Geology topics

A. Michelle Wargo Rub

Publications and source records attributed to A. Michelle Wargo Rub.

4 recordsLinked to original sources

USGS2020

Estimating population-specific predation effects on Chinook salmon via data integration

Recent success in the conservation of many marine mammals has resulted in new management challenges due to increasing conflict with fisheries. Increasing predation by pinnipeds on threatened salmon is of particular concern. Seemingly, pinniped conservation is now in conflict with the recovery of threatened salmon, creating a dilemma for managers. We use the Lower Columbia River as a case study for examining the relationship between seasonal California sea lion Zalophus californianus abundance and survival of threatened salmon. To quantify mortality associated with increasing sea lion abundance, we examined the effect of seasonal sea lion abundance on adult Chinook salmon Oncorhynchus tshawytscha survival during migrations through the Lower Columbia River. We integrated data on survival with data on population-specific migration timing, allowing quantification of the relationship between sea lion abundance and survival in 18 populations of spring–summer Chinook salmon listed as Threatened or Endangered under the U.S. Endangered Species Act. Of the 18 populations examined, earlier migrating populations experienced lower survival in association with increased exposure to higher sea lion abundance. We estimated that in years with high sea lion abundance, the nine earliest-migrating populations experienced an additional 21.1% (95% CI = 16.3–26.1) mortality compared to years with baseline sea lion abundance, while the nine latest migrating populations experienced an additional 10.1% (7.5–13.0). Synthesis and applications . Integrating datasets on seasonal survival and migration timing made it possible for us to estimate population-specific mortality associated with increased sea lion abundance in the Lower Columbia River. This information could not be produced from any one dataset, highlighting the utility of data integration approaches. The mortality experienced by early migrating Chinook salmon suggests the potential for demographic and evolutionary consequences. Management actions such as hazing, relocating, or removing individuals that are frequent predators on salmon have been proposed. Identifying the management actions that will allow for socially and legally acceptable trade-offs between multiple conservation and other social values will be facilitated by development of explicit multi-species management frameworks. Continued monitoring will help to reduce the substantial uncertainty about the effect of pinnipeds on salmon and the predicted outcomes of alternative management actions.

Oregon, Washington↗

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↗

USGS2015

Surgical insertions of transmitters and telemetry methods in fisheries research

Use of electronic transmitter and monitoring systems to track movements of aquatic animals has increased continuously since the inception of these systems in the mid-1950s. The purpose of the present report is to provide information about veterinary principles and their incorporation into surgical implantation procedures for fish. We also intend to provide insight into the unique challenges of field-based aquatic surgical studies. Within this context, 4 aspects of the process for surgical implantation of transmitters in fish (ie, handling, aseptic technique, anesthesia, and implantation) will be described. Effects of surgical insertion of transmitters (ie, tagging) and aspects of the surgical implantation process where collaboration and professional exchanges among nonveterinarian researchers and veterinarians may be most fruitful will be discussed. Although this report focuses on surgical implantation, the principles and protocols described here (other than incision and suture placement) are also applicable to studies that involve injection of transmitters into fish.

American Journal of Veterinary Research↗

USGS2012

Techniques for telemetry transmitter attachment and evaluation of transmitter effects on fish performance: Chapter 4

One assumption of nearly every biotelemetry study is that the tagged animals are representative of the untagged population. That is, that the processes by which study animals are captured, handled, and tagged, as well as the act of carrying a transmitter, will have minimal effect on their behavior and performance. This assumption, commonly stated as a lack of transmitter effects, must be valid if telemetry studies are to describe accurately the movements and behavior of an entire population of interest, rather than only of a subset of that population. Considering the sequence of events necessary to implement telemetry studies (i.e., collection, handling, transmitter attachment), as well as the intrusive nature of many transmitter attachment techniques, it is likely that there will be some effect on the study animals. These potential impacts can range from mild to severe, from transitory to permanent, and may be manifest immediately or not for several days to weeks after tagging. Direct physical impacts can include elevated stress levels, injury, or even death (Knights and Lasee 1996; Jepsen et al. 2001; Lacroix et al. 2004). Interrupted integrity of the scales, mucus, or skin can place fish at increased risk of infection (Mellas and Haynes 1985; Swanberg et al. 1999; Bauer et al. 2005; Harms 2005). Effects on fish behavior include altered buoyancy compensation ability (Gallepp and Magnuson 1972; Fried et al. 1976), reduced swimming performance (McCleave and Stred 1975; Counihan and Frost 1999; Makiguchi and Ueda 2009), reduced feeding, or changes in dominance status (Greenstreet and Morgan 1989; Armstrong and Rawlings 1993; Welch et al. 2007). Changes in behavior such as these can affect a fish’s growth, rate of maturation or migration, or increase its vulnerability to predation. At some level, these transmitter effects will be present in nearly every study using telemetry and if substantial, they can violate the critical assumption that tagged fish are representative of the untagged population.

Book chapter↗