| 11. |
- Arnott, S. A., et al.
(författare)
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Selection of prey size and prey species by 1-group cod Gadus morhua: effects of satiation level and prey handling times
- 2000
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Ingår i: Marine Ecology-Progress Series. - 0171-8630. ; 198, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- We performed laboratory experiments to investigate feeding behaviour of 1-group Atlantic cod Gadus morhua and compared the results with stomach content records from wild 1-group cod feeding within a shallow bay on the west coast of Sweden. On the basis of the field observations, 3 prey species were investigated: juvenile shore crabs Carcinus maenas, brown shrimps Crangon crangon and 0-group plaice Pleuronectes platessa. When fed single species meals in the laboratory, satiation level was mostly independent of prey size, but cod consumed more plaice than shrimps and more shrimps than crabs. Once satiated on crabs, cod ate plaice if they were subsequently offered, but the reverse was not true. The time taken to ingest crabs was independent of the prey:cod (P:C) length ratio, cod length or stomach fullness, whereas plaice and shrimp ingestion times increased with P:C length ratio, and shrimp times also increased with stomach fullness. Consequently, the profitability of crabs increased up until the maximum edible size, whereas shrimp and plaice profitability peaked at P:C length ratios lower than the maximum edible sizes. For a given prey species, size selection in the field correlated closely with the size-dependent profitability relationships. Species selection had no apparent dependence upon handling-time profitability(, species-dependent satiation level or gastric evacuation rate. Additional factors of probable importance include prey evasiveness, prey abundance, habitat patchiness and abiotic factors such as prevailing light conditions.
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| 12. |
- Attard, Karl M., et al.
(författare)
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Benthic oxygen exchange in a live coralline algal bed and an adjacent sandy habitat : an eddy covariance study
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research. - 0171-8630 .- 1616-1599. ; 535, s. 99-115
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Tidskriftsartikel (refereegranskat)abstract
- Coralline algal (maerl) beds are widespread, slow-growing, structurally complex perennial habitats that support high biodiversity, yet are significantly understudied compared to seagrass beds or kelp forests. We present the first eddy covariance (EC) study on a live maerl bed, assessing the community benthic gross primary productivity (GPP), respiration (R), and net ecosystem metabolism (NEM) derived from diel EC time series collected during 5 seasonal measurement campaigns in temperate Loch Sween, Scotland. Measurements were also carried out at an adjacent (similar to 20 m distant) permeable sandy habitat. The O-2 exchange rate was highly dynamic, driven by light availability and the ambient tidally-driven flow velocity. Linear relationships between the EC O-2 fluxes and available light indicate that the benthic phototrophic communities were light limited. Compensation irradiance (E-c) varied seasonally and was typically similar to 1.8-fold lower at the maerl bed compared to the sand. Substantial GPP was evident at both sites; however, the maerl bed and the sand habitat were net heterotrophic during each sampling campaign. Additional inputs of similar to 4 and similar to 7 mol m(-2) yr(-1) of carbon at the maerl bed and sand site, respectively, were required to sustain the benthic O-2 demand. Thus, the 2 benthic habitats efficiently entrap organic carbon and are sinks of organic material in the coastal zone. Parallel deployment of 0.1 m(2) benthic chambers during nighttime revealed O-2 uptake rates that varied by up to similar to 8-fold between replicate chambers (from -0.4 to -3.0 mmol O-2 m(-2) h(-1); n = 4). However, despite extensive O-2 flux variability on meter horizontal scales, mean rates of O-2 uptake as resolved in parallel by chambers and EC were typically within 20% of one another.
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| 13. |
- Attard, Karl M., et al.
(författare)
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Metabolism of a subtidal rocky mussel reef in a high-temperate setting : pathways of organic C flow
- 2020
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 645, s. 41-54
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Tidskriftsartikel (refereegranskat)abstract
- Mytilid mussels form abundant, species-rich reefs on rocky substrates, but the role of this key habitat in carbon (C) cycling remains poorly understood. We performed a seasonal study on a 5 m deep photic Mytilus trossulus reef in the Central Baltic Sea to investigate pathways and rates of organic C flow. Reef gross primary production (GPP) and respiration (R) were estimated seasonally using underwater O2 eddy covariance on hourly and daily timescales. Photogrammetry and biotic sampling were used to quantify reef rugosity and mussel coverage, and to derive mussel filtration and biodeposition. Mussels were highly abundant, reaching ~50000 ind. m-2, and the reef structure increased the seabed surface area by 44%. GPPhourly was up to 20 mmol O2 m-2 h-1 and GPPdaily was up to 107 mmol O2 m-2 d-1, comparable to a nearby seagrass canopy. Hourly eddy fluxes responded linearly to light intensity and flow velocity, with higher velocities enhancing reef O2 uptake at night. Reef Rdaily exceeded GPPdaily on 12 of 13 measurement days, and Rannual (29 mol O2 m-2 yr-1) was 3-fold larger than GPPannual. The reef sustained a productive community of microbes and fauna whose activities accounted for ~50% of Rannual. Horizontal water advection promoted food supply to the reef and likely facilitated substantial lateral C export of mussel biodeposits. Our analyses suggest that a reduction in mussel reef extent due to ongoing environmental change will have major implications for the transport and transformation of C and nutrients within the coastal Baltic Sea.
