Mauritanian Midwater fish in the Discovery Collections

Study Extent

Trawls were predominantly undertaken at two stations. Station 12181 was located in northerly waters adjacent to Western Sahara, with sampling events occurring between the 12th and 17th of September, 1990. Station 12183 was sampled between the 19th and 21st of September, 1990 further to the south, nearer Mauritania but inside the exclusive economic zone of Cape Verde.

Sampling

Samples were taken using a multiple rectangular midwater trawl (RMT8+1M) as described by Roe and Shale (Roe and Shale, 1979). This apparatus is made up of three separate pairs of nets, each consisting of a 1 m2 net used for sampling zooplankton and an 8 m2 net used to sample micronekton.

Quality Control

The larger net has a mesh size of 4.5 mm, suited to capture the majority of mesopelagic fish, however, some ichthyoplankton and fish with a body depth smaller than 4.5 mm may not have been retained. D195 Cruise was primarily conducted to investigate the photobiology of mesopelagic animals and was not concerned overly with creating species-level biodiversity records. As such, in addition to the removal of the eyes of certain taxa such as Malacosteus and Stylephorus, and the removal of the taxonomically-diagnostic bioluminescent lures of anglerfish, certain whole individuals were removed and frozen for genetic analysis (Herring, 1990).

Method steps

1. Samples from D195 were located during the production of a full catalogue of fish specimens held at the NOC Discovery Collections and during a search of both accessioned and un-accessioned IOS material at the NHM. 17 lots of unsorted material were located at the NOC, including one (12183#18) which may have suffered from an equipment failure as only five individual fish were retained. Fish from 16 trawl events were therefore available for analysis, with the majority coming from the southern station (12183) and just one (12181#4) originating from the northerly station.

Midwater fish

1. Melanocetidae
   rank: family
2. Myctophidae
   rank: family
3. Paralepididae
   rank: family
4. Melamphaidae
   rank: family
5. Stomiidae
   rank: family
6. Sternoptychidae
   rank: family
7. Bathylagidae
   rank: family
8. Gonostomatidae
   rank: family
9. Serrivomeridae
   rank: family

Tropical North Atlantic, off Mauritania & Cape Verde