A Seasonal Survey of Metazoan Parasites of Arctic Cisco (Coregonus Autumnalis) from Alaskan Arctic Coastal Waters

Proc. Helminthol. Soc. Wash. 51(2), 1984, pp. 245-247

A Seasonal Survey of Metazoan Parasites of Arctic Cisco (Coregonus autumnalis) from Alaskan Arctic Coastal Waters

LEWIS HALDORSON School of Fisheries and Science, University of Alaska, 11120 Glacier Highway, Juneau, Alaska 99803

ABSTRACT: A seasonal survey of metazoan parasites of arctic cisco, Coregonus autumnalis, from the Alaskan Beaufort Sea coastal area revealed only three species: two cestodes and one acanthocephalan. The most common cestode, Bothrirnonus sturionis, had high prevalence in summer samples, but was absent in winter samples. The other two parasite species, a metacestode stage of a Diphyllobothrium species and the acanthocephalan Neo- echinorhynchus tumidus, had lower prevalence and apparently were not seasonal. None of the parasites found occurred in numbers that appeared detrimental to host fishes.

The family Coregonidae includes the most im- The fresh or frozen fish were examined for external portant subsistence and commercial species in and encysted parasites. The viscera and gills were pre- coastal waters of the western Beaufort Sea. Par- served in 10% formalin and examined later. Voucher specimens of the parasite species were de- asites of northern coastal or shallow water ma- posited in the USNM Helminthological Collection, rine fish species, including coregonids, have been USDA, Beltsville, Maryland 20705 (Nos. 77592- studied in Siberian and European waters, and in 77594). eastern waters of North America (Sandeman and Pippy, 1967; Threlfall and Hanek, 1970; Hicks Results and Discussion and Threlfall, 1973; reviews in Bauer, 1970 and No parasites were found externally, encysted Lawler, 1970); however, there is little informa- in the flesh, or on the gills. The viscera were tion available on metazoan parasites of fishes in infected with three species: an adult cestode northern Alaskan coastal waters. As part of a (Bothrirnonus sturionis Duvernoy, 1842), a ces- study of trophic and ecological relationships of tode plerocercoid (metacestode) stage (Diphyl- nearshore fish species in the western Beaufort Sea lobothrium sp.), and an adult acanthocephalan a seasonal survey of the most important com- (Neoechinorhynchus tumidus Van Cleave and mercial and subsistence species, the arctic cisco Bangham, 1949). The prevalence and intensity (Coregonus autumnalis), was undertaken to pro- of infections for all samples are presented in Ta- vide information on its metazoan parasites. ble 1. Arctic cisco enter coastal brackish waters of The number of parasite species found in this the Beaufort Sea shortly after spring break-up survey was surprisingly low. Other surveys of (usually in June) of river systems where the pop- coregonid parasite faunas by Hicks and Threlfall ulations have overwintered. During the short (1973) found 12 and 13 species in Coregonus open water season they feed in shallow coastal dupeaformis and Prosopium cylindraceum, which waters on epibenthic crustaceans, principally is slightly lower than the 15 and 18 species Ar- mysids and to a lesser extent, amphipods (Craig thur et al. (1976) report for the same species, and Haldorson, 1981). By freeze-up in late Sep- respectively. Watson and Dick (1979) reported tember or early October they return to overwin- 19 and 18 species in C. dupeaformis and Cor- tering sites in river drainages. The Colville River egonus artedii, two species from which Leong system is apparently the major overwintering and Holmes (1981) reported 16 and 15 species. habitat for this species in the western Beaufort The other surveys were conducted on freshwater Sea, and is possibly a major spawning site, al- populations where the parasite species were though spawning locations for arctic cisco have dominated by copepod-vectored cestodes, mol- never been identified in Alaskan waters. lusc-generated metacercaria, and other amphi- pod-vectored parasites. The low number of par- Materials and Methods asite species encountered in this study may be Samples of arctic cisco were collected by gill net due in part to dietary differences (i.e., arctic cisco under the ice in the Colville River delta (70°25'N, 150°07'W) in November 1976 and 1977, and three feed mainly on mysids), a yearly cycle of anad- times during the 1977 open water season in nearby romy, or reduced species diversity in higher lat- (about 25 mi) Simpson Lagoon (70°30'N, 149°12'W). itudes. 245

Table 1. Infection rates (prevalence) and average number of parasites per infection (intensity) for three parasites of arctic cisco from the Colville River Delta and adjacent marine waters, with mean lengths in cm (L) and standard deviations (SD) of cisco.

