Use of recent and historical records to estimate status and trends of a rare and imperiled stream fish, Percina jenkinsi (Percidae)

Abstract

Rarely encountered animals may be present but undetected, potentially leading to incorrect assumptions about the persistence of a local population or the conservation priority of a particular area. The federally endangered and narrowly endemic Conasauga logperch (Percina jenkinsi) is a good example of a rarely encountered fish species of conservation concern, for which basic population statistics are lacking. We evaluated the occurrence frequency for this species using surveys conducted with a repeat-observation sampling approach during the summer of 2008. We also analyzed museum records since the late 1980s to evaluate the trends in detected status through time. The results of these analyses provided support for a declining trend in this species over a portion of its historical range, despite low estimated detection probability. We used the results to identify the expected information return for a given level of monitoring where the sampling approach incorporates incomplete detection. The method applied here may be of value where historic occurrence records are available, provided that the assumption of constant capture efficiency is reasonable.Résumé : Les animaux qui sont rarement rencontrés peuvent être présents mais non détectés, ce qui mène à des conclusions erronées sur la persistance des populations locales ou sur les priorités de conservation d'une région particulière. Le dardperche de Conasauga (Percina jenkinsi), une espèce figurant sur la liste fédérale des espèces menacées et possédant une ré-partition endémique étroite, est un bon exemple d'une espèce de poisson rarement observée, dont la conservation suscite des inquiétudes et pour laquelle il n'existe pas de statistiques de base. Nous évaluons la fréquence d'occurrence de cette espèce d'après des inventaires par la méthode d'échantillonnage par observations répétées réalisés en 2008. Nous analysons aussi des données de musée depuis la fin des années 1980 afin de déterminer les tendances dans le statut de détection en fonction du temps. Les résultats de ces analyses semblent confirmer une tendance vers le déclin chez cette espèce sur une partie de son aire historique de répartition, malgré la faible probabilité de détection estimée. Nous utilisons les résultats pour déterminer le retour d'information à espérer en fonction d'un niveau de surveillance donnée lorsque la méthodologie d'échantillonnage tient compte d'une détection incomplète. La méthode que nous utilisons peut être intéressante dans les cas où des données historiques d'occurrence sont disponibles, à la condition qu'on puisse assumer raisonnablement que l'efficacité de capture est constante.[Traduit par la Rédaction]

Long-Term Monitoring Data Provide Evidence of Declining Species Richness in a River Valued for Biodiversity Conservation

“…This contrasts sharply with conditions during the late 1980s, when at least two of the monitored shoals in our study reach had sufficiently low turbidity (e.g., ,5 nephelometric turbidity units) to permit snorkeling observations of Amber Darter habitat use (Freeman and Freeman 1994). Currently, visual surveys of fishes by snorkelers are only effective in the more upstream reaches of the river (Hagler et al 2011). Shifts in benthic habitat in the Conasauga study reach include loss of previously lush growths of the benthic macrophyte Podostemum ceratophyllum (Freeman and Freeman 1994).…”

“…Genetic analyses (George et al 2010) and survey data (Hagler et al 2011) have provided evidence of population decline in the endangered Conasauga Logperch. Native mollusks have disappeared from many historically occupied sites in the Conasauga River system (Evans 2001) and biologists have documented potentially harmful contaminants in the river mainstem and tributaries (Sharpe and Nichols 2007;Jacobs 2013;Lasier et al 2016).…”

Using occupancy and species distribution models to assess the conservation status and habitat use of the goldline darter (Percina aurolineata) in Georgia, USA

“…For example, 48 sites need to be sampled to achieve a desired level of precision of 5%. Similar calculations have been completed for other rare darters, including Conasauga logperch (Percina jenkinsi), olive darter (Percina squamata) and wounded darter (Etheostoma vulneratum) and have indicated much higher sample size requirements for the same level of precision Hagler et al 2011).…”

“…First, it may be difficult to detect species during surveys, which can result in underestimating the proportion of sites occupied (Bayley & Peterson 2001;MacKenzie et al 2002). Fortunately, there are now methods to adjust occupancy estimates for incomplete species detection and these are being increasingly used in studies of stream fishes (Wenger et al 2008;Hagler et al 2011;Anderson et al 2012). The risk of handling stress and mortality is also a significant issue for monitoring legally protected fishes.…”

Multispecies Occupancy Modeling as a Tool for Evaluating the Status and Distribution of Darters in the Elk River, Tennessee

“…Unfortunately, we were unable to adequately assess the extent to which cumulative species detection probability varied among repeat surveys because only 3 of the 39 sites were revisited with an additional set of quadrats. However, other studies have used a similar approach to estimate species detection probabilities for stream-dwelling fishes, including darters (Albanese et al 2007;Hagler et al 2011;Anderson et al 2012). Lastly, although there is some evidence that the use of a space-for-time approach to estimate species detection probability results in minimal or no bias of occupancy-related parameters (Kéry and Royle 2016), this aspect of occupancy and detection modeling is an area of research that requires further treatment.…”