scholarly journals The importance of predator–prey overlap: predicting North Sea cod recovery with a multispecies assessment model

2010 ◽  
Vol 67 (9) ◽  
pp. 1989-1997 ◽  
Author(s):  
Alexander Kempf ◽  
Gjert Endre Dingsør ◽  
Geir Huse ◽  
Morten Vinther ◽  
Jens Floeter ◽  
...  
Keyword(s):  
North Sea ◽  
Single Species ◽  
Assessment Model ◽  
Negative Effects ◽  
Predator Prey ◽  
The North ◽  
Recovery Potential ◽  
Increasing Temperature ◽  
Time Invariant ◽  
Prey Overlap

Abstract Kempf, A., Dingsør, G. E., Huse, G., Vinther, M., Floeter, J., and Temming, A. 2010. The importance of predator–prey overlap: predicting North Sea cod recovery with a multispecies assessment model. – ICES Journal of Marine Science, 67: 1989–1997. The overlap between predator and prey is known as a sensitive parameter in multispecies assessment models for fish, and its parameterization is notoriously difficult. Overlap indices were derived from trawl surveys and used to parametrize the North Sea stochastic multispecies model. The effect of time-invariant and year- and quarter-specific overlap estimates on the historical (1991–2007) and predicted trophic interactions, as well as the development of predator and prey stocks, was investigated. The focus was set on a general comparison between single-species and multispecies forecasts and the sensitivity of the predicted development of North Sea cod for the two types of overlap implementation. The spatial–temporal overlap between cod and its predators increased with increasing temperature, indicating that foodweb processes might reduce the recovery potential of cod during warm periods. Multispecies scenarios were highly influenced by assumptions on future spatial overlap, but they predicted a considerably lower recovery potential than single-species predictions did. In addition, a recovery of North Sea cod had strong negative effects on its prey stocks. The consequences of these findings for management are discussed.

From single-species advice to mixed-species management: taking the next step

2004 ◽  
Vol 61 (8) ◽  
pp. 1398-1409 ◽  
Author(s):  
Morten Vinther ◽  
Stuart A. Reeves ◽  
Kenneth R. Patterson
Keyword(s):  
North Sea ◽  
Fishery Management ◽  
Single Species ◽  
Mixed Species ◽  
The North ◽  
Recent Approach ◽  
Starting Point ◽  
The North Sea ◽  
Management Advice ◽  
Management Priorities

Abstract Fishery management advice has traditionally been given on a stock-by-stock basis. Recent problems in implementing this advice, particularly for the demersal fisheries of the North Sea, have highlighted the limitations of the approach. In the long term, it would be desirable to give advice that accounts for mixed-fishery effects, but in the short term there is a need for approaches to resolve the conflicting management advice for different species within the same fishery, and to generate catch or effort advice that accounts for the mixed-species nature of the fishery. This paper documents a recent approach used to address these problems. The approach takes the single-species advice for each species in the fishery as a starting point, then attempts to resolve it into consistent catch or effort advice using fleet-disaggregated catch forecasts in combination with explicitly stated management priorities for each stock. Results are presented for the groundfish fisheries of the North Sea, and these show that the development of such approaches will also require development of the ways in which catch data are collected and compiled.

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

2005 ◽  
Vol 62 (3) ◽  
pp. 412-416 ◽  
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.

Mesh-size matters in epibenthic surveys

2002 ◽  
Vol 82 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Ruth Callaway ◽  
Simon Jennings ◽  
John Lancaster ◽  
John Cotter
Keyword(s):  
Community Structure ◽  
North Sea ◽  
Processing Time ◽  
Mesh Size ◽  
Community Analysis ◽  
Single Species ◽  
Spatial Gradients ◽  
The North ◽  
Significant Difference ◽  
The North Sea

This study aimed to identify the effects of different sieve mesh-sizes on processing time, the number of species retained, diversity measures and multivariate community analysis in the North Sea. Samples were collected at 63 sites throughout the North Sea and washed through two successive sieves, 10-mm and 5-mm mesh respectively.  Processing time for whole samples (5- and 10-mm fraction) averaged 91± 25 min compared with 55±16 min for the 10-mm mesh fraction. Altogether 40% of free-living species and 9% of attached species were recorded exclusively in the 5-mm fraction. The majority of these species were rare. Spatial gradients of species diversity and community structure were identical, independent of the mesh-size used. Multivariate community analysis showed no significant difference between descriptions of community structure based on fauna from 10-mm or 5-mm mesh.  The use of coarser sieving mesh would save time and money, if the aims of an epibenthic survey were to describe broad patterns of community structure and relative diversity. It would be possible to process approximately 50% more samples, if the time saved with 10-mm mesh were allocated to additional sampling. However, if information on single species is required, then sorting with the finer sieve mesh will yield crucial information. It was decided to employ a 5-mm mesh for epibenthic monitoring of the North Sea.

scholarly journals Reconciling single-species TACs in the North Sea demersal fisheries using the Fcube mixed-fisheries advice framework

