Life history and reproductive capacity of Gammarus fossarum and G. roeseli (Crustacea: Amphipoda) under naturally fluctuating water temperatures: a simulation study

Abstract

SUMMARY 1. Mathematical functions developed in long‐term laboratory experiments at different constant temperatures were combined with daily water temperatures for 1991–93 in eight Austrian streams and rivers to simulate the complex life histories and reproductive capacities of two freshwater amphipods: Gammarus fossarum and G. roeseli. The functions describe brood development times, hatching success, times taken to reach sexual maturity, growth, and fecundity. The sex ratio was assumed to be 0.5 and an autumn–winter reproductive resting period was based on observations of six river populations. Simulations included summer‐cold mountain streams, summer‐warm lowland rivers, watercourses fed by groundwater or influenced by heated effluents, and varying amplitudes of change within each year. 2. A fortran 77 computer program calculated growth from birth to sexual maturity of first‐generation females born on the first day of each calendar month in 1991, and the numbers of offspring successfully released from the maternal broodpouch in successive broods. At the 1991–93 regimes of temperature, individual G. fossarum released 127–208 offspring and G. roeseli released 120–169 in seven or eight successive broods during life spans of less than 2 years in six rivers. Life spans extended into a third year in the relatively cool River Salzach (mean temperature 7.5 °C). They were not completed in the very cold River Steyr (mean 5.6, range 2.5–7.9 °C), where G. fossarum produced five broods (totalling 120 offspring) and G. roeseli only two broods (totalling 28 offspring) in the 3‐year period. Except in the Steyr, some offspring grew rapidly to maturity and produced several second‐generation broods during the simulation period; in the warmest rivers some third‐generation broods were also produced. Birth dates, early or late in the year, influenced the subsequent production of broods and young, depending on temperature regimes in particular rivers. Total numbers of offspring produced by the second and third generations represent the theoretical reproductive capacities of G. fossarum and G. roeseli. Minimum and maximum estimates mostly ranged from 100 to 17 300, were larger for G. fossarum except in the warmest river (March), where temperatures rose above 20 °C for 56–78 days in summer, and largest (maximum 37 600) in the River Voeckla heated by discharge from a power‐station (mean 11.5 °C). Results from the simulations agree with preliminary assessments of relative abundances for G. fossarum and G. roeseli in several of the study rivers, but in some one or both species appear to be absent. On a wider scale, the present study confirms that G. fossarum is potentially more successful than G. roeseli in cool rivers but indicates that neither species is likely to maintain viable populations in cold rivers strongly influenced by snow and ice‐melt. 3. The potential impacts of future river warming by increases of 1, 2 and 3 °C, due to climate change, vary according to river site, date of fertilisation, the extent of temperature increase, a...

First record of Gammarus roeselii Gervais, 1835 (Amphipoda: Gammaridae) from Kosovo with ecological notes

“…The lowest number of ovigerous females for G. roeselii was recorded during October. Similar studies reveal a reduced reproduction during autumn (Pöckl et al, 2003). In this study, the presence of ovigerous females has been recorded throughout the year in the other two species as well.…”

“…Similar studies have shown that Gammarus roeselii is more successful in maintaining viable and highly productive populations in waters originating from thermal springs (Pöckl et al, 2003) During this investigation we have found a continuous reproduction cycle of G. roeselii throughout the year. Previous studies of G. fossarum and G. roeselii had shown that higher temperatures are generally associated with shorter life spans, faster brood development times, a tendency to produce more broods, and greater reproductive potential capacity in terms of succeeding generations (Pöckl et al, 2003). The lowest number of ovigerous females for G. roeselii was recorded during October.…”

“…During our investigation we found that optimal temperature conditions for G. roeselii are warm streams while G. fossarum is optimally adapted for summer cool streams (Pöckl et al, 2003); G. balcanicus finds optimal conditions in summer cold streams (Grabowski & Mamos, 2011). Similar studies have shown that Gammarus roeselii is more successful in maintaining viable and highly productive populations in waters originating from thermal springs (Pöckl et al, 2003) During this investigation we have found a continuous reproduction cycle of G. roeselii throughout the year. Previous studies of G. fossarum and G. roeselii had shown that higher temperatures are generally associated with shorter life spans, faster brood development times, a tendency to produce more broods, and greater reproductive potential capacity in terms of succeeding generations (Pöckl et al, 2003).…”

Long-term changes in river temperature and the influence of climatic and hydrological factors

“…Increases in annual mean water temperature values of around 1.5°C, and changes in summer mean river temperatures of more than 2°C, would have had an impact on the thermal habitats of freshwater faunas (cf. Pöckl et al, 2003). The effects of flow changes on river temperatures are less clear cut.…”

Life history, secondary production and population dynamics of Gammarus fossarum (Koch, 1836) in a constant temperature stream

“…Furthermore, these studies must be developed in different habitats with particular characteristics, such as temporary streams, saline streams, streams with constant temperature, etc., in order to characterize the key factors that influence the life history of the organisms in a given environment. The species Gammarus fossarum (Koch, 1836) is the most frequent species of gammarids in freshwater stream of mountainous areas of central Europe (Pöckl et al 2003) and plays a major role in the breakdown of leaf litter. Because G. fossarum is so widespread, frequently abundant, an important and obvious member of most freshwater communities, it has been extensively studied from a variety of viewpoints.…”