Report of a Mass Mortality of Euastacus Valentulus (Decapoda

Report of a mass mortality of Euastacus valentulus (Decapoda: Parastacidae) in southeast Queensland, Australia, with a discussion of the potential impacts of climate change induced severe weather events on freshwater crayfish species

Author Furse, James, Coughran, Jason, Wild, Clyde

Published 2012

Journal Title Crustacean Research

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Griffith Research Online https://research-repository.griffith.edu.au CRUSTACEAN RESEARCH, SPECIAL NUMBER 7: 15–24, 2012

James M. Furse, Jason Coughran and Clyde H. Wild

Abstract.—In addition to predicted changes Leckie, 2007) including in “vast” numbers in climate, more frequent and intense severe (Viosca, 1939; Olszewski, 1980). Mass weather events (e.g. tropical cyclones, severe emersions and mortalities have also been storms and droughts) have been identified as recorded in marine crayfish in hypoxic serious and emerging threats to the World’s conditions (Jasus lalandii H. Milne Edwards) freshwater crayfish. This paper documents a (Cockroft, 2001). It is also known that some single, high intensity rainfall event (in an area freshwater crayfish species are particularly known for phenomenal rainfall events) that led sensitive to severe flooding events (Parkyn & to a flash flood and mass mortality of Euastacus Collier, 2004; Meyer et al., 2007) and mass valentulus in the Numinbah Valley of southeast emersions/strandings have been reported in Queensland in 2008. Several hundred crayfish recent years (including in the UK, Lewis & died after evidently being swept away and Morris, 2008). entrapped in vegetation or buried in alluvium during this single extremely high flow event. In light of our observations, it is clear that severe Predicted Environmental Changes and weather events have the capacity to substantially Threats to Freshwater Crayfish impact/deplete freshwater crayfish populations. Predicted changes to climate include This emerging climate–driven threat is seen as overall reduced rainfall in some areas particularly significant for freshwater crayfish and increased rainfall in others (Chiew & species that occupy single localities with highly McMahon, 2002; Hughes, 2003). Anticipated restricted ranges. Clarification of geographic changes to weather patterns include more ranges would allow a priority list of the most “at frequent and increasingly severe weather risk” populations, which could prove useful in a events (SWEs), including tropical cyclones, management response to severe weather events, droughts, and severe storms with resultant which are predicted to be more frequent in future. flooding (Hughes, 2003; IPCC, 2007; Specht, 2008). INTRODUCTION Recent assessments of the World’s freshwater crayfish for the IUCN Red List Emersions, Strandings and Terrestrial Move- of Threatened Species identified changing ments climates and increased incidence and Freshwater crayfish are well known severity of SWEs as new and emerging for emersing from the water in response to threats to many species (Coughran & Furse, poor water quality (“black water events” 2010; IUCN, 2011). In particular, these are e.g. McKinnon, 1995) during or after heavy very serious threats to many of the highly rainfalls (Wygoda, 1981; Furse & Wild, restricted–range species in the Australian genus Euastacus–of which 12 species have 2002; Furse et al., 2004), and for periodically 2 moving overland (Riek, 1951; Coughran & total distributions of <10 km (Coughran NEW THREaT To FRESHWaTER CRayFISH; SEvERE WEaTHER EvENTS 17 16 16 ET AL. & Furse, 2010; Furse & Coughran, J.2011; M. Fur secrayfish (i.e. Euastacus sp.) along a section Coughran & Furse, 2012). The 50 species in of the Nerang River in the Numinbah Valley, the genus Euastacus are the most endangered southeast Queensland. These reports were of the World’s crayfish with 40 of the from herpetologist colleagues who maintain 50 species “Endangered” or “Critically long–term ecological monitoring sites in Endangered” (see Coughran & McCormack, the Numinbah Valley, and are familiar with 2011; Furse & Coughran, 2011; IUCN, 2011). the Euastacus of the area (Malone, 2008; The genus includes a number of exceptionally Simpkins 2008, personal communications). rare species, such as the 11 species that are Descriptions of the “kill” included large only known to inhabit single localities, and numbers of dead crayfish, including crayfish have highly restricted distributions (i.e. <10 lodged some distance above ground level km2). These species are already endangered in trees and riparian vegetation. A single by a well known and common suite of threats expedition was conducted to the Numinbah to invertebrates, first highlighted in the IUCN Valley late on the afternoon of the 10th of Invertebrate Red Data Book by Wells et al. January 2008 to investigate the reported (1983): i.e. destruction of habitat, pollution, crayfish mortality. exotic species, and human exploitation (see Coughran & Furse, 2012). Meteorological Conditions Leading to Flood However, we consider that the increased There had been significant rainfalls frequency and severity of SWEs is a over the southeast corner of Queensland potentially serious emerging threat for those (ca. 153°E, 28°S) in the 7 days prior to the flooding. The highest rainfall recorded in the highly restricted–range species that occur in th areas prone to large–scale SWEs (i.e. tropical 7 days to 0900 on the 5 January was 973 cyclones, floods) but also where episodic, mm, at Springbrook, ~2.5 km east of the localised but extremely high rainfall events Numinbah Valley. Higher falls were reported occur. It is conceivable that a single localised to have occurred 10 km further upstream in SWE could extirpate a restricted–range the Numinbah Valley, but reliable records species such as any of the aforementioned are not available. Heavy rain had fallen in Euastacus. late December and early January (270 mm in The objective of this paper is to report 48 hours) and rain continued over the next 2 and document a mass mortality of Euastacus days (a further 140 mm), before heavy rain set in on 3rd January (250 mm in 24 hours to valentulus Riek resulting from a single th th localised SWE in 2008. In addition, we 0900 4 January) and intensified on the 4 January (310 mm in the 24 hours to 0900 on will discuss the broader implications of th increased incidences of SWEs to the World’s the 5 January). The heaviest falls occurred on the freshwater crayfish, and provide suggestions th on possible responses to such events for land evening of 4 January with 192 mm of managers in areas known to be inhabited by rainfall in the 3 hours to midnight, leading these animals. to the flash flooding in the upper Nerang River, the Coomera and Logan Rivers (to the North), and the Albert River to the northwest