Sunfish Jones moves slow with a relatively long attack interval, but has a lot of health and range and a 30% chance to slow your cats down for 3 seconds.
Since Sunfish Jones has massive range, the only realistic way to deal with him is to create an opening by defeating the enemies' frontline first. Once exposed, no amount of stealth can protect him from the likes of Jamiera Cat and Crazed M. Titan Cat. An alternative is to use Long Distance/Wave Attackers, but that is rarely an option.
An excellent unit to use against Sunfish Jones is Artist Cat, due to his attack, HP, and Resistance vs. Angels as well as not being knocked back until he is killed. Cats like Awakened Bahamut Cat and Uber Rare nukers/rushers make quick work of Jones, as their massive DPS can turn him into fish meat. Just make sure to clear out any peons with the Cat Cannon or support units. Jones' lowish damage for a backliner allows them to tank a few hits from him, making the window for them to be sent out much bigger, as well as allowing them to land more hits on him.