Chapter 5 Threats
5.13.6 Freshwater Fishes – Anticipated Impacts Diseases are a significant threat to the health of free-ranging and hatchery-reared populations of fishes, including a suite of important sport and restoration species (Starliper 2008). Most of the diseases are bacterial, and infection can be spread throughout the water column, making it difficult to detect and treat affected populations. Examples of bacterial disease and the species affected include Renibacterium salmoninarum (bacterial kidney disease in salmonids); Aeromonas spp. (septicemic diseases, furunculosis, in salmonids); Edwardsiella spp. (warmwater fishes); Novirhabdovirus sp. (petechial hemorrhage, exophthalmia and internal organs congestion in Muskellunge, Yellow Perch, Freshwater Drum, Smallmouth and Rock bass, Redhorse spp.) (Ellis 1997; Austin and Austin 1999; Emmerich and Weibel 1890; McCarthy and Roberts 1980; Millard and Faisal 2012; Diamanka et al. 2014) . In 2014, Brook Trout in several streams were found to be infested with Gill Lice Salmincola edwardsii . Then, in 2015, Rainbow Trout in three separate river basins were found to be infected with Gill Lice S. californiensis . This was the first time that Gill Lice have been documented in North Carolina waters. Gill Lice, which are actually copepods, attach to a fish’s gills, which can traumatize gills and inhibit the fish’s ability to breathe. While most fish are able to tolerate a moderate infestation of Gill Lice, if they are suffering from other stressors, such as drought and high water temperatures, fish kills and population impacts are more likely to occur. Relatively little research has been conducted for these two Gill Lice species. A better understanding of their distribution and life history traits will assist the determination of which fish populations may be most at risk of experiencing detrimental effects due to infestation and with mitigating negative consequences of these infections (Vigil et al. 2015) . Three Flavobacterium species ( F.psychrophilum , F.columnare, and F.psychrophilum ) cause several diseases that result in mortality to freshwater hatchery-reared and wild fishes (Starliper 2011) . These particular Flavobacterium pathogens are ubiquitous in temperate freshwater aquatic environments, within a wide range of water temperatures from just above freezing to 30°C (86°F) and above (Starliper 2011) . F.psychrophilum causes bacterial coldwater disease, which is usually fatal to coldwater fishes such as trout (Starliper 2011) . Chronic inflammation associated with the disease causes spiral or erratic swimming behaviors and/or spinal column deformities that are similar to symptoms associated with whirling disease. In 2015, whirling disease was detected in the state in Rainbow Trout from the Watauga River. Whirling disease infects young salmonids (i.e., trout, salmon) and is caused by the myxosporean parasite Myxobolus [ Myxosoma ] cerebralis (Snieszko 1975; Sarker et al. 2015). This parasite causes physical deformities that cause fish to swim in circles and is particularly fatal for young Rainbow Trout (Sarker et al. 2015) . The life cycle of the parasite alternates between two hosts, salmonid fishes and an aquatic oligochaete host Sludge Worms ( Tubifex tubifex ). Sludge Worms are a common oligochaete found in stream and lake sediments and are infected by feeding on sediments containing the parasite (Gilbert & Granath 2002; Sarker et al. 2015). Spores developed in the host are released into the water column where they attach and infect fishes. Infected fish can
5 - 57
2025 NC Wildlife Action Plan
Made with FlippingBook Ebook Creator