Climate related shifts in the NCP ecosystem, and consequences for future spatial planning
Meer, J. van der; Lindeboom, H.J. ; Woerd, H.J. van der; Eleveld, M.A. ; Gilbert, A.J. ; Peters, S.W.M. ; Peperzak, L. ; Duineveld, G.C.A. ; Bergman, M.J.N. ; Lavaleye, M.S.S. ; Daan, R. ; Saraiva, A.S. ; Hal, R. van; Tulp, I. ; Craeymeersch, J.A.M. ; Daan, N. ; Labberton, R. ; Stuke, F. ; Teal, L.R. ; Rijnsdorp, A.D. ; Witbaard, R. ; Ruardij, P. ; Meesters, H.W.G. ; Baar, H.J.W. ; Meijer, H.A.J. ; Thomas, H. ; Johannesen, T. ; Zemmelink, H.J. ; Omari, A. ; Straten, H.J. ; Klunder, M. ; Salt, L. ; Laan-Luijkx, I.T. van der - \ 2011
Amsterdam : Programme Office Climate changes Spatial Planning - ISBN 9789088150180 - 36
klimaatverandering - mariene gebieden - landgebruiksplanning - aquatische ecosystemen - broeikasgassen - noordzee - climatic change - marine areas - land use planning - aquatic ecosystems - greenhouse gases - north sea
Een uitgebreide meetinspanning op de Noordzee, in combinatie met wiskundige en statistische modellering, laat zien dat de klimaatveranderingen in de vorm van een verandering in de overheersende windrichting, een toename van de windsnelheid, een toename van de zeewatertemperatuur, als wel als een toenemende CO2 concentratie van de atmosfeer, niet alleen leidt tot een verandering van de samenstelling van het zeewater in de vorm van bijvoorbeeld opgelost anorganisch koolstof en zuurgraad, maar ook tot een, zei het beperkte, verlaging van de productiviteit van op en in de zeebodem levende filterende organismen, die op hun beurt het voedsel zijn van bodembewonende vissen.
|Chondrichthyes - Kraakbeenvissen
Heessen, H.J.L. ; Daan, N. - \ 2010
In: De Nederlandse Biodiversiteit / Noordijk, J., van Loon, A.J., Kleukers, R.M.J.C., van Nieukerken, E.J., Leiden : Nederlands Centrum voor Biodivesiteit Naturalis & European Invetabrate Survey (Nederlandse Fauna 10) - ISBN 9789050113519 - 286 p.
|Cephalochordata - Lancetvisje
Daan, N. ; Heessen, H.J.L. - \ 2010
In: De Nederlandse Biodiversiteit / Noordijk, J., van Loon, A.J., Kleukers, R.M.J.C., van Nieukerken, E.J., Leiden : Nederlands Centrum voor Biodiversiteit Naturalis & European Invertabrate Survey (Nederlandse Fauna 10) - ISBN 9789050113519 - 284 p.
|Actinopterygii - Straalvinnigen
Spikman, F. ; Heessen, H.J.L. ; Daan, N. - \ 2010
In: De Nederlandse Biodiversiteit / Noordijk, J., van Loon, A.J., Kleukers, R.M.J.C., van Nieukerken, E.J., Leiden : Nederlands Centrum voor Biodiversiteit Naturalis & European Invertabrate Survey (Nederlandse Fauna 10) - ISBN 9789050113519 - 288 p.
Size, growth, temperature and the natural mortality of marine fish
Gislason, H. ; Daan, N. ; Rice, J.C. ; Pope, J.G. - \ 2010
Fish and Fisheries 11 (2010)2. - ISSN 1467-2960 - p. 149 - 158.
