St. Thomas Grouper Analysis

Carried out under STFA FundingJosh Nowlis, Ph.D. Stock Assessment Specialist

Data Sources

• Catch Reports (Snapper/Grouper) 1974-1999• Catch Reports (by Fishing Method) 1974-2012• Catch Reports (Grouper Landings) 1997-2012• Port Sampling (TIP) 1979-2012• STFA Studies (2005-6, 2006, 2008, 2010-2012)• Rick Nemeth’s Red Hind Bank Studies• Olsen and LaPlace Nassau Grouper/Hind data

from 1974

Total St. Thomas Finfish Landingsby method

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0

100000

200000

300000

400000

500000

600000

700000

800000

Diving Nets Line Fishing Traps

Tota

l Fin

fish

Land

ings

(lbs

)

Snapper/Grouper Landings

19741976

19781980

19821984

19861988

19901992

19941996

19982000

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

800,000FISH UNCLASSIFIEDNOT SNAPPER/GROUPERSNAPPER/GROUPERTOTAL LANDINGS

Reported Grouper Landings by Fishing Method

19971998

19992000

20012002

20032004

20052006

20072008

20092010

20112012

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

Unspecified Gears Nets Diving Hook and Line Traps

RevisedACL

Species" Composition of Diving Catch

GROUPER; 15%

SNAPPER; 25%

TRIGGERFISH; 11%

PARROTFISH; 28%

JACK; 5% HOGFISH; 0%

ANGELFISH; 8% GROUPER SNAPPER TRIGGERFISH DOLPHIN WAHOO TUNA BARRACUDA SHELLFISH SQUIRRELFISH PORGY PARROTFISH KING MACKEREL JACK HOGFISHGRUNT GOATFISH GAR ANGELFISH

"Species" Composition of Line Catch

GROUPER; 7%

SNAPPER; 57%

TUNA; 10%

JACK; 14%

GROUPER SNAPPER TRIGGERFISH DOLPHIN WAHOO TUNA BARRACUDA SHELLFISH SQUIRRELFISH PORGY PARROTFISH KING MACKEREL JACK HOGFISHGRUNT GOATFISH GAR ANGELFISH

"Species" Composition of Trap Catch

GROUPER; 14%

SNAPPER; 15%

TRIG-GERFISH;

24%

SHELL-FISH; 9%

SQUIR-RELFISH;

1%

PORGY; 7%

PARROT-FISH; 13%

GRUNT; 12%

ANGELFISH; 4%

GROUPER SNAPPER TRIGGERFISH DOLPHIN WAHOO TUNA BARRACUDA SHELLFISH SQUIRRELFISH PORGY PARROTFISH KING MACKEREL JACK HOGFISHGRUNT GOATFISH GAR ANGELFISH

"Species" Composition of Seine Net Catch

SNAPPER; 39%

TUNA; 5%

JACK; 52%

GROUPER SNAPPER TRIGGERFISH DOLPHIN WAHOO TUNA BARRACUDA SHELLFISH SQUIRRELFISH PORGY PARROTFISH KING MACKEREL JACK HOGFISHGRUNT GOATFISH GAR ANGELFISH

Estimated Total Grouper Landings= Ʃ(landings by method *% Grouper by Method)

St. Thomas Grouper Landings (Estimated and Reported

19741976

19781980

19821984

19861988

19901992

19941996

19982000

20022004

20062008

20102012

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

SEFSC Grouper Estimated Grouper

National Standard 198-623 (1) Conservation and management measures shall prevent overfishing while achieving, on a continuing basis, the optimum yield from each fishery for the United States fishing industry.

(28) The term "optimum", with respect to the yield from a fishery, means the amount of fish which–

(A) will provide the greatest overall benefit to the Nation, particularly with respect to food production and recreational opportunities, and taking into account the protection of marine ecosystems;

(B) is prescribed as such on the basis of the maximum sustainable yield from the fishery, as reduced by any relevant economic, social, or ecological factor; and

(C) in the case of an overfished fishery, provides for rebuilding to a level consistent with producing the maximum sustainable yield in such fishery.

