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We examined the long-term effects on prey fish communities of introducing Northern Pike (Esox lucius), a top predator fish, into small, Boreal Shield lakes lacking natural piscivore populations. During 1987-1994, Northern Pike were introduced into Lakes 110, 221, and 227 in the Experimental Lakes Area in northwestern Ontario, Canada. In Lake 227, prey fish were undetectable three years after the addition of Northern Pike. Although Northern Pike were removed from the lake by 1996, multiple independent visual and trapping surveys have yielded no evidence of any fish in Lake 227 since then. In 1994-1995, 85% of the Northern Pike were removed from Lake 221. In 2012, despite intensive sampling efforts using baited minnow traps, fyke nets, trap netting, gill netting, angling, and visual observation, no forage fish of any species was observed or caught in Lake 110 or 221. In all three lakes where Northern Pike were added, prey fish populations were extirpated or too small to detect. In Lake 221, we estimated the current population of Northern Pike to be 49 ± 37, a 59% decrease since 2000 when prey fish were still present. The mean total length and body condition of Northern Pike in Lake 221 had not changed since the prey community collapsed. Our findings suggest that the introduction of Northern Pike into lakes without natural piscivore populations has long-lasting effects on fish community structure, to the detriment of both Northern Pike and prey fish populations. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Field-Naturalist is the property of Ottawa Field Naturalists' Club and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Field-Naturalist is the property of Ottawa Field Naturalists' Club and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We report on the presence of the parasitic Chestnut Lamprey, Ichthyomyzon casraneus, in Quebec based on three specimens from three localities spanning a distance of over 400 km. [ABSTRACT FROM AUTHOR]

Dietary analyses of juvenile Lake Sturgeon in a resource-poor habitat showed them to be a general predator. Cladocera dominated numerically the prey taxa, but were recorded in only four of the individual sturgeon examined and therefore excluded from stomach content analyses.Mayfly larvae (Ephemeroptera), primarily Hexagenia, were numericallythe next most abundant (34% of all prey items) and the most widely taken (75% of all sturgeon) of the 10 prey categories. Others were Odonata, Annelida Mollusca, Diptera and Trichoptera, each at 5-8% of allprey items. The remaining dietary categories represented < 3% of allprey items. No dietary partitioning was found over the length range of juvenile sturgeon, suggesting that fish throughout this size rangeare almost certainly competing for food. Lake Sturgeon diet did not differ from that for suckers, Lake Whitefish and, to some extent, Burbot, but was different from that for Northern Pike and Walleye. Extremely low invertebrate densities (95 individuals x m z) and occurrenceof all benthic species in the diet of juvenile Lake Sturgeon and several of the other dominant fishes suggests niche breadth to be wide and thus competition for food to be severe. The low food abundance is reflected in the comparatively slow growth rate of sturgeon in our study area. Apparently sturgeon are at survival threshold in this area.Further depletion of their food base likely would have serious repercussions for their growth and survival. [ABSTRACT FROM AUTHOR]