scholarly journals Modelling the effects of fishing on the North Sea fish community size composition

2016 ◽  
Vol 321 ◽  
pp. 35-45 ◽  
Author(s):  
Douglas C. Speirs ◽  
Simon P.R. Greenstreet ◽  
Michael R. Heath
Keyword(s):  
North Sea ◽  
Fish Community ◽  
Size Composition ◽  
Community Size ◽  
The North ◽  
The North Sea ◽  
Sea Fish

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 Modelling the direct impact of bottom trawling on the North Sea fish community to derive estimates of fishing mortality for non-target fish species

2009 ◽  
Vol 66 (9) ◽  
pp. 1985-1998 ◽  
Author(s):  
G. J. Piet ◽  
R. van Hal ◽  
S. P. R. Greenstreet
Keyword(s):  
North Sea ◽  
Fish Species ◽  
Fish Community ◽  
Direct Impact ◽  
Fishing Mortality ◽  
Bottom Trawling ◽  
The North ◽  
Target Fish ◽  
The North Sea ◽  
Sea Fish

Abstract Piet, G. J., van Hal, R., and Greenstreet, S. P. R. 2009. Modelling the direct impact of bottom trawling on the North Sea fish community to derive estimates of fishing mortality for non-target fish species. – ICES Journal of Marine Science, 66: 1985–1998. This study introduces a spatially explicit model that combines abundance data for all the main fish species in the demersal North Sea fish community with international effort data and estimates of gear-, species-, and size-dependent catch efficiency to determine the mortality of non-target fish species caused by bottom trawl fisheries and its spatial variation. Where necessary information was lacking, assumptions were made, and a sensitivity analysis performed to examine the impact of these issues on model results. Model outcomes were validated using international landings and discard data for five target species: cod, haddock, whiting, sole, and plaice. This showed that depending on its configuration, the model could reproduce recorded landings and discards of these species reasonably well. This suggests that the model could be used to simulate rates of fishing mortality for non-target fish species, for which few data are currently available. Sensitivity analyses revealed that model outcomes were most strongly influenced by the estimates of gear catch efficiency and the extent to which the distributions of fishing effort and each species overlapped. Better data for these processes would enhance the contribution that this type of model could make in supporting an ecosystem approach to fisheries management.

scholarly journals Development of the EcoQO for the North Sea fish community

2010 ◽  
Vol 68 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Simon P. R. Greenstreet ◽  
Stuart I. Rogers ◽  
Jake C. Rice ◽  
Gerjan J. Piet ◽  
Emma J. Guirey ◽  
...  
Keyword(s):  
North Sea ◽  
Fish Community ◽  
Environmental Influence ◽  
Fish Stock ◽  
Fishing Pressure ◽  
Stock Management ◽  
The North ◽  
A Value ◽  
The North Sea ◽  
Sea Fish

Abstract Greenstreet, S. P. R., Rogers, S. I., Rice, J. C., Piet, G. J., Guirey, E. J., Fraser, H. M., and Fryer, R. J. 2011. Development of the EcoQO for the North Sea fish community. – ICES Journal of Marine Science, 68: 1–11. Development of the Ecological Quality Objective (EcoQO) for the North Sea demersal fish community is described. Size-based metrics were identified as the most effective indicators of the state of the community, but such metrics are also sensitive to environmental influence. Redefining the large fish indicator (LFI) produced a metric more sensitive to fishing-induced change and therefore more useful to managers. Fish stocks were thought to be exploited at a sustainable rate in the early 1980s, so in a process echoing the precautionary approach to fish stock management, this was considered the reference period for the LFI, suggesting a value of 0.3 as the appropriate EcoQO. The LFI declined from around 0.3 in 1983 to 0.05 in 2001, followed by a recovery to 0.22 in 2008. However, analyses of the longer-term groundfish survey data suggest that, even were fishing pressure to be reduced to early 20th century levels, the LFI would be unlikely to rise much above a value of 0.3. The response of the LFI to variation in fishing pressure suggested a more complex relationship than anticipated, underscoring the need for operational theoretical size-resolved multispecies fish community models to support management towards broader ecosystem objectives.

scholarly journals Changes in the North Sea fish community: evidence of indirect effects of fishing?

