Spatial Criteria Used in IUCN Assessment Overestimate Area of Occupancy for Freshwater Taxa By Jun Cheng A thesis submitted in conformity with the requirements for the degree of Masters of Science Ecology and Evolutionary Biology University of Toronto © Copyright Jun Cheng 2013 Spatial Criteria Used in IUCN Assessment Overestimate Area of Occupancy for Freshwater Taxa Jun Cheng Masters of Science Ecology and Evolutionary Biology University of Toronto 2013 Abstract Area of Occupancy (AO) is a frequently used indicator to assess and inform designation of conservation status to wildlife species by the International Union for Conservation of Nature (IUCN). The applicability of the current grid-based AO measurement on freshwater organisms has been questioned due to the restricted dimensionality of freshwater habitats. I investigated the extent to which AO influenced conservation status for freshwater taxa at a national level in Canada. I then used distribution data of 20 imperiled freshwater fish species of southwestern Ontario to (1) demonstrate biases produced by grid-based AO and (2) develop a biologically relevant AO index. My results showed grid-based AOs were sensitive to spatial scale, grid cell positioning, and number of records, and were subject to inconsistent decision making. Use of the biologically relevant AO changed conservation status for four freshwater fish species and may have important implications on the subsequent conservation practices. ii Acknowledgments I would like to thank many people who have supported and helped me with the production of this Master’s thesis. First is to my supervisor, Dr. Donald Jackson, who was the person that inspired me to study aquatic ecology and conservation biology in the first place, despite my background in environmental toxicology. Don, your mentorship has always been thoughtful, motivating and well-placed, leading me through the transition and through the further research process. To my co-supervisor, Dr. Nicholas Mandrak, your depth of knowledge and enthusiasms towards fishes have constantly excited me and shaped my vision. I cannot express how grateful I am for your generous and inspiring inputs, as well as your encouraging and patient guidance. I am honored to be a graduate student of both of you. To my advisory committee members, Dr. Ken Minns and Dr. Keith Somers, I am blessed to have your insightful comments and questions that contributed tremendously to making this thesis complete. To the Jackson lab (Karen, Lifei, Brad, Jaewoo, Brie, Cindy, Sarah, and Georgina) and the extended members (Liset, Sarah, Danielle, Caren, Jonathon, Caroline, Henrique, Jordan and many more): thank you all for being great colleagues and friends that made grad school an enjoyable journey. I will always remember and deeply appreciate what I have learnt from you both in academically and personally. To my family: Mom, Dad, Grandpa, Juan and Rey. My most sincere appreciation goes to Mom and Dad. Thank you for the years of supporting my education and believing in me while I was away from home. You have given me the best experience growing up independently yet feeling supported. Dad and Grandpa, you are the initial inspirations for me to be interested in iii science and research. Juan and Rey, you are the most awesome aunt and uncle, and the most awesome friends. Thank you for giving me a feeling of home ever since I came to Canada. iv Table of Contents Acknowledgments....................................................................................................................iii List of Tables…………………………………………………………………………..…..…vi List of Figures………………………………………………………………………...…......viii List of Appendices……………………………………………………………………..…..….x Introduction................................................................................................................................1 Methods......................................................................................................................................8 Results......................................................................................................................................19 Discussion................................................................................................................................43 References................................................................................................................................62 Appendices...............................................................................................................................70 v List of Tables Table 1. Summary of the five quantitative criteria used by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) for assessing conservation status of wildlife species, which is adapted from the IUCN Red List Categories and Criteria………….........3 Table 2. Total number of occurrence record, number of geographically distinct localities, 2km- IAO, 1km-IAO, and 0.5km-IAO calculated using grid cells of the same position and orientation, ratio of 2km-IAO to 1km-IAO, and 2km-IAO to 0.5km-IAO in percentage for 20 at-risk freshwater fish species in Ontario……………………………………..