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The Rio Grande silvery minnow ( Hybognathus amarus ) was historically an abundant and widespread species in the Rio Grande Basin. Its decline to endangered status had many probable causes and has spanned more than a century. Specimens of H. amarus collected in July 1874 at San Ildefonso, near Santa Fe, New Mexico, allowed a retrospective assessment of the ecology and morphology of the species and the environmental conditions of the Rio Grande in areas foraged by these minnows. Analysis of diatoms from the gut showed that H. amarus foraged mainly in nutrient-enriched areas on mud substrates in 1874 and to lesser extents on periphyton associated with plant, sand, and rock substrates. Gut contents included a considerable amount of fine-grained sediment and a wide variety of organic materials including detritus, pine pollen, cyanobacteria, algae, and diatoms. Scale annuli showed that H. amarus was once a relatively long-lived minnow; all age classes from 1 to 5 were present in 1874. The presence of multiple individuals of several ages suggested that annual survival rates were high historically and that the species may be iteroparous, rather than short-lived and semelparous as widely held. The morphology of H. amarus from a captive stock in 2003 was consistent with the morphology of the 1874 specimens. [ABSTRACT FROM AUTHOR]

The distribution of epipsammic phytoplankton in the coastal shore (Ibeno beach) of Qua Iboe River estuary was studied in the early summer (between October and December) of 1998. The results revealed the presence of Actinoptychus undulatus, Aphanizomenon flos-aquae, Astasia fustis, Chromulina globosa, Cocconeis pediculus, Cymatopleura solea, Cymbella lanceolata, Euglena intermedia, Lyngbya majusculata, Microcystis sp., Nodularia spumigena, Navicular rhynocephala, Oscillatoria nigroviridis, Pinnularia viridis, Rhoicosphenia curvata, Trachelomonas volvocina and Urceolus cyclostomus in the sandy beach. The mean species density of the epipsammic algae encountered in the beach ranged from 16 to 7600 organisms per hectare. The density, however, decreased with increase in sampling distance from the low tide level. Actinoptychus undulatus was the most abundant and widely distributed phytoplankton while Aphanizomenon flos-aquae was the least encountered species. The occurrence of A. flos-aquae and other toxin producing cyanobacterial species of Lyngbya majusculata, Microcystis sp., N. spumigena and O. nigroviridis in the sandy beach are of serious health significance. [ABSTRACT FROM AUTHOR]