2005 ◽  
Vol 62 (2) ◽  
pp. 177-188 ◽  
Author(s):  
Niels Daan ◽  
Henrik Gislason ◽  
John G. Pope ◽  
Jake C. Rice
Keyword(s):  
North Sea ◽  
Indirect Effects ◽  
Fish Community ◽  
Fishing Effort ◽  
Time Lags ◽  
The North ◽  
Exploitation Rate ◽  
The North Sea ◽  
Sea Fish

Abstract We investigate changes in the North Sea fish community with particular reference to possible indirect effects of fishing, mediated through the ecosystem. In the past, long-term changes in the slope of size spectra of research vessel catches have been related to changes in fishing effort, but such changes may simply reflect the cumulative, direct effects of fishing through selective removal of large individuals. If there is resilience in a fish community towards fishing, we may expect increases in specific components, for instance as a consequence of an associated reduction in predation and/or competition. We show on the basis of three long-term trawl surveys that abundance of small fish (all species) as well as abundance of demersal species with a low maximum length (Lmax) have steadily and significantly increased in absolute numbers over large parts of the North Sea during the last 30 years. Taking average fishing mortality of assessed commercial species as an index of exploitation rate of the fish community, it appears that fishing effort reached its maximum in the mid-1980s and has declined slightly since. If the observed changes in the community are caused by indirect effects of fishing, there must be a considerable delay in response time, because the observed changes generally proceed up to recent years, although both size and Lmax spectra suggest some levelling off, or even recovery in one of the surveys. Indeed, significant correlations between all community metrics and exploitation rate were obtained only if time lags ≥6 years were introduced.

scholarly journals Tunny Investigations made in the North Sea on Col. E. T. Peel's Yacht, “St. George,” Summer, 1933. Part I. Biometric Data

1934 ◽  
Vol 19 (2) ◽  
pp. 503-522 ◽  
Author(s):  
F. S. Russell
Keyword(s):  
North Sea ◽  
South Coast ◽  
Body Proportions ◽  
The South ◽  
Biometric Data ◽  
The North ◽  
The North Sea ◽  
Sea Fish ◽  
Made In

1. Details are given of the types of hooks lost in tunny in the North Sea in the summer of 1933.2. Data are given on the measurements made on thirty-two large migrating fish caught in the North Sea in August and September, 1933.3. In certain body proportions the tunny measured differ from those in the G4 Group (200 to 260 cm. in length) given by Heldt for fish from Tunis and by Frade for fish from Algarve on the south coast of Portugal, while in some characters they resemble the Tunis fish and in others the Algarve fish, but all the North Sea fish were between 232 and 271 cm. in length.4. It was found that there was a tendency for fish with short second dorsal fins to have short first dorsal, anal, and caudal fins, and for those with long second dorsals to have these other three fins long.5. Measurements were made to supply data on the condition of the fish.

scholarly journals Comparing conceptual frameworks for a fish community MSY (FCMSY) using management strategy evaluation—an example from the North Sea

2019 ◽  
Vol 76 (4) ◽  
pp. 813-823 ◽  
Author(s):  
Robert B Thorpe ◽  
José A A De Oliveira
Keyword(s):  
North Sea ◽  
Management Strategy ◽  
Fish Community ◽  
Parameter Uncertainties ◽  
Management Strategy Evaluation ◽  
The North ◽  
Strategy Evaluation ◽  
The North Sea ◽  
Definition Of

