Leopard Shark Demographics

GENDER RATIO & STANDARD LENGTH

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HALF MOON BAYBY SHERMAN TAN

Leopard Shark, Triakis semifasciata

• Elasmobranch, Carchariniformes, Triakidae• Common in bays and estuaries• Average length is 120cm –

150cm • Feeds on clams, crabs, bony

fish, shrimp etc.• Aplacental viviparous

HypothesisH0 : There is no difference in leopard shark

demographics compared to previous beach seines

Ha : There is a difference in leopard shark demographics compared to previous beach seines

Method• A beach seine was

conducted at Half Moon Bay on February 16th

• A boat was rowed out to deploy a seine net before dragging it to shore

• The sharks were quickly measured and released to minimize stress

PredictionsMore females than males

Birth occurs between March and JuneMore juveniles than adults

Bays and estuaries are a favored nursery spot

ResultsA total of 36 leopard sharks caught

19 males, 17 females30 juveniles and 6 adults

All females were juvenilesFemales mature at 10-15 years, 100cm total

lengthMales mature at 7-13 years, 105cm total length

Sizing it up Smallest male: 43cm

Largest male: 129cm

Smallest female: 53cm

Largest female: 103cm

Standard length (cm)

  40-49 50-59 60-69 70-79 80-89 90-99100-109

110-119

120-129

Male 1 2 4 1 3 2 2 0 4

Female 0 6 2 4 4 0 1 0 0

Seine in 2012-2013

September October December February March April May June July August September October0

5

10

15

20

25

Leopard Sharks

MalesFemalesUnknown

Month

Am

ount

Caught

Results Graph

40-49 50-59 60-69 70-79 80-89 90-99 100-109 110-119 120-1290

1

2

3

4

5

6

Leopard Shark Gender and Standard Length

Male Female

Standard Length (cm)

Num

ber

ConclusionThere were more males than females

Females may be aggregating elsewhere Juveniles far outnumber adults

Bays and estuaries are good shelters and nurseries for juveniles

Ha is accepted

Thanks to:Professor Crow, TA Brooke and all my BIOL 570

classmates for helping out with the beach seine!Didn’t get any leopard sharks on the second

beach seine, but good work still!

The End