Dividing the stripes into groups of $8$, we could have $10$ groups of $8$ with $6$ left over.

If we add a stripe to $6$ groups of $8$ we will haveĀ $6$ males.

So there are $6$ males and $4$ females.

Therefore the ratio of male to female fish is $3:2$.

Alternatively, if there are f females and m males then $86=8f+9m=8(f+m)+m$.

Now $86=8\times 10+6=8 \times 9+14...$

Only the first of these is feasible so m=6 and f=4.

Therefore the ratio of male to female fish is $3:2$.

*This problem is taken from the UKMT Mathematical Challenges.*