ReSUlTS (Australian Bureau of Meteorology data On the evening of the 4th–5th January 2008 (BOM), 2008). (Southern Hemisphere Summer, the local Description of Locality wet season) a single, localised and severe The location of the observed mass crayfish storm event resulted in a rapid and dramatic mortality was along a 3rd order section (stream increase in height of local waterways, and order, Horton, 1932) of the headwaters of the extensive but temporary localised flash Nerang River, located on private property (a flooding of waterways (i.e. flooding only former farm, managed for conservation) in Fig. 1. Southeast corner of Queensland showing the City of the Gold Coast and Gold Coast Hinterland. Numbered lasting a few hours). Five days later on the the Numinbah Valley, southeast Queensland points denote, 1) The upper extent of the Hinze Dam Impoundment, 2) Environmental Education Facility, 3) 10th of January, the authors received two Numinbah valley Gage Station, 4) Site Inspected for Crayfish Mortality, 5)a uthor’s weather station, and 6) Head (coordinates 28°10'32.90"S 153°13'32.08"E, of the Numinbah Valley. Medium-grey shading denotes residential or light industrial areas. Note the considerable anecdotal reports of “numerous” dead spiny altitude ~170 m above sea level (a.s.l.) distance downstream from the site inspected by the authors to the Environmental Education Facility (where crayfish mortalities were also recorded). NEW THREaT To FRESHWaTER CRayFISH; SEvERE WEaTHER EvENTS 17 16 ET AL. 17 & Furse, 2010; Furse & Coughran, J.2011; M. Fur secrayfish (i.e. Euastacus sp.) along a section Coughran & Furse, 2012). The 50 species in of the Nerang River in the Numinbah Valley, the genus Euastacus are the most endangered southeast Queensland. These reports were of the World’s crayfish with 40 of the from herpetologist colleagues who maintain 50 species “Endangered” or “Critically long–term ecological monitoring sites in Endangered” (see Coughran & McCormack, the Numinbah Valley, and are familiar with 2011; Furse & Coughran, 2011; IUCN, 2011). the Euastacus of the area (Malone, 2008; The genus includes a number of exceptionally Simpkins 2008, personal communications). rare species, such as the 11 species that are Descriptions of the “kill” included large only known to inhabit single localities, and numbers of dead crayfish, including crayfish have highly restricted distributions (i.e. <10 lodged some distance above ground level km2). These species are already endangered in trees and riparian vegetation. A single by a well known and common suite of threats expedition was conducted to the Numinbah to invertebrates, first highlighted in the IUCN Valley late on the afternoon of the 10th of Invertebrate Red Data Book by Wells et al. January 2008 to investigate the reported (1983): i.e. destruction of habitat, pollution, crayfish mortality. exotic species, and human exploitation (see Coughran & Furse, 2012). Meteorological Conditions Leading to Flood However, we consider that the increased There had been significant rainfalls frequency and severity of SWEs is a over the southeast corner of Queensland potentially serious emerging threat for those (ca. 153°E, 28°S) in the 7 days prior to the flooding. The highest rainfall recorded in the highly restricted–range species that occur in th areas prone to large–scale SWEs (i.e. tropical 7 days to 0900 on the 5 January was 973 cyclones, floods) but also where episodic, mm, at Springbrook, ~2.5 km east of the localised but extremely high rainfall events Numinbah Valley. Higher falls were reported occur. It is conceivable that a single localised to have occurred 10 km further upstream in SWE could extirpate a restricted–range the Numinbah Valley, but reliable records species such as any of the aforementioned are not available. Heavy rain had fallen in Euastacus. late December and early January (270 mm in The objective of this paper is to report 48 hours) and rain continued over the next 2 and document a mass mortality of Euastacus days (a further 140 mm), before heavy rain set in on 3rd January (250 mm in 24 hours to valentulus Riek resulting from a single th th localised SWE in 2008. In addition, we 0900 4 January) and intensified on the 4 January (310 mm in the 24 hours to 0900 on will discuss the broader implications of th increased incidences of SWEs to the World’s the 5 January). The heaviest falls occurred on the freshwater crayfish, and provide suggestions th on possible responses to such events for land evening of 4 January with 192 mm of managers in areas known to be inhabited by rainfall in the 3 hours to midnight, leading these animals. to the flash flooding in the upper Nerang River, the Coomera and Logan Rivers (to the North), and the Albert River to the northwest ReSUlTS (Australian Bureau of Meteorology data On the evening of the 4th–5th January 2008 (BOM), 2008). (Southern Hemisphere Summer, the local Description of Locality wet season) a single, localised and severe The location of the observed mass crayfish storm event resulted in a rapid and dramatic mortality was along a 3rd order section (stream increase in height of local waterways, and order, Horton, 1932) of the headwaters of the extensive but temporary localised flash Nerang River, located on private property (a flooding of waterways (i.e. flooding only former farm, managed for conservation) in Fig. 1. Southeast corner of Queensland showing the City of the Gold Coast and Gold Coast Hinterland. Numbered lasting a few hours). Five days later on the the Numinbah Valley, southeast Queensland points denote, 1) The upper extent of the Hinze Dam Impoundment, 2) Environmental Education Facility, 3) 10th of January, the authors received two Numinbah valley Gage Station, 4) Site Inspected for Crayfish Mortality, 5)a uthor’s weather station, and 6) Head (coordinates 28°10'32.90"S 153°13'32.08"E, of the Numinbah Valley. Medium-grey shading denotes residential or light industrial areas. Note the considerable anecdotal reports of “numerous” dead spiny altitude ~170 m above sea level (a.s.l.) distance downstream from the site inspected by the authors to the Environmental Education Facility (where crayfish mortalities were also recorded). NEW THREaT To FRESHWaTER CRayayFISH; SEvERE WEaTHER EvENTS 19 18 18 ET AL. J. M. Furse

Fig. 3. Numinbah Forest Park Picnic area. Evidence of flood scour andnda depositiondeposition ofof debrisdebris inin main main channelchannel sectionsection of the upper Nerang River. This location is 7.2 km downstream of our site; photograph taken 5 days after flood.

Fig. 3. Numinbah Forest Park Picnic area. Evidence of flood scour ndanda deposition deposition of of debris debris in in main main channel channel section section of the upper Nerang River. This location is 7.2 km downstream of our site; photograph taken 5 days after flood.

