Flowering in British Lemna: A rare, cyclic or simply overlooked phenomenon?

It is largely presumed that reproduction in British Lemna, as in other British Lemnaceae, is almost entirely asexual, with new daughter fronds being produced from the side pouches of older mother fronds. Sexual reproduction is considered to be a rather rare event or even absent and because of this rarity the sexual features of Lemna, such as anthers and fruit, are often considered to be of little taxonomic value. It was with some surprise, therefore, that widespread flowering was observed in all British Lemna during the summer of 1995. Initial observations in Shropshire during June recorded flowers in minor and trisulca, with fruit production in trisulca. L.gibba, minor and minuta were noted as being in flower on several occasions in Kent, during July and August, probably fruit production occurring in both species. To what extent these events are truly representative of the sexual reproduction rate of British Lemna on a year-to-year basis, or simply reflect the unusually high summer temperatures of 1995, is unclear.

Evaluating methods for estimating rare events with zero-heavy data: a simulation model estimating sea turtle bycatch in the pelagic longline fishery

Estimating rare events from zero-heavy data (data with many zero values) is a common challenge in fisheries science and ecology. For example, loggerhead sea turtles (Caretta caretta) and leatherback sea turtles (Dermochelys coriacea) account for less than 1% of total catch in the U.S. Atlantic pelagic longline fishery. Nevertheless, the Southeast Fisheries Science Center (SEFSC) of the National Marine Fisheries Service (NMFS) is charged with assessing the effect of this fishery on these federally protected species. Annual estimates of loggerhead and leatherback bycatch in a fishery can affect fishery management and species conservation decisions. However, current estimates have wide confidence intervals, and their accuracy is unknown. We evaluate 3 estimation methods, each at 2 spatiotemporal scales, in simulations of 5 spatial scenarios representing incidental capture of sea turtles by the U.S. Atlantic pelagic longline fishery. The delta-log normal method of estimating bycatch for calendar quarter and fishing area strata was the least biased estimation method in the spatial scenarios believed to be most realistic. This result supports the current estimation procedure used by the SEFSC.