Group Title: United States Virgin Islands animal fact sheets
Title: Whelk
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 Material Information
Title: Whelk
Series Title: United States Virgin Islands animal fact sheets
Physical Description: Book
Language: English
Creator: Division of Fish and Wildlife, Department of Planning and Natural Resources, United States Virgin Islands
Publisher: Division of Fish and Wildlife, Department of Planning and Natural Resources, United States Virgin Islands
Place of Publication: St. Thomas, VI
 Record Information
Bibliographic ID: UF00093446
Volume ID: VID00015
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


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Department of Planning and Natural Resources
Division of Fish and Wildlife
U.S.V.I. Animal Fact Sheet #15
(also called the West Indian Topshell)
Cittarium pica

Whelks are large snails that occur in shallow rocky
marine habitats throughout the USVI. Their large size (to
~ 4 inches wide) and tasty flesh make them a popular and
traditional meal. In fact, whelks were an important part of
the island diet since before Columbus the Taino Indians
ate whelk quite frequently judging by their shell middens.
These days, whelks are still eaten regularly and a modest
recreational and commercial fishery makes whelks the
second most important marine snail, behind the queen
conch (Strombus gigas), in the USVI.
Whelk shells are hard and heavy about 3 of a
whelk's weight is in its shell making the shell quite
durable. These sturdy shells resist destruction by waves
and, as a result, are commonly found by beachcombers
along our shorelines. In addition to delighting shell
collectors, the attractive shell pattern with alternating
white and black bands has inspired the use of whelk shells
in Caribbean jewelry.

Although a whelk shell is easy to observe, the living
animal found inside is harder to see most of it is safely
tucked deep inside the shell. Usually, only two parts are
exposed. The first is a muscular foot, which allows the
whelk to firmly grip onto rocks, resist crashing waves, and
crawl around [when whelk are eaten, it is the foot that
forms most of the meal]. The other exposed part is the
head, which includes two stalked eyes and a snout (called
a proboscis). At the end of the proboscis is a small, hard,
tooth-like structure called a radula. A whelk uses its radula
to scrape algae from rocks. When threatened, a whelk can
withdraw completely into its shell, closing the opening
with a trapdoor-like operculum.
Adult whelks are usually easy to identify. They are
one of only a few shallow-water snails that reach such a
large size. Shell color is a useful clue heavy black or
purple stripes on a white background color. Sometimes it
is hard to see the shell pattern because of algal growth:
blue-green algae give whelk shells a greenish tint and
encrusting red algae may completely cover shells of older
Young whelks (< /2-inch wide) are common in the
splash zone of rocky areas and are distinguished by having
mostly white shells with regular black spots. Three ridges
spiral around, following the path of shell growth. As
young whelks grow, these ridges get smaller, turn to
bumps, and are eventually lost completely. Color changes
with growth too. The white color gets obscured as the
black sots become larger and more zigzagged.

X h Yo g splash zone
SThell ss than 1/2-inch wide)
& a1. / -

Common Names
Most locals in the USVI call them whelks. In other
parts of the Caribbean, they are also called West Indian
topshells or magpie shells. In Spanish, whelks are called
'Caracoles', 'Burgao', or 'Quigua' (Venezuela).

Whelks are marine invertebrates that belong to the
phylum Mollusca. Like all snails, whelks are classified in
the subphylum Gastropoda. They belong to the family
Trochidae, a diverse group that includes many species
harvested for food. Whelks are placed in the genus
Cittarium and the species pica.
Whelks are found throughout the Caribbean, ranging
from the Bahamas to the central coast of South America.
Occasionally, whelks are found in south Florida. In
Bermuda, whelks were driven to extinction by over
harvesting during the early 19th century (an effort to
reintroduce whelks to Bermuda has been successful). In
almost all places that whelks occur, people harvest them.
Life History & Habitat
Whelks live in rocky areas along the seashore in a
habitat known as the intertidal zone. The intertidal zone is
the shoreline that extends from highest high tide down to
the lowest low-water line. Whelk habitat is like a narrow
band running along the shoreline, and it does not extend
very deep most whelks are found immediately at the
waters edge. Large adult whelks may occur slightly
deeper, but generally not below about three feet deep.
Like surfers, whelks seem to prefer areas with some wave
action too. In such wave-washed rocky areas, whelks
occupy a slightly greater depth range.
Food preference is the main reason whelks are
restricted to the intertidal zone. Whelks like to eat
filamentous algae thin strands of seaweed that grow
abundantly on intertidal rocks, especially where surf
prevents fish from feeding on the shallow beds of algae.
Whelks grow slowly. If there is plenty of good food,
their shell width increases by about 1/16t-inch (1.5 mm)
per month. It may take a whelk five years to reach the
large size of reproductive adults and scientists still don't
know how long whelk can live.

Whelks reproduce mostly in the late summer around
the new moon. Females release small green eggs
(-1/100th-inch wide) that are fertilized by the sperm
released simultaneously by males. The fertilized eggs drift
away in the ocean currents, developing rapidly into a
larval stage called a veliger. Free-swimming veligers feed
on microscopic algae called phytoplankton. After 3 to 5
days, ocean currents bring the larvae to suitable rocky
shores where they settle and remain for the rest of their

Ecology & Behavior
Whelks are generally sedentary, meaning they don't
go far in their lifetimes. The longest trip recorded for a
whelk was about 160 yards over 6 months not a big trip!
Most of their movements occur at night, when whelks
actively crawl about in search of something to eat. By day,
they tend to remain in holes or crevices. This stay-at-home
attitude plus slow growth and a short larval stage -
makes local populations of whelks vulnerable to
Surprisingly, whelks are sensitive to sounds, and when
startled they will release their grip on the rocks, dropping
down into the water. In calm conditions, a predator (or
fisherman) can still grab the whelk, but if there are waves,
the whelk may get swept away or wedged deep into a
Without doubt, people are the number one predators
on whelks, but whelks have many natural predators too.
Three shallow water snails prey upon whelk: the wide-
mouthed rock shell (Pupura patula), the deltoid rock drill
(Thais deltoidea), and the rustic rock drill (Thais rustica).
Some fish also eat whelk. The porcupine fish (Diodon
hystrix) eats whelks like popcorn, as will larger
puddingwife wrasses (Halichoeres radiatus). Octopuses
regularly prey upon whelks. If that weren't enough, a bird
called the oystercatcher (Haematopomus palliatus) plucks
whelks off of intertidal rocks.
Some organisms depend upon whelks. Dwarf suck-on
limpets (Acmea luecopluera) can be found living on the
undersurface of the whelk shells. After a whelk's death,
their empty shells provide homes for hermit crabs. In fact,
following whelk extinctions in Bermuda, purple-clawed
hermit crabs (Coenobita clypeatus) began to die off. Lack
of whelk shells apparently created a housing shortage for
these hermit crabs.
Territorial regulations protect whelks in the USVI.
There is a closed season for whelk fishing that goes from
April 1st to September 30th of each year this closure
protects whelk during their reproductive phase. There is a
minimum harvest size of 27/16-inch shell width (62 mm).
Fishers are encouraged to use a measuring loop [available
from DFW] if the whelk can pass through the loop, it's
too small to keep. Whelk must be landed whole and in
their shell. Otherwise, there is no harvest limit and no
special license is required.
References for this article are available upon request
from DFW. For more information on this or other animals
in the USVI please visit our web site at:

ST. THOMAS, VI 00802
PHONE 340-775-6762 FAX 340-775-3972
PHONE 340-772-1955 FAX 340-772-3227

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