Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Monitoring cod catches of the Dutch demersal fleet in 2016
    Hal, R. van; Machiels, M.A.M. - \ 2017
    IJmuiden : Wageningen Marine Research (Wageningen Marine Research Report C056/17) - 29
    monitoring - cod - beam trawling - pulse trawling - demersal fisheries - marine fisheries - fish catches - north sea - gadus morhua - monitoring - kabeljauw - boomkorvisserij - pulsvisserij - demersale visserij - zeevisserij - visvangsten - noordzee - gadus morhua
    This report presents the results of the cod monitoring program 2016. The research was commissioned by the Dutch Ministry of Economic Affairs within the EZ-program Beleidsondersteunend Onderzoek. Cod catches of the vessels in the fleet segments BT2 (beam trawl and pulse trawl) and TR (otter trawls and seines) need to be monitored yearly, due to the Dutch implementation of the European cod recovery plan. The European cod recovery plan restricts the fishing effort of European fleets catching cod. Fishing effort, based on historical track records, is allocated to different gear groups. Fishing effort can be transferred between gear groups by use of conversion factors. In the Netherlands fishing effort is transferred yearly from the BT2 gear group to the TR group, based on a national conversion factor of 1:3 (BT:TR) kWdays instead of the European conversion factor of 1:16. This is because the cod catches in the Dutch TR fleet are not as high as the European conversion factor implies. In order to substantiate for the national conversion factor, the Dutch government is obliged to report cod catches per unit of effort (CpUE) of the vessels in these gear groups to the European Commission. An overview is provided of the fishing activity, the cod landings and the cod landings per unit of effort of the various gear categories in the BT2 and the TR fleet segments during the year 2016. First the cod Catch per Unit of Effort (CpUE) transition ratio between the BT2 on the one hand and the TR1C plus TR2 fleet segments on the other hand was calculated. And secondly the percentage of cod avoidance trips – trips during which 5% or less cod was caught – in the TR-fleet were calculated. The TR fleet has a higher cod CpUE on average than the BT fleet. When the cod targeted fisheries (TR1AB) are not taken into account, the CpUE effort transition ratio (TR1C+TR2): BT2 of 2016 lies between 4.2:1 and 5.7:1, depending on whether the ratio is calculated on the basis of minimum or maximum cod discards estimation by the Scientific, Technical and Economic Committee for Fisheries (STECF) respectively whereby in the minimum calculation the vessels participating in the CCTV program are excluded. Based on average discards estimations including all vessels, the ratio is 5.1:1. The percentage of cod avoidance trips, fishing trips with 5% cod or less in the total catches, in the TR1C and the TR2 fleets were 94% and 96% in 2016 respectively. These percentages are based on average STECF cod discards estimations. When minimum or maximum discards estimations are used, the calculated percentages of cod avoidance trips does not vary more than 2 or 3% from the percentage based on average estimations.
    Cod monitoring: Results 2015, quarter 1
    Reijden, K.J. van der; Machiels, M.A.M. ; Kraan, M.L. - \ 2015
    IJmuiden : IMARES (Report / IMARES Wageningen UR C084/15) - 15
    kabeljauw - monitoring - visvangsten - bijvangst - vistuig - visbestand - gadus morhua - cod - monitoring - fish catches - bycatch - fishing gear - fishery resources - gadus morhua
    Between 2011 and 2013, the monitoring program existed of an extended analysis of self-reported cod catch data (both landings and discards) in combination with the regular DCF discard monitoring program, an extra observer program and the CCTV-project in TR-fisheries (see Kraan et al. (2013 and 2014)). Over the years, the ministry of Economic Affairs and IMARES drew the conclusion that monitoring cod discards via the self-reporting scheme asked for disproportionately high effort of the TR-skippers while discards were hardly affecting CpUE rates (Ministry of Economic Affairs (2014)). Therefore, it was agreed upon a yearly analysis of the EU-logbook (hereafter logbook) data in combination with VMS-data, which is readily available. However, to remain updated, an overview of fishing activity, cod catches and cod Landings per Unit Effort (LpUE) of four gear types per quarter is requested by the ministry of Economic Affairs. This report presents the results of the first quarter in 2015.
