DEMOGRAPHY, GROWTH, AND REPRODUCTIVE ALLOCATION IN STREAM-SPAWNING LONGNOSE GAR

The demography of breeding populations of the longnose gar Lepisosteus osseus has heretofore remained unstudied. During the summer of 1992, longnose gars were captured en route to spawning sites in Weaubleau Cr eek, a tributary of Missouri's Harry S. Truman Reservoir. To character ize the spawners, individual age, growth, and morphometric data were o btained. The spawning population consisted of smaller, younger males a nd somewhat fewer older, larger females. As expected, Weaubleau Creek spawners exhibited heightened condition values relative to other longn ose gar populations assessed outside the breeding season. Females disp layed greater backcalculated total lengths at age and higher growth ra tes than males, with these differences being manifested early in life. Examination of individual yearly growth increments suggested that mos t longnose gars in Weaubleau Creek were annual spawners. Females made substantial investments of time and biomass in reproduction, as their gonad weight-body weight relationships, fecundities, and spawning-asso ciated weight and girth losses reflected. Males also invested heavily in reproduction, but may have recouped some biomass through postspawni ng instream foraging. Fish from nearby Truman Dam differed in their si zes, condition, growth, relative gonad sizes, and relative branchioste gal ray sizes, possibly reflecting the impact of earlier maturation as sociated with abundant forage. A novel approach for assessing breeding participation in fishes is also developed.