philip stevens, research scientist, fwriphilip stevens, erick ault, dave blewett, ross, boucek, jenn...

8:45 AM – 9:35 AM Research Update

Distribution and Habitat AssociationsPhilip Stevens, Research Scientist, FWRI

Spawning Dynamics Joy Young, Biological Scientist, FWRI

Research - Population/Behavioral traits

What is it that Snook do and why do they do it?

Diet Movement

SpawningHabitat Use

Phil Stevens Joy Young

Common Snook habitat use and diet

Philip Stevens, Erick Ault, Dave Blewett, Ross, Boucek, Jenn Rehage,

Alexis Trotter, Beau Yeiser, Joy Young, and Jim Whittington

EstuaryResidence

MovementDiet

RiverResidence

Offshore Residence

Data for Stock Assessment are largely centered on the estuary

What is going on in other habitats, namely offshore reefs and rivers?

To what extent do fish move between habitats and why do they move?

Habitat use and diet

Offshore Reefs

SE Florida

Ft. Pierce Inlet

St. Lucie Inlet

Jupiter Inlet

65 Km (40 Miles) CoastlineAbout 5-12 km (3-8 miles) offshore

Study Sampling Area

Offshore Life History

Average TL = 949 mm (37 inches) for females and 885 mm (35 inches) for males Maximum TL = 1093 mm (43 inches)Age range = 4 -19 years; average ~10 yearsDiet and genetics

0

10

20

30

40

50

60

70

80

500 600 700 800 900 1000 1100

Tota

l Nu

mb

er

of

Spe

cim

en

s

Total Length (mm)

2011-2014 Offshore Specimen Length Frequencies

Males (n=149) Females (n=202)

70% of Observed

Underwater Observations

Roving Count (Opportunistic)Group Size (Number of Fish)Length Distribution (TL) Regional BiasCondition Limited

2009 - 2014 Observation Data

Region Group (Average) Group (Maximum) TL (mm) Avg TL (mm) Max

Ft. Pierce 24 140 835 1150

St. Lucie 29 250 827 1150

Jupiter 18 50 759 1080

Offshore Life History Cont.

Acoustic Telemetry

Of snook originally tagged inshore (n=186), eleven moved offshore

Snook that were tagged offshore (n=61), mostly remained offshore (high residency to reef tract)

Once offshore, very little movement back to inlets and inshore waters (only 4 fish bounced back and forth)

Offshore Movement Patterns

Sampling occurred in evening hours when active spawning is known to occur

99% of females were spawning capable or regressing

11% of females had hydrated eggs (Imminent spawning)

Sampling and hydrated female locations

Offshore Reproduction

None12

3

# hydrated females caught

Ft. Pierce Inlet

St. Lucie Inlet

Jupiter Inlet

Use of offshore habitat has been documented throughout the state. Are these areas important at the population scale?

Rivers

Mexico CostaRica

Panama

Mexico

Mexico

SE Florida

Spring-fed rivers

Tampa Bay

CharlotteHarbor

Everglades

Acknowledgements Luiz Barbieri, Jim Estes, Tom Champeau, Bill Johnson, Bill Pouder, and Ron Taylor

FWC St Pete, Charlotte Harbor, Lakeland, Gainesville, Melbourne, Everglades (FIU)

State Wildlife Grant; Sport Fish Restoration

Southwest Florida Water Management District;

How do we sample rivers? -electrofishing

Stuns the fish – Allows researchers to take measurements and release

CharlotteHarbor

Peace River

Myakka River

Caloosahatchee River

Electrofishing 2004-05

Freshwater Fisheries

Fall04 Win05 Spr05 Sum05 Fall05 Win06 Spr06 Sum06

-0.5

0.0

0.5

1.0

1.5

2.0

2.5 Peace RiverMyakka RiverCaloosahatchee River

SeasonFall04 Win05 Spr05 Sum05 Fall05 Win06 Spr06 Sum06

CP

UE

(fis

h m

inut

e-1)

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

A

B

All rivers combined

Charlotte Harbor Rivers - Seasonality

Blewett et al. 2009

What drives seasonal movements of snook into the rivers?

