Question that nobody has a great answer for: Presence of the Krogan in Andromeda

Stowaways?

SuperIntended of the Nexus (Nakmor Kesh) is a female krogan, so no.

Probably a relatively small contingent of Krogans is the only thing that makes sense. How about: some of the clans simply sold a number of willing mercenaries for a large sum. Or perhaps some of them are just curious.

They wouldn't survive in the long run.

I wouldn't be surprised if the genophage is forgotten.

I think you're woefully underestimating individual motivations on the part of members of those races. Lumping every Krogan or Salarian under a single behavioral umbrella for their species.

Krogan coming to Andromeda for the sake of personal adventure seems perfectly plausible to me. The Andromeda Initiative leaves the Milky Way before the events of ME3, before they could see the cure of the genophage. It was already revealed from Wrex that many Krogan had given up on their species and just live lives of mercenary work or adventure. Sure some choose to stay in TMW for that, but why not go to Andromeda? Who knows what's out there to fight? Maybe they just want to do something no other Krogan has ever done. We know from ME3 that they're not as simplistic as we were initially led to believe. They were once capable of great art and culture. They may have the same itch humans do. To just do something because it's there. That would seem to make sense for Drack. He is supposed to be really old. Maybe he is in Andromeda because he wants one last grand adventure.

Also, for the Salarians, Mordin and his apprentice's storyline proves that not all Salarians are of the same mind on the entire genophage issue. As for the cure... I mean BioWare could just pull some other way of curing the genophage out of their ass. Maybe some new tech in Andromeda makes it easier? Maybe we don't need anyone who originally worked on it to be involved. 

Anyway, point is I don't think there is any ONE reason for why the Krogan will be there. They'll all have their own stories.

Some want adventure.
Some just want the challenge.
Some want to kill strange aliens.
Some hope they'll find the cure for the genophage.
Some just... have no other purpose or direction in life.

Krogan are also extremely aggressive.  Their numbers were dropping more because they kept on fighting (either each other or as mercs) than Tuchanka being a radioactive hellhole

In ME2, Mordin explains his involvement in the genophage modification project.  The krogan were adapting to the genophage, so they needed to modify it to keep it effective.  It's possible, too, that conditions on Tuchanka were such that they would naturally evolve toward lesser birthrates, given the harsh conditions on Tuchanka.  Fewer individuals would give a greater chance that each of them could survive the harsh conditions.

If those two evolutionary trends were combined, the krogan could end up in a state where all (or most) individuals are fertile, but have much fewer offspring.

They wouldn't even need to pull it out of their ass. Tank-breeding Krogan has been a thing since ME1.

The chief engineer of the Nexus is a female Krogan. Enough with the lazy stereotypes, people. The kinds of krogan shepard encountered were mostly of the mercenary thugs hired to kill you variety and not the kinds of poetry reading engineers and mechanics, etc. you'll find aboard the Nexus.

Nobody needs a fresh start more than them. If I were Krogan i'd want to get the hell away from all the sterilising, judgemental, ungrateful hypocrites and vengeful, power-hungry warmongers within my own kind as soon as possible. Krogan settlers looking for a better future should be regarded no differently to any other civilian group aboard the Nexus.

Clans have started uniting by ME2 reducing the infighting, any that travel to Andromeda would have even less reason as territorial disputes should be less of a issue.

Translation: There are no "fertile" females. Every single one of them is infected (except for Eve due to Maelon's experiments). And the Genophage adjusts their birthrates to pre-industrial levels according to Mordin. So overall, they still have high enough birthrates to maintain stable population size, but due to their violence and lack of breeding they are going extinct. Keep in mind that Krogans can live from anywhere of 1000 to 2000 years.

Solution: Stop them from killing each other (and don't raise them on Tuchanka) and enforce a strict breeding program and you can create a stable Krogan population even with the Genophage active. Provided that they brought enough Krogan to build a viable population in the first place.

The interesting thing is that the Salarians are the same as the Krogans. If they were to breed like them, their population growth would be astronomical (one female lays dozens of eggs and any number of those could be fertilized to produce females). So they have rules that prevent all but a fraction of eggs from being fertilized and complicated breeding contracts. As a result, 90% of their species is male. But since the Krogans were uplifted, they were never able to develop the necessary responsibility and maturity to limit their own birth rates. That's why the Salarians did it for them with a little help from the Turians.