Figure 6. An encrusting sponge field comprised of several morphospecies of sponges on Rosemary Bank (photo credit SEA/SAC 2007 Department of Business, Innovation and Skills).
Other potential sponge aggregations may occur on Rosemary Bank, these being primarily characterised by hexactinellid sponges and white encrusting sponges (Axelsson et al 2012) and identified as having medium confidence with regards to their designation as deep-sea sponge aggregations due to the lack of density data for these records (Table 2). These aggregations were found in waters 430–760m depth, typically on gravelly mud, sand and sandy gravel in association with Cidaris cidaris, Munida and Psolus as with the encrusting sponge fields identified with high confidence from similar depths during the SEA7 survey (Howell et al 2007).
Hatton Bank
Nine out of 10 records from Hatton Bank were verified with high confidence as deep-sea sponge aggregations (Table 2).
Four of these were derived from fisheries bycatch data during Spanish surveys (Durán Muñoz et al 2011; 2012), which constitute aggregations that conform to boreal ostur. Bycatches in excess of the recommended ICES limit (ICES 2012) of 400kg were identified, made up mostly of geodiid sponges such as Geodia spp. (Figure 7) as well as the occasional catch of axinellids and the glass sponge Pheronema carpenteri (Durán Muñoz et al 2012). These aggregations were found along the eastern slope of Hatton Bank in waters 1064–1248m deep on a contourite deposit of sands and muds. Seapens and gorgonians were also caught along with boreal ostur, but their biomass was relatively minor in comparison to sponge catches ranging from 404–3000kg and thus these appear to form an associated fauna with these grounds.
Figure 7. Black and white image of large bycatch of geodiid sponges forming boreal ostur along the eastern slope of Hatton Bank (photo credit P. Durán Muñoz, IEO).
