Anguillicola crassus infection in Anguilla rostrata from small tributaries of the Hudson River watershed, New York, USA

Abstract

We studied the invasion of the exotic nematode parasite Anguillicola crassus in the American eel Anguilla rostrata using tributaries of the Hudson River estuary. Yellow-phase American eels were sampled from 6 tributaries, and their swim bladders were examined for nematode infection. Prevalence averaged 39% with an intensity of 2.4 nematodes per eel. Parasite distribution was not significant along a latitudinal gradient; on the other hand, physical barriers (dams and natural waterfalls) significantly reduced infections upstream. Urbanization may increase the susceptibility of eels to infection; we found significantly elevated infection rates when urbanized lands exceeded 15% of the tributary catchment area. Yellow-phase eel condition was not affected by parasite infection. The invasion of the entire Hudson River watershed is ongoing and therefore will continue to be a management concern. Further analysis of the parasite-host interaction in North America is warranted.KEY WORDS: Anguilla rostrata · Anguillicola crassus · Parasite · Barriers · Urbanization Resale or republication not permitted without written consent of the publisherDis Aquat Org 79: 37-45, 2008 et al. 2000). Intense infections can cause hemorrhagic lesions of the swim bladder, swim bladder fibrosis, skin ulcers and swollen anuses (van Banning & Haenen 1990). There are contrasting findings regarding the potential negative affects of A. crassus on swimming ability (Sprengel & Lüchtenberg 1991, Nimeth et al. 2000, Münderle et al. 2004. Knopf et al. (1998) theorized that infestation of European eels may have been slowed by low water temperatures, and increased parasite intensity was found in thermal effluent when compared to cooler surrounding waters (Höglund et al. 1992b). Examination of American eel in Canadian waters has not yet shown infection with A. crassus (Marcogliese & Cone 1996, G. Verreault, Faune et Parcs Quebec, pers. comm.).Within New York State the tidal Hudson River contains infected eels with prevalence increasing downstream (Morrison & Secor 2003). However, the rate of infection and infected eel condition in Hudson River tributaries is unknown. Densities of up to 1.55 eels m -2 have been found in the tributaries (Machut et al. 2007), suggesting that they are an important habitat for declining American eel populations. As a relatively new definitive host for the parasite, eels in the Hudson River tributaries may be highly susceptible to infection.The purpose of the present study was to examine yellow-phase eels taken from small tributaries of the freshwater tidal Hudson River estuary to determine the burden of Anguillicola crassus on native American eel populations in these habitats, as well as the current effect of this parasite on the health of yellow-eels. We hypothesized that (1) the infection of eel with the A. crassus parasite would be higher in southern tributaries; (2) barriers would inhibit the upstream invasion of A. crassus in the tributaries; (3) disturbances caused by urbanization would increase the infection ...

Contamination, parasitism and condition of Anguilla anguilla in three Italian stocks

“…The relation between parasite abundance and lipid content was negative but not significant. This is in accordance with other published studies that failed to verify a relationship between infection level and yellow eel condition (Kelly et al 2000;Machut and Limburg 2008). Nonetheless, it is known that nematodes are capable of inducing stress in eels and increasing cortisol plasma levels (Sures et al 2001).…”

“…In the case of eel, Sures and Knopf (2004) showed that a dose of 100 ng/g w.w. of PCB 126 suppress antibody response, thus increasing vulnerability to infection by A. crassus. Machut and Limburg (2008) found elevated infection rates when urbanized lands exceeded 15 % of the tributary catchment area, as in the case of the lower Tevere River, and suggested that urbanization may increase eel susceptibility to infection by increasing stressors. The relation between PCB concentration and parasite abundance in Tevere eels was positive but not significant, probably because of the limited sample size.…”

Distribution, prevalence, and intensity of the swim bladder parasite Anguillicola crassus in New England and eastern Canada

“…In a study of the exotic American eel gill parasites Pseudodactylogyrus bini and P. anguillae, it was hypothesized that they were introduced along with A. crassus through either commercial imports of foreign eels or by transmission through ballast water (Hayward et al 2001). Machut & Limburg (2008) found increased infection rates in tributaries of the Hudson River that exhibited higher urbanization, indicating that anthropogenically induced eel susceptibility to the parasite may also be a factor involved in parasite distribution. The presence of the parasite in the St. Johns River can be explained by the natural advancing of the parasite along the coast from New England rivers.…”

Prevalence of Anguillicoloides crassus and growth variation in migrant yellow-phase American eels of the upper Potomac River drainage

“…It seems likely that the latter scenario, which would require the presence of paratenic or intermediate hosts in upstream areas, would result in a higher prevalence of A. crassus within eels in the Shenandoah River. Machut & Limburg (2008) found that physical barriers likely reduced A. crassus infection in the Hudson River, New York. Specifically, small paratenic or intermediate host species may be unable to circumvent dams, thus upstream migrant eels are primarily responsible for the invasion of the parasite (Machut & Limburg 2008).…”

“…During the 1980s, A. crassus was introduced to Europe (Peters & Hartman 1986, Kennedy & Fitch 1990, Kangur et al 2010) and has been implicated in population decline of European eel Anguilla anguilla (Palstra et al 2007). During the 1990s, A. crassus was observed in swim bladders of American eel in North America, and has since been documented along the Atlantic coast of the United States, as well as New Brunswick and Nova Scotia, Canada (Barse & Secor 1999, Barse et al 2001, Moser et al 2001, Geer 2003, Morrison & Secor 2003, Sokolowski & Dove 2006, Machut & Limburg 2008, Aieta & Oliveira 2009, Rockwell et al 2009, Fenske et al 2010.…”