The composition and spatial distribution of scavenging hyperbenthos in the Cape d'Aguilar Marine Reserve, Hong Kong

Abstract

Baited traps with a 5 mm diameter opening were deployed 9 cm off the seabed in the Cape d'Aguilar Marine Reserve, Hong Kong. In contrast to analogous studies from boreal waters, lysianassoids accounted for 0.5% of the total number of trapped hyperbenthos. Species of Tisbe (Copepoda: Tisbidae), Ceradocus (Gammaridea: Melitidae), Nebalia (Leptostraca: Nebaliacea), unidentified benthic ostracods, Neanthes cricognatha (Polychaeta: Nereidae) and a species of Lepidepecreum (Amphipoda: Lysianassoidea) were caught in a decreasing order of numerical importance. A spatial segregation of trapped fauna was identified between the reserve's shallow Lobster Bay (<–2 m Chart Datum (CD)) and deeper-waters (between –6 and–17 m CD) outside it. Ceradocus sp. monopolized the trapped fauna in the former area, while the other species were caught almost exclusively from the latter. Insignificant Ceradocus sp. catch differences between baited and control traps suggested that they functioned only as ‘habitat traps’ for this species. Almost all other organisms attracted to the bait were hyperbenthic scavengers. Their absence from the shallows might be due to the coarser and lower organic contents of the sediments, also related to faster flow rates here. Finally, we confirm that in subtropical Hong Kong, lysianassid amphipods are not as significant hyperbenthic scavengers as they are in boreal waters.