Are Catholic Bishops the successors of the Apostles alone or the Elders too? In researching my answer for this question I started to think about the doctrine that the Bishops are the successors of the Apostles as being a bit unfair to the other folks. For instance, if St. James who wrote the epistle wasn't the brother of John or Jude, but actually a third James or a fourth James who was the Bishop of Jerusalem, would his Episcopacy necessarily have been conferred on him by the Apostles or just by virtue of who he was. Or were the elders the first successors of the 12 apostles regardless of their functions as presbyters?
The answer you seek is here: Bishops Are Successors of the Apostles | General Audience of Pope St. John Paul II [the Great], 8 July 1992.




"Presbyters" (= elders cf. Priest | New Advent), first subordinate rank of the hierarchy, were among the "various helpers" who assisted the Apostles in their ministry.
From the article, that the Bishops are the successors to the Apostles, is in this sentence, quoting the Second Vatican Council:



  The Council says: "Thus, as St. Irenaeus testifies, through those who
  were appointed bishops by the apostles, and through their successors
  down in our own time, the apostolic tradition is manifested and
  preserved 1 " (LG 20).
  
  1. St. Irenaeus, Adv. Haer., III, 3, 1; cf. Tertullian, De
  Praescr., 20, 4-8: PL 2, 32; CC 1, 202