Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys

Comprehensive late June surveys have for decades been carried out on the Faroe shelf in order to estimate the abundance of juvenile fish – the 0-group. The abundance of cod juveniles has previously been used in recruitment studies, while the ecological implication of the 0-groups has hitherto receiv...

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Main Authors: Sólvá Jacobsen, Eilif Gaard, Hjálmar Hátún, Petur Steingrund, Karin Margretha Húsgarð Larsen, Jákup Reinert, Sólveig Rósa Ólafsdóttir, Meinhard Poulsen, Helga Bára Mohr Vang
Format: Article
Language:English
Published: Frontiers Media S.A. 2019-09-01
Series:Frontiers in Marine Science
Subjects:
Online Access:https://www.frontiersin.org/article/10.3389/fmars.2019.00559/full
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author Sólvá Jacobsen
Eilif Gaard
Hjálmar Hátún
Petur Steingrund
Karin Margretha Húsgarð Larsen
Jákup Reinert
Sólveig Rósa Ólafsdóttir
Meinhard Poulsen
Helga Bára Mohr Vang
author_facet Sólvá Jacobsen
Eilif Gaard
Hjálmar Hátún
Petur Steingrund
Karin Margretha Húsgarð Larsen
Jákup Reinert
Sólveig Rósa Ólafsdóttir
Meinhard Poulsen
Helga Bára Mohr Vang
author_sort Sólvá Jacobsen
collection DOAJ
description Comprehensive late June surveys have for decades been carried out on the Faroe shelf in order to estimate the abundance of juvenile fish – the 0-group. The abundance of cod juveniles has previously been used in recruitment studies, while the ecological implication of the 0-groups has hitherto received less attention. Here we examined the pelagic 0-group stage in four of the main fish species on the Faroe shelf: cod, haddock, Norway pout and sandeel, representing more than 90% of all juvenile fish on the shelf. A positive relationship between length and abundance at the 0-group stage is observed for all juveniles, and the inter-annual variability was highly similar among the four fish species. Based on this knowledge, we produced a new ecological indicator for the central Faroe shelf ecosystem – the 0-group length index. The 0-group length index is characterized by marked peaks in 1984, 1987, 1994, 2000, 2009, and 2017, which appear to be related to the shelf primary production from spring to mid-summer, and possibly to the marine climate surrounding the Faroe shelf. There is a better temporal overlap between the fish larvae and their prey (i.e., small- to medium sized zooplankton) in years with an early and intensive bloom, while late and/or weak blooms lead to unfavorable feeding conditions. We furthermore show that a large abundance of 0-group fish has the potential to graze down and thus regulate the biomass of large-sized zooplankton during late June. In addition to this top-down influence the 0-group fish clearly impact commercial fish stocks and seabird colonies, and our 0-group length index is therefore a key ecological indicator for the state of the entire central Faroe shelf ecosystem.
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spelling doaj.art-bbecd9acc43940b5ad64cd28845228a12022-12-22T02:10:11ZengFrontiers Media S.A.Frontiers in Marine Science2296-77452019-09-01610.3389/fmars.2019.00559441343Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile SurveysSólvá Jacobsen0Eilif Gaard1Hjálmar Hátún2Petur Steingrund3Karin Margretha Húsgarð Larsen4Jákup Reinert5Sólveig Rósa Ólafsdóttir6Meinhard Poulsen7Helga Bára Mohr Vang8Faroe Marine Research Institute, Tórshavn, Faroe IslandsFaroe Marine Research Institute, Tórshavn, Faroe IslandsFaroe Marine Research Institute, Tórshavn, Faroe IslandsFaroe Marine Research Institute, Tórshavn, Faroe IslandsFaroe Marine Research Institute, Tórshavn, Faroe IslandsFaroe Marine Research Institute, Tórshavn, Faroe IslandsMarine and Freshwater Research Institute, Reykjavík, IcelandNakskov Gymnasium og HF, Nakskov, DenmarkFaroe Marine Research Institute, Tórshavn, Faroe IslandsComprehensive late June surveys have for decades been carried out on the Faroe shelf in order to estimate the abundance of juvenile fish – the 0-group. The abundance of cod juveniles has previously been used in recruitment studies, while the ecological implication of the 0-groups has hitherto received less attention. Here we examined the pelagic 0-group stage in four of the main fish species on the Faroe shelf: cod, haddock, Norway pout and sandeel, representing more than 90% of all juvenile fish on the shelf. A positive relationship between length and abundance at the 0-group stage is observed for all juveniles, and the inter-annual variability was highly similar among the four fish species. Based on this knowledge, we produced a new ecological indicator for the central Faroe shelf ecosystem – the 0-group length index. The 0-group length index is characterized by marked peaks in 1984, 1987, 1994, 2000, 2009, and 2017, which appear to be related to the shelf primary production from spring to mid-summer, and possibly to the marine climate surrounding the Faroe shelf. There is a better temporal overlap between the fish larvae and their prey (i.e., small- to medium sized zooplankton) in years with an early and intensive bloom, while late and/or weak blooms lead to unfavorable feeding conditions. We furthermore show that a large abundance of 0-group fish has the potential to graze down and thus regulate the biomass of large-sized zooplankton during late June. In addition to this top-down influence the 0-group fish clearly impact commercial fish stocks and seabird colonies, and our 0-group length index is therefore a key ecological indicator for the state of the entire central Faroe shelf ecosystem.https://www.frontiersin.org/article/10.3389/fmars.2019.00559/full0-group fishFaroe shelfprimary productionzooplanktonsilicatesurvival
spellingShingle Sólvá Jacobsen
Eilif Gaard
Hjálmar Hátún
Petur Steingrund
Karin Margretha Húsgarð Larsen
Jákup Reinert
Sólveig Rósa Ólafsdóttir
Meinhard Poulsen
Helga Bára Mohr Vang
Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys
Frontiers in Marine Science
0-group fish
Faroe shelf
primary production
zooplankton
silicate
survival
title Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys
title_full Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys
title_fullStr Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys
title_full_unstemmed Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys
title_short Environmentally Driven Ecological Fluctuations on the Faroe Shelf Revealed by Fish Juvenile Surveys
title_sort environmentally driven ecological fluctuations on the faroe shelf revealed by fish juvenile surveys
topic 0-group fish
Faroe shelf
primary production
zooplankton
silicate
survival
url https://www.frontiersin.org/article/10.3389/fmars.2019.00559/full
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