Pascal Sweeney & Niamh Sweeney Why is the crayfish population expanding in the Munster Blackwater? Munster Blackwater Munster Blackwater Munster Blackwater Munster Blackwater Ballymaquirk Downstream of Clondulane EPA Q-value Stations 144 Q-value samples 1971-2006 No Crayfish Demers, Lucey, McGarrigle & Reynolds 2005 Awbeg Crayfish in 2009 Q-value Samples Crayfish in Deep Water Downstream of Bridge 2012 Crayfish Remains in Otter Spraints 2013 (Smiddy & Saich, 2015) Crayfish in Small Tributary Upstream of Mallow 2015 Crayfish in 3 EPA Q-value Samples 2015 2015 Survey by Standard Peay Methodology Sites with No Crayfish using Standard Methodology Current Known Crayfish Distribution in Blackwater Catchment pH pH range for Austropotamobius pallipes: 7.0-9.0 (Jay & Holdich, 1981); 6.5-9.0 (Holdich, 2003)

Lowest pH recorded by EPA: 1989-90 v 2014-2015 1300 Lombardstown (upstream Mallow): 7.0 7.6 2000 Ballyhooly (downstream Awbeg): 7.9 7.8 Calcium Calcium levels for Austropotamobius pallipes: “Well over 5mg/l ” (Peay, 2002) But this is only equivalent to Calcium Hardness of 12.5mg/l, the level at which there would be no exoskeleton calcification. “High calcium water content is important” (Gallagher et al. 2006)

Historic hardness data for Blackwater is scarce

Lowest Calcium Hardness recorded - Ballymaquirk to Mallow 40mg/l CaCO³, equivalent to 16mg/l Ca (Station 1300 in 2010) Lowest Calcium Hardness recorded - Awbeg to Clondulane 84mg/l CaCO³, equivalent to 33.6mg/l Ca (Station 2100 in 2010) Water Quality Demers et al. (2005): “More crayfish were found at sites with a Q value of 4 & 3-4, while fewer were found at Q values 5, 4-5, 3 and below than would be expected from the national average.”

2012 & 2015: Q4 at all EPA Stations except 1900 (Q4-5) Pre- 1994 Q-values Have crayfish always been present but undetected downstream? From Awbeg to Clondulane the river is mostly deep and crayfish would not easily be seen. The EPA stations are not in ideal crayfish habitat. pH, Calcium and Q-values are suitable.

What chance that crayfish were always present at Ballyhooly (Station 2000) at a density at which they would be found in 2 kick-samples of 14, but with none in first 11 kick samples? 18% Have crayfish always been present but undetected upstream? O’Sullivan, 1994: No remains found in otter spraints from Longfield’s Bridge (1400) to downstream of (1900)in 1984. No crayfish in EPA samples in good crayfish habitat or 16 samples upstream and downstream of sugar factory in 1996/1997.

Multiple Stressors Historically? pH just within acceptable range historically. Recent slight increase. Historic Calcium data sparse. Probably acceptable, but much lower than downstream of Awbeg. Q-values outside apparent preferred range historically. Recently More Suitable? How did Crayfish Arrive Upstream of Mallow? OSI Satellite Image 2000 OSI Satellite Image 2005 New House and Pond in 2003