Fig. 2. Nerang River discharge rate over 2 Month period 2007 – 2008. The rapid increase and decrease in river falls on Springbrook, as described above, a finer resolution, in time, of the event. The discharge associated with the crayfish mortality in January 2008 clearly stands out as a Severe Weather Event, and finds its way, in a very short time (much gage data shows that river discharge peaked as appreciably above the background wet-season discharge rate over the period shown (Data Source: Queensland 3 -1 Department of Environment and Resource Management). less than an hour), into the Nerang River very rapidly at 480 m s around midnight of in the Numinbah Valley. Comparative flow the 4th January, and fell equally rapidly back rate data which allow characterisation of to a background rate of <5 m3s-1 by midday the extreme nature of this event, relative to on the 5th January (Fig. 2). The height of experience in other years, are not available the river followed a similar pattern, rising (Fig. 1). The site is approximately 10 km weather, this model approximates relative, for the Nerang River. However, the above rapidly to ~6.5 m around midnight on the 4th downstream from the head of the valley, but not absolute, stream flows throughout the figures provide a reliable guide to the relative January, falling back to ~1.2 m by midday which is the source of the Nerang River. study area. flow conditions in the Numinbah Valley on on the 5th January. Turbidity increased from th Total daily flow on 5 January was 15,600 these dates, although the actual volumes in ~10 NTU to ~375 NTU before the turbidity Weather and River Gage Data 3 m , a value not reached at any time since the river would be many times greater than recording equipment failed around midnight One of the authors (CHW) has maintained th records commenced in 1987. Previous daily those reported for the headwater stream on on the 4 January (Queensland Department a weather monitoring station, including 3 totals had reached 14,000 m on 6th April Springbrook. of Environment and Resource Management rainfall gauge, on the Springbrook Plateau for 1988 after >250 mm rainfall daily for three (DERM) River Gage data). the last 25 years (6 km southeast of the site, consecutive days, and >12,500 m3d-1 for four Local River Conditions coordinates of weather station 28°12'59.92"S consecutive days from 3rd to 6th May 1996 The Springbrook rainfall and flow data General Observations–Flood Damage in the 153°15'59.18"E, altitude 780 m a.s.l., Fig. 1). after 1,350 mm of rain fell from 1st to 6th provide a picture of this event on a day– Numinbah Valley as in Furse et al. (2004), a hydraulic model May. The 2008 SWE may be set in context by–day scale, but this flood event occurred En–route to the site, the general condition based on previous rainfall in a 1st order of a median 2008 daily flow in the stream over a far shorter timeframe. The flood of the river was surveyed at three bridge stream in the study area was used to calculate of 160 m3; the 5th January flow amounted to hydrograph at the nearest river gage to the crossings and two streamside picnic areas. daily discharge in the local streams over the more than 10% of the total annual flow. site (Numinbah River Gage #146015a, Five days after the rainfall and flooding, 21 years prior to this flood. as the observed The geographic area is prone to Coordinates 28°8'57.91"S 153°13'31.77"E, 4 the river appeared to be running slightly mortality location is subject to the same phenomenal rains, and much of the rain that km downstream of the site; Fig. 1) provides faster and a little higher than typical, but a NEW THREaT To FRESHWaTER CRayFISH; SEvERE WEaTHER EvENTS 21 20 20 ET AL. great deal of damage and large amountsJ. M. ofFur seand had been trapped in vegetation or carried population in the Numinbah Valley had not from) by leaving the water or any other debris were evident in the riparian zone and away, and buried in the alluvium. been studied prior to the flood, so the actual mechanisms they employ in flood events. It vegetation. Large sections of the river had All crayfish that we found were badly effect of the flood on the population in the is also possible that the crayfish had already been completely scoured clean of all bed decomposed and there was evidence of valley is not known. However, the very large responded to the flood by emersing and material and debris that had been there for scavenging on some crayfish remains by numbers of dead crayfish in the small section moving to higher ground, or by moving to at least 8 years (i.e. large mature dead trees, other animals. In addition to the whole surveyed, and the report of additional high in–stream refuges (e.g. under rocks, debris or rocks and cobble) (Fig. 3). Flood debris was remains and scattered fragments, a single mortalities downstream suggest it is likely burrows) but the extremely high flow rates evident in roadside fences >100 m away from well defined pile (about two handfuls) of the local population of E. valentulus was and water levels overwhelmed the refuges. the river bed, and a 40 ft shipping container crayfish exoskeleton fragments was located seriously depleted and it may take many Euastacus valentulus is one of larger (presumed to be empty) had been moved to within the high–water mark, suggesting years to recover to pre–flood levels. At species in the genus, reaching at least 90 the roadside by the floodwaters. it was deposited post–flood. The pile of the very least, it is reasonable to conclude mm OCL (Coughran, 2008), but very large fragments was collected and examination that recruitment of smaller size–classes of crayfish were notably absent among the dead Site Description and Observations on the in the laboratory indicated the fragments crayfish through to adult size will have been animals. We either simply failed to locate Mortality were the remains of numerous small (<15 appreciably impacted by this mass mortality. their remains (if there were any), or the larger The site surveyed for dead crayfish was The rainfall event leading to these crayfish animals in the population somehow avoided rd mm OCL) crayfish, and was probably the a single, 500 m long, section of 3 order regurgitated indigestible contents of some mortalities was clearly a highly localised the effects of the flood. forested stream: both sides of the stream mammal’s stomach. but severe, high–intensity event. The coastal The many smaller dead crayfish that we were inspected for dead crayfish. The riparian mountains of the region are well known as located were of a size that, in Euastacus, are vegetation corridor on the eastern bank was areas that regularly receive high wet–season often shelter opportunists that hide under narrower and less dense than the western DISCUSSION rainfalls (annual average rainfall on the vegetative debris, occupy small existing bank, and was backed by an extensive