d.a. kikkert, t.a. crowl, and a.p covich

Physical and chemical factors affecting the upstream migration of amphidromous shrimp in the Luquillo Experimental Forest

D.A. Kikkert, T.A. Crowl, and A.P Covich

Persistent, undistracted movement from one habitat to another at specific life stages (sensu Dingle 1996).

Among aquatic biota the best studied migrations are those of diadromous fishes such as salmonids and eels.

MIGRATION

DIADROMYMIGRATIONS BETWEEN MARINE AND FRESHWATER

ENVIRONEMNTS AT PARTICULAR LIFE STAGES (MYERS 1949)

AMPHIDROMY

ANADROMYSPEND MAJORITY OF LIVES IN THE SEA, MIGRATE INTO FRESHWATER TO BREED

CATADROMYSPEND LIVES IN FRESHWATER, MIGRATE TO THE SEA TO BREED

AMPHIDROMY

Migration between fresh water and sea for purpose other than breeding

•Migration usually occurs during the larval life stage

•Most common on tropical oceanic islands where it may be necessary for dispersal.

Freshwater

Ocean

Adults

Larvae

LarvaePost Larvae Adults

Luquillo Experimental Forest (LEF)

•Humid, subtropical climate

•Annual rainfall ranges from 1000 to 6000mm

•Slightly seasonal with a dry season from February-April

•Nine streams originate within the LEF

Luquillo Experimental ForestSTREAMS

• Headwater streams characterized by steep gradient (10-20%)

• Primarily boulder and cobble lined with bedrock glides and waterfalls common

• Discharge is highly variable with flows increasing rapidly during rainfall



Espiritu Santo Discharge 8/ 20/ 05

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500.00

1000.00

1500.00

2000.00

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3500.00

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800 1000 1200 1400 1600 1800 2000 2200 2400

Time

Dis

ch

arg

e (

cfs)

8/20 800-2350

SHRIMP

• Headwater streams dominated by 2 species of atyid shrimp (Xiphocaris elongata and Atya spp.) and the freshwater prawn Machrobrachium spp.

• Adult populations in headwater streams are well studies as part of an NSF long term monitoring program

• Little is known about the upstream migration of post-larvae

UPSTREAM MIGRATION• Nocturnal migration

• Hypothesized increase in migration during times of low predation risk

• Critical for recruitment into adult populations

• Increasing human development in the coastal plain

• Road / stream intersections could act as barriers (Biocomplexity project)

UPSTREAM MIGRATION

OBJECTIVES

• Quantify upstream migration of Xiphocaris elongata, Atya spp., and Macrobrachium spp.

• Identify regular patterns in shrimp migration rates

• Identify environmental factors that may affect upstream migration

METHODS

FIELD STUDY ARTIFICIAL STREAMS

FIELD STUDY

• Sampled shrimp migration over 5 months (N=46 nights)

• Used multiple regression to determine if environmental variables explain variation in shrimp migration rate and timing

RESULTSSHRIMP MIGRATION RATES

-200

0

200

400

600

800

1000

1200

ALL SHRIMP Atya spp. Xiphocaris elongata Macrobrachium spp.

SH

RIM

P/

HO

UR

AverageMaxMin

RESULTS

Atya spp. F=3.18 p=0.07Xiphocaris elongata F=12.77 p=0.0005Macrobrachium spp. F=24.86 p=0.0001

DRY SEASON SAMPLING (N=12)

WET SEASON SAMPLING (N=34)

RESULTSREGRESSION

ENVIRONMENTAL VARIABLESCLOUD COVER (0-1)

PERCENT MOON ILLUMINATED

MOON PRESENCE/ABSENCE

OBSERVED MOONLIGHT

MOON POWER (% ILL.*P/A*CLOUD COVER*TIME SINCE MOONRISE)

PRECIP (IN)

PREVIOUS DAYS DISCHARGE

INSTANTANEOUS DISCHARGE

MEAN DISCHARGE (PREVIOUS 24 HOURS)

CV DISCHARGE (PREVIOUS 24)

NUMBER OF FLASHFLOODS / WEEK

TIME SINCE LAST FLASHFLOOD

TIME SINCE 1% EXCEEDANCE FLOOD (Q323)

TIME SINCE 25% EXCEEDANCE FLOOD (Q23)

RESULTSREGRESSION Atya Spp.

