Re: Approx. how many fish (become adult) from the millions of eggs they lay?

Dear Heather,

I was really sorry for the delay of my answer. You know I have to take 
some holidays and so...
But let's answer your question: yes, it could be correct that just a 
handful of eggs become adults from the million a couple of fish can lay.
However, it depends on a really big number of environmental 
factors...and luck (a not-too-well-considered factor for development and 
evolution!).

A handful of baby fish that become adults are far more 
than the number of fish necessary - for each genration - to replace the 
old parents to mantain the fish population at the same level.
Ok? In other words, with a handful of baby fishes that became adult for 
every two parents, the fish population will grow. It means the parents did 
a good job and all are happy. 

About numbers: in laboratory conditions,  1-5% of baby fishes of 
particular species could develop to adult. Much more than the result you 
considered (30 on 1 million is about the 0.00003%!). 
But these are REALLY particular conditions...(optimal temperature of 
water, age of the fish, no predators, optimal breeding, etc...)!!

Bye
Luca