BIOL 308 Lecture Notes - Lecture 20: Atlantic Cod, Food Chain, Overgrazing
Document Summary
Fishery is also a bio manipulation in a level in food web. Juvenile cod compete with sprat with zooplankton food, adult cod feed on sprat. Shift between high cod and sprat dominance in community. If juveniles can"t get enough zooplankton (low recruitment years), sprat is released from predation. High sustained fishing pressure, juvenile recruitment is no longer associated with hydrological condition. Sprat becomes abundant and continue to consume zooplankton and prevent juvenile mature. Maximum biomass can be harvest from population and it can still come back. Before cod biomass recovery (of the depleted species), the system readjust species composition to it"s original state. Overgrazing changes the soil quality and harder for vegetation to recover. E. g. plants that produce compounds when eaten by herbivores, and attracts predator for the herbivores. Glued spiders (can"t feed), still trophic regulation without consumption. Shift in grasshoppers from grass foraging to forb foraging. Direct interaction between species, e. g. fish and dragonfly larvae.
