The magnitude of the invasive plant species problem necessitates prioritization of species for control, regulatory, and public-education programs. Many such priority lists exist but few have been developed according to specified procedures and criteria. We reviewed approaches to assessing the status of nonnative plant species currently occurring in natural areas (status assessments). We identify four generalized types of status assessments, which reflect a gradation from those that simply adopt existing lists from elsewhere (type 1), to those with relatively easy and rapid development and implementation (type 2), to those that are more time-consuming and costly but may be more robust in the face of challenges (types 3 and 4). These latter assessments explicitly have greater transparency, objectivity, and consistency than the other types. We use a matrix of assessment characteristics to distinguish the types of 17 example status assessments. We also review the factors related to assessment intent, scope, structure, content, and implementation that must be considered during the development of new status assessments so that the resulting tool and its products are appropriate for the user's purposes. These analyses should facilitate evaluation of different assessment methods and provide a basis for development of improved assessments. Identification of the relatively low percentage of nonnative plant species that are inflicting ecological and economic harm using well-understood and accepted assessment methods should facilitate a more comprehensive, collective approach to implementation of effective management efforts.

This research investigates a status assessment approach for remnant lake salmonin populations, using the lake charr (Salvelinus namaycush Walbaum) of Crean Lake (105 km2) as an example. A mark-recapture program was implemented employing small-mesh gill nets to ensnare charr by the teeth at spawning. Prior to sampling, potential spawning sites were designated primary or secondary based on habitat. Most charr were caught on three primary reefs, with some spawners moving between reefs. The spawning period peaked at day 2, enhancing spawning synchrony, and lasted up to 10 days. Results produced very low sampling mortality (5.7%), consistent estimates of the number of spawning charr ( $\sim $ 60 y−1) and a very low (<2000) estimate of the total number of mature charr in Crean Lake. The approach offers an effective means of assessing remnant salmonins with minimal impact on their populations.