Benthic Organisms and the Structure of Marine Ecosystems

1975 ◽  
Vol 32 (9) ◽  
pp. 1657-1663 ◽  
Author(s):  
Eric L. Mills
Keyword(s):  
Benthic Communities ◽  
Demersal Fish ◽  
Marine Ecosystems ◽  
Benthic Organisms ◽  
Biological Oceanography ◽  
The North ◽  
The North Sea ◽  
Different Levels ◽  
Benthic Animals

The contribution of benthic ecology to biological oceanography has been relatively slight, even though the benthos may be crucial in understanding the dynamics of marine ecosystems, as J. H. Steele’s model of the North Sea indicates. Before the benthos may be accurately assigned a role in such models, we need to know at least 1) what food items are consumed and assimilated, 2) what the role of bacteria and meiobenthos may be, and 3) if there are different levels of demersal fish production from differently structured benthic communities. There seem to be no shortcuts to the kind of information about benthic animals useful in permitting assessment of fisheries production in a realistic biological framework.

scholarly journals Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community

2012 ◽  
Vol 69 (1) ◽  
pp. 8-22 ◽  
Author(s):  
Simon P. R. Greenstreet ◽  
Helen M. Fraser ◽  
Stuart I. Rogers ◽  
Verena M. Trenkel ◽  
Stephen D. Simpson ◽  
...  
Keyword(s):  
North Sea ◽  
Fish Community ◽  
Size Structure ◽  
Demersal Fish ◽  
Community Size ◽  
The North ◽  
Management Objectives ◽  
The North Sea ◽  
Composition Structure ◽  
And Function

Abstract Greenstreet, S. P. R., Fraser, H. M., Rogers, S. I., Trenkel, V. M., Simpson, S. D., and Pinnegar, J. K. 2012. Redundancy in metrics describing the composition, structure, and functioning of the North Sea demersal fish community. – ICES Journal of Marine Science, 69: 8–22. Broader ecosystem management objectives for North Sea demersal fish currently focus on restoring community size structure. However, most policy drivers explicitly concentrate on restoring and conserving biodiversity, and it has not yet been established that simply restoring demersal fish size composition will be sufficient to reverse declines in biodiversity and ensure a generally healthy community. If different aspects of community composition, structure, and function vary independently, then to monitor all aspects of community general health will require application of a suite of metrics. This assumes low redundancy among the metrics used in any such suite and implies that addressing biodiversity issues specifically will require explicit management objectives for particular biodiversity metrics. This issue of metric redundancy is addressed, and 15 metrics covering five main attributes of community composition, structure, and function are applied to groundfish survey data. Factor analysis suggested a new interpretation of the metric information and indicated that a minimum suite of seven metrics was necessary to ensure that all changes in the general health of the North Sea demersal fish community were monitored properly. Covariance among size-based and species-diversity metrics was low, implying that restoration of community size structure would not necessarily reverse declines in species diversity.

scholarly journals Spatial distribution of otter trawl effort in Icelandic waters: comparison of measures of effort and implications for benthic community effects of trawling activities

2003 ◽  
Vol 60 (6) ◽  
pp. 1200-1215 ◽  
Author(s):  
Stefán Áki Ragnarsson ◽  
Sigmar Arnar Steingrímsson
Keyword(s):  
Spatial Distribution ◽  
Scale Effects ◽  
Benthic Communities ◽  
Demersal Fish ◽  
Fishing Effort ◽  
Otter Trawl ◽  
Community Effects ◽  
The North ◽  
Swept Area ◽  
Icelandic Waters

