/fsp153

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SP - 1899

EP - 1914

JO - I C E S Journal of Marine Science

JF - I C E S Journal of Marine Science

SN - 1054-3139

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