the trafficers (in the cases of the boats) operate out of the departing coasts (probably Tunesia in this case, but generaly northern african States/Turkey). "They" (Frontex) don't have juristiction there.

"They" (The EU as a whole, more specifically the Comission I would guess) have struck deals and basically pay local authorities to somewhat keep migration in check thought. Particularly famous cases of that are Turkey and Tunesia. This method has (rightfully) been wideley criticised as booth are autocratic countries with massive human rights violations and paying them legitimizes them, gives them leverage over the EU and props up undemocratic regimes and their security aperatus in particular (as the money is often intended for border-Patrol equipment and such).

A better solution would be to enable safe and legal ways for imimigration and more immediatly to strengthen sea-rescue instead of weakening it.