Stock depletion and stock collapse are caused by recruitment overfishing. This means that the adult population was fished so heavily that the number and size of the adult population (spawning biomass) was reduced to the point that it did not have the reproductive capacity to replenish itself. Although recruitment to the American lobster resource appeared to be adequate during the 1980s and 1990s, scientists are concerned that there is a high risk of recruitment overfishing because the calculated egg production is low as the result of fishing out most of the large lobsters in most areas. When people think of overfishing, they usually mean recruitment overfishing, rather than growth overfishing.