Razorback Sucker Xyrauchen texanus Research and Monitoring in the Colorado 

River Inflow Area of Lake Mead and the Lower Grand Canyon, Arizona and 

Nevada 

Brandon Albrecht 1, Ron Kegerries 1, W. Howard Brandenberg 2, Adam L. Barkalow 2, Steven 

Platania 2

, Mark McKinstry 3, Brian Healy 4, Emily Omana 4, and James Stolberg 5 

(

1 BIO-WEST, Inc., 2 American Southwest Ichthyological Researchers, LLC, 3 U.S. 

Bureau of Reclamation, Upper Colorado Region, 4 National Park Service, 5 Lower 

Colorado River Multi-Species Conservation Program) 

The results of the larval community sampling documented reproduction by Razorback 

Sucker and Humpback Chub during the 2014 survey of the lower Grand Canyon. Larval 

Razorback Sucker (n=462) were captured in four of the six months of the survey (April – 

July). The April survey had the highest density of capture and catch increased in the 

lower portion of the study area. Larval Razorback Sucker were distributed throughout the 

study area during the May and June survey including capture of a larval Razorback 

Sucker at the top of the study area, upstream of Lava Falls Rapid. Three Razorback 

Sucker larvae were captured in July. Larval Razorback Sucker captured represented all 

larval ontogenetic stages (protolarvae, mesolarvae, and metalarvae). Mesolarvae (flexion 

and postflexion) constituted 97.2% of the total Razorback Sucker catch. No recently 

transformed juvenile was captured in the 2014 captures. 

Larval Humpback Chub were first documented during the May survey. Age-0 captures of 

this species were documented through the end of the 2014 study period (n=209). Larval 

Humpback Chub were captured during the May – August Survey and were distributed 

throughout the study area. Recently transformed juveniles were captured between June 

and September. September captures of age-0 Humpback Chub were composed entirely of 

age-0 juveniles. 

Native fishes composed 97.6% of the total age-0 catch during the 2014 survey. The three 

most abundant native species captured during the 2014 larval survey were Bluehead 

Sucker, Flannelmouth Sucker, and Speckled Dace. These three species comprised over 

99% of the total native fish catch among the six trips. 
Prepared	by:

Brandon	Albrecht	1,	Ron	Kegerries	1,	W.	

Howard	Brandenburg	2,	Adam	L.	Barkalow	2,	

Steven	P.	Platania	2,	Mark	McKinstry	3,	Brian	

Healy	5,	Emily	Omana5,	James	Stolberg	5,	and	

Zachary	ShaLuck	1

(1	BIO-WEST,	Inc.;	2	American	Southwest	

Ichthyological	Researchers,	LLC;	3	U.S.	Bureau	of	

ReclamaGon,	Upper	Colorado	Region;	4	U.S.	

NaGonal	Park	Service;	5	Lower	Colorado	River	

MulG-Species	ConservaGon	Program)

April	2015		

2014	ANNUAL	REPORT	

Razorback	Sucker	Xyrauchen	texanus	Research	and	Monitoring	in	the		

Colorado	River	Inflow	Area	of	Lake	Mead	and	the	Lower	Grand	Canyon,	

	Arizona	and	Nevada	
American Southwest 

Ichthyological Researchers 
Larval	fishes	of	the		

Lower	Grand	Canyon	2014	
Objec8ves	

• ConGnue	monitoring	the	CRI		

– Same	methods	since	2010	

• Determine	RBS	presence	and	habitat	use	in	

LGC	

– Larval	and	small-bodied	fish	community	sampling	

within	the	LGC	

• Assess	reproducGon,	spawning,	and	distribuGon	

– LGC	sonic	telemetry	

• Explore	linkages	between	Lake	Mead	and	LGC	
Why	larval	fish	surveys?	

• Good	methodology	for	documenGng	rare	fishes.	

⇁ Breeding	females	have	high	fecundity.	

• Track	temporal	and	spaGal	changes	in	larval	abundance.	

⇁ Density	and	ontogeneGc	life	stage	

⇁ IdenGfy	potenGal	boZlenecks.	

• Provides	informaGon	on	spawning	adults	

⇁ Back-calculated	spawning	dates	

⇁ DuraGon	of	spawning	

⇁ IndicaGon	of	spawning	areas	
Larval	Fish	Sampling	

• Small	seine	(1	m	x	1	m	

x	0.8	mm	mesh)	

• Generally	shallow	

habitats	

• Low-velocity	habitats	

At	each	site:	

• Four	hauls	@	10.0	m	per	haul.	

