Evaluation of Chemical Shark Repellents on Demersal Longlines

Eric M. Stroud, July 17, 2006

Requirements

Chemical characteristicsEffects on ElasmobranchsEffects on TeleostsDelivery SystemEnvironmental characteristicsCost

Chemical Characteristics

Polar and short-chainTime-release matrixStable at pH >7Targets olfaction &

gustationShort environmental fate

Chemical Characteristics

O

O

OH

H

H

3-methylbutanal

(target=gustation)

(E)-2-butenoic acid

(target=olfaction)

ACTIVES

Chemical Characteristics

O

O

OH

H

H

3-methylbutanal

(target=gustation)

(E)-2-butenoic acid

(target=olfaction)

ACTIVES

OH

O

OH

O

Chemical Characteristics

TIME-RELEASE MATRIX

Hydroxypropylmethylcelluose Diethylene glycol monoethyl ether

Chemical Characteristics

OO

OOH2+

OO

O

:

:

:

:

+ H:OH

H+ [NaI]

Possible stabilization mechanism via acetal formation

Effects on Elasmobranchs

Study the actives using tonic immobility

Study the actives in surrounding-cloud dispersion

3-Methylbutanal Effects

Average dose size to terminate tonic immobility

Needle-thin jet released at least 5cm from nares, juveniles

0

200

400

600

800

1000

1200

1400

tiger N=1 nurse N=18 lemon N=13

MIC

RO

LIT

ER

S

3-Methylbutanal Effects

Average dose size to terminate tonic immobility

Cloud released at least 15cm from nares, adult sharks

0

1000

2000

3000

4000

5000

6000

7000

blacktip N=7 nurse N=6 lemon N=5 tiger N=4 blacknoseN=1

blue N=2

MIC

RO

LIT

ER

S

3-Methylbutanal Effects

Average dose size to terminate tonic immobility

Direct oral dosage using micropipettor, juveniles

0

50

100

150

200

250

300

350

400

nurse N=5 lemon N=12

MIC

RO

LIT

ER

S

(E)-2-Butenoic Acid Effects

Average dose size to terminate tonic immobility

Cloud released at least 15cm from nares, juvs and adults

0

1000

2000

3000

4000

5000

6000

tiger N=3 blacknose N=1 lemon N=7 nurse N=7

MIC

RO

LIT

ER

S

0:000:010:020:040:050:070:080:100:110:120:14

0:0

0:0

0

48

:00

:00

96

:00

:00

14

4:0

0:0

0

19

2:0

0:0

0

24

0:0

0:0

0

28

8:0

0:0

0

Duration of attractant presentation (minutes)

Du

rati

on

of

passes a

t so

urc

e (

seco

nd

s)

(E)-2-Butenoic Acid Effects

Test on >3m S. mokarran 400mL dose released

Effects on Teleosts

IATTC Achotines, Panama Feeding preference trials in

Thunnus albacares University of Miami, RSMAS

Feeding preference trials in Rachycentron canadum

South Bimini, Bahamas Melichthys niger, Balistes

ventula, Mojarra spp., Remora remora

Crabs!!!

Effects on Teleosts

T. Albacares Feeding preference tests at IATTC, Achotines, Panama

Effects on Teleosts

Cobia feeding preference tests at RSMAS

Delivery System

Muslin bags On gangion above

hook Close to hook

Direct injection Fill bait with gel

prior to rigging

Environmental Issues and Cost

Repellents are NOT cited in: Clean Water Act, Priority Pollutants, Section 307 Marine Pollutants, per 49CFR Parts 171 and 172 Toxic Release Inventory Chemical, per EPA 260-B-

01-001 Hazardous Substances (Superfund) BCF <100 for solvent

Additional Cost:

$1.05 / bait

Longlining Protocol

4 demersal lines Each line has 15 16/0

circle hooks LP Hook Event Timers Same type of bait 24 hour rebait periods Lines checked every 4

hours 15-30 treatments / 30-45

controls

Longlining Protocol

4 demersal lines Each line has 15 16/0

circle hooks LP Hook Event Timers Same type of bait 24 hour rebait periods Lines checked every 4

hours 15-30 treatments / 30-45

controls

Check current direction using fluorescein and a digital flowrate meter

Current in and out of lagoon, normal to lines

Preliminary Results

September 2005 Trials

0

1

2

3

4

5

6

7

Controls Treatments

Nu

mb

er

of

sh

ark

s c

ap

ture

d

40 hour soak time, 15 treatments/45 controls

No sharks captured on treatment line

Preliminary Results

November 2005 Trials

02468

1012141618

Controls Treatments

Nu

mb

er

of

sh

ark

s c

ap

ture

d

Gel was not replaced (Trying to determine longevity of the gel)

67 hour soak time, 15 treatments/45 controls

1 male lemon (TL=154cm) at 27:28

Preliminary Results

February 2006 Trials

01

23

Controls Treatments

Nu

mb

er o

f sh

arks

cap

ture

d

Gel was replaced at 24 hour rebait marks

48 hour soak time, 30 treatments/30 controls

Tiger (TL=286cm) at 9:03 from rebait

Next Steps

CPUE is too lowChemistry and delivery OK

NOAA longline cruise – November ‘06Preference tests with one speciesFL bait company

Acknowledgements

Bimini Biological Field Station Dr. Samuel Gruber Steve Kessel, Tristan Guttridge, Grant Johnson, Katie Grudecki, Jo

Imhoff, and the crew NOAA – Pascagoula

Mark A. Grace Charles Bergmann

Vernon Scholey, IATTC RSMAS

Dr. Dan Benetti Patrick H. Rice

NOAA/NMFS JIMAR/PIFSC Yonat Swimmer Mike Musyl Chris Boggs Mark A. Grace Charles Bergmann