The act of requiring the life of other species in this matter raises several concerns. First, there's scientific evidence stating that a human being can take all necessary nutrients for living in perfect conditions without eating meat or fish. Even, thousands and thousands cases of whom doesn't demand a single subproduct coming from other species, in the so-called veganism.
It's adequate to discuss about this topic because each individual should ask him/herself until what degree doing this could be considered a non cruel activity. Today, there's not a lack of information or possibilities to leave this habituation that comes from ancient times, where the problem was to survive. Some places still think in those terms, but what about you?
Some species doesn't have a developed brain to think but that's not the case of mammals. Precisely several mammals are being threatened for aspects that are related to meat production. They can be called by the name, have mental processes, feel pain and know what a last moment is like us. The aspect has a critical importance, but it seems that the current age doesn't consider it as it should then putting the state of evolution in this aspect like thousands years before.
For sure, who demands meat must know that the act doesn't come free of implications at all. Business, commodity, habituation for the taste, lack of interest for changing as an effort are some keywords reminding some about ethical education in terms of respect and welfare.
Any business could modify its main production objective while the population could migrate to other species without evolved nervous systems, keeping the ethics in a rational field to guarantee that these actions don't come with a personal bill from somewhere. Because at a first glance, there's no license for using others' life for a single purpose, and words or mysticism aside.
Any solution for it even extreme ones like veganism are welcome although the population in general may focus to eggs, milk and subproducts, some molluscs, krill and other rudimentary lifeforms plus vegetables for ensuring a good balance in health for non experts without ethical / cruel implications. No one should complain if other is eating a mussel, produced without harming the ecosystem in any way. And the same for similar “meat”. A simple technique.