Juvenile white sturgeon (Acipenser transmontanus) habitat and distribution in the Lower Fraser River, downstream of Hope, BC, Canada

Abstract

The primary objective of this study was to identify and characterize juvenile white sturgeon (Acipenser transmontanus) habitat in the Lower Fraser River downstream of Hope, BC, Canada. A secondary objective was to estimate the juvenile white sturgeon population in the Lower Fraser River. A total of 1867 white sturgeon was captured with gill nets at 26 sites in the Lower Fraser River. The greatest numbers of sturgeon were caught in three sloughs; all but three sturgeon were captured in the June to August period. These three sloughs all had water deeper than 5 m and current that was multidirectional. Turbidity ranged greatly from 1.5 NTU (Nephelometric Units) to 67.0 NTU and the substrate of most sites was fine sediments, fine sand, silt and clay. Stomach contents were mysid shrimp (Mysidacea), midge larvae (Chironomidae) and peamouth chub (Mylocheilus caurinus). We identified three of 26 sites with appreciable numbers of juvenile sturgeon, identified water quality parameters of these sites, identified any incidental species that might be prey and also determined that between 1985 and 1993 the juvenile white sturgeon population had declined.

Status of White Sturgeon (Acipenser transmontanusRichardson, 1863) throughout the species range, threats to survival, and prognosis for the future

“…Less is known about habitat use of feeding larvae and early juveniles. However, in the Fraser River, juveniles use lower velocity areas such as side channels, sloughs, and deeper areas of the mainstem (Bennett et al., ; Glova et al., ). The decreased availability of such habitats has been identified as a potential threat to juvenile survival (Nelson et al., ).…”

Effect of Two Substrate Types on Feeding Efficiency by Juvenile Chinese Sturgeon Acipenser sinensis on Barcheek Goby <i>Rhinogobius giurinus</i>

“…In a previous study, we found juvenile significantly preferred sand substrate when given a choice of four substrates (numbers indicate particle diameter): sand (<0.02 cm), small gravel (1.0 -2.0 cm), medium gravel (4.0 -5.0 cm), and rubble (13.0 -15.0 cm) [16]. There are several papers that also show a preference for sand substrate by juvenile or adult sturgeons, including A. fulvescens [7] [9]; A. transmontanus [8]; A. gueldenstaedtii; A. brevirostrum [10]; and Scaphirhynchus albus [16]. Peake tested juvenile A. fulvescens preference for sand, gravel, rock or smooth plastic bottom and found a strong preference for sand [7].…”

Do riparian zones qualify as critical habitat for endangered freshwater fishes?

“…White sturgeon is the largest freshwater fish in North America. Adults occupy a range of deepwater mainstem habitats in large rivers; habitat use by young juveniles can include low-velocity habitats such as side channels, tributary confluences, backwaters and sloughs (Bennett et al 2005) or deep, low-velocity mainstem habitats and lake habitat (RL&L Environmental Services Ltd. 2000;Neufeld and Spence 2002;Golder Associates Ltd. 2003). Although riparian vegetation and large wood of riparian origin may have considerable influence on the channel and floodplain structure of medium to large rivers (Latterell et al 2006;Latterell and Naiman 2007;Naiman et al 2010), at present, there is no clear evidence that modification of the riparian zone will degrade in-stream critical habitat attributes for the listed populations of white sturgeon or decrease their probability of persistence (Table 1); consequently, recovery teams in the USA and Canada did not identify riparian habitat as biologically critical (US Fish and Wildlife Service 1999; National Recovery Team for White Sturgeon 2009).…”