Thetis, Hornby and Denman Forage Fish Report

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BC MARINE CONSERVATION AND RESEARCH SOCIETY 
 
 
 
 
 
 
 
 
 
Prepared for the Islands Trust and Islands Trust Fund 
 
Prepared by: 
Ramona C. de Graaf, BSc, MSc 
Marine Biologist 
Forage Fish Specialist 
 
British Columbia Marine Conservation and Research Society 
March 30, 2014 
Thetis, Hornby and Denman Islands 
Beach Spawning 
Forage Fish Habitat Suitability Assessments 
 
Henry Bay, Denman Island 
Photo:  D. Woodward 

BC MARINE CONSERVATION AND RESEARCH SOCIETY 
 
Beach Spawning Forage Fish Habitat Suitability Assessments 
Thetis, Hornby, and Denman Island Sept 2013 – Feb 2014 
 
 
TABLE OF CONTENTS 
 
 
  
 Page 
Number 
 
 Acknowledgements 5 
   
1.0 Introduction to Forage Fish  
 1.1 Role of Forage Fish in marine ecosystems 6 
 1.2 Connections to other valued ecosystem components 6 
   
2.0 Beach Spawning Forage Fish Habitat 7 
   
3.0 Spawning Habitat Characteristics  
 3.1 Intertidal Elevation 7 
 3.2 Sediment Characteristics 7 
 3.3 Beach Biophysical Characteristics 8 
   
4.0 Spawning Seasons 8 
   
5.0 Threats to Beach Spawners’ habitat 9 
   
6.0 Introduction to the Forage Fish Habitat Suitability Assessment 
Project 
10 
 6.1  General Introduction 10 
 6.2  Area Surveyed 10 
   
7.0 Methods 
7.1  General Methodology 
11 
 7.2 Confirmed Spawning Habitats 12 
 7.3 GPS/GIS Methodologies 12 
      7.3.1 Spatial Data Specifications   12 
      7.3.2 Digitizing Spatial Data and Map Production 13 
   
8.0 Project Limitations 13 

BC MARINE CONSERVATION AND RESEARCH SOCIETY 
   
9.0 Results 14-35 
 9.1 Thetis Island   14-20 
      9.1.1 Grain-Size Analyses and Statistical Analyses  14 
      9.1.2 Length of Suitable Forage Fish Spawning Habitat  16 
      9.1.3 Suitable Forage Fish Spawning Habitat Types   16 
      9.1.4 Geographic distribution of beach units 17 
      9.1.5 Foreshore Modification 17 
      9.1.6 Foreshore and Backshore Structures 18 
      9.1.7 Overhanging Shade Vegetation 20 
   
 9.2 Hornby Island 21-27 
      9.2.1 Grain-Size Analyses and Statistical Analyses 21 
      9.2.2 Length of Suitable Forage Fish Spawning Habitat  21 
      9.2.3 Suitable Forage Fish Spawning Habitat Types 23 
      9.2.4 Geographic distribution of beach units 24 
      9.2.5 Foreshore Modification 25 
      9.2.6 Foreshore and Backshore Structures 25 
      9.2.7 Overhanging Shade Vegetation  27 
   
 9.3 Denman Island 28-35 
      9.3.1 Grain-Size Analyses and Statistical Analyses 28 
      9.3.2 Length of Suitable Forage Fish Spawning Habitat  30 
      9.3.3 Suitable Forage Fish Spawning Habitat Types  31 
      9.3.4 Geographic distribution of beach units 31 
      9.3.5 Foreshore Modification  32 
      9.3.6 Foreshore and Backshore Structures 33 
      9.3.7 Overhanging Shade Vegetation 35 
   
10.0 Summary & Recommendations 36 
   
11.0 References Cited 40 
   
12.0 Appendices 42 
 Appendix A:  Beach Type Classifications Thetis Island    43 
 Appendix B:  Beach Type Grain-Size Curves Thetis Island 45-49 

BC MARINE CONSERVATION AND

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