Effects of groundwater fluctuations on the distribution and population structure of two cyprinid fishes in a desert spring complex

Figures & data

Figure 1. Map of the Leland Harris Spring Complex showing bathymetry isolines, locations of UGS shallow groundwater monitoring well SG25D, surface water and fish visual monitoring sites, and additional monitoring sites where visual surveys of fish were conducted from April through October 2013.

Figure 2. Groundwater levels, in terms of monthly averages of water depths with respect to ground level, at shallow groundwater monitoring well SG25D at the Leland Harris Spring Complex from 2009 through 2017.

Figure 3. Mean surface water levels measured at monitoring points in springs (n = 23) and ponds (n = 24) compared to shallow groundwater levels recorded on the same dates during 15 monitoring periods from October 2012 to August 2014.

Table 1. Groundwater level (GWL), mean surface water depth at inundated bathymetry points (SWD), estimated total inundated surface area, and estimated combined volume of all bodies of water in the Leland Harris Spring Complex during each period of surface water monitoring. The total number of bathymetry points was 3852, but only those inundated at the time of the survey were used in calculating surface water depths, area, and volume.

Date	GWL (cm)	SWD (cm)		Area (ha)	Volume (m^3)	Inundated Points
		Mean	SE
5 Oct 2012	−209.9	19.3	0.5	19.6	37,737	2719
14 Nov 2012	−197.5	25.5	0.4	33.1	84,225	3788
5 Jan 2013	−187.9	32.8	0.4	33.9	111,145	3851
18 Feb 2013	−184.4	36.1	0.5	33.9	122,218	3845
4 Apr 2013	−191.0	25.9	0.4	32.8	84,697	3769
2 May 2013	−191.5	26.3	0.4	33.6	88,506	3832
23 May 2013	−193.4	25.3	0.4	33.1	83,823	3793
20 Jun 2013	−206.7	21.0	0.5	20.9	43,911	2824
26 Jul 2013	−219.5	17.8	0.6	13.0	23,059	2200
21 Aug 2013	−224.3	18.2	0.7	9.1	16,460	1889
13 Sep 2013	−214.9	18.2	0.6	15.8	28,766	2424
21 Oct 2013	−209.4	20.3	0.5	22.7	46,160	2971
7 May 2014	−193.6	24.5	0.5	29.9	73,255	3580
8 Jul 2014	−213.1	18.6	0.6	14.5	26,970	2219
17 Aug 2014	−224.1	18.1	0.7	12.4	22,444	2033

Figure 4. Mean water depths (± 2 SE) at visual monitoring sites occupied by juvenile Least Chub, juvenile Utah Chub, adult Least Chub, and adult Utah Chub during surveys conducted from April to October of 2013. In all cases with non-overlapping error bars, Mann-Whitney U-tests indicated that there was a significant tendency for occupied sites to be deeper than unoccupied sites (P < 0.05).

Table 2. Numbers of visual monitoring sites at springs and ponds in which juvenile Least Chub, adult Least Chub, juvenile Utah Chub, and adult Utah Chub were detected during visual surveys from April through October of 2013. There were 50 monitoring sites in all, 23 in springs and 27 in ponds or lentic marsh habitat, of which 40 (19 in springs and 21 in ponds) were used by fish at least once during the visual monitoring surveys.

	Least Chub				Utah Chub
	Juveniles		Adults		Juveniles		Adults
	Springs	Ponds	Springs	Ponds	Springs	Ponds	Springs	Ponds
4 April	0	0	8	16	0	0	5	11
23 May	3	16	5	7	2	14	6	4
20 June	11	20	13	4	8	16	10	3
26 July	13	15	13	5	6	1	7	0
21 August	15	5	14	4	7	1	7	1
13 September	16	5	15	6	9	3	9	3
21 October	14	5	14	5	7	2	12	3

Figure 5. Isoline map of the Leland Harris Spring Complex based on water level measurements at surface water monitoring points and corresponding estimates of surface water depths at 3852 bathymetry points during 21 August 2013. Regions of the spring complex that became isolated, or in which movement of fish to and from other regions was greatly restricted, are labelled. Dashed lines indicate boundaries between adjacent regions.

Table 3. The number of isolated bodies of water (patches) occupied by Least Chub and by Utah Chub, the estimated combined surface area of the bodies of water inhabited by each species, and the percentage of the inundated area of the spring complex represented by these bodies of water (%) during visual monitoring surveys from April through October of 2013.

	Least Chub			Utah Chub
Date	Patches	Area (ha)	%	Patches	Area (ha)	%
4 April	2	24.5	74.7	3	23.5	71.6
23 May	2	23.9	72.2	3	22.9	69.2
20 June	6	19.3	92.3	7	18.2	87.1
26 July	9	12.3	94.6	10	10.3	79.2
21 August	10	7.6	83.5	11	6.4	70.3
13 September	9	14.3	90.5	9	13.1	82.9
21 October	5	21.7	95.6	6	20.6	90.7

Table 4. Comparison of water depths (mean, median, and 25–75% quartile range) at locations of traps in which individuals were present compared to traps in which they were absent for juvenile Least Chub, adult Least Chub, juvenile Utah Chub, and adult Utah Chub during 2013 and 2014 monitoring surveys. The Mann-Whitney U-test statistic and P-values are also shown for each comparison.

