Morphological and gonadal assessments from historical collections of Bluenose Shiners Pteronotropis welaka

Abstract

Management and conservation have begun to rely on supplemental information to make appropriate decisions. In organisms with little available information, preserved specimens may be particularly important for researchers to continue their role in the management process. Bluenose Shiners are a minnow species that can benefit from such analyses as they are of conservation concern across their native range in the Southeastern United States. To supplement conservation, the objectives were to: (a) quantify sexual dimorphism through a comprehensive morphological analysis, (b) approximate peak spawning condition of males and females through GSI measurements over the anticipated spawning season, and (c) utilize female gonad histology to refine conclusions regarding spawning condition from GSI. Historical collections of Bluenose Shiners obtained from the Tulane University Biodiversity Research Institute were used to conduct morphological and gonadal analyses. While males expressed all morphometrics to a greater degree, male dorsal and anal fin length appears to be the most distinguished characteristic beginning at a total length of approximately 45 mm. GSI displayed peaks in the samples from April 21, 1957 and June 1, 1968; female GSI from Black Creek, MS in April, May, and June of 1986 suggested a peak in late May. Gonad histology showed a progression towards final oocyte maturation through May to early June, via relative prevalence of stage IV and absence of stage I oocytes. This information can be used to supplement future morphometric analyses and reproductive studies performed on Bluenose Shiners or other fish species.