MODELPARAMETER ESTIMATES AIC (∆i ) r2 Adj r2 N

CLOUD COVER 3.9065 0 0.3527 0.3104 117

MOON POWER -0.0395

PRECIP 10.8802

CV (Q) 1.1328

FF / WEEK -1.84292

TIME SINCE FF -0.0178

TIME SINCE 1% EXCEEDANCE FLOOD

0.0103

RESULTS REGRESSION Xiphocaris elongata


ORDINAL DAY 0.00606 0.6169 0.2944 0.2629 118

CLOUD COVER 0.02759

PRECIP -1.1342

TIME SINCE Q323 -.0005

TIME SINCE Q23 0.0014

RESULTS REGRESSION Xiphocaris elongata - WET SEASON ONLY


Q INSTANTANEOUS -0.01098 0.16030.275

00.2452 77

MEAN DISCHARGE -0.00709

NUMBER OF FF / WK 0.14845

RESULTS REGRESSION Macrobrachium spp.


ORDINAL DAY 0.00834 0 0.6596 0.6444 118

CLOUD COVER 0.45092

PRECIP -3.40863

PREVIOUS DAYS Q 0.00275

TIME SINCE Q323 0.000599

RESULTS REGRESSION Macrobrachium spp. - WET SEASON ONLY


ORDINAL DAY 0.01351 1.06640.712

60.6964 76

OBSERVED MOONLIGHT 0.36332

PRECIP -2.20734

Q INSTANTANEOUS -0.00967

ARTIFICIAL STREAMS

ARTIFICIAL STREAMS

TREATMENTMETHOD

(APPLIED TO ONE SIDE OF EACH STREAM)

PREDATOR PRESENCE/ABSENCE

FISH (MOUNTAIN MULLET)

INCREASED FLOW INCREASE INSTANTANEOUS Q

TURBIDTY SEDIMENT ADDED

LEAF LITTER CONDITIONED LEAF PACKS

RESULTS ARTIFICIAL STREAMS Atya spp.

Atya spp.

0

0.20.4

0.60.8

1

CONTROL

FISH P

/A

FISH *

2

FLOW

TURBIDIT

Y

LEAF LI

TTER

TREATMENT

PR

OP

OR

TIO

N

NO

TREATMENT

* **

*

* DENOTES SIGNIFICANCE AT P=0.05

RESULTS ARTIFICIAL STREAMS Xiphocaris elongata

Xiphocaris elongata

0

0.20.4

0.60.8

1

CONTROL

FISH

FISH*2

FLOW

TURBIDIT

Y

LEAF LI

TTER

TREATMENT

PR

OP

OR

TIO

N

NO

TREATMENT

* **

* DENOTES SIGNIFICANCE AT P=0.05

CONCLUSIONS• Atya spp. make up majority of shrimp migration

• Xiphocaris elongata and Macrobrachium spp migrations seasonal

• Macrobrachium make up a large component of the shrimp migration in August

• Ayta spp effected by light levels and flow regime with increased migration following spates

• Xiphocaris and Macrobrachium spp. migrate during periods of low

• Migration rates of all species decrease during extended periods of low flow

CONCLUSIONS

• Atya and Xiphocaris avoid channels with possible low water quality (turbidity and leaf litter)

• Spates may increase water quality and shrimp migration

• Chemical cues from fish predators may play a role in shrimp migration

• Atya appear to be positively rheotactic, following the highest flow

Acknowledgments• Todd Crowl• Katie Hein• Alan Covich• Wyatt Cross• Ecology Center

(Utah State University)

• Ruth Kikkert (All the fieldwork)

d.a. kikkert, t.a. crowl, and a.p covich

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