Observational data on the effects of infection by the copepod Salmincola californiensis on the short- and long-term viability of juvenile Chinook salmon (Oncorhynchus tshawytscha) implanted with telemetry tags

Abstract

Background: Fish movements are often studied using radio or acoustic tags assuming the handling and tagging procedures have little effect on the behavior of the animal. Indeed, many studies provide guidelines for acceptable methods. However, these studies generally assume the fish are otherwise healthy but this may not always be the case. One example is the infection of juvenile salmon in the western USA by the naturally-occurring parasitic copepod Salmincola californiensis, for which little is known about the effects on results from tagged animals. We report on observational data from juvenile Chinook salmon (Oncorhynchus tshawytscha) surgically implanted with telemetry tags relative to the numbers of S. californiensis within their branchial cavities and on their bodies to determine if the intensity of infection resulted in differences in mortality shortly after tagging or post-release activity in a reservoir over a period of about 4 months. Results:The data indicate a negative effect of copepods in the branchial cavities on short-term mortality (within 24 h of tagging) and suggest negative effects on movements after release into the reservoir. Short-term mortalities were infrequent and, due to the observational nature of the data, few tagged fish had more than three copepods in their branchial cavities, although surveys of fish in the reservoir indicate much greater infection intensities are common. Copepod numbers on the body did not appear to be associated with short-term mortality or movements after release. The number of copepods on the body was unrelated to the number within the branchial cavities, indicating site-specific counts are needed to assess the infection. Conclusion:Infection with Salmincola californiensis is common in juvenile Chinook salmon in western USA reservoirs and may affect the viability of fish used in studies of telemetered animals. Our limited assessment suggests infection by Salmincola californiensis affects the short-term morality of tagged fish and may affect long-term viability of tagged fish after release; however, the intensity of infection in the sample population did not represent the source population due to the observational nature of the data. We suggest these results warrant further study into the effects of infection by Salmincola californiensis on the results obtained through active telemetry and perhaps other methods requiring handling of infected fish.

Low‐level infection of parasitic copepods on Rainbow Trout does not affect vulnerability to angling or short‐term survival following catch‐and‐release angling

“…For example, Beeman et al. (2015) reported higher posttagging mortality of Chinook Salmon when water temperatures were highest during the study.…”

Live Freshwater Parasite, Salmincola californiensis (Copepoda: Lernaeopodidae), on the Gills of an Ocean-Migrating Steelhead Trout (Oncorhynchus mykiss) and Discussion on the Origin and Survival of the Parasite at Sea

“…The geographical distribution of S. californiensis has been well documented to date. In North America, the species is native to California (Wilson, 1915, 1916; Shapovalov and Taft, 1954; Kabata, 1969; Jennings and Hendrickson, 1982), Oregon (Kabata, 1969; Beeman et al, 2015; Monzyk et al, 2015; Herron et al, 2018; Murphy et al, 2020; Neal et al, 2021), Washington (Wilson, 1916; Kabata, 1969; Bailey and Margolis, 1987; Chigbu, 2001; Barndt and Stone, 2003), Idaho (Wilson, 1915, 1916; Kabata, 1969; Jenkins et al, 2020), Colorado (Wilson, 1916; Kabata, 1969; Hargis et al, 2014; Vigil et al, 2016), Wyoming (Kabata, 1969), and Alaska (Moles, 2007), the western U.S.A., and to British Columbia, western Canada (Kabata, 1969; Arai and Mudry, 1983; Bailey and Margolis, 1987). In Asia, the species occurs in Kamchatka, Primorsky Krai, and Sakhalin, Russia (Shedko, 2005; Shedko et al, 2005; Sokolov et al, 2012) and in Hokkaido and Honshu, Japan (Hoshina and Suenaga, 1954; Kabata, 1969; Hoshina and Nishimura, 1976; Nagasawa and Urawa, 2002; Nagasawa et al, 2018).…”

“…In addition to steelhead trout, the known hosts of S. californiensis in western North America include rainbow trout, a non-anadromous form of O. mykiss (Kabata, 1969; Monzyk et al, 2015; Vigil et al, 2016; Suchomel and Billman, 2021), sockeye salmon and its lake form, kokanee (Wilson, 1915, 1916; Kabata, 1969; Bailey and Margolis, 1987; Bailey et al,1989; Chigbu, 2001; Hargis et al, 2014), Chinook salmon Oncorhynchus tshawytscha (Wilson, 1916; Kabata, 1969; Jennings and Hendrickson, 1982; Beeman et al, 2015; Monzyk et al, 2015; Heron et al, 2018; Murphy et al, 2020), coho salmon O. kisutch (Barndt and Stone, 2003), and cutthroat trout O. clarkii (Kabata, 1969; Barndt and Stone, 2003; Monzyk et al, 2015). This implies that juvenile and adult steelhead trout have numerous opportunities to become infected by copepodids of S. californiensis released from some of these other salmonids in fresh water.…”

Assessment of Operational and Structural Factors Influencing Performance of Fish Collectors in Forebays of High‐Head Dams

“…Delay poses risks because the timing of out-migration has survival consequences and may limit life history diversity, which has been shown to be important for population resilience (Scheuerell et al 2009;Schroeder et al 2016). Furthermore, residence in reservoirs may increase exposure to factors such as predation and parasitism Rieman et al 1991;Beeman et al 2015;Monzyk et al TABLE 6. Fish collection efficiency (FCE) estimates for forebay collectors at seven dams in Washington and Oregon (FCE COLL = proportion of fish that were collected among those that arrived at the collector entrance; FCE FB = proportion of fish that were collected among those that were either released into the forebay or arrived in the forebay after release near the head of the reservoir; FCE RES = proportion of fish that were collected among those released near the head of the reservoir).…”