It seems that a lot of fish that live in colder waters grow larger. Is this an actual trend? I don't understand the mechanics behind it.
Cold water and maximum size
- Thread starter Nabbig2
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I don't understand your statement. What fish are you talking agout? Fish are cold-blooded animals. Their metabolism is affected by water temperature. In cold water, a fish's netabolism slows down. With a slower metabolism, a fish would have a slower growth rate.
Yes I agree, while they may live longer they're growth is slower. I mean examples like wels catfish, antarctic tooth fish, but there are large fish in warm waters too. I guess its a rumor or something I've read about somewhere...I can't seem to find any information on the internet.
The largest fish live in the ocean and cold water lakes. For example, the Whale Shark, Basking Shark, Beluga, and Great White. These, I think all range from 3 to 13 tons.
I think it's just that there is no evolutionary advantage to being 3 tons in a large river (e.g., Amazon), or a large lake. You have less oxygen (cold water holds more oxygen) and need more food (with higher temperatures.) In shallow lakes and slow moving shallow rivers, rapidly peaking summer afternoon temperatures drive small fish to the surface. It would be far worse for a 3 ton fish.
In trout, as an example, in one study I saw, their 'optimal' temperature for growth and efficient food usage is 55-65 degrees. At 68 degrees, they hit a limit. At higher temperatures, they don't feed as efficently and they encounter respiratory distress. Since all FW fish are descendants from SW fish, it's plausible that this scenario is the same for all warm water FW fish, although they are adapted to a warmer temp.
In cold water, there is never an issue. If fish get to 3 tons, they are efficiently using food and suffer no distress from lack of oxygen since coldwater environments (oceans and the largest lakes) are extremely stable temperature wise.
Warm water fishes need to be able to adapt to temperatures that might fluctuate from 68 to 90 in their ecosystem, albeit over the course of 24 hours.
I think it's just that there is no evolutionary advantage to being 3 tons in a large river (e.g., Amazon), or a large lake. You have less oxygen (cold water holds more oxygen) and need more food (with higher temperatures.) In shallow lakes and slow moving shallow rivers, rapidly peaking summer afternoon temperatures drive small fish to the surface. It would be far worse for a 3 ton fish.
In trout, as an example, in one study I saw, their 'optimal' temperature for growth and efficient food usage is 55-65 degrees. At 68 degrees, they hit a limit. At higher temperatures, they don't feed as efficently and they encounter respiratory distress. Since all FW fish are descendants from SW fish, it's plausible that this scenario is the same for all warm water FW fish, although they are adapted to a warmer temp.
In cold water, there is never an issue. If fish get to 3 tons, they are efficiently using food and suffer no distress from lack of oxygen since coldwater environments (oceans and the largest lakes) are extremely stable temperature wise.
Warm water fishes need to be able to adapt to temperatures that might fluctuate from 68 to 90 in their ecosystem, albeit over the course of 24 hours.
Yup!
"Bergmann's rule is an ecogeographic principle that states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions. "
http://en.wikipedia.org/wiki/Bergmann's_rule
"Bergmann's rule is an ecogeographic principle that states that within a broadly distributed taxonomic clade, populations and species of larger size are found in colder environments, and species of smaller size are found in warmer regions. "
http://en.wikipedia.org/wiki/Bergmann's_rule
And yet, some of the largest freshwater fish come from warm waters - arapaima, nile perch, giant freshwater stingray, etc.
One species of Beluga sturgeon (Beluga caviar) reached 24 feet, 3,460 lbs, Caspian Sea and Black Sea. Other species of sturgeon reach 18 feet and 4,400 lbs. A ton seems quite easy to reach.
Parts of the Caspian ices over in the winter and the Black Sea gets to around 4 degrees celcius.
Parts of the Caspian ices over in the winter and the Black Sea gets to around 4 degrees celcius.
One thing to think about is the metabolism like joe jaskot said. If you are a 20 ton animal in warm water with a fast metabolism, how much do you have to eat everyday? Its all relavtive. There are many examples of large fish around the world regardless of water temp. Food supply and evolution. Certain fish evolve to do certain things. Think about the differences among american catfish. Bullhead stay small, but they also tend to live in places where it is advantageous to stay smaller and have a smaller diet. Channels get larger, but are also designed to live in larger bodies of water and travel more to find more food. I think to really answer the question of fish growing to certain sizes, you need to look at many more variables than just water temperature. We are not just designed to live in a certain temperature, we are designed for all of our environmental conditions, abiotic and biotic