Biological Opinions - Bureau of Reclamation

parasites Ceratomyxa shasta (causes ceratomyxosis) and Parvicapsula minibicornis. There is a
lack of information concerning the presence of infectious haematopoietic necrosis and bacterial
kidney disease either above or below IGD (Administrative Law Judge 2006). Columnaris is
common worldwide and present at all times in the aquatic environment. Columnaris disease in
cold water fishes is generally seen at water temperatures above 15 o C. In natural infections, the
disease is often chronic to subacute, affecting skin and gills (CDFG 2004a). Ich infestation of
gill tissue results in hyperplasia, a condition that reduces the ability of the fish to obtain oxygen.
Death is by asphyxiation. Ich can be found on any fish at any temperature, but typically only
causes disease and mortality at water temperatures above 14 o C and in crowded conditions
(CDFG 2004a). Other common pathogens are likely present in the Klamath River, but are
reported rarely.
Ich and columnaris have occasionally had a substantial impact on adult salmon downstream of
IGD, particularly when habitat conditions include exceptionally low flows, high water
temperatures, and high densities of fish (such as adult salmon migrating upstream in the fall and
holding at high densities in pools). In 2002, these habitat factors were present, and a disease
outbreak occurred, with more than 33,000 adult salmon and steelhead losses, including an
estimated 334 coho salmon (Guillen 2003). Most of the fish affected by the 2002 fish die-off
were fall-run Chinook salmon in the lower 36 miles of the Klamath River (CDFG 2004a).
Although losses of adult salmonids can be substantial when events such as the 2002 fish die-off
occur, the combination of factors that leads to adult infection by Ich and columnaris disease may
not be as frequent as the annual exposure of juvenile salmonids to C. shasta and P. minibicornis,
as many juveniles must migrate each spring downstream past established populations of the
invertebrate polychaete worm host.
The life cycles of both C. shasta and P. minibicornis involve an invertebrate and a fish host,
where these parasites complete different parts of their life cycle. In the Klamath River, P.
minibicornis and C. shasta share the same invertebrate host: an annelid polychaete worm,
Manayunkia speciosa (Bartholomew et al. 2006). Once the polychaetes are infected, they release
C. shasta actinospores into the water column. Temperature and actinospore longevity are
inversely related. In one study, actinospores remained intact the longest at 4°C, but were shortlived
at 20°C. Actinospores are generally released when temperatures are above 10°C, and
remain viable (able to infect salmon) from 3 to 7 days at temperatures ranging from 11 to 18ºC
(Foott et al. 2006). When temperatures are outside of 11 to 18ºC, actinospores are viable for a
shorter time. As actinospore viability increases, actinospore distribution may increase, raising
the infectious dose for salmon over a larger area of the river (Bjork and Bartholomew 2010).
Actinospore abundance, a primary determinant of infectious dose, is controlled by the number of
polychaetes and the prevalence and severity of infection within their population.
Salmon become infected when the actinospores enter the gills, and eventually reaching the
intestines. At that point, the parasite replicates and matures to the myxospore stage.
Myxospores are shed by the dying and dead salmon, and the cycle continues with infection of
polychaete worms by the myxospores (Bartholomew and Foott 2010). Transmission of the C.
shasta and P. minibicornis parasites is limited to areas where the invertebrate host is present.
Susceptibility to C. shasta is also influenced by the genetic type of C. shasta that a fish
encounters. Atkinson and Bartholomew (2010a, 2010b) conducted analyses of the genotypes of
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