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Age, Growth, and Population Dynamics of Threadfin Shad, Dorosoma petenense (Günther), in Central Arizona Reservoirs
Author(s) -
Johnson James E.
Publication year - 1970
Publication title -
transactions of the american fisheries society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.696
H-Index - 86
eISSN - 1548-8659
pISSN - 0002-8487
DOI - 10.1577/1548-8659(1970)99<739:agapdo>2.0.co;2
Subject(s) - dorosoma , gizzard shad , fishery , biology , population , zoology , fish <actinopterygii> , demography , sociology
Threadfin shad in the Salt River reservoirs of central Arizona were aged by length‐frequencies and scale annuli. The growing season in established populations was from April through August, surprisingly short for the desert southwest. A re‐establishing population in Saguaro Lake, however, continued to grow throughout the winter of 1967. In order to determine the growth‐limiting variables, comparisons were made between the established populations and the re‐establishing one. Extrinsic factors appeared similar in all of the reservoirs in 1967. The most probable limiting factors were related to plankton abundance and population density of the shad, with growth declining as densities increased when young‐of‐the‐year fish gained the adultˈs limnetic behavior. Year‐class strength had variable effects on the rate of growth, and is in need of further study. The first yearˈs growth was remarkably stable regardless of year‐class strength, however, with minor fluctuations showing some correlation with spring water temperatures. Both sexes demonstrated similar growth rates, with larger female shad resulting from differential mortality rather than growth.