My scientific publication on the habitat specialisation and population structure of gorgonian-associated pygmy seahorses has just been published in the journal Marine Ecology Progress Series (Link to the MEPS page):


Smith RE, Grutter AS & Tibbetts IR (2012).  Extreme habitat specialisation and population structure of two gorgonian-associated pygmy seahorses.  Marine Ecology Progress Series 444: 195-206


The study was conducted on the two species of pygmy seahorse, Bargibant’s (Hippocampus bargibanti) and Denise’s species (H. denise), which require a living gorgonian coral for their survival.  The main findings of my study are below in the paper’s abstract but I’ve also written some of the study’s important findings below.

– Bargibant’s (Hippocampus bargibanti) and Denise’s pygmy seahorses (H. denise) have some of the lowest densities of any unexploited seahorse populations studied thus far.
– Bargibant’s pygmy seahorse is an extreme habitat specialist, being found exclusively in association with a single genus of gorgonian coral, Muricella spp.
– Denise’s pygmy is a relative generalist as it is found in association with at least eight genera of gorgonian corals.
– It is possible to distinguish between male and female pygmy seahorses by examining the area at the base of the abdomen where males have a small slit-like opening to the brood pouch (figure b) and females have a raised, circular urinogential pore (figure a) (see image).



ABSTRACT: Pygmy seahorses are a group of little-known miniature hippocampid fish that differ considerably in biology and ecology from their larger congeners. We estimated the population density, sex ratio and habitat of 2 sympatric, obligate gorgonian-associated pygmy seahorses, Hippocampus bargibanti and H. denise, in a 20 km long coastal marine protected area in southeast Sulawesi, Indonesia. Belt transects covering 200 m2 each were established at 7 sites and 5 depth contours to record the density of seahorses and their host gorgonians. The population density (± SE) was 1.17 (± 0.27) per 200 m2 for H. denise and 0.34 (± 0.20) per 200 m2 for H. bargibanti, some of the lowest densities for unexploited seahorse populations studied thus far. Male-female pairs (43.9%) were the most common group composition for H. denise, with single, 3 or 4 individuals found on 19.5, 7.3 and 29.3% of inhabited gorgonians, respectively. Denise’s pygmy seahorses inhabited 7.8% of Annella reticulata gorgonians within the survey area but were recorded from a total of 8 gorgonian genera during extensive opportunistic ad hoc searches. Annella spp. density was 10.7 times higher than that of Muricella spp., the sole host of H. bargibanti, of which 20.0% were inhabited. The small population size, occurrence of pygmy seahorses in groups on their hosts with the resulting skew in sex ratios and habitat specialisation likely all impact the species’ population dynamics, and hence these need to be considered in conservation management strategies.

Key words:  Habitat specialist . Miniature species . Abundance . Rare species . Hippocampus . Syngnathidae . Pygmy seahorse . Gorgonian


Please contact me if you would like a full pdf version of the paper.