Parasite communities in four study lakes in 1986 reflected the influences of eutrophication, pollution, and habitat fragmentation. Discriminant analyses of communities at the individual host level revealed two major axes. One contrasted communities in a lake affected by chemical pollution from a pulp mill with those from two eutrophic, less polluted lakes. Changes in the density of intermediate hosts, direct effects on ectoparasites, and impaired immune systems were regarded as important mechanisms. The second contrasted communities in an oligotrophic, unpolluted lake with those from the two eutrophic lakes and was more complex, reflecting habitat fragmentation (the absence of glochidia and some digeneans) and pollution or eutrophication, probably mediated by the same mechanisms as above. Changes in some index parasites in Lake Vatia monitored in 1994, following 8 years of reduced pollutant loading, supported our conclusion that parasite faunas in Lake Vatia in 1986 involved the effects of pollution.
The parasite fauna of 336 adult Pacific halibut (Hippoglossus stenolepis) from 15 geographic localities along the North American coast, ranging from northern California to the northern Bering Sea, was examined to assess zoogeographic and latitudinal zonation of Pacific halibut parasites in the eastern North Pacific. Results show the existence of three zoogeographic zones in the northeast Pacific with boundaries near the southern Queen Charlotte Islands and in the vicinity of Kodiak Island. "Fuzziness" around these boundaries probably reflects small-scale fish movement and the complexity of parasite life cycles. These boundaries roughly correspond to those previously established using the fish and invertebrate faunas. Parasite species richness appears to be more directly correlated with halibut abundance than with latitude; parasite abundance appears to be correlated with temperature and therefore negatively correlated with latitude.
Sea snakes from the eastern Gulf of Carpentaria were regularly sampled from April to December 1976. Thirteen species of snakes were represented among the 341 individuals collected. Over 61 % of these were of one species, Lapemis hardwickii, and none of the other 12 species represented more than 10% of the catch. There were several major differences between our sample and earlier studies in the Gulf and none of these differences could be accounted for. We speculate that earlier studies may have been due to biased samples or to real changes in sea snake distribution and abundance patterns caused by fishing.
Fifty-nine metazoan parasite taxa were identified from 536 Pacific halibut (Hippoglossus stenolepis) of three size classes (recruits (<10 cm), juveniles (10-55 cm), and subadults/adults (55-102 cm)). Pacific halibut harbor parasite communities that are among the richest and most abundant found in those marine fishes studied to date. The parasites are largely host generalists, being found in a wide variety of marine fishes. These three features appear to be due, in part, to the interplay of the large size, wide diet, extensive mobility, and long life-span of halibut, plus the lack of specificity in the marine system and the ability of marine parasites to be transferred trophically from prey fishes to piscivorous fishes. The parasite community in halibut is more similar to those in other flatfishes than to those in ecological analogs, suggesting that phylogeny is an important determinant as well. There are no differences in infections due to host sex. Recruits harbor few parasites, but parasite species and particularly individuals accumulate with host age and length and reflect the shift from a crustacean to a fish diet. Growth rate influences the number of parasite individuals in a given fish, probably reflecting food intake. The smallest fish in the 5-, 6-, and 7-year age-classes have more parasite individuals than slightly larger fish in the same age-class and weigh less than expected for their size; they may be debilitated by parasites.Résumé : Cinquante-neuf taxons de métazoaires parasites ont été identifiés chez 536 Flétans du Pacifique (Hippoglossus stenolepis) de trois classes de taille (recrues (<10 cm), juvéniles (10-55 cm), et subadultes/adultes (55-102 cm)). De tous les poissons marins étudiés à ce jour, les Flétans du Pacifique supportent l'une des communautés les plus riches et les plus abondantes de parasites. Les parasites identifiés sont en grande partie des généralistes trouvés chez une grande variété de poissons marins. Cette situation semble en partie attribuable à l'interaction de la grande taille, du régime alimentaire généraliste, de la mobilité importante et de la longévité particulièrement grande du flétan, en plus de l'absence de spécificité dans le système marin et de la transmission des parasites le long de la chaîne trophique, des poissons proies aux poissons piscivores. La communauté de parasites du flétan est plus semblable à celles des autres poissons plats qu'à celles de ses analogues écologiques, ce qui semble indiquer que la phylogénie joue aussi un rôle déterminant. Les infections ne sont pas reliées au sexe de l'hôte. Les recrues portent peu de parasites, mais le nombre d'espèces et encore plus le nombre d'individus augmentent avec l'âge et la longueur de l'hôte et reflètent le passage d'un régime alimentaire de crustacés à un régime constitué de poissons. Le taux de croissance influence le nombre de parasites chez un poisson donné, probablement en fonction de la quantité de nourriture consommée. Les petits poissons des classes d'âge 5, 6, et 7 ans portent un plus grand nombre d...
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