Ghosts of fisheries-induced depletions: do they haunt us still?

The depletion of several North Atlantic gadoids in the 1980s and 1990s stimulated an unprecedented amount of research on the recovery of marine fish. Some of this work addressed long-standing questions of teleost population dynamics: (i) Does per capita population growth rate (r) always increase as abundance declines? (ii) Do teleost fish possess greater intrinsic recovery abilities (as reflected by rmax) than terrestrial vertebrates? (iii) Does the magnitude of population reduction influence the probability of recovery? (iv) If fish evolve in response to fishing, changing average fitness and thus rmax, are the population-dynamic consequences likely to be negative, positive, or neutral? Challenging some long-standing perceptions and beliefs, recent meta-analyses and empirically based model simulations on marine teleost fish support theoretically based postulates that: (i) rmax does not differ from that of terrestrial mammals; (ii) high fecundity has no influence on recovery potential; (iii) Allee effects can be manifest in some depleted populations; (iv) the greater the magnitude of population reduction, the greater the uncertainty of recovery; and (v) the consequences of fisheries-induced evolution for recovery need not always be negative. An emerging imperative of the work examined here is the need to more fully embrace and comprehensively examine the links that exist between fitness and per capita population growth, given that what happens at the level of the individual will have consequences for how populations respond to natural and anthropogenic environment change.