Prevalence/intensity Diphyllo- Neoechino- Bothrimonus bothrium rhynchus Date N L/SD sturionis sp. tumidus

11/76 25 337/18.5 0/0 12/10 36/1.8 6/77 25 356/14.2 12/1.0 12/3.3 40/3.2 7/77 25 357/17.7 92/35.6 28/2.6 52/4.3 9/77 25 358/13.7 84/5.7 28/3.1 44/3.4 11/77 21 322/30.0 0/0 10/1.0 33/2.7

The adult tapeworm, Bothrimonus sturionis, sue. Most specimens measured 2-3 mm in di- occurred in the lumen of pyloric caeca and in- ameter. Bauer (1970) reports similar parasites in testine. Burt and Sandeman (1969) synonymized Russian populations, and suggests that they ma- B. sturionis and Diplocotyle olrikii, and that con- ture in fish-eating birds. In addition, he reports vention will be followed in this report. B. stu- the occurrence of D, dendriticum, a species ca- rionis is a widely distributed, circumarctic species pable of infecting man, in Russian coregonid (Sandeman and Burt, 1972), and has been re- populations. ported from arctic char in Alaskan waters (Mu- The acanthocephalan (Neoechinorhynchus dry and McCart, 1976). Bauer (1970) reports that tumidus) was found in the lumen of intestines, in Russia this species infects fish in marine waters, usually attached to the intestine wall. Adult par- but perishes when the host migrates into fresh asites were 0.5-1.0 cm in length. Bauer (1970) water. The pattern of infection in this study (Ta- has reported this species infecting riverine cor- ble 1) coincides with that observation. Fish col- egonids in eastern Russia, and it has been re- lected in brackish nearshore waters during mid- ported from four freshwater coregonid species in to late summer were highly infected (84-92%), Alaska (Schmidt, 1965). Acanthocephalan in contrast to those fish collected in early winter (Echinorhynchus sp.) infections have been re- under Colville River ice (0% infected). The in- ported to cause deterioration in coregonid fishes tensity was highest in July (35.6); these were small when intensities of over 250 per fish occur; how- tapeworms about 1 cm in length. By early Sep- ever, infections of less than 30 have shown little tember the average length had increased to 3-4 effect (Bauer, 1970). It seems unlikely, therefore, cm and the intensity had decreased to 5.7 worms that intensity levels in these samples (Table 1) per infection. The temporary nature of B. stu- were high enough to be detrimental to the hosts. rionis infections has also been noted by Sande- The intensity levels of parasites found in this man and Burt (1972), and the generality of these study do not appear to significantly harm host observations suggests that Dick and Belosevic's fishes. The fish feed and increase in weight and (1981) use of this parasite as a marker for sea- fat content during the open water season. Ful- run arctic char is inappropriate. Lawler (1970) ton's condition factor was calculated for the sam- reported that D. olrikii may retard fish growth ple of fish taken at the end of the open water and cause general deterioration, but apparently season in September 1977. There was a very weak this occurs at higher intensity than found in this correlation (r = 0.06) of total parasite numbers study. The assumption that all samples were part and condition factor in that sample. of the same migratory population is supported by tagging studies, by the absence of arctic cisco Acknowledgments in nearshore marine habitats during winter, and L. Jensen and M. Moser identified the ces- by similar size frequencies in all samples (Craig todes, and A. Moles identified the acanthoceph- and Haldorson, 1981). alan. P. Craig provided support and encourage- A second tapeworm, Diphyllobothrium sp., oc- ment. The study was funded by the Bureau of curred in the metacestode stage on the stomach Land Management through a cooperative agree- walls, pyloric caeca walls, and in mesenteric tis- ment with NOAA under the Outer Continental

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