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FI SH D  I V ER SI T Y

S2

What

What Is It?

BENCHMARK

Fish diversity is a measure of the variety of fishes

No loss of fish diversity (averaged for

living in a given area.

subregions of MAR, habitat type) from

levels

levels observed in 2006 MAR survey.

Diversity can be assessed in many ways. Here, we

TA R G E T

express fish diversity as the product of species

richness and evenness (where richness is equal to

To

To be developed once additional data

the number of species present, and evenness is a

and analyses are available.

and

measure of how equal in number the different fish

RED FL AG

species are).

Any loss of fish diversity (averaged for

Any

Key Mesoamerican fish "guilds" or functional groups

subregions of MAR, habitat type) from

are the herbivorous fishes (e.g., parrotfishes) and

levels

levels observed in 2006 MAR survey.

the commercially significant fishes (e.g., grouper,

snapper). We can also measure diversity within these

selected groups.

Usefulne s s

WH Y DO WE ME A SURE IT ?

The scientific expertise needed to measure total fish

diversity is beyond the technical capacity of most

High fish diversity is generally equated with better

regional monitoring programs. Monitoring total fish

reef health. (But measures of fish abundance and size

diversity over large spatial scales would be extremely

distribution must also be considered.)

time-consuming and costly. However, measuring the

Shannon-Wiener diversity index from a limited list of

A long history of fishing in the MAR has directly

commonly identifiable species from various trophic

affected fish populations by eliminating individual

levels or guilds is feasible, relatively easy to measure,

organisms, reducing reproductive potential and larval

and can serve as a proxy for overall fish biodiversity.

recruitment, and disrupting trophic structure. Fish

populations are characterized to help understand

The REEF roving diver method provides a practical

changes in community dynamics and identify human

management tool, enabling many sites across large

impacts such as overfishing or habitat destruction.

spatial scales to be assessed in a relatively uniform

and easy manner. An added benefit of using the

On reefs, there are generally a few "driving" species

REEF method is that the data can be submitted to

that play a critical role in reef processes or functions.

a large web-based database, and analyzed results

Often, there may not be another species locally

are returned to the surveyor. Interpretation of REEF

capable of playing that driving role. Many more

fish data has limitations, but the caveats are well-

"passenger" species also live on the reef. Their role

defined by REEF. (For example, more REEF surveys are

is less critical, or there may be many "redundant

available from popular dive locations, and many areas

species" that could fill that passenger role (a type of

have not been surveyed yet.)

ecological redundancy).

Measurements of total fish biodiversity are useful but

Maintaining ample biodiversity within these key

require numerous experienced taxonomists and can

functional guilds (e.g., herbivores) is critical in ensuring

be very costly.

that functionality can be maintained even if a key

driving species declines (e.g., Diadema sea urchins).

Status

St atus

HOW DO WE ME A SURE IT ?

OW

Diversity of reef fish in the MAR is similar to other reef

areas in the Caribbean. The "condition" is considered

Many different protocols are used to estimate fish

fair to good based on the number of species, but

species diversity, richness and relative abundance.

not abundance. At least 245 species of marine reef

One example is the roving diver method developed

fish are found along the Yucatan Peninsula, 317

by the Reef Environmental Education Foundation

in Belize, 218 in Guatemala, and 294 in Honduras.

(REEF): a diver makes a timed swim while recording

Important families include Scaridae (parrotfishes),

fish observations7. (See Appendix 3 for details).

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