Good fences make good neighbors: Habitat partitioning by spinyhead (Acanthemblemaria spinosa) and secretary (Acanthemblemaria maria) blennies.
Spinyhead blennies (Acanthemblemaria spinosa) and secretary blennies (Acanthemblemaria maria) are abundant, tube-dwelling fishes on the reefs of Bonaire, Netherlands Antilles. In other areas of the Caribbean A. maria are relatively rare and although habitat partitioning has been described for A. spinosa, little is known concerning habitat partitioning in A. maria or about the competitive interactions between the two species. This study determines the species distribution and density of A. spinosa and A. maria in the nearshore reefs of Bonaire and documents the competitive interactions between the 2 species using a manipulative experiment. The distribution of A. spinosa and A. maria was determined using transects on the reef slope and by observations of patch reefs on the reef flat. Experimental condos were constructed and placed on sand flats at 6 m depth, where there is overlap of the ranges. Five individuals from both species were captured and placed on a condo to observe the competitive interactions between A. spinosa and A. maria. A. maria are more abundant on the reef flat while A. spinosa are primarily found on the reef slope (> 6 m). In the condo experiments A. maria were dominant over A. spinosa. It is hypothesized that the slightly larger size and increased competitive nature due to higher densities of A. maria give them an advantage over A. spinosa. This study supports previous findings on the distribution of A. maria and A. spinosa on coral reefs and documents competitive dominance of A. maria over A. spinosa.