posted by Jack .
Why is it beneficial that many predatory fish have larval and juvenile stages that feed at a low trophic level, while the adults feed at a tertiary or quaternary trophic level?
My answer was that the larval and juvenile stages would get more energy but my teacher said that this was wrong!!
It would have been useful for your teacher to have given an example fish species with the question. Sharks, for example, have few young and which eat small fish, crabs etc (depends on the species). The diet is therefore protein rich and enables fast growth. There is a lot of the food about so energy is not wasted looking for the food. Feeding at a higher trophic level usually means that there are less meals about and the individual needs to be larger to tackle it.
Does this help?
By having them feed at different trophic levels they are not competing for the same foods. The foods the adults eat are not the foods the juvenile eats so they are not intruding and competing against each other. That separation in trophic levels assists in the survival of the juveniles to the adult stage.