St. Thomas Estimated Grouper Landings (and OFL/ACL)

0

10,000

20,000

30,000

40,000

50,000

60,000

70,000

80,000

Grouper Landings (SEFSC)Estimated Grouper LandingsMoving average (Estimated Grouper Landings)

OFLRevised

ACL

Timing of ClosureSt. Thomas Grouper Landings by Month (1999-2006)

January

February

March

AprilMay

JuneJuly

August

September

October

November

December

0.0%

2.0%

4.0%

6.0%

8.0%

10.0%

12.0%

14.0%

16.0%

18.0%

20.0%

19992000200120022003200420052006Average

Red Hind Average TL

1970 1975 1980 1985 1990 1995 2000 2005 2010 2015240

260

280

300

320

340

360

380

Avg TL

Red Hind Total Mortality (Z)

1970 1975 1980 1985 1990 1995 2000 2005 20100

0.2

0.4

0.6

0.8

1

1.2

Hind Bank MCD

Total Mortality and Fork Length

0.000 0.200 0.400 0.600 0.800 1.000 1.200250

270

290

310

330

350

370

f(x) = − 64.602223585469 x + 355.613944077716R² = 0.384323545878584

Total Mortality (Z)

Fork

Len

gth

(mm

)

STT Red Hind Lengths

1975 1980 1985 1990 1995 2000 2005 2010 2015225

250

275

300

325

350

375

400

Traps

Spawning

50% maturity

Year

Fork

Len

gth

(mm

)

STT Grouper Abundance Measures

1998 2000 2002 2004 2006 2008 2010 20120

0.2

0.4

0.6

0.8

1

1.2

1.4

Standardized Red Hind Bank Density

Red Hind Trap CPUE

Grouper Trap CPUE

Year

Rela

tive

Abun

danc

e)

Implications• The St. Thomas/St. John grouper fishery shows some mixed

signals. • Data limitations prevent us from doing a full species-specific

analysis. We did not have Rick Nemeth’s data from 2006 to present and this needs to be examined.

• We can do some focal work on the dominant species in this complex, red hind, in part because its principal spawning site has been monitored periodically since the mid-1970s.

• The average size of red hind at that aggregation has increased dramatically since the temporary and then full closure of the Red Hind Bank MCD.

• The average size of red hind in the catch has also been increasing, and is well above the size at 50% maturity.

• The density of red hind at the aggregation has also increased markedly since the full closure of the Red Hind MCD.

Implications• Analysis of catch per unit effort data must be qualified by the

problems in obtaining accurate trap hauls information since trap fishing is the primary capture method.

• Catch per unit effort data present a different picture than size data. Since 2004, when data collection became sufficient to infer red hind catch levels, CPUE has been gradually declining while total mortality has been increasing.

• It is difficult to present a coherent story to explain the CPUE results if we assume they are a true indication of stock decline.

• Catches on this complex peaked in 2004, troughed in 2007, peaked again in 2009 and then dropped again. We do not see signals in the CPUE indices that would mirror these changes in fishing pressure.

• This is consistent with Nemeth’s (pers. comm.) observations on the MCD where he is now seeing fluctuations around a stable average rather than increases.

Implications• The best conclusion we could draw, while assuming that CPUE is a valid measure of

abundance, would be that the revised OFL is about right and that excessive fishing pressure since the early 2000s has led to a general decline.

• The problem with this conclusion comes from examining the size information, where we see consistent evidence of increased stock health since 1990. Together with the CPUE indices, this information suggests we may have a shrinking and aging population. It is possible that the presence of larger red hind has increased mortality for younger fish, or that extrinsic factors have dampened recruitment in recent years.

• Without that additional information, there are two viable strategies for St. Thomas/St. John grouper complex annual catch limits. One would be to continue allowing fishing at current levels (55,000 to 60,000 lbs), but with the recognition of a need to cut catches if average catch size or the density on spawning grounds shows signs of decline.. Ultimately this strategy would be precautionary.

Implications

• Given its dominance of the complex, monitoring of red hind could be the key to an effective management strategy.

• In addition to ongoing port sampling of the size distribution of catch, the CFMC could work to ensure that Dr. Nemeth's ongoing surveys of the Red Hind Bank MCD are supported and the data made available for annual stock reviews.

Recommendations• The OFL should serve as the ACL guide.• Dr. Nemeth should be funded to carry out an annual survey

on the hind bank MCD. These normally take place in February to March.

• Following the survey, the results should be assessed and the ACL adjusted to accounted for variations in recruitment on the MCD.

• Fishermen should be involved in this review and adjustment process.

• The CFMC should not only insure funding for Dr. Nemeth’s surveys but also establish a mechanism for review and adjustment (if required) of the ACL on an annual basis.

• We note that this approach is similar to the manner in which many fisheries are managed (e.g.. Salmon, Alaska King crab).