Population ecology and seasonal demography of the endangered grotto sculpin (Cottus specus)

Abstract

Subterranean fishes are understudied worldwide and often at risk before their populations are discovered and described. The nature of karst systems limits the applicability of ecological paradigms and hinders our ability to identify and preserve endemic fauna. Aquatic karst taxa in particular are subject to environmental threats that increase in severity over time. Once a population or species is recognised as distinct, it is imperative we gain understanding of its biology to inform effective resource management and mitigate risk factors. The grotto sculpin (Cottus specus) is endemic to Perry County, Missouri, U.S. caves and was formally described and listed as endangered under the U.S. Endangered Species Act in 2013. We used mark–recapture methods to quantify population densities and estimate population sizes in two caves and two corresponding spring branches. Size structure varied among habitats and seasons. Spring branches were dominated by juveniles year‐round with peak young‐of‐year (YOY) densities in May. Adult densities in both macrohabitats decreased in winter, possibly due to recruitment or seasonal stress, and were lower at spring branches compared to caves and declined further during late winter which may be indicative of cave spawning. YOY were captured variably underground with peak densities in summer. The ecology of grotto sculpin appears to be more complex than has been reported previously for subterranean fishes. Variable patterns of demography requiring multiple contiguous habitats are unique for cave species and support the recently substantiated suggestion that subterranean systems are not as simple or disconnected as once thought.

March of the sculpin: measuring and predicting short‐term movement of banded sculpin Cottus carolinae

“…We suggest this paradox represents the march of the sculpin, in which constant arrival of individuals at headwater streams mediates densitydependent ecosystem effects (Flecker 1984) and links local community properties with regional processes (Taylor 1996). Such landscape-scale perspectives in fish ecology (Schlosser 1991) enhance our understanding and predictability of fish movement and ultimately aid in freshwater resource conservation and management (Cooke et al 2012;Day et al 2016).…”

“…However, validation of these models is currently lacking for benthic stream fishes whose movements have generally not been studied (Petty & Grossman ; Hudy & Shiflet ; Day et al. ).…”

“…These theoretical advances and newly developed modelling frameworks fill a gap in research related to stream fish movement by allowing for the estimation of dispersal for unstudied fishes. However, validation of these models is currently lacking for benthic stream fishes whose movements have generally not been studied (Petty & Grossman 2004;Hudy & Shiflet 2009;Day et al 2016).…”

Subterranean movement inferred by temporary emigration in Barton Springs salamanders (Eurycea sosorum)

“…Cave-dwelling vertebrates are typically observed only in relatively small portions of their habitat, where humans can enter or remotely access their environment. Sampling generally occurs in human-accessible caves or through “windows” into their environment such as wells or spring outlets ( Miller & Niemiller, 2008 ; Graening et al, 2010 ; Day, Gerken & Adams, 2016 ; Niemiller et al, 2016 ; Phillips et al, 2017 ; Krejca & Reddell, 2019 ). Moreover, many cave-adapted species are of conservation concern because of their high endemicity and the sensitivity of subterranean habitats to disturbance and pollution ( Chippindale & Price, 2005 ; Miller & Niemiller, 2008 ; Fenolio et al, 2013 ; Devitt et al, 2019 ; Gorički et al, 2019 ), underscoring the need for basic research on the biology of subterranean fauna ( Mammola et al, 2019 ).…”

“…Direct observations of recaptured individuals have been used to quantify movement patterns where habitat is accessible ( Means & Johnson, 1995 ; Trajano, 1997 ; Balázs, Lewarne & Herczeg, 2020 ). Where animals retreat to inaccessible habitat, e.g., from a cave stream or spring outlet to the aquifer that feeds it, capture-recapture data may indicate immigration to or emigration from these areas ( Means & Johnson, 1995 ; Day, Gerken & Adams, 2016 ). Explicitly modeling transitions between observable and unobservable states using capture-recapture data (so-called temporary emigration) allows for estimates of demographic parameters ( Kendall, Nichols & Hines, 1997 ), breeding status (e.g., Kendall & Bjorkland, 2001 ), habitat use ( Bailey, Simons & Pollock, 2004a ; Cecala, Price & Dorcas, 2013 ), and movement ( Băncilă et al, 2018 ).…”