Our new Biological Assessment is out - Klamath Basin Crisis

Klamath Project Operations Biological Assessment
Endangered Suckers: Environmental Baseline for Suckers
Other Impacts
Fish Health
Disease and parasite prevalence were not identified as threats at the time of listing
for either suckers species. However, information since 1988 indicates that
pathogens affect sucker health and survival, especially during adverse water
quality events (USFWS 2007 LRS, 2007 SNS). Fish susceptiblility to pathogens
in the Upper Klamath Basin may, in part, be affected by stressful water quality
conditions.
Although the quality of water in lakes throughout the upper basin can surpass
critical thresholds that may lead to direct die off of adult suckers (Loftus 2001),
poor water quality events periodically occur below these thresholds and, while not
lethal, may stress suckers. Stress during poor water quality events may make
suckers more susceptible to a host of naturally-occurring diseases, parasites, and
other ailments in the waters of the upper basin.
Year-old juvenile suckers have been typically scarce in recent sampling efforts of
UKL. Body conditions and general fish health has been indicated as a factor
influencing survival and abundance of juvenile suckers between autumn and the
following spring. Investigation of several health parameters of juvenile suckers
captured in UKL and in the A-canal fish bypass indicated a general decline in
growth occurred in September (Foott and Stone 2005). The poor growth in late
summer-early autumn may be a result of reduced feeding (Foott and Stone 2005).
Reduced feeding may be a response to many things including stress from seasonal
poor water quality events.
Examination of age 0 juvenile suckers captured from the early 1990s through
2003 indicated an increasing prevalence of ectoparasites (i.e., Digenea and
Lernaea sp.) through time (Simon and Markle 2004). It is not yet understood
how, or if, these external parasites impact sucker populations but the increase in
infection rates through the last decade indicate another potential stressor on
suckers.
Furthermore, there is evidence that disease outbreak may have played a role in the
adult sucker die off event of 2003 (Foott 2004). Septicemia (blood-borne
bacteria) appeared increased following in the samples following April. The
identified bacteria responsible for septicemia tend to be opportunistic pathogens
often associated with stress or are part of multiple infections (Foott 2004). Blood
and plasma samples from these fish captured in April, July, and August, typically
were no different from each other. General health of ‘sick’ or moribund fish was
poorer than that of other sample groups, and Columnaris was the primary
pathogen associated with morbidity (Foott 2004). Disease outbreak and poor
health conditions may be exacerbated from poor, but not lethal, water quality
events.
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