Pteroplatytrygon (Dasyatis)violacea A Review

Henry F. Mollet, Juan M. Ezcurra, John B. O'Sullivan

Monterey Bay Aquarium, 886 Cannery Row, Monterey, CA 93940, USA

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Acknowledgements

• Monterey Bay Aquarium Brorsen Steve, Greenwald Scott, Farwell Charles, Franklin Veronica, Ingram Kris, Kochevar R, Scott R, Wrobles Dave, Welsh Joe

• California Catania Dave (CAS), Ebert Dave (US Abalone), Holts Dave (NOAA/NMFS), Morales Pat (CAS), O'Brian John (DFG), Shaw Mike (Sea World), Smirl Kent (DFG), Walker H.J. (SIO), Zorzi George (CAS)

• USA Bourdon Jim, Conlin Mark, Crow Jerry (Waikiki Aq,), Henningsen Alan (Baltimore Aq.), Neer Julie (LSU), Pooley S (NOAA/NMFS), Rosenberger L (UC)

• Brazil & Mexico Rincon Getulio (Rio Grande U.), Villavicencio Carlos (UABCS )

• Europe Bentivegna Flegra (Zoological Station Naples), Bortolotto Alessandro, (Fondazione Cetacea Milan),Garibaldi Fulvio (LBMLR Genova), Haynes Rod (Benalmadena SLC), Henderson Aaron (NUI Galway)

• Japan Nishida Kiyonori (Osaka Aquarium), Chai Kiyoshi (KAMPA )

• South Africa Compagno Leonard (SAM), Dudley Sheldon (NSB)

• Australia & New Zealand Francis Malcolm (NIWA), Last Peter (CSRIO), Ministry of

Fisheries, Stevens John (CSIRO), Stewart Andrew (MNZ)

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Introduction

• La Paz 2000

• Penn State 1999 (Jim Bourdon)

• Guelph 1998• Seattle 1997

(plus poster with Scott Greenwald and Jim Bourdon)

• New Orleans 1996

• Edmonton 1995

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Timeline 1800-2000

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Worldwide Distribution

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Disc width Distribution

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Taxonomy

• Bonaparte (1832-1941). Trygon violaceum, Trygon Cuv. junior synonym to Dasyatis Raf.

• Fowler (1910). Pteroplatytrygon subgenus of Dasyatis.

• Compagno (1987). Pteroplatytrygon available as a monotypic genus. Elevated to genus, based on morphometrics, disc color, streamlined eyes.

• P. Deynat, J. Bourdon (pers. comms.). Dermal denticles and dentition within Myliobatiformes indicated that Dasyatis violacea is clearly set apart from the other Dasyatis.

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Mass -DW Relationship(back transformed Y-on-X power regressions)

• M = 49.5 DW3.607 (n = 15, Edmonton 1995)

• DW in meters, 50 kg was predicted mass for 1 m DW pelagic stingray

• April 2000, largest female 0.96 m DW, 49.0 kg

• M = 44.9 DW3.321 (n = 181, Monterey 2000)

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Tooth Replacement Rateswith Jim Bourdon and Scott Greenwald

• Shed rate3.4 ray-1 day-1

• Replacement rate• 20.7 days row -1

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File splittingwith Jim Bourdon

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Dermal Denticles Shed Rate with Jim Bourdon and Scott Greenwald

• First shed rate for any batoid0.68 ray-1 day-1

• Guesstimate for replacement rate44-88 days

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Population Genetics Projectwith Joe Quattro

• Now in progress• Atlantic: Brazil (Getulio Rincon); Ireland (Aaron

Henderson)

• Med Sea: Western Med (Rod Hayes); Ligurian Sea (Fulvio Garibaldi)

• Pacific: California (John O'Sullivan, Julie Neer); Hawaii (Jerry Crow, Ed Heist); New Zealand (Malcolm Francis)

• Additional samples needed & welcome

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One Big Problem with VBGF

• VBGF reasonable with good statistics

• Applies to captive rays 2 years old and older

• 1st year growth rates much too large!

• Affects age estimate of our rays at capture!

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Comparison of Gompertz & VBGF(3 parameter fits using estimated age)

DWoo DWo k

Fem 100 15 0.44Male 71 19 0.55 Male 68 -38 0.71

Fem 104 -7.7 0.32

DWoo DWo k

VBGFGompertz

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Comparison of Gompertz & VBGF(3 parameter fits incl. captive pup data)

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Density Related Fecundity?

• Review of reproductive data

• Feeding data at the Monterey Bay Aquarium

• Could feeding cycles indicate possibility of 2 litters per year if food is available? (i.e. lower density)

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Gestation and Parturition Review of Med. Sea and Japanese Aq. data

Med. Sea Embryos

Mean DW for 10 Japanese AQ litters

DWo

Mo

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Gestation and ParturitionReview of NW Atlantic and NE Pacific data

NW Atlantic ? NE Pacific?

suggested off C. Am.

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Weekly Feeding Amounts Phase 2 (Food Intake is Seasonal)

4 females & 2 males of phase 2

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Feeding is Seasonal for Both Sexes

Males

Females

X Combined

P1?P2??

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Summary

• I covered distribution, taxonomy, morphometrics, dentition, dermal denticles. No problems.

• Growth: Gompertz better than VBGF because 1st year growth rates are likely smaller than what VBGF suggests.

• Seasonal food intake variation with 2 cycles/year. Probably related to reproduction. Might suggest density dependent fecundity. Need more data for Pacific.

• Model for pelagic sharks which are difficult to study and impossible to keep in captivity?