2011 ◽  
Vol 68 (7) ◽  
pp. 1535-1547 ◽  
Author(s):  
Clara Ulrich ◽  
Stuart A. Reeves ◽  
Youen Vermard ◽  
Steven J. Holmes ◽  
Willy Vanhee
Keyword(s):  
North Sea ◽  
Single Species ◽  
Simple Approach ◽  
Total Allowable Catch ◽  
Traditional Management ◽  
The North ◽  
Management Objectives ◽  
Species Management ◽  
The North Sea ◽  
Management Advice

Abstract Ulrich, C., Reeves, S. A., Vermard, Y., Holmes, S. J., and Vanhee, W. 2011. Reconciling single-species TACs in the North Sea demersal fisheries using the Fcube mixed-fisheries advice framework. – ICES Journal of Marine Science, 68: 1535–1547. Single-species management is a cause of discarding in mixed fisheries, because individual management objectives may not be consistent with each other and the species are caught simultaneously in relatively unselective fishing operations. As such, the total allowable catch (TAC) of one species may be exhausted before the TAC of another, leading to catches of valuable fish that cannot be landed legally. This important issue is, however, usually not quantified and not accounted for in traditional management advice. A simple approach using traditional catch and effort information was developed, estimating catch potentials for distinct fleets (groups of vessels) and métiers (type of activity), and hence quantifying the risks of over- and underquota utilization for the various stocks. This method, named Fcube (Fleet and Fisheries Forecast), was applied successfully to international demersal fisheries in the North Sea and shaped into the advice framework. The substantial overquota catches of North Sea cod likely under the current fisheries regimes are quantified, and it is estimated that the single-species management targets for North Sea cod cannot be achieved unless substantial reductions in TACs of all other stocks and corresponding effort reductions are applied.

scholarly journals Weighting of acoustic- and trawl-survey indices for the assessment of North Sea herring

2003 ◽  
Vol 60 (3) ◽  
pp. 463-471 ◽  
Author(s):  
E.J Simmonds
Keyword(s):  
North Sea ◽  
Assessment Model ◽  
The Other ◽  
Trawl Survey ◽  
Acoustic Survey ◽  
Weighting Method ◽  
The North ◽  
The North Sea ◽  
Using Data ◽  
Almost All

Abstract Acoustic surveys are used in 20 stock assessments within the ICES community, and almost all as relative indices of abundance, but little has been done to explore their performance in detail. The North Sea herring acoustic survey started in 1979 and by 1984 had become an internationally-coordinated survey conducted annually in July. Along with trawl- and larvae-survey indices, it has been used to tune a catch-at-age assessment model of North Sea herring. In this article, the precision of the survey is estimated, using data at ICES statistical-rectangle level from 1989 to 2001, and bootstrap-resampling methods modified by geostatistical estimates of the spatial autocorrelation. Similar techniques are applied to the larvae, Methot and trawl surveys that provide the other data on the distribution and abundance of North Sea herring. The comparison of survey performance is also examined using the bootstrap estimates of abundance to give 1000 simulated assessments of North Sea herring using the integrated catch-at-age (ICA) method. The results of these analyses are compared and the annual acoustic survey is shown to provide the most precise estimate of relative abundance for adult North Sea herring each year. The weighting of the various indices within the assessment is investigated. A weighting method is presented that provides a more precise method for estimating the stock. The more precise assessments are compared for retrospective pattern. An assessment is proposed which provides the most precise stock estimates with the best retrospective pattern. This assessment has been reviewed and accepted by the ICES Advisory Committee on Fisheries Management. The importance of the acoustic survey and its contribution to the assessment in relation to the other indices is discussed.

Structure of Pelagic Food Chain and Relationship Between Plankton and Fish Production

1977 ◽  
Vol 34 (12) ◽  
pp. 2344-2353 ◽  
Author(s):  
R. W. Sheldon ◽  
W. H. Sutcliffe Jr. ◽  
M. A. Paranjape
Keyword(s):  
North Sea ◽  
Gulf Of Maine ◽  
Standing Stock ◽  
Phytoplankton Production ◽  
Structural Elements ◽  
Pelagic Ecosystem ◽  
Predator Prey ◽  
The North ◽  
Plankton Production ◽  
The North Sea

Further observations on the standing stocks of pelagic organisms confirm the occurrence of approximately equal biomass over logarithmically equal size ranges. A simple theoretical framework is developed that shows that the structural elements of the pelagic ecosystem can be described in terms of the sizes of predator and prey and of the efficiencies of their interactions. In practice this means that if the standing stock at any size range is known, the standing stock at any other size can be estimated, and if the growth rate at this size is known, the production can be estimated. The theory is tested on three fisheries. For the Gulf of Maine and the North Sea, phytoplankton production is estimated from fishery production. For the area off Peru the fishery production is estimated from the plankton production. Key words: pelagic ecosystem, predator–prey relationships, plankton production, marine fisheries, Peru, North Sea, Gulf of Maine

scholarly journals Emergence of a new predator in the North Sea: evaluation of potential trophic impacts focused on hake, saithe, and Norway pout

