Some aspects of the biology of landlocked smelt, Osmerus Mordax (Mitchill) 1815, in selected Avalon Peninsula lakes

Bruce, W.J. (William Joseph) (1975) Some aspects of the biology of landlocked smelt, Osmerus Mordax (Mitchill) 1815, in selected Avalon Peninsula lakes. Masters thesis, Memorial University of Newfoundland.

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Abstract

Smelt populations in four lakes on the Avalon Peninsula, Newfoundland, were investigated in this study. Sympatric populations of large (giant) and small (dwarf) smelt live in one of these lakes, Black River Pond. The remaining three lakes contain only the small race smelt. -- Small race smelt have a very short life span, usually two years, while the large race may attain an age of six years. Small race smelt seldom exceed a length of 130 mm and many large race smelt exceed 250 mm. Small race smelt rarely attain a weight of 10 g while it is not unusual for giant smelt to weigh more than 10 times this amount. -- Four of the six measured morphological characteristics showed a significant difference between the two sympatric races. -- Both races are spring spawners, with the actual time of spawning varying from one locality to the next, and from year to year. They spawn both in tributaries and around the shores of the lake. Small race smelt reach sexual maturity at the end of their second growing season and the large race smelt a year later. The sympatric populations at Black River Pond are reproductively isolated temporally and perhaps spatially. The large race spawns first, starting almost two weeks prior to the beginning of spawning in the small race. -- Food analysis studies showed that small race smelt are principally benthic feeders relying mainly on aquatic insect larvae and nymphs and to a lesser degree on amphipods. The relative importance of any particular aquatic invertebrate group showed regional variability. The large race at Black River Pond are very cannibalistic, feeding upon younger small race smelt. They forage on immature stages of aquatic insects to a lesser-degree. -- Combining information on rate of growth, life span, age and size at sexual maturity, time of spawning, feeding habits, and morphological differences, it appears evident that the two sympatric forms at Black River Pond are discrete populations, and that at least a partial barrier to gene flow exists between them.

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