area of Although we were only able to inspect a Springbrook Plateau is very strongly affected interstices, or excavate simple burrows recently mown grassland (a former pasture). small section of the flood–affected waterway, by location and varies from 1700 to more or shallow scrapes under small rocks and Debris trapped in the riparian vegetation, than 4000 mm yr–1: at the weather station site debris (Borsboom, 1998; Smith et al., and only some time after flood, there was –1 and alluvium and debris deposited in the clearly a major mortality of E. valentulus it has averaged just over 2500 mm yr over 1998; Coughran, 2005; 2007; Furse, 2010). surrounding grassland, indicated the extent to in the upper reaches of the Nerang River. the last 25 years) and the montane headwater Larger crayfish in this genus are often found which the stream had risen at the site; it was About a year after the flood, an additional streams of the area flood regularly (usually occupying more permanent refuges, such as clear that the stream had risen appreciably and unsolicited anecdotal report of “many 1–3 times per annum). However, localised large well–established burrow networks or from its normal level during the flood. Debris stranded, dead crayfish in the 2008 flood” rainfalls leading to floods of this intensity are substantial excavations around immovable was entrained at least 3.5 m above ground was received by one of the authors (JMF) uncommon: this was the highest in 25 years, objects (such as boulders) within stream level in the riparian vegetation, and a well from a long–time staff member of an but floods greater than 70% this intensity channels or imbedded in stream banks defined high–water mark, a line of alluvium environmental education facility situated have occurred 4 times in the data period. (Furse et al., 2004). It is possible the smaller and debris, was ~70 m out from the stream 11 km downstream of the site (Fig. 1). This To our knowledge, mass mortalities of crayfish were washed away in their refuges channel in the grassland. established that the crayfish mortalities crayfish such as this have not been recorded by the flood, but the larger crayfish were A very strong smell of decomposing from the flooding were not restricted to the before in this reasonably well–populated secure in their more permanent, immovable animal matter was noticeable at the site. site we inspected, and possibly extended valley. In fact, Euastacus sulcatus Riek, refuges. Remains of E. valentulus were found which inhabits the very upper reaches of some considerable distance downstream; Broader Implications of Severe Weather entrained in the riparian ground cover and potentially as far as the upper extent of waterways in the Numinbah Valley, is well Events for Freshwater Crayfish debris directly adjacent to the stream channel, the Hinze Dam impoundment ~12 km known by local landowners and bushwalkers Although E. valentulus is a widespread but also in very large numbers buried in the downstream from our site (Fig. 1; flooding for its tendency to leave the water and move species and not of any immediate alluvium over a wide area in the surrounding was not recorded at, or downstream of the overland, particularly during or after heavy conservation concern (IUCN status “Least grassland (up to 50 m away from the stream dam, which had been very low before this rainfall events (Riek, 1951; Furse & Wild, Concern”, IUCN, 2011), there are other channel). Remains of about 60 “whole” dead event). Considering the numbers of crayfish 2002). We are confident that mass crayfish Critically Endangered restricted–range crayfish were located, plus large numbers we recorded, it is likely that the total crayfish mortalities such as this one would be well Euastacus species in the same area. The of various crayfish fragments (e.g. chelae, mortality along the river was very high and known amongst local residents, other predicted increase in severity and frequency periopods, telsonic plates and pleonites). most probably extended into thousands of researchers and National Parks Rangers if of SWEs, including localised events, all crayfish located were small, less than animals. they were indeed common in this area. potentially has very serious implications ~40 mm Occipital–Carapace Length (OCL, Any major mortality of Euastacus is cause This major mortality could possibly be for freshwater crayfish. In particular, it is Morgan, 1997), and remains or fragments of for concern as Euastacus spp. are typically attributable to the very highly concentrated clear that species occupying single localities large adult crayfish were not found during slow–growing, and amongst the longest– rainfall, over a relatively short period of with small distributions are at considerable the survey. It appeared that the crayfish had lived of the World’s freshwater crayfish (over time, leading to very rapid increases in flow risk from such events. Similarly, widely apparently been directly overwhelmed by 30 years in Euastacus bispinosus Clark, rates and water levels that the crayfish simply distributed species with fragmented the large volumes of storm–induced flow, Honan & Mitchell, 1995). The crayfish could not avoid (i.e. “outrun” or seek refuge NEW THREaT To FRESHWaTER CRayFISH; SEvERE WEaTHER EvENTS 21 20 ET AL. 21 great deal of damage and large amountsJ. M. ofFur seand had been trapped in vegetation or carried population in the Numinbah Valley had not from) by leaving the water or any other debris were evident in the riparian zone and away, and buried in the alluvium. been studied prior to the flood, so the actual mechanisms they employ in flood events. It vegetation. Large sections of the river had All crayfish that we found were badly effect of the flood on the population in the is also possible that the crayfish had already been completely scoured clean of all bed decomposed and there was evidence of valley is not known. However, the very large responded to the flood by emersing and material and debris that had been there for scavenging on some crayfish remains by numbers of dead crayfish in the small section moving to higher ground, or by moving to at least 8 years (i.e. large mature dead trees, other animals. In addition to the whole surveyed, and the report of additional high in–stream refuges (e.g. under rocks, debris or rocks and cobble) (Fig. 3). Flood debris was remains and scattered fragments, a single mortalities downstream suggest it is likely burrows) but the extremely high flow rates evident in roadside fences >100 m away from well defined pile (about two handfuls) of the local population of E. valentulus was and water levels overwhelmed the refuges. the river bed, and a 40 ft shipping container crayfish exoskeleton fragments was located seriously depleted and it may take many Euastacus valentulus is one of larger (presumed to be empty) had been moved to within the high–water