Least Chub	2013				2014
	Juveniles		Adults		Juveniles		Adults
	Present	Absent	Present	Absent	Present	Absent	Present	Absent
Mean	29.0	29.8	33.2	26.4	27.7	29.5	32.0	24.7
Median	27	28	30	25	27	27	30	23.5
25–75% QR	20–32	16–35	24–36	15–30	18.5–34	17.5–34.5	23.8–36.5	16–30
n	55	63	52	66	45	49	50	44
	U = 1731		U = 1008		U = 1098		U = 696
	P = 0.996		P < 0.001		P = 0.96		P = 0.002
Utah Chub
Mean	32.8	27.5	49.8	23.6	30.2	27.5	42.4	25.2
Median	29	25	36	24	29	27	34.5	25
25–75% QR	20–37	18–30	30.5–55	17–29.5	22–37.3	16–32.8	32.5–45	16–30.8
n	37	81	25	93	34	60	18	76
	U = 1144.5		U = 284		U = 800		U = 193
	P = 0.04		P < 0.001		P = 0.08		P < 0.001

Table 5. The mean and range of total length (TL) measurements of juvenile and adult Least Chub captured and measured in each region of the Leland Harris Spring Complex during August and September of 2012–2014.

Region	Year	Juvenile TL (mm)		Adult TL (mm)		n	% Juv.
		Mean	Range	Mean	Range
Barbell Springs	2012	30.3	28–33	44.0	37–59	143	2.8
	2013	---	---	49.7	34–57	213	0
	2014	27.2	24–31	42.7	32–56	29	20.7
Mystery Spring	2012	30.3	19–33	36.1	33–53	395	26.5
	2013	24.6	17–33	40.4	34–52	331	33.6
	2014	22.7	17–30	40.2	32–54	345	37.4
Chub Haven Spring	2012	24.8	20–30	38.3	32–49	216	30.1
	2013	23.8	17–29	41.1	34–49	427	46.1
	2014	21.8	17–26	38.4	33–48	219	26.0
Isosceles Pond	2012	30.0	25–34	39.8	34–51	70	38.6
	2013	28.1	19–37	39.6	35–47	418	91.9
	2014	22.2	17–32	37.6	34–42	146	36.3
Grand Central Spring	2012	27.7	19–34	38.8	32–51	320	2.3
	2013	25.1	19–32	39.7	34–49	309	17.2
	2014	23.8	20–29	40.5	32–49	276	6.3
Pools Mosaic	2012	27.3	18–35	38.6	34–52	143	40.6
	2013	27.0	15–36	41.5	34–56	734	52.3
	2014	28.1	19–35	40.4	33–51	728	46.2
Northeast Bulrush Marsh	2012	26.9	19–34	37.9	34–52	471	26.5
	2013	27.1	20–33	40.6	35–50	809	24.8
	2014	23.9	18–33	36.8	31–50	558	19.9

Table 6. Total number and number per trap of Least Chub and Utah Chub captured in each region of the Leland Harris Spring complex during population monitoring surveys conducted in August-September of 2012–2014. The mean and range of total length (TL) measurements obtained from Utah Chub that were captured and measured in each region is also given.

Region	Year	Least Chub		Utah Chub		Utah Chub TL (mm)
		n	n/trap	n	n/trap	Mean	Range	n
Barbell Springs	2012	151	11.6	4	0.3	92.5	53–154	4
	2013	214	23.8	4	0.4	54.3	48–61	4
	2014	29	4.8	1	0.2	35.0	35.0	1
Mystery Spring	2012	470	18.8	524	21.0	60.3	32–121	190
	2013	342	17.1	144	7.2	68.9	18–128	144
	2014	594	74.3	100	12.5	33.2	21–87	100
Chub Haven Spring	2012	518	57.6	21	2.3	55.8	37–92	21
	2013	427	53.4	89	11.1	60.6	28–95	89
	2014	804	201.0	9	2.3	39.8	32–70	9
Isosceles Pond	2012	79	4.4	199	11.1	53.4	30–85	169
	2013	418	27.9	4	0.3	43.5	39–55	4
	2014	153	11.8	29	2.2	37.3	27–45	29
Grand Central Spring	2012	486	28.6	120	7.1	59.9	28–102	117
	2013	842	38.3	233	10.6	54.8	22–106	171
	2014	974	81.2	56	4.7	65.8	30–103	56
Pools Mosaic	2012	189	3.9	246	5.0	58.4	34–105	246
	2013	735	23.7	56	1.8	55.5	25–87	53
	2014	754	19.3	291	7.5	45.6	30–78	245
Northeast Bulrush Marsh	2012	741	29.6	59	2.4	50.4	18–80	59
	2013	809	62.2	72	5.5	73.0	29–151	72
	2014	1091	90.2	44	3.7	77.5	52–140	44

Data availability

The data collected and analyzed in this study is accessible to the public under the DOI: 10.6084/mp.figshare.7121699.