EA3009 A PRELIMINARY REPORT ON JUVENILE WHITE STURGEON HABITAT USE IN THE LOWER FRASER RIVER, 2007-2008 Prepared for Fraser River Sturgeon Conservation Society Prepared by: G. Glova1, T. Nelson2, K. English1, and T. Mochizuki1 1LGL Limited environmental research associates 9768 Second Street Sidney, British Columbia V8L 3Y8 2Fraser River Sturgeon Conservation Society, Vancouver, BC May 2008 Surveys of Juvenile White Sturgeon and Their Habitat in the Lower Fraser River 2007-08 EA3009 Table of Contents Executive Summary........................................................................................................... iv 1. Introduction.................................................................................................................1 1.1 Literature Review................................................................................................4 1.2 Sampling Rationale............................................................................................. 5 2. Methods....................................................................................................................... 6 2.1 Field Sampling.................................................................................................... 6 2.2 Sturgeon Ageing................................................................................................. 7 2.3 Sturgeon Diet...................................................................................................... 7 2.4 Data Compilation and Analysis .......................................................................... 8 3. Results......................................................................................................................... 8 3.1 General................................................................................................................ 8 3.2 Distribution of Sturgeon................................................................................... 10 3.3 Size of Sturgeon................................................................................................ 15 3.4 Other Fish Species ............................................................................................ 19 3.5 Significance of Environmental Variables ......................................................... 19 4. Discussion................................................................................................................. 24 5. Conclusion ................................................................................................................ 25 6. Recommendations..................................................................................................... 25 7. Acknowledgments..................................................................................................... 25 8. References................................................................................................................. 27 Appendix........................................................................................................................... 29 Page i Surveys of Juvenile White Sturgeon and Their Habitat in the Lower Fraser River 2007-08 EA3009 List of Figures Figure 1: Map of Lower Fraser River. Circles indicate sites >15 m deep (from Canadian Hydrographic Series, Sept 2004). ..................................................................... 3 Figure 2: Relative frequency of juvenile white sturgeon caught, lower Fraser River, September 2007-March 2008.......................................................................... 10 Figure 3: Sites sampled and juvenile white sturgeon caught in lower Fraser River, September-November 2007 ............................................................................ 11 Figure 4: Sites sampled and juvenile white sturgeon caught in lower Fraser River, December 2007-March 2008 .......................................................................... 12 Figure 5: Juvenile white sturgeon caught ≤300 mm fork length in lower Fraser River, September 2007-March 2008.......................................................................... 13 Figure 6: Plot of effort (number of nets set) and number of white sturgeon caught in the lower Fraser River, September 2007-March 2008.......................................... 14 Figure 7: Plot of effort (number of nets set) and number of white sturgeon caught <450 mm long in the lower Fraser River, September-November 2007................... 15 Figure 8: Size frequency of white sturgeon caught in the lower Fraser River, September 2007-March 2008............................................................................................ 16 Figure 9: Size frequency of juvenile white sturgeon caught <450 mm long in the lower Fraser River, September-November 2007. ..................................................... 16 Figure 10: Size frequency of juvenile white sturgeon <450 mm long caught above and below Mission, lower Fraser River, September 2007-March 2008................ 18 Figure 11: Scatter-plots of sturgeon catch as a function of surface water temperature (ºC) and water depth (m), lower Fraser River, September2007-March 2008. ....... 20 Figure 12: Scatter-plots of sturgeon catch as a function of catch of the three most common bycatch species: sculpins, peamouth chub, and northern pikeminnow, lower Fraser River, September2007-March 2008..................... 21 Figure 13: Plot of sturgeon catch for two size groups in relation to water depth, lower Fraser River, September2007-March 2008..................................................... 22 Figure 14: Relative frequency of juvenile sturgeon catch by substrate type, for substrates with n >10, lower Fraser River, September2007-March 2008. ...................... 23 Page ii Surveys of Juvenile White Sturgeon and Their Habitat in the Lower Fraser River 2007-08 EA3009 List of Tables Table 1: Condition of juvenile white sturgeon sampled in the lower Fraser River, September 2007-March 2008............................................................................ 9 Table 2: Spearman rank correlation coefficients (rs), and P-values, for relationships between sturgeon catch and 5 habitat variables in 518 tangle-net sets........... 19 Table 3: Parameter estimates, model tests (chi sq), and P-values for logistic .............. 20 List of Plates Plate 1: Upper: juvenile white sturgeon 210 mm fork length caught in the Matsqui area (7 November 2007)..........................................................................................17 Page iii Surveys of Juvenile White Sturgeon and Their Habitat in the Lower Fraser River 2007-08 EA3009 Executive Summary Juvenile white sturgeon (Acipenser transmontanus) were sampled in the lower Fraser River (from the mouth to the Harrison River area) by soft mesh tangle netting in a wide range of habitats from September 2007 to March 2008 to gather baseline habitat use information on the younger sector of this endangered subpopulation of fish. The bulk of sampling was carried out during the September-November period, with a minimal effort (3-4 days/month) in December, January and March to identify possible shifts in habitat use seasonally. In addition to sturgeon catch data, information on physical habitat and non-sturgeon fish caught at each of the sites sampled were recorded. Water temperature ranged from a high 18.6 °C in September to a low 1.7 °C in January, and was still low (~5 °C) by late March. Salinity values up to 5.7 ppt were recorded on the bottom in the lower river, with trace levels (0.01 to 0.05 ppt) up to approximately 80 km upstream from the river mouth. Dissolved oxygen ranged from approximately 4-11 mg/l. The main findings of this baseline study are as follows: Of the total 518 nets set, sturgeon were caught at 129 of the sites, a total of 304 fish in all, with the catches ranging from 1- 7 fish, but most frequently consisted of a single individual. The fish ranged in size from 193 to 1500 mm fork length, with 42% of them being less than 300 mm long. Very few fish were caught below 220 mm in length. The sturgeon caught were widely scattered from Deas Island to the Sumas River area, with the higher catches occurring in the Annacis and Hatzic areas, and to some extent in the Port Mann Bridge, Stave and Matsqui areas. They occupied a wide range of water depths (1.3-26 m), but more commonly were found in slow-flowing areas less than 5 m deep with fine substrates in side channels, side pools, backwaters and nearshore mainstem open channels. No sturgeon were caught at bottom salinities >0.6 ppt. The catch dropped off markedly with decreasing water temperatures, with very few (14 in all) sturgeon caught during the winter period. Northern pikeminnow (Ptychocheilus oregonensis), although abundant in the catch, had no statistically significant effect on the catch of juvenile white sturgeon. From the catch information gathered during the September-November period, it appears that the juveniles of this subpopulation of white sturgeon are widely scattered, with preferred sites being the Annacis, Matsqui and Hatzic areas – these may be the preferred areas year round. Because of exceedingly low catch rates, further sampling during low water temperatures (<7 °) is not recommended. Sampling during the May-June period (before the onset of high flows in summer) is more likely to give results indicative of where juvenile sturgeon spend the winter. Page iv Surveys of Juvenile White Sturgeon and Their Habitat in the Lower Fraser River 2007-08 EA3009 1. Introduction The ongoing