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CONCH ABUNDANCE

ORITY ON

D10

RI

RE

TH

EF

S FOR HEAL

What

What Is It?

BENCHMARK

Adult conch populations of 50-300

Adult

Queen conch (Strombus gigas) are large, herbivorous

individuals per hectare (depending on

marine mollusks usually found in shallow sandy

habitat and management zone) within

areas with seagrass-algal meadows or mixed coral

communities. Throughout the MAR region, the queen

the next 5-10 years.

the

conch has important economic, social and cultural

value -- for which reasons it is a targeted commercial

TA R G E T

species. The conch abundance indicator is measured

Adult conch populations of 300-800

Adult

as the number of individuals per hectare (i.e.,

individuals per hectare within the next

density).

20-25 years.

The queen conch has been listed in CITES Appendix

RED FL AG

II since 1992, which means that CITES permits must

Any consistent (3-4 year) reduction

be issued for all exports. Exporting nations must

in average density, particularly when

demonstrate that their stocks are stable and well-

correlated with a drop in production

managed. This requirement has spurred research and

(indicator D9).

(indicator

documentation of stocks in the region.

Why Do We Measure It?

Queen conch have an important ecological role as

How Do We Measure It?

herbivores, as well as a socioeconomic role as an

important fishery in the region. Conch populations

The most significant parameter to measure the status

in the MAR are considered important to the wider

of conch populations is overall abundance (measured

Caribbean and may include both "source" and "sink"

as their density or number of individuals per hectare),

populations (both providing and receiving recruits) for

which is surveyed by using belt transects to count the

areas outside the MAR.

number of conch in a spatially defined area. Population

structure is estimated by taking direct measurements

The density of conch (number of adult individuals per

of shell size and lip thickness to estimate age.

hectare) is a significant indicator of population status,

Usefulness

as scientific studies have demonstrated that densities

lower than 50 conch/ha result in reproductive

Conch abundance is a good indicator as it provides

failure36,37. More recent studies indicate that the

immediate feedback regarding overfishing impacts

critical threshold for reproductive success may be as

and is responsive to management strategies.

high as 200 conch/ha38. Equally important are data on

essential nursery grounds, which are often defined by

This indicator also has high ecological relevance as

specific abiotic and biotic characteristics (e.g., water

conch are important herbivores associated with sandy

circulation, food availability, benthic community, and

seagrass habitats. Comparing field-based abundance

sediment type).

data to production (catch) volume from the same

area (e.g., fishing zone or MPA) provides enhanced

Overexploitation, illegal harvesting of undersized

understanding of the fishing effects and production

animals, poor regulatory enforcement, and lack of

capacity of each area.

transboundary management over the last 30 years

have resulted in declining conch populations and

Data collection methods for assessing conch

decreases in catches. Moreover, the complex biology

abundance are usually simple and inexpensive.

of S. gigas does not lend itself well to recovery after

Collecting data on larval dispersal may require more

populations have been heavily depleted. The result

fieldwork and expertise, but such data are essential

has been local extinctions and economic collapse of

in understanding connectivity of populations and

the fishery in some areas.

effectiveness of management actions. The usefulness

of the data can be improved by standardizing collection

and reporting methods in the region.

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