Patterns of change in the size spectra of numbers and diversity of the North Sea fish assemblage, as reflected in surveys and models

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.

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Running the gauntlet: the predation environment of small fish in the northern Gulf of St Lawrence, Canada

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2004.11.005 ◽

2005 ◽

Vol 62 (3) ◽

pp. 412-416 ◽

Cited By ~ 14

Author(s):

Daniel E. Duplisea

Keyword(s):

Body Size ◽

North Sea ◽

Prey Size ◽

Small Fish ◽

Size Spectra ◽

Predator Prey ◽

The North ◽

Prefer Prey ◽

Seal Population ◽

The North Sea

Abstract Predation size spectra were constructed for the northern Gulf of St Lawrence, covering prey size ranges that include pre-recruit cod. Predation by fish and harp seals was modelled with a log-normally distributed predator–prey size ratio along with a relationship between predator body size and the energy required. Fish concentrate predation on prey of weight 0.5–2 g, whereas harp seals prefer prey of 60–125 g. It is speculated that predation caused by harp seals on pre-recruits could be a major factor limiting cod recruitment in the system. The northern Gulf of St Lawrence is a cold boreal system with a large predatory seal population, and cod recruit older than elsewhere. Therefore, cod recruitment may be more strongly affected by predation in the northern Gulf of St Lawrence than in warmer systems such as the North Sea, where recruitment is strongly influenced by temperature.

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

ICES Journal of Marine Science ◽

10.1093/icesjms/fsr201 ◽

2012 ◽

Vol 69 (2) ◽

pp. 343-345 ◽

Cited By ~ 13

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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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 ◽

10.1093/icesjms/fsp162 ◽

2009 ◽

Vol 66 (9) ◽

pp. 1985-1998 ◽

Cited By ~ 32

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.

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Ecotypes as a concept for exploring responses to climate change in fish assemblages

ICES Journal of Marine Science ◽

10.1093/icesjms/fsq183 ◽

2010 ◽

Vol 68 (3) ◽

pp. 580-591 ◽

Cited By ~ 39

Author(s):

Georg H. Engelhard ◽

Jim R. Ellis ◽

Mark R. Payne ◽

Remment ter Hofstede ◽

John K. Pinnegar

Keyword(s):

Climate Change ◽

North Sea ◽

Trophic Level ◽

Fish Assemblages ◽

Environmental Drivers ◽

Trawl Survey ◽

The North ◽

The North Sea ◽

Increasing Trends ◽

Sea Fish

Abstract Engelhard, G. H., Ellis, J. R., Payne, M. R., ter Hofstede, R., and Pinnegar, J. K. 2011. Ecotypes as a concept for exploring responses to climate change in fish assemblages. – ICES Journal of Marine Science, 68: . How do species-rich fish assemblages respond to climate change or to other anthropogenic or environmental drivers? To explore this, a categorization concept is presented whereby species are assigned with respect to six ecotype classifications, according to biogeography, horizontal and vertical habitat preference, trophic guild, trophic level, or body size. These classification schemes are termed ecotypology, and the system is applied to fish in the North Sea using International Bottom Trawl Survey data. Over the period 1977–2008, there were changes in the North Sea fish community that can be related to fish ecotypes. Broadly speaking, there were steady increases in abundance of species that were either Lusitanian, small-bodied, or low-/mid-trophic-level ecotypes, and generally declining or only marginally increasing trends of most Boreal, large-bodied, or high-trophic-level ecotypes or combinations of them. The post-1989 warm biological regime appears to have favoured pelagic species more than demersal species. These community-level patterns agree with the expected responses of ecotypes to climate change and also with anticipated vulnerability to fishing pressure.

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Development of the EcoQO for the North Sea fish community

ICES Journal of Marine Science ◽

10.1093/icesjms/fsq156 ◽

2010 ◽

Vol 68 (1) ◽

pp. 1-11 ◽

Cited By ~ 87

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.

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

Ecological Modelling ◽

10.1016/j.ecolmodel.2015.10.032 ◽

2016 ◽

Vol 321 ◽

pp. 35-45 ◽

Cited By ~ 4

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

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

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2004.08.020 ◽

2005 ◽

Vol 62 (2) ◽

pp. 177-188 ◽

Cited By ~ 201

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.

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