• Document	physical	characterisGcs	of	each	habitat	

• Maintain	released	fish	in	live	wells	
Backwater	 Embayment	

Isolated	

pool	

Shoreline	

pool	 Slackwater	

Habitats	Sampled	
Generalized	PaFern		

of	spawning	

Catostomids			–			(March),	April,	May,	June	

Cyprinids									–			May,	June,	July,	August	
Discharge	&	Water	Temperature	
Thermographs	

270	

230	

180	
LGC	Larval	and	Small-bodied	
April	larval	Razorback	Sucker	

10.3	–	18.2	mm	TL	

n	=	6									protolarvae	

n	=	396									mesolarvae	

Razorback	Sucker		n	=	402	

n	=	20	sites	
April	larval	Razorback	Sucker	

60	

96	

80	

39	

36	

23	

13	

17	

15	

10.3	–	18.2	mm	TL	

n	=	6									protolarvae	

n	=	396									mesolarvae	

Razorback	Sucker		n	=	402	

n	=	20	sites	
May	larval	Razorback	Sucker	

Razorback	Sucker		n	<	640		 n	=	3									protolarvae	

n	=	37									mesolarvae	

Razorback	Sucker				n	=	40	

n	=	20	sites	
June	larval	Razorback	Sucker	

Razorback	Sucker		n	<	440		 n	=	15									mesolarvae

n	=	2									metalarvae

Razorback	Sucker		n	=	17	

n	=	13	sites	
July	larval	Razorback	Sucker	

Razorback	Sucker		n	=	140		 n	=	12									mesolarvae

n	=	11												metalarva

Razorback	Sucker		n	=	13	

n	=	13	sites	
2014	larval	Razorback	Sucker	

Frequency	of	occurrence	

=4	 =3	 =2	 =1	
Razorback	Sucker	CPUE	

UPSTREAM	 DOWNSTREAM	
Razorback	Sucker	CPUE	
Razorback	Sucker	Lengths	
Bluehead	Sucker	CPUE	
Flannelmouth	Sucker	CPUE	
May	YOY	Humpback	Chub	

10.2	–	14.5	mm	TL	

n	=	18									mesolarvae	

Humpback	Chub			n	=418	

n	=	11	sites	
June	YOY	Humpback	Chub	

9	

22	

n	=	25									mesolarvae	

n	=	31										metalarvae	

n	=	12																juvenile	

Humpback	Chub			n	=468	

n	=	20	sites	

9.4	–	30.8	mm	TL
July	YOY	Humpback	Chub	

29	 Humpback	Chub			n	=458	

n	=	13	sites	

n	=	4									mesolarvae	

n	=	14										metalarvae	

n	=	40																juvenile	
August	YOY	Humpback	Chub	

Age	0	

n	=	30															juvenile	

	Humpback	Chub			n	=	430	

n	=	17	sites	
Sept	YOY	Humpback	Chub	

Age	0	

n	=	35															juvenile	

Humpback	Chub			n	=	435	

n	=	8	sites	
2014	YOY	Humpback	Chub	

=4	 =3	 =2	 =1	

Frequency	of	occurrence	
Humpback	Chub	CPUE	
Humpback	Chub	Lengths	
Na8ve	vs	Non	Na8ve	CPUE	
Monthly	CPUE	
Spawning	dates	of	Razorback	Sucker	

24	February	-	6	April	2014	

0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

24 25 26 27 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 1 2 3 4 5 6 7 8 

FEB	 MARCH	

N=412

APRIL	

Number	per	date	
0 

5 

10 

15 

20 

25 

30 

35 

40 

45 

50 

55 

60 

65 

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 1 2 3 4 5 6 7 8 9 10 11 12 13 14 

APRIL	 MAY	

Spawning	dates	of	Razorback	Sucker	

1	April	-	14	May	2014	

N=	61	

Number	per	date	
Discharge	&	Water	Temperature	
Discharge	&	Water	Temperature	
Conclusions	

Razorback	Sucker	

• Larval	Razorback	Sucker	present	through	

study	area	from	Lava	Falls	to	Pearce	Ferry	

• Spawning	occurring	above	Lava	Falls	

• Razorback	Sucker	present	at	32	of	50	sites	

• April	distribuGon	skewed	downstream	

• Spawning	had	begun	prior	to	first	(April)	

sampling	effort	
Conclusions	

Humpback	Chub	

• Humpback	Chub	present	through	study	area	

from	Lava	Falls	to	upstream	of	Pearce	Ferry	

• Humpback	Chub	present	at	27	of	50	sites	

• DistribuGon	increased	monthly	

• Present	in	samples	throughout	study	period	
Recommenda8ons	

1) ConGnue	monitoring	the	CRI	under	current	methods	

including	sonic-tagging	wild	Razorbacks,	as	needed	

2) More	frequent	sampling	from	SeparaGon	to	the	CRI	

during	lake	sampling	events,	parGcularly	for	adults	

3) ConGnue	small-bodied	and	larval	fish	sampling	within	

the	LGC	

4) Maintain	telemetry	efforts	with	SURs	and	release	

sonic	fish	as	needed,	within	the	LGC	

5) Explore	the	use	of	dual	funcGoning	(acousGc/RF)	tags	

for	implantaGon	

6) Discuss	opGons	for	determining	extent	of	spawning	

7) Need	for	a	comprehensive	report	detailing	and	

analyzing	Razorback	Sucker	data	from	Lake	Mead	and	

the	LGC	to	date.	
Recommenda8ons	

3) ConGnue	small-bodied	and	larval	fish	sampling	

within	the	LGC	

A. Consider	spaPal	(upstream)	and	temporal	(earlier)	

expansion	of	larval	study	

5) Discuss	opGons	for	determining	extent	of	spawning	

A. Age	larval	fish	using	otoliths	

B. Determine	spawning	dates	

C. Correlate	with	flow	and	water	temperature	
GRTS	
Habitat	Use