Date

1/7/2008 1/14/2008 1/21/2008 1/28/2008 6

8

10

12

14

16

18

20

22

24

26EstuaryRiverCanal

Date

1/5/2009 1/12/2009 1/19/2009 1/26/2009

Tem

pera

ture

(°C

)

6

8

10

12

14

16

18

20

22

24

26

Date

1/4/2010 1/11/2010 1/18/2010 1/25/2010 6

8

10

12

14

16

18

20

22

24

26

Water temperatures of the habitats do not differ leading into winter

EstuaryRiverCanal

Water temperatures of the habitats “spread” for three days post-cold front

2 °C

Temperature cue? Not the whole story.

Blewett et al. 2014

Season

F04W

05SP05 S05 F05

W06SP06 S06 F06

W07SP07 S07 F07

W08SP08 S08 F08

W09SP09 S09 F09

W10SP10 S10 F10

W11SP11 S11 F11

W12SP12 S12 F12

W13SP13 S13 F13

Fish

/100

m s

hore

line

0

2

4

6

8

10

12

Flow

(m3 /s

)

0

20

40

60

80

100Fish abundanceActual river flow

Appear to cue on river flow

Summer/fall abundance of snook

Estuary = 3 fish per haul in 183-m seine * gear efficiency of 30% = 10 snook/100m shorelineRivers (summer) = ~1.5 fish per 100m in electrofishing * gear efficiency of 15% = 10 snook/100m shoreline

Annual snook abundance vs. flow

River flow (ln)

1.5 2.0 2.5 3.0 3.5 4.0 4.5

Com

mon

sno

ok a

bund

ance

(ln)

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

R2 = 0.90

More Flow = More Snook

Peace River – summer

Peace River – mid fall

Estuary Prey River Prey

Stevens et al. 2010Blewett et al. 2006

By late summer/early fall

Post-spawning fish from the bay

Summer resident snook

Everglades

Study system: ecotonal sites in Everglades National Park

Boucek and Rehage 2013

Study system: ecotonal sites in Everglades National Park

0

Dec Jun Dec Jun Dec Jun Dec Jun

Mar

sh D

epth

(CM

)

-20

0

20

40

60

2011 2012 20142013

Mars

h w

ate

r d

ep

th (

CM

)

20102009

Sampling windowMarsh drying

Marsh stage

ilSunfishes are the dominant prey items

Dec Jun Dec Jun Dec Jun Dec Jun

# of

sun

fish

per 1

00m

0

5

10

15

20

25

30

35# of

sno

ok p

er 1

00 m

eter

s

02468

10121416

Snook and sunfish abundance increases in the dry season, but varies across years

Snook

Sunfishes

Push into river occurs in April/May

Tampa Bay

Southwest Florida Rivers

WetSummer

TransitionFall

DryWinter/Spring

Tampa Bay’s rivers

0.00

1.00

2.00

3.00

4.00

5.00

6.00

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cat

ch p

er 1

00

m s

amp

led

Month

2014

2015

Tampa Bay Rivers

0

0.5

1

1.5

2

2.5

3

3.5

Dec-Feb Mar-May Jun-Aug Sep-Nov

Sno

ok

per

10

0 m

of

sho

relin

e

Tampa Bay Rivers

There are about 15 snook per 100m of shoreline (the length of a football field) in both estuary and river habitats

Estuary = 5 fish per haul in 183-m seine * gear efficiency of 30%Rivers = 2.6 fish per 100m shoreline in electrofishing * gear efficiency of 15%

The rivers in TB appear to be an extension of the estuary habitat

Year-round occurrence; no seasonal changes apparent.

SE Florida

Indian River Lagoon Rivers

There are about 15 snook per 100m of shoreline (the length of a football field) in the estuary and 9 snook per 100m in the rivers.

However, other snook species (e.g., fat snook) boost numbers of “snook” per 100m of shoreline to that comparable to the estuary.

Estuary = 5 fish per haul in 183-m seine * gear efficiency of 30%Rivers = 1.3 fish per 100m shoreline in electrofishing * gear efficiency of 15%

The rivers in IRL appear to be an extension of the estuary habitat

Year-round occurrence; no seasonal changes apparent.

Fat Snook

Common Snook

Spring-fed rivers

Overwintering is apparent at this latitude

<50 deg F Gulf temp vs. 72 deg F spring temp

(Picture from observation bubble at Homosassa Springs)

Abundance in rivers less than half that of lower latitudes

0.2-0.6 snook/100m * gear efficiency of 15% =<4 snook/100m

20152013

EstuaryResidence

MovementDiet

RiverResidence

Offshore Residence

Conclusions

Population traits will vary based on the size and shape of the estuary, habitat types, and prey

presented to the species

Thank you!