Removal of seagrass canopy: effects

In an experiment in a southern Australian estuary, patches of seagrass canopy were removed to test the importance of the canopy to fish in areas where all other factors were known to be consistent with seagrass presence. The total number of fish was slightly lower in patches cleared of seagrass than in patches of undisturbed seagrass, but was not as low as in unvegetated patches. The benthic habitat was expected to be especially important to non-pelagic species, yet their numbers, and those of the most important commercial species, Sillaginodes punctata, were not lower in patches cleared of seagrass, despite being lower in unvegetated patches. The disturbance associated with removing seagrass was simulated and was not found to affect fish numbers. The diet of all fish caught consists mainly of invertebrates associated with the seagrass canopy and sediment surface (epifauna). Epifaunal abundance and production were highest in seagrass patches, lowest in unvegetated patches and intermediate in patches cleared of seagrass. Patterns of fish abundance did not provide evidence of the importance of seagrass canopy in attracting increased fish abundances compared with unvegetated areas but were consistent with a model stressing the importance of prey availability in the role seagrass plays as habitat for small fish,