mark, suggesting years to recover to pre–flood levels. At species in the genus, reaching at least 90 the roadside by the floodwaters. it was deposited post–flood. The pile of the very least, it is reasonable to conclude mm OCL (Coughran, 2008), but very large fragments was collected and examination that recruitment of smaller size–classes of crayfish were notably absent among the dead Site Description and Observations on the in the laboratory indicated the fragments crayfish through to adult size will have been animals. We either simply failed to locate Mortality were the remains of numerous small (<15 appreciably impacted by this mass mortality. their remains (if there were any), or the larger The site surveyed for dead crayfish was The rainfall event leading to these crayfish animals in the population somehow avoided rd mm OCL) crayfish, and was probably the a single, 500 m long, section of 3 order regurgitated indigestible contents of some mortalities was clearly a highly localised the effects of the flood. forested stream: both sides of the stream mammal’s stomach. but severe, high–intensity event. The coastal The many smaller dead crayfish that we were inspected for dead crayfish. The riparian mountains of the region are well known as located were of a size that, in Euastacus, are vegetation corridor on the eastern bank was areas that regularly receive high wet–season often shelter opportunists that hide under narrower and less dense than the western DISCUSSION rainfalls (annual average rainfall on the vegetative debris, occupy small existing bank, and was backed by an extensive area of Although we were only able to inspect a Springbrook Plateau is very strongly affected interstices, or excavate simple burrows recently mown grassland (a former pasture). small section of the flood–affected waterway, by location and varies from 1700 to more or shallow scrapes under small rocks and Debris trapped in the riparian vegetation, than 4000 mm yr–1: at the weather station site debris (Borsboom, 1998; Smith et al., and only some time after flood, there was –1 and alluvium and debris deposited in the clearly a major mortality of E. valentulus it has averaged just over 2500 mm yr over 1998; Coughran, 2005; 2007; Furse, 2010). surrounding grassland, indicated the extent to in the upper reaches of the Nerang River. the last 25 years) and the montane headwater Larger crayfish in this genus are often found which the stream had risen at the site; it was About a year after the flood, an additional streams of the area flood regularly (usually occupying more permanent refuges, such as clear that the stream had risen appreciably and unsolicited anecdotal report of “many 1–3 times per annum). However, localised large well–established burrow networks or from its normal level during the flood. Debris stranded, dead crayfish in the 2008 flood” rainfalls leading to floods of this intensity are substantial excavations around immovable was entrained at least 3.5 m above ground was received by one of the authors (JMF) uncommon: this was the highest in 25 years, objects (such as boulders) within stream level in the riparian vegetation, and a well from a long–time staff member of an but floods greater than 70% this intensity channels or imbedded in stream banks defined high–water mark, a line of alluvium environmental education facility situated have occurred 4 times in the data period. (Furse et al., 2004). It is possible the smaller and debris, was ~70 m out from the stream 11 km downstream of the site (Fig. 1). This To our knowledge, mass mortalities of crayfish were washed away in their refuges channel in the grassland. established that the crayfish mortalities crayfish such as this have not been recorded by the flood, but the larger crayfish were A very strong smell of decomposing from the flooding were not restricted to the before in this reasonably well–populated secure in their more permanent, immovable animal matter was noticeable at the site. site we inspected, and possibly extended valley. In fact, Euastacus sulcatus Riek, refuges. Remains of E. valentulus were found which inhabits the very upper reaches of some considerable distance downstream; Broader Implications of Severe Weather entrained in the riparian ground cover and potentially as far as the upper extent of waterways in the Numinbah Valley, is well Events for Freshwater Crayfish debris directly adjacent to the stream channel, the Hinze Dam impoundment ~12 km known by local landowners and bushwalkers Although E. valentulus is a widespread but also in very large numbers buried in the downstream from our site (Fig. 1; flooding for its tendency to leave the water and move species and not of any immediate alluvium over a wide area in the surrounding was not recorded at, or downstream of the overland, particularly during or after heavy conservation concern (IUCN status “Least grassland (up to 50 m away from the stream dam, which had been very low before this rainfall events (Riek, 1951; Furse & Wild, Concern”, IUCN, 2011), there are other channel). Remains of about 60 “whole” dead event). Considering the numbers of crayfish 2002). We are confident that mass crayfish Critically Endangered restricted–range crayfish were located, plus large numbers we recorded, it is likely that the total crayfish mortalities such as this one would be well Euastacus species in the same area. The of various crayfish fragments (e.g. chelae, mortality along the river was very high and known amongst local residents, other predicted increase in severity and frequency periopods, telsonic plates and pleonites). most probably extended into thousands of researchers and National Parks Rangers if of SWEs, including localised events, all crayfish located were small, less than animals. they were indeed common in this area. potentially has very serious implications ~40 mm Occipital–Carapace Length (OCL, Any major mortality of Euastacus is cause This major mortality could possibly be for freshwater crayfish. In particular, it is Morgan, 1997), and remains or fragments of for concern as Euastacus spp. are typically attributable to the very highly concentrated clear that species occupying single localities large adult crayfish were not found during slow–growing, and amongst the longest– rainfall, over a relatively short period of with small distributions are at considerable the survey. It appeared that the crayfish had lived of the World’s freshwater crayfish (over time, leading to very rapid increases in flow risk from such events. Similarly, widely apparently been directly overwhelmed by 30 years in Euastacus bispinosus Clark, rates and water levels that the crayfish simply distributed species with fragmented the large volumes of storm–induced flow, Honan & Mitchell, 1995). The crayfish could not avoid (i.e. “outrun” or seek refuge NEW THREaT To FRESHWaTER CRayFISH; SEvERE WEaTHER EvENTS 23 22 22 ET AL.