Abstract Maximum sustainable yield (MSY) is a well-established concept that is mandated by legislation, and has a clear theoretical meaning in terms of a single stock. However, its definition is problematic in a multispecies setting, which makes it more difficult to apply the MSY principle. In this study of the North Sea fish community, we consider several possible MSY candidates, and evaluate them in terms of their ability to produce optimum long-term yield whilst avoiding unacceptable risk of stock impairment. We perform this evaluation with an ensemble of size-structured models using a management strategy evaluation approach, in which harvest control rules (HCRs) are used to determine levels of fishing as a function of the proposed MSY target and stock status, taking account of recruitment and model parameter uncertainties. We find that HCRs of the type considered here are always useful in the scenarios we tested, as they reduce overfishing risk much more than average long-term yield. This is independent of the precise form of the HCR, so it is more important to implement one rigorously than obsess over the rule details. For a lax definition of overfishing, which accepts relatively severe stock depletion (B < 10% B0), and using HCRs, risks are “low” across all strategies, and the Nash equilibrium is the best performing MSY approach considered here. For more stringent definitions of “at risk” (e.g. likelihood of B < 20% of B0), the application of HCRs can allow a range of alternative formulations of MSY. Thus, the definition of MSY may be sensitive to judgements about acceptable levels of risk, and consistent application of a sensible management framework may be more important than developing the best possible theoretical definition of MSY.

Feeding ecology of the shrimp Crangon allmanni Kinahan, 1860 (Decapoda, Crangonidae) in the North and White seas

Crustaceana ◽  
2017 ◽  
Vol 90 (7-10) ◽  
pp. 865-881
Author(s):  
R. N. Burukovsky
Keyword(s):  
North Sea ◽  
White Sea ◽  
Size Composition ◽  
Food Composition ◽  
Foraging Mode ◽  
The North ◽  
Onega Bay ◽  
Plant Remains ◽  
The North Sea ◽  
Food Composition Data

The food composition of the shrimp Crangon allmanni from the Helgoland Trench (North Sea) and Onega Bay (White Sea) is described. The main food items (>60%) include detritus, representatives of about 30 benthic species, dominated by polychaetes, malacostracans, ophiuroids, bivalves and ophistobranchs (Cylichna, Diaphana spp.) as well as plant remains. In the North Sea, C. allmanni is closer to an attacking predator than to a predator-gatherer like in the White Sea. This difference may be caused by diverging habitat- and community characteristics and dissimilar size composition of the two studied shrimp populations. Moreover, C. allmanni changes its foraging mode (grazing, gathering, attacking) during ontogenesis. A comparison of the obtained food composition data of C. allmanni with literature data on six other species of the same genus showed all to be benthos feeders, predator-gatherers with elements of detrito- and necrophagia, using grains of sand as millstones in their gastric mill.

scholarly journals A reassessment of trends in the North Sea Large Fish Indicator and a re-evaluation of earlier conclusions

2012 ◽  
Vol 69 (2) ◽  
pp. 343-345 ◽  
Author(s):  
Simon P. R. Greenstreet ◽  
Stuart I. Rogers ◽  
Jake C. Rice ◽  
Gerjan J. Piet ◽  
Emma J. Guirey ◽  
...  
Keyword(s):  
North Sea ◽  
Previous Analysis ◽  
Fish Communities ◽  
Marine Science ◽  
Large Fish ◽  
The North ◽  
The North Sea ◽  
Corrected Data ◽  
Sea Fish

Abstract Greenstreet, S. P. R., Rogers, S. I., Rice, J. C., Piet, G. J., Guirey, E. J., Fraser, H. M., and Fryer, R. J. 2012. A reassessment of trends in the North Sea Large Fish Indicator and a re-evaluation of earlier conclusions. – ICES Journal of Marine Science, 69: 343–345. Previous analysis of the Large Fish Indicator, the basis for the North Sea “fish communities” EcoQO, suggested a strong recovery between 2001 and 2008. Discovery of a mistake in this earlier analysis now suggests that this recovery is not as strong as first thought, but reanalysis of the corrected data still supports the majority of conclusions drawn in the original paper.

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