Distribution of sympatric seahorse species along a gradient of habitat complexity in a seagrass-dominated community

Abstract

We present estimates of local population abundance, distribution and habitat preference for 2 European seahorse species, Hippocampus guttulatus and H. hippocampus. We predicted that these sympatric species would partition their habitat into 2 broadly defined habitat types: complex vegetated habitats and sparsely vegetated sand flats. We sampled populations using underwater visual census techniques over landscape (100s to 1000s m) and microhabitat scales (<1 m). Over landscape scales, we estimated abundance and quantified habitat associations using generalized linear models. Over microhabitat scales, we tested for holdfast (attachment site) preferences using selection indices. Both species were patchy in distribution, but H. guttulatus mean density (0.073 ind. m ). At a landscape scale, H. guttulatus abundance was positively correlated with an index of habitat complexity, the percentage of substrate covered by flora and sessile fauna. Conversely, H. hippocampus used more open and less speciose habitats that were subjected to greater oceanic influences. At microhabitat scales, both species significantly preferred grasping holdfasts over barren surfaces, but the species differed in holdfast preferences: H. guttulatus grasped all prospective holdfast types with equal probability while H. hippocampus significantly avoided both fauna and flora that formed large colonies or tracts of dense vegetation. Patterns in habitat use were consistent with differences in morphology and foraging strategy. Despite similar life histories, these sympatric species may respond differently to disturbances that modify habitat structure and complexity over landscape or microhabitat scales.KEY WORDS: Habitat selection · Habitat complexity · Hippocampus · Syngnathidae · Habitat suitability models · Underwater visual census · Foraging strategy Resale or republication not permitted without written consent of the publisher

Extreme habitat specialisation and population structure of two gorgonian-associated pygmy seahorses

“…Low numbers of juveniles were found for both Hippocampus bargibanti and H. denise, which is similar to findings for other seahorse species (Bell et al 2003, Curtis & Vincent 2005, Martin-Smith & Vincent 2005, Rosa et al 2007. The record of a recently settled juvenile male H. denise in the present study, at 13 mm SL, indicates that sexual maturity is attained soon after settlement.…”

A conspicuous population of the long-snouted seahorse, Hippocampus guttulatus (Actinopterygii: Syngnathiformes: Syngnathidae), in a highly polluted Mediterranean coastal lagoon

“…This is probably due to the fact that the western part of the lagoon is in direct Uncommonly for this species, we found only 3 specimens of Hippocampus guttulatus on algal meadows. Other researchers (Foster and Vincent 2004, Curtis and Vincent 2005, 2006, Vincent et al 2011 reported that H. guttulatus inhabited seagrass-or algal beds. The presently reported study is also in partial disagreement with the recent work of Gristina et al (2014), who also studied the Mar Piccolo of Taranto.…”

Habitat Preference and Population Structure of Two Data Deficient Seahorse (Syngnathidae) Species

“…While juveniles may have been missed due to a planktonic stage it is unclear as to why seahorses between 3-5 cm were not recorded. Other fisheries studies also show that intervening size classes between small juveniles and adults of several marine fish including two species of seahorses (H. guttulatus and H. hippocampus) are rarely seen in benthic surveys and plankton tows (Pérez-Ruzafa et al, 2004;Curtis & Vincent, 2005). While smaller seahorses may have been missed due to the sampling methodology they may be utilizing a different habitats has been observed in H. comes in the Philippines (Perante, 2002;Morgan & Vincent, 2007).…”