environmental-temperature - spatial patchiness - teleost fishes - metabolic-rate - rates - parameters - ecosystem - evolution - community - juvenile
The natural mortality of exploited fish populations is often assumed to be a species-specific constant independent of body size. This assumption has important implications for size-based fish population models and for predicting the outcome of size-dependent fisheries management measures such as mesh-size regulations. To test the assumption, we critically review the empirical estimates of the natural mortality, M (year-1), of marine and brackish water fish stocks and model them as a function of von Bertalanffy growth parameters, L8 (cm) and K (year-1), temperature (Kelvin) and length, L (cm). Using the Arrhenius equation to describe the relationship between M and temperature, we find M to be significantly related to length, L8 and K, but not to temperature (R2 = 0.62, P <0.0001, n = 168). Temperature and K are significantly correlated and when K is removed from the model the temperature term becomes significant, but the resulting model explains less of the total variance (R2 = 0.42, P <0.0001, n = 168). The relationships between M, L, L8, K and temperature are shown to be in general accordance with previous theoretical and empirical investigations. We conclude that natural mortality is significantly related to length and growth characteristics and recommend to use the empirical formula: ln(M) = 0.55 - 1.61ln(L) + 1.44ln(L8) + ln(K), for estimating the natural mortality of marine and brackish water fish.
Honey, I cooled the cods: Modelling the effect of temperature on the structure of Boreal/Arctic fish ecosystems
Pope, J.G. ; Falk-Pedersen, J. ; Jennings, S. ; Rice, J.C. ; Gislason, H. ; Daan, N. - \ 2009
Deep-Sea Research. Part II, tropical studies in oceanography 56 (2009)21-22. - ISSN 0967-0645 - p. 2097 - 2107.
north-sea cod - gadus-morhua - species-diversity - transient dynamics - predator-prey - marine fish - food webs - coexistence - size - biodiversity
Historically colder regions of the North Atlantic had fisheries dominated by only a few fish species; principally cod and capelin. Possible population dynamic mechanisms that lead to such dominance are investigated by considering how a charmingly simple published multispecies model of the North Sea would react if the system operated at a lower temperature. The existing model equations were modified to describe temperature effects on growth, fecundity and recruitment and the model was rerun based on typical temperatures for the North Sea and a colder system. The results suggest that total fish biomass in the colder system increases but the community is more vulnerable to a given rate of fishing mortality. In the colder system, within species density dependence is reduced but relative predation rates are higher. Consequently, intermediate-sized species are vulnerable to relatively high levels of predation throughout their life history and tend to be excluded, leading to a system dominated by small and large species. The model helps to explain how temperature may govern coexistence and competitive exclusion in fish communities and accounts for the observed dominance of small and large species in Boreal/Arctic ecosystems.
Biased stock assessment when using multiple, hardly overlapping, tuning series if fishing trends vary spatially
Kraak, S.B.M. ; Daan, N. ; Pastoors, M.A. - \ 2009
ICES Journal of Marine Science 66 (2009)10. - ISSN 1054-3139 - p. 2272 - 2277.
north-sea plaice - age data - catch
Fishing-effort distributions are subject to change, for autonomous reasons and in response to management regulations. Ignoring such changes in a stock-assessment procedure may lead to a biased perception. We simulated a stock distributed over two regions with inter-regional migration and different trends in exploitation and tested the performance of extended survivors analysis (XSA) and a statistical catch-at-age model in terms of bias, when spatially restricted tuning series were applied. If we used a single tuning index that covered only the more heavily fished region, estimates of fishing mortality and spawning-stock biomass were seriously biased. If two tuning series each exclusively covering one region were used (without overlap but together covering the whole area), estimates were also biased. Surprisingly, a moderate degree of overlap of spatial coverage of the two tuning indices was sufficient to reduce bias of the XSA assessment substantially. However, performance was best when one tuning series covered the entire stock area
Marine Protected Areas and commercial fisheries: the existing fishery in potential protected areas, and a modelling study of the impact of protected areas on North Sea Plaice
Dekker, W. ; Deerenberg, C.M. ; Daan, N. ; Storbeck, F. ; Brinkman, A.G. - \ 2009
IJmuiden : IMARES (Report / Wageningen IMARES C066/09) - 50
natuurbeleid - eu regelingen - zeereservaten - habitatrichtlijn - visserij-ecologie - visserij - scenario-analyse - noordzee - nature conservation policy - eu regulations - marine protected areas - habitats directive - fisheries ecology - fisheries - scenario analysis - north sea
Dit rapport presenteert resultaten van onderzoek, dat in 2005/2006 is uitgevoerd. In het kader van de Europese Vogel en Habitat Richtlijnen dienen lidstaten te beschermen gebieden op zee aan te wijzen, wat mogelijk zou leiden tot beperkingen van visserijactiviteiten in deze gebieden. De vraag was, welke invloed dit zou hebben op de vis en visserij. In dit onderzoek is enerzijds een statische beschrijving opgesteld van de visserijinspanning en de vangsten in de voorgestelde gebieden, en is anderzijds een eerste analyse (simulatie-model) opgezet van het lange-termijn effect op migrerende vis (schol). Dit onderzoek werd eind 2006 afgerond met een concept-rapport.
