Several hypotheses concerning the role of fishes in influencing nutrient dynamics in freshwater ecosystems were examined in Lake Memphremagog (Quebec-Vermont). Phosphorus excretion by fishes provides a negligible amount (< 0.33%) in comparison to the quantity taken up by the seston. The phosphorus pools present in the seston and fish community were approximately equal and both were twice the phosphorus content in the zooplankton. Part of this nutrient reservoir is released during the decomposition of fish carcasses. The potential is dependent upon post-spawning mortality rate, the fate of phosphorus in decomposing fish tissue, and the concentrations of allochthonous phosphorus entering the lake. Daily losses of epilimnetic phosphorus from the seston due to fish (up to 40%) and enhancement of nutrient excretion by zooplankton due to size-selective predation are important when open water fish populations are mainly planktivores. When benthic, detrital, or faculative consumers predominate, as in Lake Memphremagog, the effect of fishes on nutrient dynamics through foraging pressure is probably small.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.68508 |
| Date | January 1979 |
| Creators | Nakashima, Brian Shyozo. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 000089146, proquestno: AAINK50521, Theses scanned by UMI/ProQuest. |
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