The win has allowed the Sharks to leapfrog the Bulls in the Africa Group and, although they have played an extra game, they are in touching distance of the log-leading Lions and Stormers.
The Sharks started brightly and centres Andre Esterhuizen and Paul Jordaan combined well to earn a penalty which flyhalf Pat Lambie, in his first start this season, pushed wide.
But the Jaguares began dominating possession and they found cracks in a Sharks defence that was not as well organised as it usually is. And the visitors were made to pay in the eighth minute as Joaquin Tuculet slipped through some poor tackles and then passed inside for lock Tomas Lavanini to gallop over for the opening try.
Flyhalf Nicolas Sanchez converted and the Jaguares led 7-0, before Lambie made no mistake with his second kick at goal, a penalty awarded at a scrum for illegal binding, and cut the lead to 7-3 in the 11th minute.
The Sharks were struggling to create try-scoring chances, but the ill-discipline of the passionate Argentinians meant that they were able to keep the scoreboard ticking over via penalties, with Lambie kicking his second in the 16th minute to cut the lead to just one point.
That advantage was stretched again by the Jaguares in the 18th minute, but it was through a controversial try that they were awarded. Scrumhalf Martin Landajo was swung towards the Sharks tryline by lock Lubabalo Mtyanda, but replays showed that he had dotted the ball down short of the line. Sharks fullback Willie le Roux then arrived and dragged the ball out of his grasp, touching it down in-goal in the process.
Referee Marius van der Westhuizen ruled, however, that the try was good, contradicting the views of his TMO.
Sanchez converted and the match was rapidly turning sour for the Sharks as they were 14-6 down, plus they lost flank Jean Deysel to what appeared to be a serious neck injury after he had landed poorly in a collision.
They had earlier lost scrumhalf Michael Claassens shortly before kick-off, meaning Stefan Ungerer was promoted to the starting line-up, but they were without a reserve scrumhalf, with Joe Pietersen forced to fill in in the closing minutes.
An intimidating crowd and the fiery, spoiling efforts of the Jaguares added to the challenges, with the weak officiating also corrupting the contest.
The Sharks did manage to eat away at the Jaguares’ lead though with a pair of Lambie penalties in the 27th and 30th minutes (12-14) and the spoiling efforts at the breakdown by flank Pablo Matera saw him yellow-carded four minutes later.
He had just gone off the field when eighthman Daniel du Preez shrugged off the desperate defensive efforts of the home side to power over the line, Lambie converting for a 19-14 lead.
The Jaguares managed to launch one more attack just before the teams went off for halftime, and the Sharks paid the fee for being trapped offsides as Sanchez kicked a penalty to cut the gap to 17-19.