Marine Environmental Indicators: Utility in Meeting Regulatory Needs
Daan, N. ; Rees, H.L. ; Jagtman, E. ; Hillewaert, H. ; Kirby, S. - \ 2008
In: Proceeedings of an ICES symposium / Daan, N., Copenhagen : ICES - p. 1381 - 1540.
The utility of environmental indicators in meeting regulatory needs was addressed at an international symposium held in November 2007. This paper summarizes the attributes and range of uses of indicators and highlights key points from theme sessions and a workshop on unifying concepts. The symposium attracted regulators and scientists, who supported the need to promote dialogue during the construction of indicator-based management frameworks and at key stages towards operational use. Scientists expressed willingness to engage with the wider societal context for indicator applications, which is essential to the development of ecosystem-based management. For the latter to be effective, more effort is needed to combine indicators with thresholds to guide management actions and, in the process, to assess the full range of consequences of non-compliance. There are clear benefits to periodic interdisciplinary reviews of progress in this area, and a follow-up event with a regulatory emphasis is suggested.
Coexistence in North Sea fish communities: implications for growth and natural mortality
Gislason, H. ; Pope, J.G. ; Rice, J.C. ; Daan, N. - \ 2008
ICES Journal of Marine Science 65 (2008)4. - ISSN 1054-3139 - p. 514 - 530.
cod gadus-morhua - life-history - marine fishes - trade-off - environmental-temperature - teleost fishes - west-coast - population - predation - biology
For a fish community to persist over time, all species must be able on average to replace themselves on a one-for-one basis over their lifetime. We use this principle and a size-based equilibrium model where asymptotic length is used as a functional trait to investigate how natural mortality should scale with size within and across pelagic and demersal species of North Sea teleosts. The model predicts natural mortality to scale with body length raised to a power of ¿1.66 at current levels of exploitation. Additionally, natural mortality of demersal species should be proportional to asymptotic length raised to a power of 0.80, so generating a higher natural mortality at a given length for large species than for small ones. The model also suggests that the exponent in the scaling of the von Bertalanffy growth parameter K with asymptotic length should be more negative for pelagic than for demersal species. We test our results by analysing independent estimates of predation mortality, the scaling of maximum recruitment per unit of spawning-stock biomass with asymptotic length, and the general relationship between K and asymptotic length for demersal and pelagic families of fish. All tests are consistent with our modelling results.
The effect of management choices on the sustainability and economic performance of a mixed fishery: a simulation study
Kraak, S.B.M. ; Buisman, F.C. ; Dickey-Collas, M. ; Poos, J.J. ; Pastoors, M.A. ; Smit, J.G.P. ; Oostenbrugge, J.A.E. van; Daan, N. - \ 2008
ICES Journal of Marine Science 65 (2008)4. - ISSN 1054-3139 - p. 697 - 712.
north-sea plaice - stock assessment - fishing effort - advice - experiences - uncertainty - strategies - trends - impact
Alternative management scenarios were evaluated in a simulation framework that mimicked the recent exploitation of sole and plaice in the North Sea. A large proportion of plaice is taken as bycatch of the beam trawl fleet targeting sole, yet current management of the two stocks assumes no interaction in their exploitation. The evaluation criteria included biological and economic sustainability, and stability in the management measures. The fishery was assumed to respond to management restrictions by dropping the least profitable trips. We investigated two contrasting management strategies, single-species total allowable catches, and effort regulation. Under the assumptions made, the latter strategy performed better. The results suggest that, given assessment error and bias, a strategy that accounts for the mixed nature of a fishery and that occasionally results in perceived underexploitation may work best. Stability in fishing mortality reinforces itself, through lower assessment bias, and management corrections become less frequent. The common assumption in many stock assessments in EC waters that fishing mortality in the most recent year should resemble the value obtained in previous years ("shrinkage") had a negative effect on the stability of control measures.