2016 ◽  
Vol 73 (5) ◽  
pp. 1370-1381 ◽  
Author(s):  
Xochitl Cormon ◽  
Alexander Kempf ◽  
Youen Vermard ◽  
Morten Vinther ◽  
Paul Marchal
Keyword(s):  
North Sea ◽  
Negative Impact ◽  
Stock Assessment ◽  
Single Species ◽  
Bottom Up ◽  
The North ◽  
Spatial Shift ◽  
Spawning Stock ◽  
The North Sea ◽  
Indirect Impacts

Abstract During the last 15 years, northern European hake (Merluccius merluccius) has increased in abundance, and its spatial distribution has expanded in the North Sea region in correlation with temperature. In a context of global warming, this spatial shift could impact local trophic interactions: direct impacts may affect forage fish through modified predator–prey interactions, and indirect impacts may materialize through competition with other resident predators. For instance, North Sea saithe (Pollachius virens) spatial overlap with hake has increased while saithe spawning-stock biomass has decreased recently notwithstanding a sustainable exploitation. In this context, we investigated the range of potential impacts resulting from most recent hake emergence in the North Sea, with a particular focus on saithe. We carried out a multispecies assessment of North Sea saithe, using the Stochastic MultiSpecies (SMS) model. In addition to top-down processes already implemented in SMS, we built in the model bottom-up processes, relating Norway pout (Trisopterus esmarkii) abundance and saithe weight-at-age. We simulated the effects, on all North Sea species being considered but focusing on Norway pout and saithe, of combining different hake abundance trends scenarios with the inclusion of bottom-up processes in SMS. North Sea saithe FMSY was then evaluated in a multispecies context and contrasted with single-species value. The different scenarios tested revealed a negative impact of hake emergence on saithe biomass, resulting from an increase of predation pressure on Norway pout. These results confirm the competition assumption between saithe and hake in the North Sea and might partially explain the most recent decrease of saithe biomass. This study also highlighted that taking into account bottom-up processes in the stock assessment had a limited effect on the estimation of saithe FMSY which was consistent with single-species value.

Influence of trends in fishing power on bioeconomics in the North Sea flatfish fishery regulated by catches or by effort quotas

2002 ◽  
Vol 59 (5) ◽  
pp. 829-843 ◽  
Author(s):  
Clara Ulrich ◽  
Sean Pascoe ◽  
Per J Sparre ◽  
Jan-Willem De Wilde ◽  
Paul Marchal
Keyword(s):  
North Sea ◽  
Fishery Management ◽  
Single Species ◽  
Simulation Modelling ◽  
Economic Benefits ◽  
Total Allowable Catch ◽  
The North ◽  
Control Rules ◽  
Solea Solea ◽  
The North Sea

Total allowable effort quotas (TAEs) are often considered as promising alternatives to single-species total allowable catch quotas (TACs) in fisheries management. However, implementing TAEs would primarily require converting nominal effort into fishing mortality rate, i.e., developing a relevant model of the dynamics of catchability. Assuming that trends in the catchability may occur through fishing-power creeping linked to increased capital invested and technology, we compare, by stochastic and dynamic simulation modelling, the relative biological and economic benefits and drawbacks of TAEs and TACs in the North Sea sole (Solea solea L.) and plaice (Pleuronectes platessa L.) fishery. Management targets are based on the Precautionary Approach and Harvest Control Rules developed by the International Council for the Exploration of the Sea (ICES). Fishermen are assumed to set their effort at the most (TAE) or least (TAC) conservative level. Overall, the outcomes are more sensitive to the catchability model when implementing TAEs, especially in the medium and long term, but the variability in catchability has a much greater impact on stock levels than on the fisheries profit.

scholarly journals Chela-height vs. body-weight relationships for North Sea hermit crabs (Paguridae)

2005 ◽  
Vol 62 (4) ◽  
pp. 723-726 ◽  
Author(s):  
Henning Reiss ◽  
Hermann Neumann ◽  
Ingrid Kröncke
Keyword(s):  
Body Weight ◽  
North Sea ◽  
Hermit Crab ◽  
Regression Function ◽  
Single Species ◽  
The Body ◽  
Hermit Crabs ◽  
Crab Species ◽  
Weight Relationship ◽  
The North

Abstract Biomass determination of hermit crabs is difficult without destroying the gastropod shells of the specimens. To minimize the number of animals destroyed in the process of determining this parameter over time, the chela-height vs. body-weight relationship of each of the three hermit-crab species was recorded in different areas of the North Sea. Linear regression was carried out for the species Pagurus bernhardus, P. pubescens, and P. prideauxi, in order to allow calculations of individual biomass on the basis of the chela height of specimens. No spatial differences in the chela-height vs. body-weight relationship were found for single species, whereas the relationship between the three species differed significantly. Thus, for each species a regression function is given, valid for the whole North Sea, that allows estimations of the body weight of the three hermit-crab species from measuring the chela height alone.

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