Disentangling Porpoise Bycatch
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Disentangling porpoise bycatch Interaction between areas of finless porpoise occurrence and spatial distribution of fishing gear Catarina Fonseca September 2013 A thesis submitted in partial fulfilment of the requirements for the degree of Master of Science and the Diploma of Imperial College London Declaration of own work I declare that this thesis: Disentangling porpoise bycatch: Interaction between areas of finless porpoise occurrence and spatial distribution of fishing gear is entirely my own work and that where material could be construed as the work of others, it is fully cited and referenced, and/or with appropriate acknowledgement given. Signature …………………………………………………….. Name of student: Catarina Fonseca Name of Supervisor: Samuel Turvey Marcus Rowcliffe i Contents list List of Figures .......................................................................................................... iv List of Tables ............................................................................................................ v List of Acronyms ...................................................................................................... vi Abstract ................................................................................................................. vii Acknowledgments ................................................................................................. viii 1. Introduction ......................................................................................................... 1 1.1 Problem statement ............................................................................................................. 1 1.2 Study aim ............................................................................................................................. 3 1.3 Research objectives ............................................................................................................. 3 2. Background .......................................................................................................... 5 2.1 Yangtze River: China’s Golden Channel .............................................................................. 5 2.2 Yangtze finless porpoise: ecology and population status ................................................... 8 2.3 Research methodology ..................................................................................................... 10 2.4 Conservation action implementation ............................................................................... 12 3. Methods ............................................................................................................. 15 3.1 Data ................................................................................................................................... 15 3.1.1 The Yangtze Freshwater Dolphin Expedition ............................................................. 15 3.1.2 Questionnaire survey 2008 ........................................................................................ 16 3.1.3 Questionnaire survey 2011 - 2012 ............................................................................. 16 3.2 Statistical analyses ............................................................................................................ 17 3.2.1 Pattern analysis along the river .................................................................................. 17 3.2.2 Pattern analysis across the river ................................................................................ 21 3.2.3 Target species ............................................................................................................. 22 4. Results ............................................................................................................... 23 4.1 Pattern analysis along the river ......................................................................................... 23 4.1.1 Mainstem ................................................................................................................... 23 4.2 Pattern analysis across the river ....................................................................................... 28 4.2.1 Mainstem ................................................................................................................... 28 4.2.2 Dongting Lake ............................................................................................................. 31 4.2.3 Poyang Lake ................................................................................................................ 32 ii 5. Discussion .......................................................................................................... 34 5.1 Model and predictor variables adequacy.......................................................................... 34 5.2 Relevance of fishing patterns ............................................................................................ 36 5.3 Conservation actions: recommendations ......................................................................... 37 6. References.......................................................................................................... 41 7. Appendices ...................................................................................................... 45 Appendix 1 – Yangtze fishers survey questionnaire 2008 ...................................................... 45 Appendix 2 – Yangtze fishers survey questionnaire 2012 ...................................................... 51 Appendix 3 – Interview locations from 2008 and 2011-2012 surveys .................................... 62 Cover image: Yangtze finless porpoise with her calf ©Xiaoqiang Wang iii List of Figures Figure 2.1 – The Yangtze River basin (Chen et al. 2012). Figure 2.2 - Map of the Yangtze river system showing high dam and dredging projects (underway and finished) (Reeves et al. 2000). Figure 2.3 – The male porpoise calf just after birth (Wang et al. 2005). Figure 3.1 - Map of the middle-lower Yangtze river basin featuring interview locations (stars), boundaries of the numbered river sections and the division into upper, middle and lower regions used by Zhao et al (2008). Figure 3.2 - Stratification of the river bank and mid channel area (Zhao et al. 2008). Figure 4.1 – Distribution of live and dead porpoises along the river. Figure 4.2 – Variation of total gear usage along the Yangtze main channel according to 2008 informants. Figure 4.3 – Variation of total gear usage along a 400km stretch of the Yangtze main channel according to 2012 informants. Figure 4.4 – Cause of death reported by 2008 informants. Figure 4.5– Coarse scale usage of the main gear types across the river according to 2008 informants. Figure 4.6 – Fine scale usage of the main gear types across the river according to 2012 informants. Figure 4.7 – Most caught species in the mainstem according to 2008 respondents. Figure 4.8 – Most caught species in the mainstem according to 2012 respondents. Figure 4.9 - Coarse scale usage of the main gear types across Dongting Lake according to 2008 informants. Figure 4.10 - Fine scale usage of the main gear types across Dongting Lake according to 2012 informants. Figure 4.11 - Coarse scale usage of the main gear types across Poyang Lake according to 2008 informants. iv Figure 4.12 - Fine scale usage of the main gear types across Poyang Lake according to 2012 informants. List of Tables Table 2.1 – Population estimates for the Yangtze finless porpoise population. Table 2.2 – Summary of cetacean reserves in the Yangtze main stem (Adapted from Zhao et al. 2013). Table 4.1 - Chi-squared test results on gear usage variation along the mainstem for both questionnaires. Table 4.2 – Values of AIC, AICΔ and AICW for the best generalised linear models of porpoise mortality rate index obtained from the 2008 questionnaire that include electrofishing as a mortality predictor. Table 4.3 - Values of AIC, AICΔ and AICW for the best GLMs of porpoise mortality rate index obtained from the 2012 questionnaire. Table 4.4 – Chi-squared test results on temporal variation of porpoise mortality for each questionnaire. Table 4.5 – Linear regression results on the influence of fishers’ presence in reported number of dead porpoises. Table 4.6 – Chi-squared test results on spatial variation of each gear type usage across the river for both questionnaires. Table 4.7 – Chi-squared test results on gear usage variation within each stratum for both questionnaires. Table 4.8 - Chi-squared test results on spatial variation of each gear type usage across Dongting Lake for both questionnaires. Table 4.9 - Chi-squared test results on gear usage variation within each stratum for both questionnaires. Table 4.10 - Chi-squared test results on spatial variation of each gear type usage across Poyang Lake for both questionnaires. Table 4.11 - Chi-squared test results on gear usage variation within each Poyang Lake stratum for both questionnaires. v List of Acronyms TGD – Three Gorges Dam IUCN – International Union for Conservation of Nature LEK – Local ecological knowledge YRDE – Yangtze River Dolphin Expedition AMC – Agriculture Ministry of China IH – Institute of Hydrobiology WWF – World Wide Fund for Nature PVA – Population Viability Analysis ADD – Acoustic Deterrent Devices AIC – Akaike Information Criteria AICΔ – Akaike Information Criteria differences AICW – Akaike weights vi Abstract The Yangtze River is the largest river in China and one of the three largest in the world. Supporting c.