Building on the concept of marine biological valuation with respect to translating it to a practical protocol: viewpoints derived from ajoint ENCORA-MARBEF initiative
Derous, S. ; Austen, M.C. ; Claus, S. ; Daan, N. ; Dauvin, J.C. ; Deneudt, K. ; Heessen, H.J.L. ; Hofstede, R. ter - \ 2007
Oceanologia = Oceanology 49 (2007)4. - ISSN 0078-3234 - p. 579 - 586.
Marine biological valuation provides a comprehensive concept for assessing the intrinsic value of subzones within a study area. This paper gives an update on the concept of marine biological valuation as described by Derous et al. (2007). This concept was based on a literature review of existing ecological valuation criteria and the consensus reached by a discussion group of experts during an international workshop in December 2004. The concept was discussed during an ENCORA-MARBEF workshop in December 2006, which resulted in the fine-tuning of the concept of marine biological valuation, especially with respect to its applicability to marine areas.
Sustainable use of flatfish resources: addressing the credibility crisis in miced fisheries management
Rijnsdorp, A.D. ; Daan, N. ; Dekker, W. ; Poos, J.J. ; Densen, W.L.T. van - \ 2007
Journal of Sea Research 57 (2007)2-3. - ISSN 1385-1101 - p. 114 - 125.
north-sea plaice - beam trawl fleet - fishing vessels - competitive interactions - effort allocation - science - area - cod - dynamics - policy
Many flatfish species are caught in mixed demersal trawl fisheries and managed by Total Allowable Catch (TAC). Despite decades of fisheries management, several major stocks are severely depleted. Using the Common Fisheries Policy (CFP) as an example, the failure of mixed-fisheries management is analysed by focussing on: the management system; the role of science; the role of managers and politicians; the response of fisheries to management. Failure of the CFP management could be ascribed to: incorrect management advice owing to bias in stock assessments; the tendency of politicians to set the TAC well above the recommended level; and non-compliance of the fisheries with the management regulations. We conclude that TAC management, although apparently successful in some single-species fisheries, inevitably leads to unsustainable exploitation of stocks caught in mixed demersal fisheries as it promotes discarding of over-quota catch and misreporting of catches, thereby corrupting the basis of the scientific advice and increasing the risk of stock collapse. This failure in mixed demersal fisheries has resulted in the loss of credibility of both scientists and managers, and has undermined the support of fishermen for management regulations. An approach is developed to convert the TAC system into a system that controls the total allowable effort (TAE). The approach takes account of the differences in catch efficiency between fleets as well as seasonal changes in the distribution of the target species and can also be applied in the recovery plans for rebuilding specific components of the demersal fish community, such as plaice, cod and hake.
What is a large fish? - taking a species perspective
Daan, N. - \ 2006
- 10 p.
Spatial and temporal trends in species richness and abundance for southerly and northerly components of the North Sea fish community separately, based on IBTS data 197702005
Daan, N. - \ 2006
vissen - soortendiversiteit - klimaatverandering - mariene gebieden - noordzee - fishes - species diversity - climatic change - marine areas - north sea
Based on the North Sea International Bottom Trawl Survey, the number of species recorded after 20 hauls is used as an index of biodiversity at a spatial scale of 10*10nm. The results show a clear pattern: species richness is lowest in the central North Sea and highest in Scottish waters, in the Kattegat and in the Channel area. When the community is split into its northerly and southerly components, the former reaches its highest diversity in waters typically deeper than 100m and the latter in waters less than 50m. The area of high richness of northerly species extends from Scottish waters along the Norwegian trench into the Kattegat. High richness of southerly species is not restricted to the southern North Sea but is observed also along the Scottish coast and in the Kattegat. These patterns are discussed in relation to hydrographical features that may control these differences. Temporal trends indicate that both components are characterized by a gradual increase in species richness over the past 25 years, a process that has affected the whole area while rates of change did hardly differ between the components or areas. A standardized index of abundance also indicates long-term gradual increases for both northerly and southerly species, although in this case the increase in southern species is larger. I argue that overexploitation is a more plausible explanation for the observed phenomena, although climate change may have had add-on effects.
Effort management for mixed fisheries in EU waters: a viable alternative for failing TAC management?
