Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Fish Help

  1. Dec 31, 2005 #1
    Does anyone know what fish eat if they don't have teeth? I drew a fish (As was instructed.) and gave it different adaptations. For example, my fish is dark on the top and light on the bottom- countershading. It's shaped like a torpedo and has small scales which makes it a fast swimmer. However, I don't know if it can lack teeth if it lives in a lake as the list I found online of fish adaptations has such fish eating plankton. Can plankton be found in large lakes and, if so, could a small toothless fish eat them?:confused:

    Oh, and another thing...if my fish is a fast swimmer, what would make more sense? It having large fins or small fins?
    Last edited: Dec 31, 2005
  2. jcsd
  3. Jan 1, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper

    These are my guesses, fish are not my specialty.

    Small life forms are found in freshwater, although I am not sure whether they are called plankton technically. And I don't see why small fish cannot eat those. At higher speeds a fish would need larger fins for stability. See Wikipedia entry "Fin"
    Last edited: Jan 1, 2006
  4. Jan 3, 2006 #3


    User Avatar
    Science Advisor

    Hey Angleshare,
    There are numerous fish that live on freshwater zooplankton. They typically use specialized adaptations on their gills called gill rakers that can strain out the plankton from the water as they swim through it. Some examples I can think of are from the Clupeidae family: Alewife, Alosa pseudoharengus, American Shad, Alosa sapidissima and Atlantic menhaden, Brevoortia tyrannus. These fish may have some teeth (I think they do because some eat small fish and invertebrates as well), but they are not large teeth like one sees on sharks or walleye or barracuda. Which bring me to the next part, speed and fins.
    It is somewhat dependent on what "type" of speed you are talking about. Is it a fast ambush predator that only gives bursts of speed, like the barracuda, or does it cruise open waters for longer periods of time chasing prey, like marlin or sailfish? You should be able to find pictures of these fish easily on the web and you can see that these different fish have different fin shapes but roughly similar body shapes. The larger fins of the marlins and sailfins are used for fast, open water maneuvering and catching prey. The barracuda, while it caudal fin is fairly large, is mostly a 'slam in fast and bite" prey hunter, not a chaser and does not need "large" fins for maneuvering.
  5. Jan 4, 2006 #4


    User Avatar
    Gold Member

    Last edited by a moderator: Apr 21, 2017
  6. Jan 4, 2006 #5


    User Avatar
    Gold Member

    Most fish don't have teeth (obviously). The ones that do I suspect tend to eat prey that are large in comparison to their own size, so that they can tear the food into bite-sized chunks. Most fish eat food that can be taken into the mouth whole, thus no need for teeth. Small crustaceans, algae, worms, other smaller fish etc.
  7. Jan 4, 2006 #6


    User Avatar
    Science Advisor

    I think you'd be surprised how many fish do have teeth, most telosts, or bony fish have some form of tooth (see cichlid article below). Part of that lies in what one views as teeth. I think we can all agree that sharks, piranha, barracuda, etc all have teeth, but there are many fish that have very small teeth, or teeth that are localized to regions other than the ridges of the jaw.
    One of the best examples of fish teeth and their variation amoung species and across evolution is found in the cichlid fishes of Africa. Check http://www.biology.gatech.edu/professors/labsites/streelman%20web%20pg/toothed.pdf" [Broken] which by outward apprearance have a very fleshy soft mouth only to find very obvious pharyngeal teeth located further down the oral cavity/esophagous, cichlids share the trait of pharyngeal teeth as well.
    Last edited by a moderator: May 2, 2017
  8. Jan 6, 2006 #7
    Thanks for the help, everyone.:biggrin:

    However, I'm still a bit stuck...I did what I was told...

    Draw, build, create a PowerPoint, or other representation to show your new fish species. Include the information you researched above on Fishbase.

    Include the following information about your fish:

    New name of your fish. (be creative!)
    In what habitat your fish would live?
    Describe at least two adaptations your fish has to live in the habitat.
    Why would your fish have adapted? (competition for food, habitat, or other)

    ...but my teacher's comment was as follows...