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| 14. |
- Baden, Susanne P., 1952, et al.
(författare)
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Shift in seagrass food web structure over decades is linked to overfishing
- 2012
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 451, s. 61-73
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Tidskriftsartikel (refereegranskat)abstract
- Empirical field studies in seagrass have revealed that overgrowth by filamentous algae which reduces seagrass growth can be explained by a top-down cascading effect caused by declines in top predators, which is enforced by eutrophication. On the Swedish west coast, 60% of the seagrass has disappeared since the 1980s. We hypothesised that overfishing, responsible for a >90% decline in the cod stock, and the 4 to 8 times increase in nutrient load since the 1930s have altered the seagrass structure and function during recent decades. We used quantitative samples from the 1980s and 2000s and analysed the trends in abundance of the 4 feeding guilds: top predatory fish, intermediate predatory fish, crustacean omnivores and mesoherbivores. Since the 1980s, the commercial catch of gadoids on the Swedish west coast has decreased by >90 %, and here we found that the biomass of top predators (gadoids and trout) that forage in seagrass has decreased by approximately 80%. In contrast, the biomass of intermediate predatory fish (gobids and sticklebacks) has increased 8 times during summer and 11 times during autumn, while mesoherbivores (idoteids and gammarids >7 mm) have more or less disappeared from the seagrass bed. We thus found clear evidence that a shift in seagrass food web structure has taken place over the last 3 decades. Combining these findings with our recent empirical results from field cage experiments in the Skagerrak seagrass, where we manipulate top-down and bottom-up regulation, we conclude that lack of grazers in concert with eutrophication most likely contributed to the overgrowth by filamentous algae and disappearance of the seagrass on the Swedish west coast.
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| 15. |
- Bartolino, Valerio
(författare)
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Role of prey abundance and geographical variables in a demersal top predator's feeding habits (Merluccius merluccius)
- 2015
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 541, s. 165-177
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Tidskriftsartikel (refereegranskat)abstract
- Demersal predators can take advantage of a large pool of potential prey including benthic, demersal and pelagic species; therefore disentangling the variables that influence their diet is of key relevance for food web ecologists. To this aim, we analysed a large dataset of the stomach contents of European hake Merluccius merluccius, a top predator in the demersal food web of the Cantabrian Sea. We combined 2 modelling approaches: a zero-truncated generalised additive model targeting fullness variability, and a multinomial model on the probability of consumption for each prey. Predator size, geographical variables (i.e. longitude and depth), and abundance of prey were considered as independent variables, and had significant effects on predator stomach fullness. We also documented a positive effect of continental shelf width on predator stomach fullness. The hake's main prey, blue whiting Micromesistius poutassou, had the strongest effect on predator feeding success. However, in the absence of this prey species, consumption of all other prey items increased. Consumption was highly influenced by prey abundance, but predator density dependence was only evident in instances of cannibalism. Both the full/empty ratio and stomach fullness decreased during ontogeny, and a change from low-energy demersal to high-energy pelagic prey was documented, matching the onset of maturity. While the abundance of prey significantly affected feeding success, a large diet breadth rather than prey surrogates seemed to act as an effective buffer, ensuring feeding at low abundance of specific prey.
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| 16. |
- Bartolino, Valerio
(författare)
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Scale-dependent detection of the effects of harvesting a marine fish population
- 2012
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 444, s. 251-272
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Tidskriftsartikel (refereegranskat)abstract
- Certain ecological processes dominate others at particular scales, and the response of populations to exogenous and endogenous forces are typically scale dependent. In spite of this central role played by scale, the temporal and spatial scales of human impacts on ecosystems and populations remain almost unknown. We applied a multiscale regression analysis to investigate the spatiotemporal scales which characterize the fisheries exploitation of yellowfin sole Limanda aspera in the Bering Sea. We found that harvesting affects the abundance of this species simultaneously at local and regional scales. At the local scale harvesting produced a negative effect on local fish densities, particularly in those areas and seasons of high fish aggregation, when both the vulnerability of the fish and the fishing effort increase. At the regional scale harvesting was characterized by a widespread negative effect on the whole fish population. Our findings demonstrate that (1) detection of the fisheries exploitation effects on natural populations is sensitive to the scale of investigation, (2) fisheries harvesting can simultaneously affect multiple ecological scales which are not linearly correlated with each other. We developed analytical techniques for the detection of scale-dependent processes, which can be readily applied to other systems. Our results provide insights on the risks of extrapolating the effects of harvesting on natural populations across scales, making the issues of scale and space central to the management and conservation of natural populations.
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| 17. |
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| 18. |
- Bekkevold, D., et al.
(författare)
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Genetic mixed-stock analysis of Atlantic herring populations in a mixed feeding area
- 2011
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 442, s. 187-199
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Tidskriftsartikel (refereegranskat)abstract
- Determining spatio-temporal distributions of fish populations is of interest to marine ecology, in general, and to fisheries science in particular. Genetic mixed-stock analysis is routinely applied in several anadromous fishes for determining migratory routes and timing but has rarely been used for marine fishes, for which population differentiation is commonly weak and the method presumably less powerful. We used microsatellite information for Northeast Atlantic herring Clupea harengus L. populations and mixed stocks to address 2 questions. We used simulated mixture samples and 3 different statistical approaches to determine whether mixed stock composition could be determined with accuracy. Simulations showed that the applied approaches and mixture samples of 100 individuals enabled detailed composition analyses on a regional level, with resolution for tracing the ecologically dominant Rügen (Greifswalder Bodden) herring population. We then estimated spatio-temporal variation in herring migratory behaviour in the Skagerrak from 17 mixed samples collected over 2 seasons and 2 yr, and identified hitherto undescribed differences in distributions among populations that feed and winter in the area.
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| 19. |
- Berg, Florian, et al.
(författare)
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Genetic origin and salinity history influence the reproductive success of Atlantic herring
- 2019
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Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 617, s. 81-94
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Tidskriftsartikel (refereegranskat)abstract
- Atlantic herring populations inhabit environments ranging in salinity from fully marine to nearly freshwater, but their relative reproductive success in these respective environments remains unclear. We conducted factorial crossing experiments using parents from 3 wild populations associated with different salinity environments: the Baltic Sea (similar to 6 psu), an inland brackish lake in Norway (Landvikvannet, similar to 16 psu), and the Atlantic (similar to 30 to 35 psu). Further experiments used crosses within and between Atlantic purebreds and Atlantic/Baltic hybrids reared until first maturity at 3 yr of age. Crossing experiments were conducted at 6, 16 and 35 psu. Fertilization and hatching rates were estimated, and egg sizes were measured. Fertilization rates were highest at 16 psu for all combinations. The paternal genetic and salinity origin influenced fertilization rates at 6 and 35 psu, indicating a genetic adaptation to their original environment. Fertilization rates for males originating from 16 psu were low at 35 psu. Atlantic/Baltic hybrids had lower fertilization rates than Atlantic purebreds at 35 psu. Hatching rates were not influenced by any parental factors or salinity. Maternal effects and salinity influenced egg size. Atlantic females had significantly larger eggs than the Atlantic/Baltic hybrid females. For all genetic groups, egg size decreased with increasing salinity at incubation mainly due to osmotic effects. The observed lower fertilization success at salinities other than those of the parental fish habitat would have evolutionary consequences when herring colonize new habitats with different salinities or if interbreeding occurred between populations originating from different salinity habitats.
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| 20. |
- Berg, Florian, et al.
(författare)
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Respiration rates of herring larvae at different salinities, and effects of previous environmental history
- 2020
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Ingår i: Marine Ecology Progress Series. - : INTER-RESEARCH. - 0171-8630 .- 1616-1599. ; 650, s. 141-152
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Tidskriftsartikel (refereegranskat)abstract
- Metabolic rates of early life history stages of marine fishes show considerable interindividual differences, and are highly influenced by extrinsic factors like temperature or food availability. Measuring oxygen uptake rates is a proxy for estimating metabolic rates. Still, the relationship between respiration rates and ambient or previous salinity conditions as well as parental and developmental acclimation to changes in salinity remains largely unexplored. In the present study, we conducted experiments to investigate the effects of salinity on the routine metabolic rates (RMR) of euryhaline Atlantic herring Clupea harengus larvae at 3 levels of salinity: low (6 psu), intermediate (16 psu) and high (35 psu), reflecting ecologically relevant conditions for herring populations in the Atlantic Ocean and Baltic Sea. The larvae originated from different genetic backgrounds and salinity adaptations to account for cross-generation effects on metabolic rates. Closed respirometry carried out over 24 h on individual fish larvae generally confirmed near isometric respiration rates at all salinity regimes, with rates being 15.4% higher at 6 psu and 7.5% higher at 35 psu compared to 16 psu conditions. However, transgenerational acclimation to different salinity regimes of the parents had no effect on the salinity-specific metabolic rates of their offspring. Our study demonstrates the ability of herring to cope with a wide range of salinity conditions, irrespective of parental environmental history and genetic origin. This phenotypic plasticity is considered to be one of the main contributing factors to the success of herring as a widely distributed fish species in the North Atlantic and adjacent waters.
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