The center (black spot) isn't the same in diameter as the 1 and 3 bar. How big? I know in most orino's, the 3 "bar" are more evenly alike.
As such......
View attachment 501576
Mono's tend to have the #2 "bar" not as symmetrical as of the 1 and 3 bars.
As such....
View attachment 501577
This might be redundant, but I'll add it as well.
In a full season, all they caught was these fish.
http://www.scielo.br/img/revistas/ni/v6n2/14t3.gif
Good read.....Read under "Results" .....
http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1679-62252008000200014