Table 1. Infestation of unionids by Dreissena spp. in the waterbodies surveyed in 2011–2012.

Parameter	LakeErie	LakeOntario	LakeSt. Clair	BurtLake	DouglasLake	LakeParadise	Detroit River
Infested unionids	33.3%	29.1%	45.8%	97.8%	97.3%	90.8%	85.2%
(sample size)	(1,914)	(1,493)	(461)	(45)	(74)	(109)	(27)
Dreissena spp. to hostunionid wet weight ratios:
mean ± standard error	0.065±0.01	0.061±0.007	0.64±0.05	0.65±0.08	1.09±0.18	0.55±0.08	n.r.
median (sample size)	0.005 (178)	0.019 (295)	0.38 (169)	0.670 (22)	0.718 (34)	0.350 (45)	n.r.
[Q25–Q75]	[0.0004–0.046]	[0.006–0.49]	[0.07–1.00]	[0.36–0.67]	[0.33–0.72]	[0.19–0.35]
Unionids with past infestation	32% (1,580)	50% (1,301)	84% (461)	98% (45)	99% (74)	98% (109)	96% (27)
Uninfestedunionids of totalwith pastinfestation	47%	54%	47%	0%	1%	7%	12%
Time since invasiona (years) by
D. polymorpha	25	23	23	18	10	18	23
D. r. bugensis	22	21	22	-	-	-	22
reference	[31],[99]	[99],[100]	[30],[63]	[63]	[63]	[101]	[102]
D. polymorpha of total dreissenid abundance in the waterbody	5%	1%	90%	100%	100%	100%	90%
reference	[64]	[62]	b	[63]	[63]	[63]	b

Percent unionids infested by dreissenid mussels, the ratio of total wet weight of attached Dreissena spp. (>2 mm in size) to host unionid wet weight (mean ± standard error, median, lower and upper quartiles, sample size in parentheses), percent unionids with past infestation (unionids with or without Dreissena and with byssal threads) and percent D. polymorpha of total lake-wide dreissenid abundance are given for each waterbody studied (the lower Great Lakes, Lake St. Clair, the Detroit River, and inland lakes in north Michigan (Burt, Douglas, and Paradise lakes)).

^aTime since the first recorded finding. No D. r. bugensis was reported from lakes Burt, Douglas and Paradise.

^bD. Zanatta, unpublished data.