Using standardized fish-specific autonomous reef monitoring structures (FARMS) to quantify cryptobenthic fish communities

1. Biodiversity inventories and monitoring techniques for marine fishes
often overlook small (<5cm), bottom-associated (‘cryptobenthic’)
fishes, and few standardized, comparative assessments of cryptobenthic
fish communities exist. We sought to develop a standardized, quantitative
survey method for cryptobenthic fishes that permits their sampling across
a variety of habitats and conditions. 2. Fish-specific autonomous reef
monitoring structures (FARMS) are designed to sample cryptobenthic fishes
using a suite of accessible and affordable materials. To generate a
variety of microhabitats, FARMS consist of three layers of stacked PVC
pipes in three different sizes, as well as a bottom and top level of loose
PVC-pipe fragments in a mesh basket. We deployed FARMS across a variety of
habitats, including coral reefs, seagrass beds, oyster reefs, mangroves,
and soft-bottom habitats across six locations (Hawai’i, Texas, Panama,
Saudi Arabia, Brazil, and Curaçao). 3. From shallow estuaries to coral
reefs beyond 100 m depth, FARMS attracted distinct communities of native
cryptobenthic fishes with strong site or habitat specificity. Comparing
the FARMS to communities sampled with alternative methods (enclosed
clove-oil stations on coral reefs in Panama and oyster sampling units on
oyster reefs in Texas) suggests that FARMS yield a subset of cryptobenthic
species representative of those present on local coral and oyster reefs.
While FARMS yield fewer individuals per sample and are restricted to
cryptobenthic species, they are efficient sampling devices relative to the
sampled area. 4. We demonstrate that FARMS represent a useful tool for
standardized collections of cryptobenthic fishes. While natural substrata
are bound to yield more mature communities with a larger number of
individuals and wider range of specialist species, the potential to deploy
and retrieve FARMS in turbid environments, beyond regular SCUBA depth, and
where fish collections using anesthetics or ichthyocides are forbidden
suggests that they are a valuable complementary technique to survey fishes
in aquatic ecosystems. Deploying FARMS in locations and habitats where
cryptobenthic fish communities have not been studied in detail may yield
many valuable specimens of unknown or poorly known species.