My definition of sustainability would be to have our wildlife be able to replace the populations that were being taken out, whether dying from natural things, from prey, or from being fished out of the wild. I believe that to sustain is to have the populations at a healthy capacity such that the birth rate is equal to the death rate. As of Solow’s definition of sustainability I agree with it. I agree that we need to be aware of how much we take from the environment and be sure that it is spread overtime because if we do not do this and constantly take then at a point there will be nothing else to take because everything is gone because the needs of humans were all met before the environments and this is how species become endangered and later become extinct. I do not think that sustainability depends on substitutes because we should not be dependent on a back up plan for the future right away, I believe that we should be dependent on humans putting back what we take from the environment or even taking the time away to let the environment or the species be able to put it back into ecosystems so that they are not completely destroyed. I do think that aquaculture can sustain wild fisheries but I do not think that this is the next best step or what we should be doing. I think that the idea of aquaculture can be helpful to an extent, to the extent of being helpful when there is not much other salmon for people to eat, or even helpful for other countries to learn this technique and improve their food resources or their availability of food.
Your definition of sustainability is equal to mine, I also believe that aquaculture can be used to supply food in a global need. But it is more important to sustain wild populations than to replace them all with farmed fish.
I agree that substitutes are unreliable and we have no guarantee of finding them in the future. Like in the case of aquaculture. It tends to be a poor substitute for wild-caught salmon. If we continue to use up resources I think we’ll have to turn towards using materials that are poor substitutes for what we had in the past.