distributions are also at risk. J. M. Fursereviewers for providing useful comments on Australia. Crustacean Research, Special Horton, R. E., 1932. Drainage basin In the case of Euastacus, 21 of the 50 an earlier version of this paper. This research Number 7: 25–35. characteristics. Transactions of the species have total distributions <500 km2 and project was supported by the Environmental Coughran, J., & Leckie, S. R., 2007. american Geophysical Union: 350–361. are at considerable risk from the predicted Futures Centre, and the Griffith School of Invasion of a New South Wales stream Hughes, L., 2003. Climate change and increased severity and frequency of SWEs. Environment, Griffith University, Gold Coast by the Tropical Crayfish, Cherax Australia: Trends, projections and In addition, nearly all of the restricted–range campus, Queensland, Australia. quadricarinatus (von Martens). In: impacts. Austral Ecology, 28: 423–443. Euastacus are the smaller species in the genus D. Lunney, P. Eby, P. Hutchings & S. IPCC, 2007. Climate Change 2007 – with maximum OCL’s typically between 30– Burgin, (eds.), Pest or Guest: the Zoology Synthesis Report. An assessment of the lITeRATURe CITeD 40 mm (Coughran, 2008); around the same of Overabundance. Royal Zoological Intergovernmental Panel on Climate size as the ones overwhelmed in this event. BoM, 2008. South East Queensland Floods Society of New South Wales, Mosman, Change. Fourth assessment Report. 52 Other similar restricted– or fragmented– –January 2008. 46 pp, Australian Bureau New South Wales, Australia. pp. 40–46, pp, Intergovernmental Panel on Climate range species in other regions of the world of Meteorology, Brisbane, Australia. ISBN 978–0–9803272–1–2. Change, Geneva, Switzerland. are probably similarly threatened by SWEs. Borsboom, A., 1998. Aspects of the biology Coughran, J., & McCormack, R. B., IUCN, 2011. The IUCN Red List of and ecology of the Australian freshwater 2011. Euastacus morgani sp. n., a new Threatened Species (Version 2011.1), The Management Suggestions crayfish, Euastacus urospinosus spiny crayfish (Crustacea, Decapoda, International Union for Conservation of Considering that the driver of the current (Decapoda: Parastacidae). Proceedings Parastacidae) from the highland Nature and Natural Resources. Gland, trend of increasing SWEs is evidently a of The Linnean Society of New South rainforests of eastern New South Wales, Switzerland. global atmospheric process (and problem), Wales, 119: 87–100. Australia. Zookeys, 85: 17–26. Lewis, a., & Morris, F., 2008. Report on a there is little that can be done to reduce Chiew, F., & McMahon, T., 2002. Modelling Furse, J. M., 2010. Ecosystem engineering major stranding of crayfish at Meldon, immediately the increasing frequency and the impacts of climate change on by Euastacus sulcatus (Decapoda: River Wansbeck, UK. Crayfish News, 30: severity of SWEs. However, it is probable Australian streamflow. Hydrological Parastacidae) in the Hinterland of the 7–8. that at least some of the stranded crayfish Processes, 16: 1235–1245. Gold Coast, Queensland, australia. PhD Malone, M., 2008. Personal Communication. we observed could have been easily saved Cockroft, A. C., 2001. Jasus lalandii Thesis. Griffith School of Environment, Environmental Futures Centre, Griffith by simply being collected and returned to 'walkouts' or mass strandings in South Griffith University. Gold Coast, University, Gold Coast, australia. the water as soon as possible after the flood Africa during the 1990s: an overview. Queensland, Australia. McKinnon, L. J., 1995. Emersion of Murray (as in the case of Lewis and Morris in 2008 Marine and Freshwater Research, 52: Furse, J. M., & Coughran, J., 2011. an Crayfish, Euastacus Armatus (Decapoda: for Pacifastacus leniusculus (Dana) in the 1085–1094. assessment of the distribution, biology, Parastacidae), from The Murray River due UK). With suitable resources (i.e. adequate Coughran, J., 2005. New crayfishes threatening processes and conservation to post–flood water quality. Proceedings – staff) collection of stranded animals could (Decapoda: Parastacidae: Euastacus) from status of the freshwater crayfish, genus Royal Society of Victoria, 107: 31–38. be a realistic emergency–action option northeastern New South Wales, Australia. Euastacus (Decapoda: Parastacidae), Meyer, K. M., Gimpel, K., & Brandl, R., in the event of severe flood events for Records of The Australian Museum, 57: in Continental Australia. II. Threats, 2007. Viability analysis of endangered land managers in the case of Critically 361–374. Conservation Assessments and Key crayfish populations. Journal of Zoology, Endangered, highly restricted–range species Coughran, J., 2007. Distribution, habitat Findings. Crustaceana Monographs, 273: 364–371. like Euastacus jagabar Coughran. Clarifying and conservation status of the freshwater 15 (Special edition: New Frontiers in Morgan, G. J., 1997. Freshwater crayfish of the geographical distributions of rare and crayfishes, Euastacus dalagarbe, E. Crustacean Biology): 253–263. the genus Euastacus Clark (Decapoda: endangered restricted–range species would girurmulayn, E. guruhgi, E. jagabar and Furse, J. M., & Wild, C. H., 2002. Terrestrial Parastacidae) from New South Wales, allow prioritisation of the most “at risk” E. mirangudjin. Australian Zoologist, 34: activities of Euastacus sulcatus, the with a key to all species of the genus. populations, and a priority list could prove 222–227. Lamington Spiny Crayfish (Decapoda: Records of The Australian Museum useful as a management and conservation Coughran, J., 2008. Distinct groups in the Parastacidae). Freshwater Crayfish, 13: Supplement, 23: 110. tool for researchers and land managers in the genus Euastacus? Freshwater Crayfish, 604 (note). olszewski, P., 1980. a salute to the humble event of SWEs. 16: 125–132. Furse, J. M., Wild, C. H., & villamar, N. yabby. 150 pp, Angus and Robertson, Coughran, J., & Furse, J. M., 2010. an N., 2004. In–stream and terrestrial Sydney. ISBN 0207140936. Acknowledgements.—Many thanks assessment of genus Euastacus (49 movements of Euastacus sulcatus in the Parkyn, S. M., & Collier, K. J., 2004. to Mikalah Malone and Clay Simpkins species) versus IUCN Red List criteria. Gold Coast hinterland: Developing and Interaction of press and pulse disturbances for originally bringing this event to our Report prepared for the global species testing a method of accessing freshwater on crayfish populations: flood impacts in attention. Thanks are also extended to David conservation assessment of crayfishes for crayfish movements. Freshwater Crayfish, pasture and forest streams. Hydrobiologia, Lyons for kindly allowing us access to his the IUCN Red List of Threatened Species. 