An evaluation of artificial substrates for monitoring the quagga mussel (Dreissena bugensis) in Lake Mead, Nevada–Arizona

Figures & data

Figure 1 Location of substrate experiment in Lake Mead indicated by dot with arrow. 1 = Boulder Basin, 2 = Virgin Basin, 3 = Overton Arm, 4 = Temple Basin, 5 = Gregg Basin. Image by Dr. Chad Cross at UNLV.

Figure 2 Substrate sampler field design. Odd numbers were permanent substrates; even numbers were removable substrates.

Figure 3 Mussel settlement on removable substrates by type and depth. Averages were taken for each 2 month sampling period and reported on this graph. Note similar patterns of decline for all substrate types after 30 m.

Figure 4 Mussel settlement on removable substrates (mean ± 1 standard deviation) by date compared with water temperatures at depth. The lake was stratified from May 2008 to Nov 2008 destratified between Jan 09 and March 09.

Figure 5 Veliger abundance in the water column with number of mussels on the substrate plates. Data from Mar–Jul 2008 are from Denise Hosler, Bureau of Reclamation, Denver, CO. Data from Aug 2008–Mar 2009 were collected by the authors.

Table 1 Substrate sampler experimental design.

Stratification Level	Depth (ft)	Depth (m)	Sampler 1	Sampler 2	Sampler 3	Sampler 4
Epilimnion	19.0	5.79	Al-P1	F-P2	ABS-P3	CUB-P4
Epilimnion	33.5	10.2	Al-R1	F-R2	ABS-R3	CUB-R4
Epilimnion	48.0	14.6	F-P1	ABS-P2	HDPE-P3	Steel-P4
Metalimnion	62.5	19.1	F-R1	ABS-R2	HDPE-R3	Steel-R4
Metalimnion	77.0	23.5	ABS-P1	HDPE-P2	F-P3	Al-P4
Metalimnion	91.5	27.9	ABS-R1	HDPE-R2	F-R3	Al-R4
Metalimnion	106.0	32.3	HDPE-P1	CUB-P2	Steel-P3	F-P4
Hypolimnion	120.5	36.7	HDPE-R1	CUB-R2	Steel-R3	F-R4
Hypolimnion	135.0	41.1	CUB-P1	Steel-P2	Al-P3	HDPE-P4
Hypolimnion	149.5	45.6	CUB-R1	Steel-R2	Al-R3	HDPE-R4
Hypolimnion	164.0	50.0	Steel-P1	Al-P2	CUB-P3	ABS-P4
Hypolimnion	178.5	54.4	Steel-R1	Al-R2	CUB-R3	ABS-R4
Al = aluminum, F = fiberglass, ABS = Acrylonitrile butadiene styrene plastic, HDPE = high density polyethylene plastic, CUB = concrete underlayment board, Steel = stainless steel, P = permanent substrate that remained in the water for 1 yr, R = removable substrate removed and replaced every 2 mo.

Table 2 Non-parametric correlations between mussel settlement and water quality characteristics. Only temperature and mussel density were significantly correlated.

		Temperature	Conductivity	pH	Dissolved Oxygen
Average	Spearman's rho	0.705	0.038	0.161	−0.106
# Mussels	p-value	<.001	0.814	0.308	0.504