Geology topics

Benjamin P. Sandford

Publications and source records attributed to Benjamin P. Sandford.

3 recordsLinked to original sources

USGS2019

Changes in adult Chinook salmon (Oncorhynchus tshawytscha) survival within the lower Columbia River amid increasing pinniped abundance

Significant effort towards conservation has contributed to the recovery of historically depleted pinniped populations world-wide. However, in several locations where pinnipeds have increased, they have been blamed for preventing the recovery of commercially valuable fish species through predation. Prompted by increasing pinniped abundance within the Columbia River (CR) USA, over a six year period, we used Passive Integrated Transponder tags to measure the survival of adult spring-run Chinook salmon (Oncorhynchus tshawytscha) through the estuary and lower CR to Bonneville Dam (Rkm 234). We estimated 51 751 - 224 705 salmon died annually from sources other than harvest. Mixed-effects logistic regression modelling identified pinniped predation as the most likely source. The odds of survival was estimated to decrease by 32% (95% CI: 6%-51% decrease) for every additional 467 sea lions, and to increase by 32% (95% CI: 8%-61% increase) for every increase of 1.5 in the log of American shad (Alosa sapidissima), a potential prey item for sea lions. A third covariate was the adipose clip status of the fish, indicating whether it was eligible for harvest.

Oregon, Washington↗

USGS2012

Using mark-recapture models to estimate survival from telemetry data: Chapter 9.2

Analyzing telemetry data within a mark–recapture framework is a powerful approach for estimating demographic parameters (e.g., survival and movement probabilities) that might otherwise be difficult to measure. Yet many studies using telemetry techniques focus on fish behavior and fail to recognize the potential of telemetry data to provide information about fish survival. The sophistication of both mark–recapture modeling and telemetry has dramatically improved since the 1980s, largely due to technological advancements in computing power (for mark–recapture models) and electronic components (for telemetry). Such advances now allow mark–recapture models to take advantage of the detailed information that telemetry techniques can provide. The key feature of mark–recapture models is simultaneous estimation of detection and survival probabilities. With telemetry, a “capture” event consists of detecting a given tag code one or more times at a specific location or time. By contrast, in some studies interest may focus on the probability of detecting a single tag transmission (see Sections 7.2 and 9.1). Compared to conventional mark and recapture methods, telemetry methods often have greater detection probabilities due to large detection ranges, increased “effort” (i.e., continuous monitoring with autonomous receivers), and ability to simultaneously monitor multiple locations. Nonetheless, perfect detectability is rare in telemetry studies because both random (e.g., from electronic noise) and nonrandom processes (e.g., receiver loses power temporarily) can allow a fish to pass a receiver undetected. Failure to account for imperfect detection can lead to serious bias in survival estimates. When using telemetry to estimate survival, it is therefore critical to explicitly estimate detection probabilities to ensure unbiased estimates of survival (see Section 7.2). Fortunately, using telemetry techniques and mark–recapture models together yields the best of both worlds: Well-designed telemetry systems deliver high detection probabilities that result in precise estimates from small sample sizes. Mark–recapture models ensure estimates of the demographic parameters are unbiased with respect to the detection process.

Book chapter↗

USGS2012

Alternative barging strategies to improve survival of salmonids transported from Lower Granite Dam: Final report from the 2006-2008 spring/summer Chinook salmon and Steelhead juvenile migrations

In 2011, the final year class of adult salmon Oncorhynchus spp. returned from smolt groups released for a multi-year study to evaluate an alternate release site for transported fish. Smolts were collected and tagged at Lower Granite Dam, transported, and released at the alternate site near Astoria, Oregon (river kilometer 10) or at the traditional release site near Skamania Landing (rkm 225) just downstream of Bonneville Dam. Study fish were juvenile steelhead O. mykiss and yearling spring/summer Chinook salmon O. tshawytscha , and our evaluation was based on comparisons of smolt-to-adult return rates (SARs) between replicate paired groups. Our hypothesis was that moving the traditional barge-release site 215 km downstream could increase adult returns by decreasing smolt mortality due to predation by piscivorous fish and birds. Paired groups were released weekly over 6 weeks during the migration seasons of 2006, 2007, and 2008. The last adult steelhead from these releases returned in May 2011 (2-ocean), and the last adult Chinook salmon in August 2011 (3-ocean). We found no evidence of a consistent difference in SARs for fish released at the two barge-release locations. Data were not sufficient to evaluate the effects of fish pathogens on avian predation. There was clear evidence that fish of both species released at Astoria were less vulnerable to avian predators than those released at the customary site at Skamania Landing. Unfortunately, this survival benefit did not translate to higher SARs, as it was offset by higher rates of straying by fish released from Astoria. This was likely a result of greater impairment to homing ability for fish released at Astoria.

Oregon, Washington↗