Daan, N. ; Rijnsdorp, A.D. - \ 2006
- 6 p.
Modelling an exploited marine fish community with 15 parameters - results from a simple size-based model
Pope, J.G. ; Rice, J.C. ; Daan, N. ; Jennings, S. ; Gislason, H. - \ 2006
ICES Journal of Marine Science 63 (2006)6. - ISSN 1054-3139 - p. 1029 - 1044.
north-sea - fisheries - spectra - indicators - diversity - assemblages - management - predation - biomass - ecology
To measure and predict the response of fish communities to exploitation, it is necessary to understand how the direct and indirect effects of fishing interact. Because fishing and predation are size-selective processes, the potential response can be explored with size-based models. We use a simulation approach to describe the relationship between size spectrum slope and overall fishing mortality and to try to understand how a linear spectrum might be maintained. The model uses 15 parameters to describe a 13 `species¿ fish community, where species are defined by their maximum body size and the general relationship between size and life history characteristics. The simulations allow us to assess the role of changes in the strength and type of density dependence in controlling the response to fishing and to investigate the tradeoffs between catches and the status of the different species. The outputs showed that the linear slope of the size spectrum was a function of community exploitation rate. Density dependent controls, specifically predation mortality and the extent of compensation in the stock-recruitment relationship, were key mechanisms in maintaining a linear spectrum. Compensation caused by the dependence of predation mortality on predator abundance can linearise the spectrum even when the compensation caused by the dependence of recruitment on spawning stock biomass is weak. However, as compensation in the stock-recruit relationship was increased, the effects of changes in fishing mortality dominated those of the dynamic changes in predation mortality. The approach allows us to explore the effects of different fishing mortality schedules on properties of the fish community, to assess how fishing affects species with different life histories in mixed fisheries and to assess the effects of selectively fishing different size classes. The simulations indicate that the size classes to be included when developing and interpreting sized-based metrics must be carefully considered in relation to the trophic structure and likely strength of predatory interactions in the community. Runs with differential fishing mortality by size suggest that the dynamics of predation cannot compensate fully for changing rates and patterns of exploitation, implying that the effects of selectively fishing different size classes should be assessed on a case by case basis.
|Quality check surveys: DATRAS North Sea IBTS
Hofstede, R. ter; Daan, N. - \ 2006
In: ICES Annual Science Conference 2006. - Copenhagen : ICES - p. 216 - 292.
Partial fishing mortality per fishing trip: a useful indicator of effective fishing effort in mixed demersal fisheries
Rijnsdorp, A.D. ; Daan, N. ; Dekker, W. - \ 2006
ICES Journal of Marine Science 63 (2006)3. - ISSN 1054-3139 - p. 556 - 566.
plaice pleuronectes-platessa - north-sea plaice - solea-solea l - fleet dynamics - trawl fishery - competitive interactions - flatfish - power - behavior - management
Effort management has been proposed as an alternative for quota management in mixed demersal fisheries. It requires a metric to estimate the fishing mortality imposed by a given quantity of nominal fishing effort. Here, we estimate the partial fishing mortality rate imposed by one unit of fishing effort (Fpue) during individual fishing trips and explore the usefulness of this indicator for managing North Sea beam trawlers >300 hp targeting sole (Solea solea) and plaice (Pleuronectes platessa). Fpue is positively related to vessel engine power, and increased annually by 2.8% (sole) and 1.6% (plaice). The positive trend was due to an increase in skipper skills and investment in auxiliary equipment, the replacement of old vessels by new ones and, to a lesser extent, to upgrade engines. The average Fpue imposed per day at sea by a 2000 hp beam trawler was estimated to be 1.0 × 10¿5 (sole) and 0.6 × 10¿5 (plaice), and it showed substantial seasonal and spatial variations. The Fpue of sole and plaice were negatively related in summer and showed no relationship in winter. The existence of predictive seasonal and spatial patterns in Fpue opens up the possibility of fine-tuning management by directed effort restrictions and uncoupling management of plaice and sole
|ICES - FishMap
Heessen, H.J.L. ; Hofstede, R. ter; Daan, N. - \ 2006
IJmuiden : RIVO (Internal report RIVO 06.002) - 40 p.