Larval mortality rates and population dynamics of Lesser Sandeel (Ammodytes marinus) in the northwestern North Sea

Michael Heath, Jens Rasmussen, M.C. Bailey, J. Dunn, J. Fraser, A. Gallego, S.J. Hay, I. Inglis, S. Robinson

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

Intense fishing of a stock of sandeels (Ammodytes marinus) on the sand banks off the Firth of Forth, northeast Scotland, during the 1990s led to a decline in catch per unit effort to uneconomic levels and collateral failures of piscivorous seabird breeding success at nearby colonies. A prohibition on fishing in 1999 was followed by a short-term recovery of stock biomass, but then a sustained decline to very low levels of abundance. Demographic survey data show that despite the decline in stock, recruit abundance was maintained implying an increasing larval survival rate, and that the stock decline was not due to recruitment failure. To verify this hypothesis we analysed a 10-year long data set of weekly catches of sandeel larvae at a nearby plankton monitoring site to determine the patterns of larval mortality and dispersal. We found that the loss rate of larvae up to 20 d age decreased over time, corresponding with the trend in survival rate implied by the stock demography data. The pattern of loss rate in relation to hatchling abundance implied that mortality may have been density dependent. Our study rules out increased larval mortality as the primary cause of decline in the sandeel stock.
LanguageEnglish
Pages47-57
Number of pages11
JournalJournal of Marine Systems
Volume93
DOIs
Publication statusPublished - May 2012

Fingerprint

Ammodytes
North Sea
population dynamics
mortality
survival rate
fishing
larvae
larva
seabirds
demography
demographic survey
Scotland
plankton
catch per unit effort
demographic statistics
seabird
sand
reproductive success
monitoring
biomass

Keywords

  • fish
  • larvae
  • otolith
  • mathematical analysis

Cite this

Heath, Michael ; Rasmussen, Jens ; Bailey, M.C. ; Dunn, J. ; Fraser, J. ; Gallego, A. ; Hay, S.J. ; Inglis, I. ; Robinson, S. / Larval mortality rates and population dynamics of Lesser Sandeel (Ammodytes marinus) in the northwestern North Sea. In: Journal of Marine Systems. 2012 ; Vol. 93. pp. 47-57.
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Larval mortality rates and population dynamics of Lesser Sandeel (Ammodytes marinus) in the northwestern North Sea. / Heath, Michael; Rasmussen, Jens; Bailey, M.C.; Dunn, J.; Fraser, J.; Gallego, A.; Hay, S.J.; Inglis, I.; Robinson, S.

In: Journal of Marine Systems, Vol. 93, 05.2012, p. 47-57.

Research output: Contribution to journalArticle

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AU - Heath, Michael

AU - Rasmussen, Jens

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AU - Gallego, A.

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AB - Intense fishing of a stock of sandeels (Ammodytes marinus) on the sand banks off the Firth of Forth, northeast Scotland, during the 1990s led to a decline in catch per unit effort to uneconomic levels and collateral failures of piscivorous seabird breeding success at nearby colonies. A prohibition on fishing in 1999 was followed by a short-term recovery of stock biomass, but then a sustained decline to very low levels of abundance. Demographic survey data show that despite the decline in stock, recruit abundance was maintained implying an increasing larval survival rate, and that the stock decline was not due to recruitment failure. To verify this hypothesis we analysed a 10-year long data set of weekly catches of sandeel larvae at a nearby plankton monitoring site to determine the patterns of larval mortality and dispersal. We found that the loss rate of larvae up to 20 d age decreased over time, corresponding with the trend in survival rate implied by the stock demography data. The pattern of loss rate in relation to hatchling abundance implied that mortality may have been density dependent. Our study rules out increased larval mortality as the primary cause of decline in the sandeel stock.

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