    Residence time and behaviour of sole and cod in the Offshore Wind farm Egmond aan Zee (OWEZ)
    Winter, H.V. ; Aarts, G.M. ; Keeken, O.A. van - \ 2010
    IJmuiden [etc.] : IMARES Wageningen UR (Report / IMARES Wageningen UR OWEZ_R_265_T1_20100916) - 50
    tong (vis) - gadus morhua - kabeljauw - diergedrag - windmolenpark - milieueffect - dover soles - gadus morhua - cod - animal behaviour - wind farms - environmental impact
    ‘Noordzeewind’ (a Nuon and Shell Wind Energy consortium) exploits a wind farm with 36 wind turbines off the coast of Egmond aan Zee: the Offshore Wind farm Egmond aan Zee (OWEZ). This project serves to evaluate the economical, technical, ecological and social effects of offshore wind farms in general. To gather knowledge which will result from this project, a Monitoring and Evaluation Program (NSW6MEP) has been developed. Knowledge on environmental impact gained by this project will be made available to all parties involved in the realization of large6scale offshore wind farms. The construction and operation of offshore wind farms may result in possible negative impacts on fish populations, e.g. disturbance by noise or electromagnetic fields around cables, and consequent loss and degradation of habitats. On the other hand, due to the creation of new structures, i.e. additional habitats, that might act as artificial reefs or fish aggregation devices in combination with banning fisheries and shipping within wind farms, also positive impacts on fish populations are possible (Inger et al. 2009). In the latter case, wind farms might act as marine6protected areas or refuges for some fish species. The overall effect of the potential negative and positive impacts of the construction and operation of wind farms for fish is highly dependent on individual behavioural responses of fish to wind farms. This study focuses on exploring the potential benefits of the wind farm OWEZ, i.e. whether the wind farm can act as a refuge against fisheries for some fish species, by studying individual behaviour of fish during the operation phase of the wind farm. A key factor in this is individual residence time of fish within the wind farm. The longer individual fish spend in the wind farm, the stronger potential benefit of wind farms can be expected.
    Is the metapopulation concept applicable to the North Sea?
    Held, M.E. den - \ 2009
    Wageningen : Alterra (Alterra-rapport 1928) - 60
    mariene ecologie - marien milieu - mariene gebieden - kustgebieden - habitatselectie - populatiedynamica - zeedieren - noordzee - zeehonden - krabben (schaaldieren) - kabeljauw - gadus morhua - cancer pagurus - halichoerus grypus - verspreiding - metapopulaties - marine ecology - marine environment - marine areas - coastal areas - habitat selection - population dynamics - marine animals - north sea - seals - crabs - cod - gadus morhua - cancer pagurus - halichoerus grypus - dispersal - metapopulations
    The metapopulation concept could provide an additional way of designating areas for protective measures in the North Sea, by delineating habitat preferences and population dynamics. The current study looks into the applicability of the metapopulation concept to the North Sea underwater environment. It also seeks out species in the North Sea that could possibly be suitable metapopulations for study. The North Sea clearly is a heterogeneous environment, but habitat characteristics, like substratum type, tend to be wide ranged and without obvious physical barriers. Processes and structures in the seascape are mainly known on a rough scale, and even at that level, the available knowledge is only an interpretation from data. The same lack of knowledge is a bottleneck in defining connectivity among subpopulations, as dispersal capabilities are unknown for the majority of marine species. The species that seems most suitable for study in a metapopulation model in this test is the grey seal. Additionally, edible crab and cod emerged as species for potential use in a metapopulation model. Neither inhabit a discrete habitat patch, but both are known to have a strategy to ensure that their offspring recruits into their own population. For species that at first seemed to suitable because they have a discrete underwater habitat patch, insufficient knowledge was available to apply the theory further.
    Gadoids per hour caught by demersal trawl in the North Sea
    Beare, D.J. ; Helmond, A.T.M. van - \ 2009
    IJmuiden : IMARES (Rapport / Wageningen IMARES no. C057/09) - 19
    demersale visserij - boomkorvisserij - vis vangen - bemonsteren - gadus morhua - merlangius merlangus - discards - bijvangst - demersal fisheries - beam trawling - fishing - sampling - gadus morhua - merlangius merlangus - discards - bycatch
    In this project we summarise the numbers of gadoids landed by the Dutch beam trawl and otter trawl fleet in 2007 and 2008. We then make the best estimates possible of discarded numbers using data from the Discard Sampling Programme. These data will be used in negotiations between Norway and the EU to decide sample sizes for the possible implementation of 'Real Time Closures' in the North Sea and Skagerak.
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