Abstract We examined the spatial distribution of trawling effort from logbook data from all Icelandic vessels fishing for demersal fish between 1991 and 1997 with a spatial resolution of 1 degree of latitude and 1 degree of longitude. The trawling effort was widely distributed but was intensive only in small and localised areas. Three measures of effort were compared; tow frequency, tow duration and separate estimates of swept area for otter boards and trawls. In each year, the area swept with otter trawl was 1.7 times greater than the total area in which fishing occurred over the 7 year period. In contrast, the area swept with otter boards was 4% of the total fishing area. Most of the fishing effort was confined to depths shallower than 400 m. With increasing depth, the size of trawls became larger and accordingly, also the area swept per haul. Calculations assuming no variation in the size of the trawl in relation to depth, produced inaccurate swept area estimates. Furthermore, swept area estimates based on depth corrected door spreads were greater than estimates where no such correction was made. Swept area was considered to be a more appropriate measure of effort than tow frequency and tow duration as long as variation in the size of the gear (e.g. in relation to depth) was taken into account. Effort within Icelandic waters was compared in five depth strata within seven zones. Effort was highest off the south and NW coasts and lowest off the north and east coasts. Effort was most intensive at the 100–500 m depth in all zones but in some areas (such as off NW Iceland), effort extended to deeper waters. Knowledge of the distribution of fishing effort is important for predicting larger scale effects of fishing gears on benthic communities.

The macrobenthos of the Beatrice Oilfield, Moray Firth, Scotland

1986 ◽  
Vol 91 ◽  
pp. 221-245
Author(s):  
J. P. Hartley ◽  
J. D. D. Bishop
Keyword(s):  
New Records ◽  
Benthic Communities ◽  
Fine Sand ◽  
Faunal Composition ◽  
Qualitative And Quantitative ◽  
The North ◽  
Moray Firth ◽  
Faunal Communities ◽  
The North Sea

SynopsisThe benthic ecology of the Beatrice Oilfield area is described from preproduction surveys carried out in 1977, 1980 and 1981. and from earlier published information. Variations in the water depth (from 33m to > 60 m) over the area were mirrored by sedimentary and faunal gradients. The sediments ranged from very fine, through fine to medium sands and were inhabited by faunal communities characterised by Thyasira flexuosa, Tellina fabula and Tellina pygmaea, respectively. Two fades of the fine sand community were noted, typified by the abundance of Thyasira flexuosa in muddier sediments and Crenella decussala in coarser deposits. Localised patches of shell gravel in which the fauna was characterised by reduced densities of Tellina fabula with elevated numbers of Scoloplos armiger and Lumbrineris gracilis occurred in medium depths. Examination of the faunal composition indicates that the Beatrice Oilfield lies at the interface between Glemarec's infralittoral and coastal étages.Comparison with earlier reports of the benthic communities of the area suggests a degree of long term persistence of the fauna in qualitative and quantitative terms. A list of all taxa found during the recent surveys is given; this includes a number of new records from the North Sea.

scholarly journals Different bottom trawl fisheries have a differential impact on the status of the North Sea seafloor habitats

2020 ◽  
Vol 77 (5) ◽  
pp. 1772-1786 ◽  
Author(s):  
A D Rijnsdorp ◽  
J G Hiddink ◽  
P D van Denderen ◽  
N T Hintzen ◽  
O R Eigaard ◽  
...  
Keyword(s):  
North Sea ◽  
Management Strategies ◽  
Demersal Fish ◽  
Time Interval ◽  
The North ◽  
The Status ◽  
Fisheries Conservation ◽  
The North Sea ◽  
The Impact ◽  
Trawl Fisheries

Abstract Fisheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to seafloor habitats. To mitigate such disturbances, the development of fisheries-, conservation-, and ecosystem-based management strategies requires the assessment of the impact of bottom trawling on the state of benthic biota. We explore a quantitative and mechanistic framework to assess trawling impact. Pressure and impact indicators that provide a continuous pressure–response curve are estimated at a spatial resolution of 1 × 1 min latitude and longitude (∼2 km2) using three methods: L1 estimates the proportion of the community with a life span exceeding the time interval between trawling events; L2 estimates the decrease in median longevity in response to trawling; and population dynamic (PD) estimates the decrease in biomass in response to trawling and the recovery time. Although impact scores are correlated, PD has the best performance over a broad range of trawling intensities. Using the framework in a trawling impact assessment of ten métiers in the North Sea shows that muddy habitats are impacted the most and coarse habitats are impacted the least. Otter trawling for crustaceans has the highest impact, followed by otter trawling for demersal fish and beam trawling for flatfish and flyshooting. Beam trawling for brown shrimps, otter trawling for industrial fish, and dredging for molluscs have the lowest impact. Trawling is highly aggregated in core fishing grounds where the status of the seafloor is low but the catch per unit of effort (CPUE) per unit of impact is high, in contrast to peripheral grounds, where CPUE per unit of impact is low.

