Annual Movements of Acoustic‐Tagged White Sturgeon in the Lower Reaches of the Fraser River and its Tributaries

Abstract

Details of the spatial ecology of White Sturgeon Acipenser transmontanus in the lower Fraser River, British Columbia, are needed for habitat conservation, assessments of impacts from spatially delimited threats, and refinement of abundance estimation methods. The abundance of threatened lower Fraser River White Sturgeon is assessed annually using a Bayesian, closed‐population, mark–recapture model. If individuals make prolonged departures from the lower Fraser River, either into marine waters or a tributary, the validity of the model's assumed closed population is questionable. There is also concern that fish might move far enough to be exposed to harvest in Puget Sound, Washington. From 2008 to 2012, White Sturgeon of various sizes were acoustically tagged in the Pitt River (n = 58) and in the lower reaches of the Fraser River (near Douglas Island, n = 52) to determine the timing, rate, and spatial extent of movements. Movements were monitored using acoustic receivers at 17 locations in the lowermost 92 km of the main‐stem Fraser River, three in the first 21 km of the Pitt River (a tributary to the lower Fraser River), and nine in the coastal waters of British Columbia and Washington State. Travel speeds showed a strong skew toward slower movements (74% were <1 km/h) and did not differ significantly between upstream and downstream directions. On average, 33.2% of the sample was mobile (displacing ~13.4 km/month) and 66.8% was sedentary (displacing ~1.87 km/month). In general, White Sturgeon were significantly more sedentary during winter months and more mobile during spring and fall. Annual or seasonal migratory movements and patterns were observed for 73% of fish tracked. Repeated use of specific locations within the lower Pitt River during midwinter suggested White Sturgeon have a high fidelity for specific overwintering sites. Several of the tagged fish showed annual movements to the lowest reaches of the Fraser River for 1–3 months between May and September, although there was no direct evidence that they left the Fraser River and entered the Strait of Georgia. By contrast, there was strong evidence for extended and repeated movement into the lower Pitt River. Given that the lower Pitt River is outside the mark–recapture assessment area, our results suggest either that the area's boundaries need expansion, or alternative models should be considered for abundance estimations of lower Fraser River White Sturgeon. Received September 7, 2016; accepted February 3, 2017 Published online April 27, 2017

Catch‐and‐Release Angling Effects on Lake Sturgeon in Wisconsin, USA

“…These results were consistent with those of prior studies that found relatively low rates of angling‐related mortality for a similar species (0.01–4.0%, White Sturgeon, Robichaud et al. 2006; McLean et al. 2016).…”

“…Discard mortality rates that are associated with hook‐and‐line angling and simulated angling stress were low, 0.01% and 4%, respectively, for White Sturgeon Acipenser transmontanus (Robichaud et al. 2006; McLean et al. 2016).…”

“…Discard mortality for sturgeon species is assumed to be low based on the relatively low number of mortalities that researchers directly observed in previous studies (Robichaud et al. 2006; McLean et al. 2016; Struthers et al.…”

Spatial structure of large‐river fish populations across main‐stem and tributary habitats

“…Additionally, tributaries may establish favourable habitat conditions that promote fish recruitment within altered main‐stem habitats (Pracheil, Pegg, & Mestl, ). The occurrence of movement between main‐stem and tributary habitats by fishes is well established (Koster, Dawson, O'Mahony, Moloney, & Crook, ; Nunn et al, ; Robichaud, English, & Nelson, ). Less understood, however, is the magnitude and direction of movement patterns as well as differences in population demographic parameters between main‐stem and tributary habitats.…”

The role of salinity in recovery of white sturgeon (Acipenser transmontanus) from stimulated angling stress

“…Primarily due to conservation concerns of this iconic fish, there have been numerous studies investigating the impact of C&R on WS populations ( McLean et al, 2016 , 2019 , 2020 ). Experimental work suggests that WS recover quickly from C&R angling in general and seldom experience mortality ( McLean et al, 2016 , 2019 , 2020 ), with an estimated direct mortality of angled fish <0.012% and 3-d postangling mortality rate of 2.6% ( Robichaud et al, 2006 ). Angling events can vary, with fight times ranging from seconds to >2 h with a median time of 5.78 min ( McLean et al, 2016 ), and WS are likely captured multiple times over their life.…”