The queen conch, Strombus gigas, is an important fisheries resource in the Western Tropical Atlantic. In order to maintain harvesting success, improve
fisheries management and contribute to mariculture pursuits, a detailed
understanding of the life history traits of this species is required.
Traditionally, this has been achieved by tedious and time-consuming
long-term field observations. This study presents a highly versatile and
rapid technique to estimate the timing and rate of shell growth based on
sclerochronology. The Belizean S. gigas specimens (N = 2) from the offshore atoll,
Glovers Reef, reached their final shell size (maximum shell height: 22.7 and
23.5 cm, respectively; completed formation of the flared lip) after only two
years. However, seasonal growth rates varied considerably. Shells grew up to
6 mm d−1 during spring (April-June) and fall (September-November) but
only 1 to 2 mm d−1d uring July and August. Furthermore, shell growth
ceased between December and March. Fastest shell growth occurred nearly
contemporaneously with times of maximum precipitation which probably
resulted in increased food availability. Slowest shell growth however,
occurred during times of reduced rainfall and reduced riverine runoff, i.e.
during times of reduced food supply. Sea-water temperature apparently did
not exert a major control on shell growth. Notably, the slow winter growth
was marked by a distinct purple-colored growth line in the cross-sectioned
flared lip. Formation of a second major growth line (brown) fell together with the main
reproduction period (late October/early November). Shell microgrowth
patterns potentially represent daily or semidiurnal periods but cannot be
used to assign exact calendar dates to each shell portion, because they were
not visible across the entire cross-section of the whorl. Also, the
protruding spines developed on the outer shell surface do not function as
time gauges. The time represented by the shell portion between consecutive
spines varies greatly from 1 to 72 days. Sclerochronology can potentially
facilitate maricultural strategies and aid in site pre-testing and selection
to grow S. gigas.