14: 213–220. 527: 113–124. property and taking the time to discuss the 170 pp, The International Association of Honan, J. a., & Mitchell, B. D., 1995. Riek, E. F., 1951. The freshwater crayfish flood event. Much appreciated and essential Astacology, Auburn, Alabama, USA., Growth of the large freshwater crayfish (family Parastacidae) of Queensland, with assistance during the field expedition was ISBN: 978–0–9805452–1–0. Euastacus bispinosus Clark (Decapoda: an appendix describing other Australian kindly provided by Kathryn Lee Dawkins. Coughran, J., & Furse, J. M., 2012. Parastacidae). Freshwater Crayfish, 10: species. Records of The Australian Thanks are extended to our 2 anonymous Conservation of Freshwater Crayfish in 118–131. Museum, 22: 368–388. NEW THREaT To FRESHWaTER CRayFISH; SEvERE WEaTHER EvENTS 23 22 ET AL. 23 distributions are also at risk. J. M. Fursereviewers for providing useful comments on Australia. Crustacean Research, Special Horton, R. E., 1932. Drainage basin In the case of Euastacus, 21 of the 50 an earlier version of this paper. This research Number 7: 25–35. characteristics. Transactions of the species have total distributions <500 km2 and project was supported by the Environmental Coughran, J., & Leckie, S. R., 2007. american Geophysical Union: 350–361. are at considerable risk from the predicted Futures Centre, and the Griffith School of Invasion of a New South Wales stream Hughes, L., 2003. Climate change and increased severity and frequency of SWEs. Environment, Griffith University, Gold Coast by the Tropical Crayfish, Cherax Australia: Trends, projections and In addition, nearly all of the restricted–range campus, Queensland, Australia. quadricarinatus (von Martens). In: impacts. Austral Ecology, 28: 423–443. Euastacus are the smaller species in the genus D. Lunney, P. Eby, P. Hutchings & S. IPCC, 2007. Climate Change 2007 – with maximum OCL’s typically between 30– Burgin, (eds.), Pest or Guest: the Zoology Synthesis Report. An assessment of the lITeRATURe CITeD 40 mm (Coughran, 2008); around the same of Overabundance. Royal Zoological Intergovernmental Panel on Climate size as the ones overwhelmed in this event. BoM, 2008. South East Queensland Floods Society of New South Wales, Mosman, Change. Fourth assessment Report. 52 Other similar restricted– or fragmented– –January 2008. 46 pp, Australian Bureau New South Wales, Australia. pp. 40–46, pp, Intergovernmental Panel on Climate range species in other regions of the world of Meteorology, Brisbane, Australia. ISBN 978–0–9803272–1–2. Change, Geneva, Switzerland. are probably similarly threatened by SWEs. Borsboom, A., 1998. Aspects of the biology Coughran, J., & McCormack, R. B., IUCN, 2011. The IUCN Red List of and ecology of the Australian freshwater 2011. Euastacus morgani sp. n., a new Threatened Species (Version 2011.1), The Management Suggestions crayfish, Euastacus urospinosus spiny crayfish (Crustacea, Decapoda, International Union for Conservation of Considering that the driver of the current (Decapoda: Parastacidae). Proceedings Parastacidae) from the highland Nature and Natural Resources. Gland, trend of increasing SWEs is evidently a of The Linnean Society of New South rainforests of eastern New South Wales, Switzerland. global atmospheric process (and problem), Wales, 119: 87–100. Australia. Zookeys, 85: 17–26. Lewis, a., & Morris, F., 2008. Report on a there is little that can be done to reduce Chiew, F., & McMahon, T., 2002. Modelling Furse, J. M., 2010. Ecosystem engineering major stranding of crayfish at Meldon, immediately the increasing frequency and the impacts of climate change on by Euastacus sulcatus (Decapoda: River Wansbeck, UK. Crayfish News, 30: severity of SWEs. However, it is probable Australian streamflow. Hydrological Parastacidae) in the Hinterland of the 7–8. that at least some of the stranded crayfish Processes, 16: 1235–1245. Gold Coast, Queensland, australia. PhD Malone, M., 2008. Personal Communication. we observed could have been easily saved Cockroft, A. C., 2001. Jasus lalandii Thesis. Griffith School of Environment, Environmental Futures Centre, Griffith by simply being collected and returned to 'walkouts' or mass strandings in South Griffith University. Gold Coast, University, Gold Coast, australia. the water as soon as possible after the flood Africa during the 1990s: an overview. Queensland, Australia. McKinnon, L. J., 1995. Emersion of Murray (as in the case of Lewis and Morris in 2008 Marine and Freshwater Research, 52: Furse, J. M., & Coughran, J., 2011. an Crayfish, Euastacus Armatus (Decapoda: for Pacifastacus leniusculus (Dana) in the 1085–1094. assessment of the distribution, biology, Parastacidae), from The Murray River due UK). With suitable resources (i.e. adequate Coughran, J., 2005. New crayfishes threatening processes and conservation to post–flood water quality. Proceedings – staff) collection of stranded animals could (Decapoda: Parastacidae: Euastacus) from status of the freshwater crayfish, genus Royal Society of Victoria, 107: 31–38. be a realistic emergency–action option northeastern New South Wales, Australia. Euastacus (Decapoda: Parastacidae), Meyer, K. M., Gimpel, K., & Brandl, R., in the event of severe flood events for Records of The Australian Museum, 57: in Continental Australia. II. Threats, 2007. Viability analysis of endangered land managers in the case of Critically 361–374. Conservation Assessments and Key crayfish populations. Journal of Zoology, Endangered, highly restricted–range species Coughran, J., 2007. Distribution, habitat Findings. Crustaceana Monographs, 273: 364–371. like Euastacus jagabar Coughran. Clarifying and conservation status of the freshwater 15 (Special edition: New Frontiers in Morgan, G. J., 1997. Freshwater crayfish of the geographical distributions of rare and crayfishes, Euastacus dalagarbe, E. Crustacean Biology): 253–263. the genus Euastacus Clark (Decapoda: endangered restricted–range species would girurmulayn, E. guruhgi, E. jagabar and Furse, J. M., & Wild, C. H., 2002. Terrestrial Parastacidae) from New South Wales, allow prioritisation of the most “at risk” E. mirangudjin. Australian Zoologist, 34: activities of Euastacus sulcatus, the with a key to all species of the genus. populations, and a priority list could prove 222–227. Lamington Spiny Crayfish (Decapoda: Records of The Australian Museum useful as a management and conservation Coughran, J., 2008. Distinct groups in the Parastacidae). Freshwater Crayfish, 13: Supplement, 23: 110. tool for researchers and land managers in the genus Euastacus? Freshwater Crayfish, 604 (note). olszewski, P., 1980. a salute to the humble event of SWEs. 16: 125–132. Furse, J. M., Wild, C. H., & villamar, N. yabby. 