1. Spatial and temporal variation in stock abundance of queen conch, Strombus gigas, in the US Virgin Islands
Research conducted by Gordon & Tobias
Department of Planning and Natural Resources
Division of Fish and Wildlife

2. About 3-3.5 years to reach sexual maturity Reaches 12 inches in length
Biology of Queen Conch
About years to reach sexual maturity
Reaches 12 inches in length
Mature conch has flared lip
Lifespan as long as 20 years (Berg, 1987)

3. Conch Reproduction Mate during the warm summer months
Require at least 50 conch/hectare for reproduction (Stoner & Ray 1996)
Produce about 400,000
eggs per spawn
Spawn about 6 times
a summer

4. Conch Reproduction
Planktonic larvae stage (veligers) drift in water column for
2-3 weeks
Settle to the bottom and change into regular conch form

5. Habitat & Feeding Habits
Commonly found in seagrass and algae habitat
Can be found in all habitats
Graze on various species of algae and seagrass
Reported to depths
of 400 feet
Burying behavior
(juveniles)

6. Territorial Regulations in the USVI
Harvest size limits
-minimum length – 9 inches (23 cm) OR
-minimum lip thickness – 3/8 inch (9.5 mm)
Closed season extension*
June 1 – October 31 each year
*In 2008 VI government extended seasonal closure by 2 months for the territory because of overfishing concerns on STX

7. Territorial Harvest Quota
Recreational quota
-6 conch per day per recreational fisher
-maximum of 24 per boat per day
Commercial quota
-maximum of 200 conch per day per
registered commercial fishing vessel
No sale of undersized conch shell permitted

8. Territorial Landing Restrictions
Landing quota developed in June 2008:
-50,000 lbs. annually per district
-Thereafter, the season will be closed until November 1 of that year.
All conch must be landed and reported in the district from which they were harvested.
Must be landed whole in the shell

9. Total queen conch by fishing year
Total queen conch by fishing year. MSY is a range of 30,000 (CFMC) - 60,000 lbs (Olsen 2007). USVI MSY set at 50,000 lbs.

10. Federal Regulations
Harvest size limits (9” length or 3/8” lip thickness)
Recreational limit= 3 conch per person or 12 per boat
Commercial limit= 150 conch per day
No hookah
Conch must be landed with meat and shell intact
No harvest in EEZ except Lang Bank, STX from October 1 – June 30

11. Underwater Scooter Transects
USVI = total of 52 sites/114 transects (STT=12 sites/28T; STJ= 12/24T; STX=30 sites/62T)

12. Conch transect sites around St. Thomas/St. John, 2008-2009
Conch transect sites around St. Thomas/St. John, Note: Two new sites were added to the original 22 based on fisher input.

13. Conch transect sites around St. Croix, 2009-2010
Conch transect sites around St. Croix, Note: Eight new sites were added to the original 22 based on fisher input and areas of concern such as Lang Bank.

14. 28 scooter transects around St. Thomas.
*New sites based on commercial fisher input .

15. 24 scooter transects around St. John.

16. 62 scooter transects around St. Croix
62 scooter transects around St. Croix. *New sites based on commercial fisher input and areas of concern (Lang Bank).

17. Area surveyed, number and density of adult, juvenile, and total queen conch observed on scooter transects,
Is.
Num. of Transects
Area (m2)
Num.
Conch
Avg. Adult
Density
Avg.
Juvenile
Total
STT 28
31,059
253
412.80
170.58
583.37
STJ 24
32,716
119
35.34
38.33
73.67
STX 62
101,789
641
28.88
34.09
62.97
114
165,564
1013
28.21
33.00
61.19

18. Location Conch/ha Reference
Conch densities throughout the Caribbean determined by extensive surveys
Location
Conch/ha
Reference
US Virgin Islands
St. John
St. Thomas
St. Croix
73.67
583.37
62.97
Gordon and Tobias (2010)
Puerto Rico
Florida Keys
17.50
0.50
Jimenez (2007)
Berg et al. (1996)
Bahamas
Little Bahama Bank
Great Bahama Bank
28.50
20.80
Smith and van Nierop (1984)

19. Note: Error bars are standard error

20. Note: Error bars are standard error

21. Note: Error bars are standard error

25. Note: size at sexually maturity ~20cm (Stoner and Ray 1996)

26. Maturity categories from Appeldoorn (1996) and Friedlander (1997).
Lip Thickness: Juvenile = no lip, New adult =1-7mm, Adult (sexually mature) = 8-15mm, Old = 16-33mm, Very Old = 34-59mm.
Maturity categories from Appeldoorn (1996) and Friedlander (1997).

27. Only 10 sites/transects common to all survey years were used
Only 10 sites/transects common to all survey years were used. Error bars are standard errors.

28. Only 9 sites/transects common to all survey years were used.
*Note: No juvenile data available for St. John in 1981 and 1985.

29. Notes: (1) only adults were sampled in 1981; (2) only 16 of the 22 original transects were surveyed in 2001; (3) all 22 original sites were surveyed again in 2009

30. Summary
USVI overall conch densities are higher than previous years; however, adult densities <50 conch/ha.
Most juveniles were found in the 0-6m depth range, while most adults were found in the 25-30m depth range. Overall for USVI majority of the conch were in the 25-30m depth range.
Conch densities were greatest in seagrass habitat
Majority (>50%) of the conch found on scooter transects for USVI were sexually mature in terms of shell length (>20cm).
STX had the highest percent (%) frequency of sexually mature adults. STJ had the highest % frequency for old and very old conch, and STT and STX had the highest % frequency for juveniles.

31. Questions???