Do Fish Populations Recover From Over-Exploitation?
Although there is a popular perception that marine fish populations are generally highly resilient and able to recover substantially from severe depletions, there is in fact "very little evidence for rapid recovery from prolonged declines." This according to a paper in the journal Nature.
The paper analyzes 90 populations which had experienced declines of 13 to 99% over a 15-year period. An additional 15 years after the end of that period, 12% of the marine populations for which data was available had exhibited full recovery, whereas 40% had experienced no recovery at all. All of the species which had fully recovered were clupeids: herring, sprat, and their relatives; the species which showed no recovery at all after 15 years were primarily gadids ? for example, cod and haddock.
The data suggest, notes the paper's author, "that, after prolonged decline, clupeids are more likely to recover to previously experienced population sizes and are more resilient than other marine fishes." Such an increased rate of recovery may, he suggests, be attributable to the younger age at which clupeids mature relative to other fish, and the "higher intrinsic rate of increase that earlier maturity generally effects." In addition, "being at a lower trophic level than other families considered here, clupeids may be better able to 'track' temporal and spatial fluctuations in primary and secondary productivity."
Regardless of the relative robustness of clupeids and other fish species, the fundamental point remains, however: "5-15 years after 15-year declines of 50 and 80% … gadid and other non-clupeid populations, on average, have increased marginally or not at all. Thus, although the effects of overfishing may indeed be generally reversible, the time required for population recovery in many marine fishes appears to be considerably longer than previously believed."
Source: J.A. Hutchings. 2000. Collapse and recovery of marine fishes. Nature 406: 882-885.
Contact: Jeffrey A. Hutchings, Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4JI, Canada. E-mail: firstname.lastname@example.org.