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The trophic structure of aquatic ecosystems can potentially be controlled by two sets of factors: resource availability and predation. The importance of nutrients was demonstrated by two observations: first, that plankton abundance among lakes is strongly correlated with resource levels, and second, that experimental manipulations of resources lead to changes in plankton abundance. In contrast, while experimental manipulations have shown that predators can affect prey abundance, it is less clear whether variation in plankton abundance among lakes is related to variation in predators. To test this, we sampled 29 lakes in Quebec and Ontario. We found strong relationships between plankton biomass and resource levels. Effects of predation were evident between zooplankton and phytoplankton. However, neither chlorophyll nor zooplankton biomass was related to piscivorous fish presence, after controlling for phosphorus. Other published studies that have reported correlations between plankton abundance and characteristics of the fish community failed to control for trophic status. Thus, there appears to be no published correlative evidence that variance in plankton abundance among lakes is related to variation in fish assemblages, even though the link is mechanistically plausible.

This article presents the phylogenetic conclusions of an osteological study of species belonging to the subfamilies (Soleinae and Achirinae) of the dextral flatfish family Soleidae (Pieuronectiformes; Soleoidei). A cladistic analysis of the data revealed that the subfamilies, but not the family, are monophyletic. The Soleinae were found to be more closely related to the other soleoid family, the Cynoglossidae, than to the Achirinae. If we accept the principle that only monophyletic groups are to be admitted into Linnean classification, it is suggested that the two subfamilies be raised to the family level. The anatomical data led to the proposal (with caution) that the sister group of the achirid–soleid–cynoglossid lineage is the pleuronectid subfamily Samarinae. Consequently, it is suggested that the suborder Soleoidei be eliminated by incorporating its three families into the Pleuronectoidei which becomes monophyletic. Also, it is proposed that the Pleuronectid subfamilies (Pleuronectinae, Poecilopsettinae, Paralichthodinae, Rhombosoleinae, Samarinae) be raised to the family level. However, since the monophyletic status of these taxa is dubious (except for the Samarinae) any hypothesis including them must await a proper cladistic analysis of their intra- and inter-relationships.

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A reported case of stunting was examined in a population of yellow perch, Perca flavescens, from a monospecific lake (Lac du Printemps) in Gatineau Park, Quebec. In total, 516 specimens were sampled in early October 1992. Females grew significantly faster than males, and also attained a greater length and age (241 mm, 10 years) than males (172 mm, 7 years). Compared with other populations in Quebec, the growth rate of this population was well below average; age-classes converged towards a similar size at earlier ages; the maximum age attained by males was less than average for the species, and males and females reached sexual maturity at an earlier age (0+ and 1+, respectively). These results are consistent with those found in stunted populations. Males aged 0+ had an average gonadosomatic index of 9.3%, which is one of the highest ever reported for this species. The index decreased gradually with age. Fish were absent from the stomach contents of 300 specimens examined. Owing to their large size, young-of-the-year yellow perch were not preyed upon by older perch at that time of year. The lack of availability of fish prey may contribute to the stunted state of this population. Other contributing factors are intraspecific competition and the absence of top predators in the population. A comparison of the population in 1981 and 1992 indicated that it has been stunted for at least a decade.

This article contains the first detailed osteological study of several flatfish species belonging to the three currently recognized genera of tongue soles (Cynoglossidae). The resulting information was used to reassess, following the cladistics methodology, the monophyletic status of the family and to put forward a hypothesis of generic relationships. The polarity of the character states was determined by outgroup comparison using the Soleidae as the sister group of the Cynoglossidae and the Achiridae as the sister group of the soleid–cynoglossid lineage. An analysis of numerous characters corroborated the monophyletism of the Cynoglossidae. It was also found that the genus Symphurus (Symphurinae) is monophyletic and is the sister group of the monophyletic Cynoglossus–Parapaglusia (Cynoglossinae) lineage. Parapaglusia was shown to be monophyletic, but no evidence was found to corroborate a similar status for Cynoglossus. An examination of the osteology of more species belonging to the speciose genera Symphurus and Cynoglossus is needed to further test this hypothesis of relationships.