Variation in the calorific value and total energy content of the lesser sandeel (<i>Ammodytes marinus</i>) and other fish preyed on by seabirds

Hislop, J. R. G.; Harris, Michael; Smith, J. G. M.

doi:10.1111/j.1469-7998.1991.tb06039.x

Cited by 184 publications

(157 citation statements)

References 22 publications

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“…It is thus possible that at least in some seasons, the decline in energy content has been even more pronounced. These findings have major implications for the many predators of sandeels because energy density, in particular lipid content, shows a non-linear relationship with fish length, and thus the total energy value of a small fish is markedly lower than that of a larger one (Hislop et al 1991). 0-group sandeels are a major item in the diet of many seabirds in the Firth of Forth, including the 3 most abundant spp: northern gannet Morus bassanus, Atlantic puffin Fratercula arctica and common guillemot Uria aalge .…”

Section: Discussionmentioning

confidence: 99%

Mechanisms of long-term decline in size of lesser sandeels in the North Sea explored using a growth and phenology model

Frederiksen¹,

Elston²,

Edwards³

et al. 2011

Mar. Ecol. Prog. Ser.

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The lesser sandeel Ammodytes marinus is a key species in the North Sea ecosystem, transferring energy from planktonic producers to top predators. Previous studies have shown a longterm decline in the size of 0-group sandeels in the western North Sea, but they were unable to pinpoint the mechanism (later hatching, slower growth or changes in size-dependent mortality) or cause. To investigate the first 2 possibilities we combined 2 independent time series of sandeel size, namely data from chick-feeding Atlantic puffins Fratercula arctica and from the Continuous Plankton Recorder (CPR), in a novel statistical model implemented using Markov Chain Monte Carlo (MCMC). The model estimated annual mean length on 1 July, as well as hatching date and growth rate for sandeels from 1973 to 2006. Mean length-at-date declined by 22% over this period, corresponding to a 60% decrease in energy content, with a sharper decline since 2002. Up to the mid-1990s, the decline was associated with a trend towards later hatching. Subsequently, hatching became earlier again, and the continued trend towards smaller size appears to have been driven by lower growth rates, particularly in the most recent years, although we could not rule out changes in size-dependent mortality. Our findings point to major changes in key aspects of sandeel life history, which we consider are most likely due to direct and indirect temperature-related changes over a range of biotic factors, including the seasonal distribution of copepods and intra-and inter-specific competition with planktivorous fish. The results have implications both for the many predators of sandeels and for age and size of maturation in this aggregation of North Sea sandeels. KEY WORDS: Ammodytes marinus · Growth model · MCMC · North Sea · Phenology · SandeelResale or republication not permitted without written consent of the publisher Mar Ecol Prog Ser 432: 137-147, 2011 138 dynamics and to impact higher trophic levels, and indeed have already been linked with fluctuations in both commercially exploited fish stocks , Castonguay et al. 2008 and reproductive performance of land-based predators (Frederiksen et al. 2006, Sydeman et al. 2006.The lesser sandeel Ammodytes marinus (hereinafter sandeel) is a key species in the ecology of the North Sea and other parts of the NE Atlantic (Daan et al. 1990). It is generally the most abundant small planktivorous fish, and provides a critical trophic link between secondary producers (zooplankton, particularly calanoid copepods) and a wide variety of top predators, including larger fish, marine mammals and seabirds. Several studies have highlighted the critical importance of the availability and quality of sandeels for successful reproduction of North Sea seabirds (Monaghan 1992, Rindorf et al. 2000, Wanless et al. 2005. Sandeels are also the target of a major industrial fishery for fishmeal and fish oil (Furness 2002). However, evidence from several sources has indicated that conditions for sandeels in the North Sea are less favourable than...

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Section: Discussionmentioning

confidence: 99%

Mechanisms of long-term decline in size of lesser sandeels in the North Sea explored using a growth and phenology model

Frederiksen¹,

Elston²,

Edwards³

et al. 2011

Mar. Ecol. Prog. Ser.

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“…Hislop et al 1991) and study. Hence, it was impossible to obtain precise values for all organisms or occasions during the experimental discarding sessions.…”

Section: Methodsmentioning

confidence: 99%

Amounts of discards by commercial fisheries and their significance as food for seabirds in the North Sea

Garthe¹,

Camphuysen²,

Furness³

1996

Mar. Ecol. Prog. Ser.

204

193

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Most types of fishery produce discards and offal in considerable quantities which are fed upon by seabirds. This paper demonstrates the importance to seabirds of fishery waste in the North Sea. The total amount of fishery waste in the North Sea region is estimated at 62800 t of offal, 262200 t of roundfish, 299300 t of flatfish, 15000 t of elasmobranchs and 149700 t of benthic invertebrates per year, representing 4 % of the total biomass of fish and 22% of the total landings This equals an energy value of about 3.4 X 10" kJ. Beam trawl f~sheries discharge discards at the highest rates of all fishing fleets. Their discard fraction is dominated by flatfish which are less favoured by seabirds because of their shape. In contrast, the amounts of discards from pelagic and gadid fisheries are less, but fish species and lengths are more appropriate as food for seabirds. The number of seabirds potentially supported by fishery waste in the North Sea is estimated to be roughly 5.9 million individuals in an average scavenger community (composition in proportion to the seasonal abundance of scavenging species). During expenmental discard studies, the proportions of fishery waste consumed by seabirds was calculated. We estimated that the mass of discards and offal consumed by birds during our study amounted to 55000 t of offal, 206000 t of roundfish, 38000 t of flatfish, 2000 t of elasmobranchs and 9000 t of benthic invertebrates.

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“…15 From these data estimates of the body weight of prey items and the energy density (KJ/g wet weight) were calculated using published relationships. 16,17 Information on adult activity patterns during chick rearing was obtained by different methods in the 2 years. In 1989 observations were made on 10 broods of 1 young and 19 broods of 2 young at numbered nests where members of the pair were individually recognizable either because of unique colour-ring combinations or dye markings.…”

Section: Methodsmentioning

confidence: 99%

Activity budgets, diet and breeding success of KittiwakesRissa tridactylaon the Isle of May

Wanless¹,

Harris²

1992

Bird Study

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Variation in the calorific value and total energy content of the lesser sandeel (Ammodytes marinus) and other fish preyed on by seabirds

Cited by 184 publications

References 22 publications

Mechanisms of long-term decline in size of lesser sandeels in the North Sea explored using a growth and phenology model

Mechanisms of long-term decline in size of lesser sandeels in the North Sea explored using a growth and phenology model

Amounts of discards by commercial fisheries and their significance as food for seabirds in the North Sea

Activity budgets, diet and breeding success of KittiwakesRissa tridactylaon the Isle of May

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