Recreational Fishing for Nephrops in Hordaland, Norway - Catches and Potential Mercury Intake
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Recreational fishing for Nephrops in Hordaland, Norway - catches and potential mercury intake Christine Djønne Thesis for the Partial Fulfillment of the Degree Master of Science in Marine biology Department of Biological sciences University of Bergen June 2018 ii Acknowledgments First and foremost, I would like to thank my supervisors Keno Ferter, Jeppe Kolding and Martin Wiech for essential feedback throughout this entire year. A special thanks to Keno for always being available to answer questions through Facebook, even during fieldwork. Next, I would like to thank Jon Helge Vølstad, for letting me take part in the Fisheries Dynamics research group and conduct this study. My gratitude also extends to Knut Helge Jensen and Edvin Fuglebakk for their help with the statistical parts of my thesis, and to Berit Solli for her help with the DMA-analyses. Thanks to Marian Kjellevold for help with the questionnaire, and to Martin Ohldieck for helping me with ArcGIS collector and making the polygon maps. Thanks to Hanne Trømborg for helping me stay focused and positive this entire year. Thanks to Henry Seal for his friendship and writing advice. Also, thanks to Ina Nilsen and Hanne Trømborg for helping me with some of the sample preparation. Finally, I would like to thank all the participants who took the time to complete the questionnaires, and a special thanks to those providing samples for Hg analyses. Without their co-operation, it would not have been possible to conduct this study. iii iv Table of Contents Abbreviations ................................................................................................................................. 1 Abstract .......................................................................................................................................... 2 Summary in Norwegian ............................................................................................................... 3 1. Introduction ............................................................................................................................... 4 1.1 Marine recreational fishing in Norway...................................................................................4 1.2 Environmental contaminants in Norway ................................................................................5 1.3 Mercury (Hg) as a problematic environmental pollutant ......................................................6 1.4 Potential exposure of recreational fishers to mercury ...........................................................7 1.5 Contaminants and recreational fishing around Bergen .......................................................10 1.6 Nephrops around Bergen, delicious or dangerous? .............................................................12 1.7 Objectives of this thesis .........................................................................................................14 2. Materials and Methods .......................................................................................................... 16 2.1 Mapping and identification of standing gear........................................................................16 2.1.1 General information about the study .................................................................................16 2.1.2 Survey ..............................................................................................................................16 2.1.3 Telephone survey to retrieve information about the owners of the buoys ...........................18 2.1.4 Assessment of contamination in the study area ..................................................................20 2.2 Follow-up interviews of recreational Nephrops fishers........................................................22 2.3 Mercury analysis ...................................................................................................................23 2.3.1 Direct mercury analyzer (DMA-80) ..................................................................................23 2.3.2 Sample preparation ...........................................................................................................24 2.3.3 Mercury analysis using DMA-80 ......................................................................................25 2.4 Statistical methods and calculations .....................................................................................26 2.4.1 Catch calculations.............................................................................................................26 2.4.2 Factors influencing mercury concentrations ......................................................................26 2.4.3 Analysis of correlation between age, education and perception of pollution.......................27 2.4.4 Risk assessment ................................................................................................................28 3. Results ....................................................................................................................................... 30 3.1. Results of the survey mapping standing gears.....................................................................30 3.1.1 Registered buoys in different fjords divided into categories ...............................................30 3.1.2 Density of buoys in the selected sample ............................................................................33 3.1.3 General information about the recreational Nephrops fishers .............................................34 3.1.3.1 The recreational fishers’ perception of contamination in Nephrops ............................................ 34 v 3.1.3.2 Fishing motivations ...................................................................................................................... 35 3.1.3.2 CPUE in the different fjords ........................................................................................................ 36 3.1.3.3 Release motivations ..................................................................................................................... 37 3.2 Nephrops norvegicus; size, sex and mercury concentrations ................................................37 3.2.1 Size and sex determination for the different locations........................................................37 3.2.2 Mercury concentration in Nephrops ..................................................................................38 3.3 Consumption pattern and risk assessment ...........................................................................42 3.3.1 Consumption pattern.........................................................................................................42 3.3.2 Risk assessment ................................................................................................................43 4. Discussion ................................................................................................................................. 46 4.1 Recreational fishing for Nephrops is popular ......................................................................46 4.1.1 Catch data and CPUE estimations .....................................................................................46 4.1.2 Release motivations: voluntary or regulatory ....................................................................47 4.1.3 Recreational fisher’s perception of pollution in Nephrops in Hordaland ............................49 4.2 Mercury concentrations in Nephrops tail muscle.................................................................49 4.3 Risk assessment of methylmercury intake from Nephrops including other seafood...........51 4.3.1 Consumption pattern and risk assessment..........................................................................52 4.3.2 Consumption pattern and risk assessment regarding the families of the recreational fishers .................................................................................................................................................54 4.4 Survey choices and data bias issues ......................................................................................56 4.4.1 Survey mapping standing gears .........................................................................................56 4.4.1.1 Recreational Nephrops fishers: sample representativeness .......................................................... 56 4.4.1.2 Catch and CPUE related limitations............................................................................................. 57 4.4.2 Questionnaire ...................................................................................................................58 4.4.3 DMA-80 ...........................................................................................................................59 4.4.4 Risk assessment ................................................................................................................60 4.5 Conclusions and recommendations ......................................................................................61 5. Reference list............................................................................................................................ 62 6. Appendices ............................................................................................................................... 84 Appendix I: Maps of surveyed polygons ....................................................................................84