Life-history characteristics of an age-validated established invasive African sharptooth catfish,Clarias gariepinus, population in a warm–temperate African impoundment

Abstract

It has been suggested that the invasive, omnivorous Clarias garipienus is capable of rapid invasions and long-term persistence in recently inhabited freshwater systems. To test this hypothesis, the life history of the established, extralimital Darlington Dam (33°10'31"S, 25°09'13"E) population was investigated. By counting post-fluorescent mark increments on otoliths from 21 chemically tagged wild fish recaptured 244-537 days later, the deposition of growth zones, comprising alternating opaque and translucent bands, was validated as annual. Examination of sectioned otoliths from 175 fish revealed that the oldest fish, two males of 840 and 1074 mm total length (TL), were 25 years old -10 years older than previously described for any C. gariepinus population. The oldest female was 885 mm TL and 21 years old. Lengthat-age was subsequently described using the von Bertalanffy growth model. Combined-sex growth was best described as L t = 931.7 ( 1 -exp(-0.15(t +2.43))) mm TL. Total mortality (Z) was calculated using catch curve analysis and the Chapman & Robson estimator to be 0.35/yr. The presence of specimens 15 years and older indicates that these fish established quickly and supports the finding that mortality rates are low, which, in turn, suggests likely long-term population persistence.

The invasibility of small headwater streams by an emerging invader, Clarias gariepinus

“…All specimens of C. gariepinus fell within a narrow length range of 109-450 mm TL (Fig. 2), indicating ages of \5 years (Wartenberg et al 2013). An established population of C. gariepinus in the Darlington Dam displayed a relatively wide range of length (200-1,200 mm TL) and age (0-25 years) classes The invasibility of small headwater streams 59 (Wartenberg et al 2013), further supporting the assumption that these headwater populations were most likely not established.…”

“…2), indicating ages of \5 years (Wartenberg et al 2013). An established population of C. gariepinus in the Darlington Dam displayed a relatively wide range of length (200-1,200 mm TL) and age (0-25 years) classes The invasibility of small headwater streams 59 (Wartenberg et al 2013), further supporting the assumption that these headwater populations were most likely not established. Key drivers of establishment success may include propagule pressure (Simberloff 2009), limiting biotic (food availability) and abiotic factors (river flow patterns) (Moyle and Light 1996).…”

“…During snorkel and spotlighting surveys, lengths of C. gariepinus were estimated. Clarias gariepinus were first recorded in the mainstem of the adjacent Sundays River system in 1981 (Wartenberg et al 2013). Incursions of C. gariepinus into two episodic headwater tributaries (Klein Uie and Coerney streams) of the Sundays River were monitored from 2007 to 2014.…”

“…While the species is highly successful in such environments in its invaded range (e.g. Wartenberg et al 2013), the ability of C. gariepinus to invade clear, high gradient headwater streams is not known. Therefore, the aim of this study was to use field data collected from three CFR headwater streams to assess whether C. gariepinus could invade these streams and if so, determine how far they penetrated upstream during the study period.…”