Improving catch quality and lowering coral reef habitat damage:

Anthony R. Marshak1, Ronald L. Hill2, and Richard S. Appeldoorn3

Modifying the fishing strategy for Antillean traps in Puerto Rico

1University of South Alabama/Dauphin Island Sea Lab2NOAA Fisheries Galveston Laboratory

3University of Puerto Rico – Recinto de Mayagüez

Five Year Broad Study Objectives

• Monitor shelf-wide distribution of Antillean fish traps (2002-06)• Informs about degree of fishing effort for the region and per

habitat

• Examine benthic impacts of trap fishing in coralline habitats

• Quantify and monitor damage and recovery of sessile invertebrates

• For this component, the major objective was to examine catch trends as related to fished habitat and habitat damage potential

Antillean fish traps

• Commonly used in Caribbean artisanal fisheries

• Wood or steel-rebar frame with galvanized wire mesh

• Highly effective at capturing reef fishes and spiny lobster

• Non-selective passive gear that may be deployed in massive quantities

• Heavy use of traps, and their non-selectivity, have contributed to overfished Caribbean waters

Recent focus upon habitat degradation • Damage to sessile benthic fauna/flora

during placement, fishing, and hauling

Geography of the Caribbean

Current study

• Monitored shelf-wide distribution of traps off La Parguera, PR– Evaluate benthic impacts of trap fishing within coralline

habitats– Focus upon relation of trap non-selectivity and fished

habitat

Map of the Puerto Rico Archipelago and insular platform, with La Parguera study area highlighted

• Compare observed trap contents in areas of high/med/low relief and corresponding habitat damage potential

• Provide commentary upon how to improve current trap fishing strategy

Current study

Colonized Hardbottom(Intermediate Damage

Probability)

Hard Coral Reef(High Damage

Probability)

Vegetated/Sand/Mud(Low Damage Probability)

Methods• Monitored seasonal trap distribution 3-4 times per yr (2002-06)

• Divers recorded:– Habitat outside a 5 m radius of the trap– Trap construction and configuration– # individuals per fish/mobile invertebrate sp. within each

trap• Total Length (mm)

• Actual trap soak time and final catch were unknown

Methods

• From 2002-06:– 1438 traps surveyed in La Parguera

– 161 diver-assessed traps

– 39% observed traps were empty at the time of inspection

Results

Results: Inspected Trap Habitat

0

50

100

150

200

250

300

350

Soft Coral Algal Sand Hard Coral Mud Sand

Num

ber o

f Ind

ivid

uals

Invertebrates

Fishes

0

20

40

60

80

100

120

Soft Coral Algal Sand Hard Coral Mud Sand

Num

ber o

f Tra

ps In

vest

igat

ed

0

20

40

60

80

100

120

140

160

180

3 6 9 12 15 18 21 24 27

Depth (meters)

Nu

mb

er o

f In

div

idu

als

Invertebrates

Fishes

0

10

20

30

40

50

60

70

80

3 6 9 12 15 18 21 24 27

Depth (meters)

Nu

mb

er o

f Tra

ps

Inve

stig

ated

Results: Inspected Trap Depth

Results: Catch per Unit Effort

0

0.5

1

1.5

2

2.5

3

Hard Coral Soft Coral Algal Sand Mud Sand Seagrass

CP

UE

(# fi

shes

/trap

)

0

0.5

1

1.5

2

2.5

3

Hard Coral Soft Coral Algal Sand Mud Sand Seagrass

CP

UE

(# in

vert

ebra

tes/

trap

)

02

468

10

121416

1820

0 3 6 9 12 15 18 21 24 27

Depth (m)

CP

UE

(# fi

shes

/trap

)

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 3 6 9 12 15 18 21 24 27

Depth (m)

CP

UE

(# in

vert

ebra

tes/

trap

)

Results: Catch Composition (Fishes)

0 10 20 30 40 50 60 70 80

Panulirus argusChaetodon striatus

Chaetodon capistratusHaemulon plumieri

Acanthurus bahianusAcanthostracion quadricornis

Acanthurus chirurgusBalistes vetula

Haemulon flavolineatumLutjanus apodus

Holocentrus rufusLactophrys triqueter

Sparisoma aurofrenatumSparisoma viride

Holocentrus adscensionisMithrax spinosissimus

Scarus taeniopterus

Number of Individuals

Soft Coral

Hard Coral

Algal Sand/Mud

Results: Catch Composition (Species)

• Majority of surveyed/inspected traps in colonized hardbottom (12-18 m)

– Large number of traps also in deeper offshore algal sand– Previous studies have highlighted the significance of these

regions– Further movement offshore due to inshore depletion/degradation

• Majority of inspected trap contents were reef fishes– Predominantly herbivorous fishes– Low numbers of snappers/groupers

• P. argus remains the most frequently captured/targeted trap sp.

– Although decreased trap landings over time– Increased SCUBA and gill net fishing for lobster

Summary

Trap Associated Habitat Damage• Potential for habitat damage in colonized hardbottom is

high– Little topographic relief to protect sessile inverts from traps– Variation in water clarity and unknown habitat delineations

• Higher probability for catches in colonized hardbottom, but greater associated bycatch, and intermediate habitat damage

• Algal Sand/Mud Contents Summary:– Grunts, trunkfishes, and snappers proportionally higher– P. argus most frequently encountered species– Lower bycatch in lowest relief habitats

• Moving traps into lowest relief habitats could benefit fishermen and ecosystem

– Higher CPUE of commercially important species in lower relief habitats

– Maintain reef structure and decrease bycatch

Changing Fishing Strategy

• Recently observed decreased densities of Antillean traps in Puerto Rico

– Traps being phased out due to recovery cost > catch value

• Increased observations of buoyed gill nets in trap habitats

– Causes increased by-catch and fishing pressure– May lead to further depletion of fish communities

• Propose more favorable ecological/economical strategy:

– Move traps away from reefs– Lower fishing intensity in colonized hardbottom– Prevent shifts to less selective fishing gears– Can lead to increases in first-class species captures and

minimized degradation

Shifts in Puerto Rico Fishing Strategy

• Observed coincident presence of spiny lobster, and greater proportion of commercially important reef fishes in low-relief habitats.

• Increased numbers of low value herbivorous fishes in higher relief habitats.

• Suggests that there may be economic incentive to persuade fishers to decrease fishing intensity in areas more prone to habitat damage.

• May work to prevent shifts to increased use of even less selective gear, and maintain habitat integrity.

Conclusions

Acknowledgements• NOAA Coral Reef Conservation

– Funded project: “Distribution of trap fishing and effects on habitats in coral reef ecosystems”

• Department of Marine Sciences, University of Puerto Rico

– Mr. Marcos Rosado– Michelle Scharer

– Michael Nemeth– Martha Prada– Sylvia Rodriguez– Idelfonzo Ruiz– Wessley Merten

*The views contained in this presentation do not necessarily reflect the views of NOAA

– Alfonso Aguilar-Perera

– Ivonne Bejarano– Bjorn Bouwmeester– Kassandra Cerveny– Cecile Jadot