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Settlement processes induce differences in daily growth rates between two co-existing ecotypes of juvenile cod Gadus morhua

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Settlement processes induce differences in daily growth rates between two co-existing ecotypes of juvenile cod Gadus morhua. / Jørgensen, Kris Emil M.; Neuheimer, Anna B.; Jorde, Per Erik; Knutsen, Halvor; Grønkjær, Peter.

In: Marine Ecology Progress Series, Vol. 650, 09.2020, p. 175-189.

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@article{1b2bd62a6f804037aaf63f8ec3976931,
title = "Settlement processes induce differences in daily growth rates between two co-existing ecotypes of juvenile cod Gadus morhua",
abstract = "Co-existence of sympatric populations of a fish species is a common phenomenon. In the fjords of southern Norway, 2 ecotypes of Atlantic cod Gadus morhua co-exist during their juvenile life stage. Cod of the North Sea ecotype are on average 2 cm larger than the fjord ecotype at the end of their first growing season in October, suggesting either differences in spawning time or differences in growth during the larval and early juvenile phase. We analysed 24 352 daily otolith increments from 145 cod sampled in September 2000, 2003, 2008 and 2015 at 2 locations to estimate individual hatching times and daily growth rates. There was no significant difference in hatching time between ecotypes, locations or years. Population-specific models of the effect of year, temperature and fish length on growth rates showed that the North Sea ecotype grew significantly faster than the fjord ecotype, but growth rate differences were small until the juveniles reached ~40 mm and disappeared again in juveniles larger than 110 mm. The size range (40− 110 mm) corresponds to the period following settling. This study documents how vital rates (e.g. growth rates) may change rapidly at ontogenetic transition points, leading to different phenotypic trajectories in co-existing ecotypes. It also highlights the importance of settlement as a key life-history transition that may amplify small existing differences in growth rates through positive feedback of size on competitive ability and eventually recruitment.",
keywords = "Competition, Growth, Local adaptation, Nursery, Otoliths, Temperature",
author = "J{\o}rgensen, {Kris Emil M.} and Neuheimer, {Anna B.} and Jorde, {Per Erik} and Halvor Knutsen and Peter Gr{\o}nkj{\ae}r",
year = "2020",
month = sep,
doi = "10.3354/meps13433",
language = "English",
volume = "650",
pages = "175--189",
journal = "Marine Ecology - Progress Series",
issn = "0171-8630",
publisher = "Inter-Research",

}

RIS

TY - JOUR

T1 - Settlement processes induce differences in daily growth rates between two co-existing ecotypes of juvenile cod Gadus morhua

AU - Jørgensen, Kris Emil M.

AU - Neuheimer, Anna B.

AU - Jorde, Per Erik

AU - Knutsen, Halvor

AU - Grønkjær, Peter

PY - 2020/9

Y1 - 2020/9

N2 - Co-existence of sympatric populations of a fish species is a common phenomenon. In the fjords of southern Norway, 2 ecotypes of Atlantic cod Gadus morhua co-exist during their juvenile life stage. Cod of the North Sea ecotype are on average 2 cm larger than the fjord ecotype at the end of their first growing season in October, suggesting either differences in spawning time or differences in growth during the larval and early juvenile phase. We analysed 24 352 daily otolith increments from 145 cod sampled in September 2000, 2003, 2008 and 2015 at 2 locations to estimate individual hatching times and daily growth rates. There was no significant difference in hatching time between ecotypes, locations or years. Population-specific models of the effect of year, temperature and fish length on growth rates showed that the North Sea ecotype grew significantly faster than the fjord ecotype, but growth rate differences were small until the juveniles reached ~40 mm and disappeared again in juveniles larger than 110 mm. The size range (40− 110 mm) corresponds to the period following settling. This study documents how vital rates (e.g. growth rates) may change rapidly at ontogenetic transition points, leading to different phenotypic trajectories in co-existing ecotypes. It also highlights the importance of settlement as a key life-history transition that may amplify small existing differences in growth rates through positive feedback of size on competitive ability and eventually recruitment.

AB - Co-existence of sympatric populations of a fish species is a common phenomenon. In the fjords of southern Norway, 2 ecotypes of Atlantic cod Gadus morhua co-exist during their juvenile life stage. Cod of the North Sea ecotype are on average 2 cm larger than the fjord ecotype at the end of their first growing season in October, suggesting either differences in spawning time or differences in growth during the larval and early juvenile phase. We analysed 24 352 daily otolith increments from 145 cod sampled in September 2000, 2003, 2008 and 2015 at 2 locations to estimate individual hatching times and daily growth rates. There was no significant difference in hatching time between ecotypes, locations or years. Population-specific models of the effect of year, temperature and fish length on growth rates showed that the North Sea ecotype grew significantly faster than the fjord ecotype, but growth rate differences were small until the juveniles reached ~40 mm and disappeared again in juveniles larger than 110 mm. The size range (40− 110 mm) corresponds to the period following settling. This study documents how vital rates (e.g. growth rates) may change rapidly at ontogenetic transition points, leading to different phenotypic trajectories in co-existing ecotypes. It also highlights the importance of settlement as a key life-history transition that may amplify small existing differences in growth rates through positive feedback of size on competitive ability and eventually recruitment.

KW - Competition

KW - Growth

KW - Local adaptation

KW - Nursery

KW - Otoliths

KW - Temperature

UR - http://www.scopus.com/inward/record.url?scp=85092184681&partnerID=8YFLogxK

U2 - 10.3354/meps13433

DO - 10.3354/meps13433

M3 - Journal article

AN - SCOPUS:85092184681

VL - 650

SP - 175

EP - 189

JO - Marine Ecology - Progress Series

JF - Marine Ecology - Progress Series

SN - 0171-8630

ER -