Plastic ingestion by pelagic and demersal fish from the North Sea and Baltic Sea

2016 ◽  
Vol 102 (1) ◽  
pp. 134-141 ◽  
Author(s):  
Christoph D. Rummel ◽  
Martin G.J. Löder ◽  
Nicolai F. Fricke ◽  
Thomas Lang ◽  
Eva-Maria Griebeler ◽  
...  
Keyword(s):  
Baltic Sea ◽  
North Sea ◽  
Demersal Fish ◽  
The North ◽  
The North Sea

scholarly journals Changes in the structure and function of the North Sea fish foodweb, 1973–2000, and the impacts of fishing and climate

2005 ◽  
Vol 62 (5) ◽  
pp. 847-868 ◽  
Author(s):  
Michael R. Heath
Keyword(s):  
North Sea ◽  
Secondary Production ◽  
Demersal Fish ◽  
Biological Data ◽  
Similar Species ◽  
The North ◽  
Production And Consumption ◽  
The North Sea ◽  
Vacant Niches ◽  
And Function

Abstract North Sea environmental and biological data were analysed to examine 30-year changes in production and consumption in the fish foodweb. The analysis revealed that the demand for secondary production placed on the ecosystem by fish declined from approximately 20 g C m−2 y−1 in the 1970s to 16 g C m−2 y−1 in the 1990s. Over the same period, the proportion of demand provided by zooplankton production increased from around 70% to 75%. The overall decrease was mainly due to a reduction in piscivorous demersal fish. Average secondary production by omnivorous zooplankton was estimated to be 35 g C m−2 y−1, and annual fluctuations were positively correlated with the gross production of planktivorous fish. The results suggest a “bottom-up” control of the pelagic foodweb. Individual planktivore species have been impacted by fishing, but the populations of other functionally similar species have expanded to fill the vacant niches, thus maintaining the planktivore role in the system. In contrast, the results indicate that benthos production was more “top-down” controlled. Overall, demersal fish species have been depleted by fishing, with no obvious species expansions to fill the vacant niche, releasing the benthos from predation pressure, and leading to an increase in benthic production and fisheries for invertebrates.

scholarly journals The consumption of zooplankton by early life stages of fish in the North Sea

2007 ◽  
Vol 64 (9) ◽  
pp. 1650-1663 ◽  
Author(s):  
Michael R. Heath
Keyword(s):  
North Sea ◽  
Early Life ◽  
Life Stages ◽  
Early Life Stages ◽  
The North ◽  
The North Sea ◽  
Zooplankton Consumption ◽  
Zooplankton Production ◽  
Fish Early Life Stages

Abstract Heath, M. R. 2007. The consumption of zooplankton by early life stages of fish in the North Sea. – ICES Journal of Marine Science, 64: 1650–1663. Previous work has shown that during the 1970s, fish and carnivorous macrozooplankton together consumed ∼22 gC m−2 year−1 of mesozooplankton, principally copepods. Consumption declined to ∼17 gC m−2 year−1 during the 1990s, mainly because of a reduction in fish production. The zooplankton production required to meet this demand seems to be approximately accounted for by estimates of new primary production, but there are additional sinks for zooplankton production attributable to predation by, for example, gelatinous species. Additionally, the consumption of zooplankton by early life stages of fish is difficult to assess and could be larger than implied by the earlier analysis. Here, the role of fish early life stages in zooplankton consumption is re-assessed, and found to be approximately double that previously estimated. Some 28% of the zooplankton consumption by fish is now estimated to be attributable to early life stages, resulting in an estimate of zooplankton consumption by the fish community as a whole 14% higher. Taken overall, the consumption of zooplankton production by fish and other planktivorous predators is now estimated to be 19–25 gC m−2 year−1.

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