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Vital Statistics of the Pacific Sardine (Sardinops Caerulea) and the Population Consequences
Author(s) -
Murphy Garth I.
Publication year - 1967
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1933730
Subject(s) - sardine , anchovy , fecundity , population , fishing , biology , ecology , fishery , population model , density dependence , reproduction , logistic function , statistics , demography , mathematics , fish <actinopterygii> , sociology
The population parameters of the Pacific sardine are estimated from growth, mortality, and fecundity data, together with the increase per generation R o estimated by fitting the Ricker equation. R o is 4.01, r m is .388 and generation, T, is 401 yr. The estimation of these parameters for a large natural population (equilibrium level about 2.4 x 10 6 tons) was possible because of a well—documented fisher. The environmentally induced, density independent variation in reproductive success is in the order of eight times. In theory, an organism can better tolerate widely variable reproductive success if there is repeated reproduction. Exploitation of the Pacific sardine reduced the number of reproductions, setting the stage for the population to collapse following two consecutive, unsuccessful spawnings. The Ricker function generates a population growth curve not unlike the logistic at low values of r m . Even if fishing were stopped, the recovery of the population would require more than a decade. It will likely be even slower, as a species of with similar ecological requirements (the northern anchovy) has increased by a factor of five following the decline of the sardine, undoubtedly preempting resources once available to the sardine.