    "Why did your fish develop it's adaptations (10 pts)?
    What is the name of the fish that yours evolved from (3 pts)"

    My fish developed its adaptations because...

    "The Mano Estratta, being a small, plankton eating fish in a large lake, needs its torpedo shaped body and small scales for quick getaways as both make it a fast swimmer. Its coloring, being dark on top and light on the bottom, helps to hide it from, not only predators above it but ones beneath it as well. It has a small mouth and no teeth so it eats mainly plankton.

    It requires such adaptations as it, unlike larger fish around it, is harmless."

    Now he's adding junk.:grumpy: I drew the damn fish, named it, researched fish adaptations on other sites besides the one he provided us with, and threw it all together in PowerPoint and yet he only gave me 27 points out of 40...I need those points.:frown:

    His second question is a bit harder for me to answer...I have no clue. Could someone help? http://www.fishbase.org/search.cfm" [Broken] is the site he gave us to use. I wouldn't know how to go about answering it...
    Last edited by a moderator: May 2, 2017
  9. Jan 9, 2006 #8


    User Avatar
    Science Advisor

    So he took off 13 pts because you didn't address the issues of why the fish developed the adaptations it did and what fish it evolved from, correct? Is the next part of your post your response to this or was that included in your previously submitted project? Regardless, it needs a little work. The last sentence bothers me. Typically animals don't aquire characteristics because they don't do something (in this case it doesn't prey on other fish), they generally acquire characteristics or traits or adaptations to fulfill a need or fill a niche. Thus, if a species is introduced into a new habitat it will adapt to best fit into that environment. Perhaps a hypothetical example, say a very large lake exists with a normal complement of fish, bottom feeders, large predators, etc., but nothing exists that activiely cruises open water eating zooplankton. A nearby stream overflows and some minnows get dumped in, they normally eat small invertebrates and some larger plankton, but there are already fish in the lake that eat the invertebrates so the minnows eventually evolve traits like you describe to better pursue zooplankton as a food source and at the same time avoid predation by the resident predators. They don't live on the bottom or near structure, so they have to "outswim" their predators, perhaps they also start schooling in large numbers another good way to aviod predation. You need to think about what the adaptations do for the fish, thus the last sentence in the first part reads better as "They eat plankton, thus have small teeth..... (plus many plankton eaters have relativley large mouths to collect more food, think about whale sharks or other filter feeders). As far as the ancestor, you need to find a fish that is similar to your fish, but not identical. Use the fish base to search for fish that share some things in common with your like eating plankton or open water, fast swimmers. I think this will help.
  10. Jan 11, 2006 #9
    Aye, it was the answer I provided in my assignment. I knew it wasn't terribly in depth but since his question had the examples "competition for food, habitat, or other" I thought that's what he wanted. Alright, I can do the Fishbase thing, I just gotta look around...but the other part might need a bit of work, as you said. Let me see...I should start off by changing my statement a bit...

    "The Mano Estratta, being a small, plankton eating fish in a large lake, needs its torpedo shaped body and small scales for quick getaways as both make it a fast swimmer. Its coloring, being dark on top and light on the bottom, helps to hide it from, not only predators above it but ones beneath it as well. It eats mainly plankton thus it having a small mouth and no teeth.

    It acquired such adaptations because..."

    Now, in your scenario, my fish would be the one that was newly introduced somehow, right? That means my fish would have had to have evolved from a slower fish thus it adapting by becoming faster? In that case...oh no, I can't get that Fish Base link to work. o_O

    ...Ah, nevermind, it works now. ^_^ Eh, I was going to post the fish I found but it looks like it may take a while...anyways, would it work if I were to say my fish evolved from [insert name here] because it was...does it make sense to say that it was put in the lake for fishing? I think I've heard of people doing that...introducing fish into nearby lakes and such for fishing. Or is that wrong?:redface:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook