Deep rock wall/high gradient hard bottom habitats
deeper than 200m
Map ID Number: Not mapped during the workshop
Location: This habitat type is located throughout the New Zealand Exclusive Economic Zone, but is especially associated with continental margins, seamounts, ridge features, submarine canyon walls, and fiord walls
Approximate area: Not recorded during the workshop
Description of habitat type:
Steep gradient areas with a rocky substratum beyond the photic zone, from 200m to kilometers in depth. This environment experiences a range of current conditions, from weak to very strong.
Biological attributes:
Biodiversity on deep rock walls can be high, and differs significantly from surrounding communities. A wide range of sub-habitats are encompassed by the category, including coral communities and boulder fields. Many long-lived species are attached to rock walls at these depths including the giant bubblegum coral (Paragorgia arborea), and Gorgonian corals, including bamboo corals, Antipatharians, Scleractinians, and hydrocorals.
Status and management:
Coral communities are susceptible to even light trawling, with recovery time measured in centuries. Such communities have become iconic globally. These areas are becoming increasingly impacted with advances in fishing technology. Trawling is moving from “flat” features to adjacent hills and seamounts and is able to access progressively deeper sites.
State of information:
The location of deep rock walls is increasingly better known through swath-mapping exercises, but biological characteristics have been investigated only in a small subset of seamounts and canyons. Taxonomic work is required by many specialists.
References and further reading:
Clark et al. (2000), Rowden et al. (2004).