'%Healthy Reefs for Healthy People - A Guide to Indicators of Reef Health and Social Well-being in the Mesoamerican Reef Region%'%by Melanie McField and Patricia Kramer%

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Usefulness

Data

Data Needs

Urchin surveys are quick and easy to conduct, and

Historical baselines (pre-die-off) are not available for

several monitoring programs (e.g., MBRS Project,

most of the MAR region.

AGRRA, CARICOMP) include this component.

The 2006 comprehensive regional AGRRA survey, in

Because Diadema urchins are often cryptic and less

conjunction with MBRS SMP data, will help quantify

active during the day, analysts should be aware that

the distribution and (anticipated) return of this key

most methods involve daytime counts, which may not

herbivore. In 2004 The Nature Conservancy compiled

capture total abundance.

a comprehensive database of known MAR Diadema

occurrences42.

Status

Future urchin surveys should be accompanied by

Prior to the 1983 die-off, Diadema antillarum densities

measurements of associated changes in reef structure

in the MAR ecoregion ranged from 4 to 25 urchins/m2

-- particularly indicators S4, S5 and S6.

. Between 1998 and 2001, the regional average

was 0.03 urchins/m2 -- about one-fifth the average

Management interventions, such as reseeding

Caribbean value of 0.15 urchins/m2 9.

programs, could be considered in areas with

slower natural recovery or highly imperiled remnant

Urchin populations reportedly declined after the 1998

populations of stony corals.

disturbance events (coral bleaching and Hurricane

Research is needed to understand the conditions

Mitch). More recent surveys (2004) suggest some

required for sustaining viably productive Diadema

populations are recovering, with reported densities

populations. Of particular interest would be analyses

between 0.19 and 0.53 urchins/m2 9. Higher

of the potential effects of management (e.g., MPAs)

abundances are generally observed on reef crests

and physical factors (e.g., marine currents) on the

and patch reefs than on fore reefs.

recovery rates of urchin populations.

The pathogen responsible for the 1983 die-off has

not been identified, and further research is needed

-- especially on how to respond if another outbreak

occurs.

Lisa Carnes

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