150 pp, Angus and Robertson, Coughran, J., & Furse, J. M., 2010. an N., 2004. In–stream and terrestrial Sydney. ISBN 0207140936. Acknowledgements.—Many thanks assessment of genus Euastacus (49 movements of Euastacus sulcatus in the Parkyn, S. M., & Collier, K. J., 2004. to Mikalah Malone and Clay Simpkins species) versus IUCN Red List criteria. Gold Coast hinterland: Developing and Interaction of press and pulse disturbances for originally bringing this event to our Report prepared for the global species testing a method of accessing freshwater on crayfish populations: flood impacts in attention. Thanks are also extended to David conservation assessment of crayfishes for crayfish movements. Freshwater Crayfish, pasture and forest streams. Hydrobiologia, Lyons for kindly allowing us access to his the IUCN Red List of Threatened Species. 14: 213–220. 527: 113–124. property and taking the time to discuss the 170 pp, The International Association of Honan, J. a., & Mitchell, B. D., 1995. Riek, E. F., 1951. The freshwater crayfish flood event. Much appreciated and essential Astacology, Auburn, Alabama, USA., Growth of the large freshwater crayfish (family Parastacidae) of Queensland, with assistance during the field expedition was ISBN: 978–0–9805452–1–0. Euastacus bispinosus Clark (Decapoda: an appendix describing other Australian kindly provided by Kathryn Lee Dawkins. Coughran, J., & Furse, J. M., 2012. Parastacidae). Freshwater Crayfish, 10: species. Records of The Australian Thanks are extended to our 2 anonymous Conservation of Freshwater Crayfish in 118–131. Museum, 22: 368–388. CRUSTACEAN RESEARCH, SPECIAL NUMBER 7: 25–34, 2012 24 24 ET AL. Simpkins, C. A., 2008. P e r sJ. o M. n aFur l se Review, 8: 17–18. Communication. Environmental Futures Wells, S. M., Pyle, R. M. & Collins, N. Conservation of Freshwater Crayfish in Australia Centre, Griffith University, Gold Coast, M., 1983. The IUCN Invertebrate Red Australia. Data Book. 632 pp, The IUCN, Gland, Smith, G., Borsboom, a., Lloyd, R., Lees, Switzerland. ISBN 2–88032–602–X. N., & Kehl, J., 1998. Habitat changes, Wygoda, M. L., 1981. Notes on the terrestrial Jason Coughran and James M. Furse growth and abundance of juvenile activity of the crayfish Procambarus Giant Spiny Crayfish, Euastacus alleni (Faxon) in West–Central Florida. hystricosus (Decapoda: Parastacidae), Florida Scientist, 44: 56–59. Abstract.—Recent conservation assessments crayfish are detritivorous, herbivorous in the Conondale Ranges, South–east rank the world's freshwater crayfish in the and carnivorous, and thereby act as major Queensland. Proceedings of the Linnean five most endangered animal groups, and the processors of organic material as shredders, Society of New South Wales, 119: 71–86. a ddresses: (JMF, JC, CHW) Australian fauna as the most endangered of all predators, collectors and grazers (i.e. acting Specht, A., 2008. Extreme natural events Environmental Futures Centre and Griffith the world's crayfish. In this paper, we introduce as shredders, Anderson & Sedell, 1979; and effects on tourism: central eastern School of Environment, Gold Coast campus, the 135 described species of freshwater crayfish in Huryn & Wallace, 1987; Parkyn et al., 1997; coast of Australia. The Cooperative Griffith University, Queensland 4222, Australia, and provide an overview of this fauna Usio & Townsend, 2001). They facilitate Centre for Sustainable Tourism Pty Ltd, Australia. (JC) Outback Ecology, 1/73 Troy and their current IUCN Red List conservation the release of energy and nutrients (Momot, status. The Australian crayfish fauna is almost 66 pp, Griffith University, Gold Coast, Terrace, Jolimont, Western Australia, 6014. 1995), and act as “geomorphic agents” entirely endemic, and displays enormous variation through bioturbation of sediments (Statzner Queensland, Australia. Email: (JMF) [email protected], in biology, distribution and ecology. Some viosca, R., 1939. Where to fish in Louisiana (JC) [email protected], et al., 2000; 2003) and pedoturbation of Australian species are the world's fastest growing, soils (Richardson, 1983; Stone, 1993). These (for crawfish). Louisiana Conservation (CHW) [email protected] most highly fecund and widely distributed natural activities of freshwater crayfish are crayfishes, and are tolerant of extreme variation in environmental conditions. Conversely, Australia examples of “ecosystem engineering” (sensu is also home to many crayfish that are remarkably Jones et al., 1994). Crayfish can occur in high abundance slow growing, late maturing and poorly fecund. –2 Many species have highly restricted distributions (densities of up to 77 m have been recorded and require specific environmental conditions for Orconectes limosus (Rafinesque) in that restrict them to particular areas and habitat Europe (Nystrom, 2002)), and they can types. These crayfish face a wide range of existing dominate biomass in aquatic ecosystems and emerging threats, and we discuss the research (Mason, 1975; Huryn & Wallace, 1987; imperatives, practical actions, legislative changes Momot, 1995; Nystrom, 2002). Therefore, and collaboration required to facilitate the given the range of ecological services they recovery of crayfish populations. provide, crayfish often play major roles in shaping the aquatic habitats in which they occur. They are therefore recognised as INTRODUCTION “Keystone Species” (Hart, 1992; Krebs, 1994; Collier et al., 1997; Lodge et al., 2000; Why Conserve Crayfish? Nature, 2009). There are many reasons to care about However, the ecosystem services provided and conserve freshwater crayfish including by crayfish may only become apparent when cultural, social, aesthetic and economic a species is removed or eliminated from reasons (Holdich, 2002a; 2002b; Horwitz, the habitat. One such example involves the 2010); there are also a number of very loss of Astacus astacus (Linnaeus) from compelling biological and ecological reasons ponds in Sweden by the crayfish plague to conserve these animals. (Aphanomyces astaci Schikora) in 1964. The ecological roles of freshwater Abrahamsson (1966) reported dramatic crayfish are reasonably well understood changes to the aquatic flora and fauna of the after some decades of study, and they are ponds, apparently attributable to the loss of recognised as having an important and rather the crayfish. Submerged aquatic macrophyte unique position in aquatic food webs (Hogger, growth increased to the extent that the 1988). Being completely polytrophic surface of the ponds were, on occasions,