Spike Fish is one of the three skins released in the second part of the MadJawZ's Shop offer. It could be purchased as part of an item deal in mid June 2018.
Spike Fish could be purchased for $14.99 in the limited time "Best Deal!" which included 25000 coins, 1200 DNA and the Cool Lion skin. This skin was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.
Note: The second part of the MadJawZ's Shop offer was released again for a limited time in early March 2020. The price and included items for Spike Fish remained the same.