Do birds of a feather flock together? Comparing habitat preferences of piscivorous waterbirds in a lowland river catchment

Waterbirds can move into and exploit new areas of suitable habitat outside of their native range. One such example is the little egret (Egretta garzetta), a piscivorous bird which has colonised southern Britain within the last 30 years. Yet, habitat use by little egrets within Britain, and how such patterns of habitat exploitation compare with native piscivores, remains unknown. We examine overlap in habitat preferences within a river catchment between the little egret and two native species, the grey heron (Ardea cinerea) and great cormorant (Phalacrocorax carbo). All species showed strong preferences for river habitat in all seasons, with other habitat types used as auxiliary feeding areas. Seasonal use of multiple habitat types is consistent with egret habitat use within its native range. We found strong egret preference for aquatic habitats, in particular freshwaters, compared with pasture and arable agricultural habitat. Egrets showed greater shared habitat preferences with herons, the native species to which egrets are most morphologically and functionally similar. This is the first study to quantify little egret habitat preferences outside of its native range

Spatial Patterns of Parrotfish Corallivory in the Caribbean: The Importance of Coral Taxa, Density and Size

The past few decades have seen an increase in the frequency and intensity of disturbance on coral reefs, resulting in shifts in size and composition of coral populations. These changes have lead to a renewed focus on processes that influence demographic rates in corals, such as corallivory. While previous research indicates selective corallivory among coral taxa, the importance of coral size and the density of coral colonies in influencing corallivory are unknown. We surveyed the size, taxonomy and number of bites by parrotfish per colony of corals and the abundance of three main corallivorous parrotfish (Sparisoma viride, Sparisoma aurofrenatum, Scarus vetula) at multiple spatial scales (reefs within islands: 1–100 km, and between islands: >100 km) within the Bahamas Archipelago. We used a linear mixed model to determine the influence of coral taxa, colony size, colony density, and parrotfish abundance on the intensity of corallivory (bites per m2 of coral tissue). While the effect of colony density was significant in determining the intensity of corallivory, we found no significant influence of colony size or parrotfish abundance (density, biomass or community structure). Parrotfish bites were most frequently observed on the dominant species of reef building corals (Montastraea annularis, Montastraea faveolata and Porites astreoides), yet our results indicate that when the confounding effects of colony density and size were removed, selective corallivory existed only for the less dominant Porites porites. As changes in disturbance regimes result in the decline of dominant frame-work building corals such as Montastraea spp., the projected success of P. porites on Caribbean reefs through high reproductive output, resistance to disease and rapid growth rates may be attenuated through selective corallivory by parrotfish

Fussy Feeders: Phyllosoma Larvae of the Western Rocklobster (Panulirus cygnus) Demonstrate Prey Preference

The Western Rocklobster (Panulirus cygnus) is the most valuable single species fishery in Australia and the largest single country spiny lobster fishery in the world. In recent years a well-known relationship between oceanographic conditions and lobster recruitment has become uncoupled, with significantly lower recruitment than expected, generating interest in the factors influencing survival and development of the planktonic larval stages. The nutritional requirements and wild prey of the planktotrophic larval stage (phyllosoma) of P. cygnus were previously unknown, hampering both management and aquaculture efforts for this species. Ship-board feeding trials of wild-caught mid-late stage P. cygnus phyllosoma in the eastern Indian Ocean, off the coast of Western Australia, were conducted in July 2010 and August-September 2011. In a series of experiments, phyllosoma were fed single and mixed species diets of relatively abundant potential prey items (chaetognaths, salps, and krill). Chaetognaths were consumed in 2–8 times higher numbers than the other prey, and the rate of consumption of chaetognaths increased with increasing concentration of prey. The highly variable lipid content of the phyllosoma, and the fatty acid profiles of the phyllosoma and chaetognaths, indicated they were from an oligotrophic oceanic food chain where food resources for macrozooplankton were likely to be constrained. Phyllosoma fed chaetognaths over 6 days showed significant changes in some fatty acids and tended to accumulate lipid, indicating an improvement in overall nutritional condition. The discovery of a preferred prey for P. cygnus will provide a basis for future oceanographic, management and aquaculture research for this economically and ecologically valuable species

Habitat Associations of Juvenile Fish at Ningaloo Reef, Western Australia: The Importance of Coral and Algae

Habitat specificity plays a pivotal role in forming community patterns in coral reef fishes, yet considerable uncertainty remains as to the extent of this selectivity, particularly among newly settled recruits. Here we quantified habitat specificity of juvenile coral reef fish at three ecological levels; algal meadows vs. coral reefs, live vs. dead coral and among different coral morphologies. In total, 6979 individuals from 11 families and 56 species were censused along Ningaloo Reef, Western Australia. Juvenile fishes exhibited divergence in habitat use and specialization among species and at all study scales. Despite the close proximity of coral reef and algal meadows (10's of metres) 25 species were unique to coral reef habitats, and seven to algal meadows. Of the seven unique to algal meadows, several species are known to occupy coral reef habitat as adults, suggesting possible ontogenetic shifts in habitat use. Selectivity between live and dead coral was found to be species-specific. In particular, juvenile scarids were found predominantly on the skeletons of dead coral whereas many damsel and butterfly fishes were closely associated with live coral habitat. Among the coral dependent species, coral morphology played a key role in juvenile distribution. Corymbose corals supported a disproportionate number of coral species and individuals relative to their availability, whereas less complex shapes (i.e. massive & encrusting) were rarely used by juvenile fish. Habitat specialisation by juvenile species of ecological and fisheries importance, for a variety of habitat types, argues strongly for the careful conservation and management of multiple habitat types within marine parks, and indicates that the current emphasis on planning conservation using representative habitat areas is warranted. Furthermore, the close association of many juvenile fish with corals susceptible to climate change related disturbances suggests that identifying and protecting reefs resilient to this should be a conservation priority