….…....25 Table 3. Mean, standard deviation, maximum, minimum values of 2km-IAO calculated using 13 layers of grid cells at varying positions for 20 at-risk freshwater fish species in Ontario. Also shown are COSEWIC reported 2km-IAO, and ratio of COSEWIC-reported values to the calculated mean IAO values in percentage…..………………………………....……..28 Table 4. Habitat classification for the 20 at-risk freshwater fish species included in this study…………………………………………………………………………………….....33 Table 5. Home range estimates based on average body length reported in Ontario (Holm et al. 2010) and the equation of Woolnough et al. (2009), and the adjusted buffer scales used for BioAO calculation for the 20 at-risk freshwater fish species included in this study……...34 Table 6. Stream width (m) predicted by relationship with Strahler stream order. Values are anti-loge transformed and corrected with bias estimator (Sprugel 1983)…. ………..……36 Table 7. Proposed BioAO as sum of stream occupancy calculated in terms of occupied stream length x stream width, and lake/wetland occupancy calculated in terms of suitable habitat area within circular buffer, in comparison to COSEWIC reported biological AO for 20 at- risk freshwater fish species in Ontario. …………………………………………..….........37 Table 8. Summary of species status designated under COSEWIC and after application of BioAO, and the corresponding reasons for designation for 20 at-risk freshwater fish species in Ontario………………………………………………………..……………..….40 vi Table 9. Summary of advantages and drawbacks of each AO measurement approach for freshwater taxa………………………………………………………………………….....50 vii List of Figures Figure 1. Study area……………………………………………………………………..……...10 Figure 2. Example of Index of Area of Occupancy (IAO) measurements for Black Redhorse in the Grand River, Ontario, at three spatial scales: 0.5km, 1km and 2km……………...……11 Figure 3. Example of BioAO measurement for stream occupancy of Black Redhorse in the Grand River, Ontario. The highlighted stream stretch indicates the segments considered occupied habitat. Localities distant from others were considered single locations.……….15 Figure 4. Example of BioAO calculation for lakeshore occupancy for Grass Pickerel in Long Point Bay, Lake Erie……………………………………………………………………….17 Figure 5. Number of freshwater fish (a) and mollusc (b) species listed under COSEWIC in each threat category and the number of Endangered (EN) and Threatened (TH) freshwater fish (c) and mollusc (d) species designated by criterion………………………………………..21 Figure 6. Primary and secondary threats identified responsible for species decline in freshwater fish (a) and mollusc (b) species of Canada that are classified as extinct, extirpated, endangered, threatened and special concerned…………..…………………………………22 Figure 7. Grid-based IAO calculations for 20 freshwater fish species measured at three spatial scales: 2km X 2km (circles); 1km X 1km (triangles); 0.5km X 0.5km (squares), with species arranged on the x-axis in the order of decreasing 2km-IAO size. Dashed lines indicate threshold values for IUCN criteria……………...……………………………..…..24 Figure 8. Mean values of calculated 2km-IAO (triangles) based on 13 placements of grids, COSEWIC-reported 2km-IAO (squares), proposed BioAO (circles), COSEWIC-reported biological AO (diamonds), and HR-BioAO (crosses) for 20 at-risk freshwater fish species in Ontario, with species arranged on the x-axis in the order of decreasing mean 2km-IAO size. Dashed lines indicate threshold values for IUCN criteria….…………………………31 viii Figure 9. Linear regression (solid line) between Strahler stream order and loge-transformed stream width (m) based on 2431 DFO survey records in Ontario (open circles), P < 0.0001.Predicted stream width (see Table 4) at each Strahler order is estimated by the regression………….……………………………………………………………………..…35 Figure 10. Frequency distribution of total BioAO using adjusted buffer size…………………………………………………………………….……………………38 Figure 11. Linear regression (solid lines) between number of geographically unique occurrence sites and the resultant (a) mean 2km-IAO calculated using 13 gird layers at varying positions (all 20 at-risk freshwater fish species in Ontario, P < 0.0001); (b) Stream BioAO in stream length multiplied by stream width (17 of the 20 species, P =0.097); (c) suitable habitat area within circular buffer (17 of the 20 species, P < 0.001)…..…………………..42 Figure 12.