Rainbow Smelt - Ecology

Ecology

In 1885 Stedman and Argyle found that the rainbow smelt consumed bloaters (Coregonus hoyi) and alewives (Alosa pseudoharengus). However, they also stated that this predator had not impacted the population of bloaters but that impact could be a possibility. A 2003 study by Horppila et al. shows that smelt densities can exceed 40,000 individuals per hectare and may create a large predation pressure on the lake. Horppila et al. also states that a single smelt can consume between .12 grams and .14 grams. Another study showed that in Lake Ontario the primary food sources for rainbow smelt were slimy sculpins (Cottus cognatus) and opossum shrimp (Mysis relicta), but nothing was said on whether this predation had significant impact on the populations. In 1973 Havey reported that there was increased growth in landlocked Atlantic salmon populations after the introduction of the smelt. It was also shown by Brandt and Madon in 1986 that adult lake trout (Salvalinus namaycush) could be a keystone predator species for the smelt. Hrabik et al. (1998) found evidence of competition for food between introduced rainbow smelt and native yellow perch (Perca flavescens) in Wisconsin lake habitats, and smelt may be partially responsible for the decline of Great Lakes whitefish (Coregonus spp.). The U.S. EPA stated in 2008 that they believe the smelt contributed to the extinction of the blue pike (Stizostedion vitreum glaucum) by outcompeting for food. Acidity may alter smelt distributions because they were not found in small lakes with pH less than 6.0 in several surveys. Because of snowmelt, rainbow smelt eggs might be exposed to lethal pH decreases in poorly buffered lakes.