Rather than resulting in a plain predator pit from direct consumption of sea lions, the age-structured sigmoid response yields a predation-driven productivity pit mediated by female recruitment from which the population cannot escape even at a theoretical natality of 1.0 without reduced predation pressure.
http://plosone.org/article/info:doi/10.1371/journal.pone.0030173#article1.body1.sec3.sec5.p1

Horning and Mellish attempt to make a distinction that Steller sea lions are in a “predation-driven productivity pit”, as opposed to a “plain predator pit from direct consumption of sea lions”. Such a distinction is unnecessary. Notwithstanding the fact that the data in Horning and Mellish don’t establish the predation rate on adult females for comparison, predation on most mammals is usually higher on vulnerable juveniles, which inevitably affects recruitment. The first mention of the term ”predator pit” that I can find (Messier F and Crete M, 1985, Moose-wolf dynamics and the natural regulation of moose populations. Oecologia 65:603-502) is in reference to wolf-moose systems to describe the possibility for a stable, low density, “predator-pit” equilibrium in contrast to a high-density equilibrium driven by forage limitation for moose. The high vulnerability of juvenile moose to predation was a well-known aspect of that system and in that context and, hence, inherent in the concept of a “predator pit” for large mammals.