Recently, many reports on the MMP-9 function in fishes has also been investigated, and the overexpression of MMP-9 is determined to protect fishes, such as yellow catfish (Pelteobagrus fulvidraco) [4], zebrafish (Danio rerio) [11,12], and grass carp (Ctenopharyngodon idella) [13] from the infection of pathogens. This evidence concerns the gene MMP9 and infection.