Lecture 23- Feeding, Diet and growth Flashcards
Feeding is a complex set of actions that includes:
- perception/recognition of food
- capturing of food
- processing (digestion, absorption and elimination)
what are the three major categories of herbivorous fish?
- ) phytoplankton eaters- feed on planktonic plants and or filter feed. ex.) paddlefish
- ) algae scrapers- rasp/scrape algae off surfaces ex.) stoneroller
- ) macrophyte eater- feed on large plants ex.) grass carp
whats the issue with being a herbivore?
feed low on the trophic pyramid on abundant and easy to catch prey but it is hard to extract nutrition because of the cell wall so they need to consume large quantities of food to get vital nutrients and protein
what techniques do herbivore fish have?
longer gut to increase abdosorption, a gizzard for grinding food and flat grinidng teeth
detritivores- feeding on partly decomposed material has 2 major benefits:
- easier to digest decomposed cellulose
2. you get access to protein without the energy and risk involved in predator/prey interactions
fish will drift in and out of categories like detiritviore, herbivore and carnivore because…..
they won’t turn down a free lunch.
carnivores feed on living animal tissue and include three major groups?
- zooplankton feeders- feed on planktonic animals either by filtering or picking ex.) whale shark
- carnivorous grazers: feed on sessile or slow moving animals ex.) humphead parrotfish
- ) predatory fish- capture relatively large, mobile prey and often swallow the prey whole as seen in the deep sea angler fish
perhaps the most derived portion of the predators body is their …..
mouth and associated teeth. ex.) alligator gar have long specilaized mouths to grab fish
growth in most fish is ————
indeterminate; meaning they do not stop growing like other vertebrates!
when does growth slow down in fish?
once reproductive maturity is reached. But growth never totally stops as the growth plates never fuse
in many species final size is often dictated by ———-
lifespan
fish growth is facultative; meaning what?
it is resource or situation dependent. growth can slow down and even cease in times of food shortage and then proceed once food is available. temperature and water quality can even dictate this.
how can overfishing affect growth in fish?
overfishing can often produce stunted populations by simply removing large fish from the population. Aside from removing fish from a population fishing pressure can also select for individuals that mature at a faster rate and smaller size; changing the adult size of the population.
how can social factors affect growth in both negative and positive ways?
Positive: social facilitation can increase food consumption and hence growth rate as seen in the farming of ainbow trout. The higher the denisty the higher the overall feeding rate. Basically the lower the density the less they will eat!
negative: in social fish, dominant individuals can often monopolize resources slowing down growth of subordinate fish as seen in many cichlids including in which the dominant male develops specific colouration.
several studies have shown that willingness to take risks to feed is directly related to what?
hunger level!
