Status of the sympatric smelt (Genus osmerus) populations of Lake Utopia, New Brunswick

Lake Utopia, southwestern New Brunswick. contains phenotypically and geneti cally distinct populations of smelt, genus Osmerus. One form, "Dwarf Smelt" , matures at between 100 to 120 mm total length, has 35 to 36 gill rakers, and spawns in small streams in May. The other form, " Normal Smelt", mature s at 150 to 250 mm total length, has 30 to 32 gill rakers and spawns in lar ger, lake-headed streams in early April. The two forms are genetically dist inct as assessed by differences in the frequencies of mitochondrial and nuc lear DNA restriction fragment length polymorphisms. Quantitative genetic di fferences between the forms are suggested by inter-annually stable differen ces in morphology and spawning time and site. The two forms in Lake Utopia: ti) are reproductively isolated in sympatry and behave as distinct species , (ii) appear to have originated independently from sympatric forms in othe r lakes, and (iii) may have resulted from speciation within Lake Utopia. Bo th forms are subject to annual dip-net recreational fisheries. The Normal S melt appears to be in no immediate danger, but Dwarf Smelt may be especiall y vulnerable owing to its apparently lower abundance and limited spawning d istribution in small, easily disturbed streams.