Data from: Disentangling drivers of the abundance of coral reef fishes in the Western Indian Ocean

Aim: Understanding the drivers of the structure of coral reef fish
assemblages is vital for their future conservation. Quantifying the
separate roles of natural drivers from the increasing influence of
anthropogenic factors, such as fishing and climate change, is a key
component of this understanding. It follows that the intrinsic role of
historical biogeographical and geomorphological factors must be accounted
for when trying to understand the effects of contemporary disturbances
such as fishing. Location: Comoros, Madagascar, Mozambique and Tanzania,
western Indian Ocean (WIO). Methods: We modelled patterns in the density
and biomass of an assemblage of reef-associated fish species from 11
families, and their association with 16 bio-physical variables. Results:
Canonical Analysis of Principal Coordinates revealed strong country
affiliations of reef fish assemblages and distance-based linear modelling
confirmed geographic location and reef geomorphology were the most
significant correlates, explaining 32% of the observed variation in fish
assemblage structure. Another 6-8% of variation was explained by
productivity gradients (chl_a), and reef exposure or slope. Where spatial
effects were not significant between mainland continental locations,
fishing effects became evident explaining 6% of the variation in data. No
correlation with live coral was detected. Only 37 species, predominantly
lower trophic level taxa, were significant in explaining differences in
assemblages between sites. Main Conclusions: Spatial and geomorphological
histories remain a major influence on the structure of reef fish
assemblages in the WIO. Reef geomorphology was closely linked to standing
biomass, with ‘ocean-exposed’ fringing reefs supporting high average
biomass of ~1,000 kg/ha, while ‘lagoon-exposed fringing’ reefs and ‘inner
seas patch complex’ reefs yielded substantially less at ~500kg/ha.
Further, the results indicate the influence of benthic communities on fish
assemblages is scale dependent. Such insights will be pivotal for managers
seeking to balance long-term sustainability of artisanal reef fisheries
with conservation of coral reef systems.