Reservoir refilling enhances growth and recruitment of an endangered remnant riverine fish

Abstract

Rapid increases in native riverine fish populations associated with trophic upsurge immediately following reservoir construction are well documented. Repeated upsurge periods and extended benefits to populations are, however, less understood. We used sclerochronology to investigate fish growth and netting surveys to estimate recruitment and abundance of a lacustrine population of an Australian riverine fish, the Macquarie perch (Macquaria australasica) in Lake Dartmouth. Record low inflows from 1997 to 2008 caused the reservoir to shrink to its lowest volume since construction. Refilling began in 2008, reaching 99% capacity in 2013. We hypothesized that fish growth, recruitment, and abundance would increase in response to the refilling of the lake, reproducing a similar response to the initial filling period. Our findings supported this hypothesis. Macquarie perch growth, recruitment, and abundance were enhanced during the refilling of Lake Dartmouth. Growth, best explained by the effects of dam height, change in dam height, temperature (and their interactions), and recruitment, were highest during the first years of refilling when lake levels and temperatures were low. We propose one or a combination of varying levels of intraspecific competition (low during initial filling and high following population expansion) and improved riverine conditions for reproductive success as the most plausible explanation. Our results suggest extended periods of low lake levels followed by rapid inundation events are likely to enhance recruitment and population growth opportunities for this species. While reservoir construction in general impacts negatively on native fish populations, the potential to offset these impacts for conservation management purposes should be considered.Résumé : Les augmentations rapides de populations de poissons de rivière indigènes associées à la poussée trophique qui suit immédiatement la construction d'un réservoir sont bien documentées. La compréhension de périodes de poussée trophique successives et de leurs avantages pour les populations demeure toutefois plus limitée. Nous avons utilisé la sclérochronologie pour étudier la croissance des poissons et des relevés au filet pour estimer le recrutement et l'abondance d'une population lacustre d'un poisson de rivière australien, la perche de Macquarie (Macquaria australasica) dans le lac Dartmouth. Des débits entrants d'une faiblesse record de 1997 à 2008 ont fait diminuer le volume du réservoir jusqu'au point le plus bas enregistré depuis sa construction. Le nouveau remplissage a débuté en 2008, pour atteindre 99 % de la capacité du réservoir en 2013. Nous avons postulé que la croissance, le recrutement et l'abondance des poissons augmenteraient en réponse à ce nouveau remplissage du lac, une réaction semblable à celle observée durant le remplissage initial. Nos constatations appuient cette hypothèse. La croissance, le recrutement et l'abondance des perches de Macquarie ont augmenté durant le nouveau remplissage du lac Dartmouth. La croissance, qu'ex...

Who do you move? A stochastic population model to guide translocation strategies for an endangered freshwater fish in south-eastern Australia

“…If as anticipated, there is a trophic upsurge in the Cotter Reservoir and there is an increase in the number of adults (Lintermans, 2012) then the translocation strategy can be enhanced with the addition of adult fish in combination with 1+ fish, which was a successful strategy implemented in the more highly impacted scenarios modelled. Trophic upsurge has recently been identified as contributing to increased survival and individual growth of Macquarie perch in Lake Dartmouth (Tonkin et al, 2014), but individual growth rates only increased in the initial phases of trophic upsurge. The levellingoff of individual growth rates some years after reservoir filling was hypothesised to be a result of increased intraspecific competition following Macquarie perch population increase (Tonkin Table 4 Results of modelling different release strategies with differing length of stocking program, numbers of individuals and age classes released.…”

“…The translocation program may be enhanced if a trophic upsurge were to occur as a result of enlarging the Cotter Dam and there may be an increase in the number of adults available for translocation (Lintermans, 2012). Macquarie perch can form significant populations in impoundments, but are truly a riverine fish that can only breed in flowing waters (Cadwallader and Rogan, 1977;Lintermans, 2007;Tonkin et al, 2014).…”

“…Macquarie perch have an estimated life span of at least 25 years (Lintermans and Ebner, 2010;Tonkin et al, 2014), grow rapidly in the first few years of life and approach maximum size of around 420-450 mm after about 10 years, with a maximum recorded size of 550 mm (Lintermans and Ebner, 2010). Age at sexual maturity is thought to be 3-4 years for females and 2-3 years for males (Koehn and O'Connor, 1990;Lintermans, 2007).…”

Rethinking refuges: Implications of climate change for dam busting

“…Such artificial refuges include water storage reservoirs, drainage ditches, irrigation pipes, borrow pits, water transport canals and golf course lakes, among others (see Chester and Robson, 2013). Importantly, they have also been identified as refuge habitat for a range of endangered aquatic organisms, including freshwater fishes (Tonkin et al, 2010(Tonkin et al, , 2014Ebner et al, 2011), molluscs (Clements et al, 2006) and waterbirds (Li et al, 2013).…”

The Effects of Rapid Water Level Changes on Fish Assemblages: The Case of a Spillway Gate Collapse in a Neotropical Reservoir

“…Several studies on fish have shown the importance of water level in determining size structure and reproduction of species (e.g. Winfield et al ., ; Ozen and Noble, ; Kahl et al ., ; Gaboury and Patalas, ; Tonkin et al ., ; Chizinski et al ., ). However, in most cases, they consider only a single species (usually large‐bodied, commercially valuable, or sport‐fish), evaluating reproduction or growth aspects, and many studies lacks methodological criteria that allows for broader conclusions.…”