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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    Diversity, spatial distribution and relative abundance of reef sharks using stereo baited remote underwater video around the windward islands of the Caribbean Netherlands
    Graaf, M. de; Beek, I.J.M. van; Looijengoed, W. van; Kuijk, T. van; Stoffers, T. ; Nagelkerke, L.A.J. - \ 2014
    In: Book of abstracts of the 67th Annual Gulf and Caribbean Fisheries Institute Conference. - - p. 48 - 48.
    The most likely cause for the decline of many elasmobranchs is the combination of high fishing pressure and slow reproductive life-history characteristics. Akey ambition of the Dutch Caribbean Nature Policy Plan 2013-2017, is the effective implementation of shark protection. The first step towards effective protection is to conduct a base-line survey and to develop robust, quantifiable objectives and reference points for conservation (and fisheries) in order to be able to evaluate the performance of management actions. Stereo Baited Remote Underwater Video Survey (BRUVS) is a non-invasive method to study species richness, relative abundance and accurate length frequency of fish species such as sharks. In this study we used BRUVS to conduct a base-line survey of sharks on St Eustatius, Saba, and the Saba Bank. Shark assemblages were structured by habitat complexity, depth and to a lesser extend management zone. Overall, the shark populations appeared to be in reasonably healthy state. Relative abundance of the different shark species was higher than reported for similar BRUV studies within the Caribbean. A possible explanation for the current status of the shark populations in the Caribbean Netherlands is the lack of destructive industrial-scale fishery practices (directed shark fisheries, shark finning, long-lining, or gillnetting). The establishment of a formal shark sanctuary in the Caribbean Netherlands would prevent the future development of such destructive fishery practises without completely restricting the occasional landing of sharks as by-catch in the existing artisanal, small-scale fisher.
    Diversity, spatial distribution and relative abundance of reef sharks using stereo baited remote underwater video around the windward islands of the Caribbean Netherlands
    Graaf, M. de; Beek, I.J.M. van; Looijengoed, W. van; Kuijk, T. van; Stoffers, T. ; Nagelkerke, L.A.J. - \ 2014
    In: Proceedings of the European Elasmobranch Association 2014 Scientific Conference. - - p. 64 - 64.
    The most likely cause for the decline of many elasmobranchs is the combination of high fishing pressure and slow reproductive life-history characteristics. A key ambition of the Dutch Caribbean Nature Policy Plan 2013-2017, is the effective implementation of shark protection. The first step towards effective protection is to conduct a base-line survey and to develop robust, quantifiable objectives and reference points for conservation (and fisheries) in order to be able to evaluate the performance of management actions. Stereo Baited Remote Underwater Video Survey (BRUVS) is a noninvasive method to study species richness, relative abundance and accurate length frequency of fish species such as sharks. In this study we used BRUVS to conduct a base-line survey of sharks on St Eustatius, Saba and the Saba Bank. Shark assemblages were structured by habitat complexity, depth and to a lesser extend management zone. Overall, the shark populations appeared to be in reasonably healthy state. Relative abundance of the different shark species was higher than reported for similar BRUV studies within the Caribbean. A possible explanation for the current status of the shark populations in the Caribbean Netherlands is the lack of destructive industrialscale fishery practices (directed shark fisheries, shark finning, long-lining or gillnetting). The establishment of a formal shark sanctuary in the Caribbean Netherlands would prevent the future development of such destructive fishery practices without completely restricting the occasional landing of sharks as by-catch in the existing artisanal, small-scale fishery.
    Hoe giftig zijn ammonia en nitraat voor snoekbaars?
    Schram, E. ; Roques, J.A.C. ; Kuijk, T. van; Abbink, W. ; Heul, J.W. van der; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de; Flik, G. - \ 2014
    Aquacultuur 29 (2014)1. - ISSN 1382-2764 - p. 12 - 17.
    snoekbaars - recirculatie aquacultuur systemen - aquacultuur - nitraat - ammoniak - voeropname - pike perch - recirculating aquaculture systems - aquaculture - nitrate - ammonia - feed intake
    In intensieve recirculatiesystemen lopen vissen het risico blootgesteld te worden aan ammonia en nitraat. Hoe hoog mogen de nitraat- en ammoniaconcentratie zijn zonder dat dit negatieve effecten heeft op de vissen? IMARES onderzocht dit in samenwerking met de Radboud Universiteit Nijmegen en de Universiteit van Amsterdam voor juveniele snoekbaars. Conclusie: de ammonia (NH3) concentratie moet onder de 0.05 mg NH3-N/I gehouden worden. Van nitraat lijken juveniele snoekbaarzen zelfs bij 358 mg NO3-N/I nog weinig hinder te ondervinden.
    The impact of elevated water ammonia and nitrate concentrations on physiology, growth and feed intake of pikeperch (Sander lucioperca)
    Schram, E. ; Roques, J.A.C. ; Kuijk, T. van; Abbink, W. ; Heul, J.W. van der; Vries, P. de; Bierman, S.M. ; Vis, J.W. van de; Flik, G. - \ 2014
    Aquaculture 420-421 (2014). - ISSN 0044-8486 - p. 95 - 104.
    trout oncorhynchus-mykiss - acid-base regulation - early-life stages - rainbow-trout - salmo-gairdneri - recirculating aquaculture - scophthalmus-maximus - clarias-gariepinus - chronic toxicity - aquatic animals
    The ammonia (NH3) and nitrate (NO3-) threshold concentrations in rearing water of juvenile pikeperch (Sander lucioperca) were assessed. Pikeperch with an initial mean (SD) weight of 17.7 (4.2) g were exposed to 0.9 (control), 3.6, 5.2, 7.1, 11.2 and 18.9 µM NH3 in the water for 42 days. Plasma NH4+ concentrations stayed at control levels (~ 650 µM) up to 11.2 µM NH3 in the water. At the highest water NH3 concentration tested, plasma NH4+ had more than doubled to 1400 µM. Based on the specific growth rate, the EC10 value for NH3 was 5.7 µM. When pikeperch (initial mean (SD) weight of 27.0 (4.9) g) were exposed to 0.1 (control), 1.5, 2.3, 3.7, 6.1, 10.2, 15.8 and 25.6 mM NO3- for 42 days, mean (SD) plasma NO3- concentrations increased linearly from 88 (47) to 5993 (899) µM at the highest ambient NO3- level. Feed intake, specific growth rate and feed conversion ratio were not affected. Neither NH3 nor NO3- exposure significantly affected haematocrit, plasma concentrations of cortisol, glucose, lactate, osmolality, gill morphology or branchial Na+/K+-ATPase activity in pikeperch. For juvenile pikeperch we advise not to exceed a water NH3 concentration of 3.4 µM (0.05 mg NH3–N/L), the lower limit of the 95% confidence interval of the EC10 value for SGR, to ensure proper physiology and growth. For NO3- we advise not to exceed 25 mM (350 mg NO3-–N/L). This criterion is based on the highest NO3- concentration tested (25.6 mM). As no negative effects were detected at the highest concentration tested, the actual NO3- threshold probably exceeds 25.6 mM.
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