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Fish fauna, and new or unusual findings [4]

In order to achieve a comprehensive understanding of the composition and distribution of MAR fishes, a range of methods and technologies for observation and sampling was applied:

  • Leg 1 of the expedition focused on mid-water fishes and applied three trawls of different designs and sizes to obtain catches from different size ranges and depth strata. Hydroacoustic observations of sound-scattering layers were also central.
  • Leg 2 fished on the bottom using trawl (RV G.O.Sars) and passive gears such as longlines, gillnets and traps (MS Loran). In addition, visual fish observations were made by remotely operated vehicles (ROVs) and baited video and still photo landers. Video clips show a varied fauna near the bottom, including also target species of fisheries, e.g. orange roughy (Hoplostethus atlanticus) and roundnose grenadier (Coryphaenoides rupestris). All size ranges of fish were observed and captured, from the tiniest larvae of a few mm total length, to a Greenland shark of 4,5 m caught on longline by MS Loran.

During Leg 1, 179 mid-water fish species were identified, but several specimens could not readily be identified to more than family or genus level. The number of species will increase, probably well beyond 200. On Leg 2, there is more uncertainty, but (as of 22 July) at least 87 different near-bottom fish had been identified to species, and again the number is certain to increase when the samples are analysed further. The remarkable news is that 13 of the species are new to the North Atlantic, and another 44 have only been recorded 5 or less times previously.

The material collected (at least 80,000 specimens), includes specimens of uncertain identity, but further analyses are required to determine if any of these represent new species to science. Some candidate new species are:

New ceratioid anglerfish?


Fig. 8: The ceratioid anglerfish of the genus Lophodolus that may be a new species. (Photo: Tracey Sutton)

The deep-sea anglerfishes (suborder Ceratioidei) are the most diverse group of bathypelagic (1000 m and below) fishes, with 157 currently recognized species. During the MAR-ECO cruise, an anglerfish was captured which could not be assigned to species. The specimen could easily be assigned to the family Oneirodidae, genus Lophodolos, by the form of its head spines and the placement of the luring apparatus. The specimen differed from the two known species in the genus by the structure of the head and the form of the ‘lure’ at the tip of the luring apparatus. The ‘lure’ structure, known as the ‘esca,’ is a primary character used to differentiate species.  Further detailed analysis of this specimen and comparisons with museum specimens will be required for verification. Several specimens of other anglerfish species were diagnosed only to genus during the cruise, but given the lack of sampling in this specific location, and the lack of sampling in the bathypelagic zone in general, it would not be surprising if some of these forms proved to be new to science as well after detailed examination.

Scientist to be credited:  Tracey Sutton

New Ophidiiform fish?


Fig. 9: The ophidiiform fish of the genus Porogadus that may be a new species. (Photo: Franz Uiblein)

One of the most common fish orders in the deep sea is the Ophidiiformes, and from this group new records or species may still be expected. Two specimens collected in the central rift valley in the southern MAR-ECO box could only be identified to the genus Porogadus, but they turned out to be different from the three Porogadus species known from the western Atlantic and other candidate species from the eastern Atlantic. These two specimens may represent a new species, but further comparisons and detailed taxonomic investigations need to be carried out to provide the necessary clarification.

Scientist to be credited: Franz Uiblein

Rare occurrence of the Aphyonus gelatinosus


Fig. 10: Aphyonus gelatinosus, a peculiar fish caught only rarely in the North Atlantic. (Photo: David Shale)

This peculiar fish was captured twice in the bottom trawl. Previously it has only been recorded once in the North Atlantic, near the Azores. It appears to occur in several of the world’s oceans, yet, in total only a few specimens are known. The species belongs to the family Aphyonidae which contains 20 species, all of which have been found on or near the bottom at great depths. All of them are semitransparent, covered in a gelatinous layer, and they have very poorly developed eyes.

The species captured on the MAR-ECO cruise is pinkish and has a blue-coloured stomach. The previous North Atlantic record was from 1100-1200m depth. The present specimens were taken from even greater depths, about 1750 and 3000m.

The members of this fish family are viviparous, which means that instead of spawning eggs, they give birth to young. Practically nothing else is known about their biology.

This peculiar fish was captured twice in the bottom trawl. It has only been recorded very few times in the Atlantic Ocean.

Scientist to be credited: Ingvar Byrkjedal

Evidence of past fisheries

While it is not a specific aim of MAR-ECO to assess the impact of anthropogenic activities such as fishing on the MAR ecosystems and fauna, evidence of past activities were observed during the expedition. There has been commercial fishing along the MAR since the early 1970s, so these are not to be regarded as pristine fishing ground. Trawling and longline fisheries have been conducted on many hills, mainly targeting near-bottom fishes such as roundnose grenadier, alfonsino, orange roughy, and redfish. Assessment of the impact of these fisheries on abundance of target species, communities, and habitats is beyond the remit of the project, but a few observations of human influence were made:

During ROV dives we observed occasionally lost fishing gear, primarily in rugged terrain on top of mounds. On one occasion a trawl net was found. MS Loran also recorded lost longlines, that appeared to have been lost recently.

Another sign of anthropogenic influence is the frequent occurrence of garbage, e.g. plastic bags and other objects, in the bottom trawl catches at all depths over very wide areas.

Scientists to be credited: Ricardo Serrao Santos, Gui Menezes, Odd Aksel Bergstad

Scientists to be credited for these findings: Pelagic and demersal nekton teams, PIs: Tracey Sutton, Uwe Piatkowski, Franz Uiblein, Ingvar Huse.

reAD MORE

See the full press release with selected highlights from the scientists’ findings!  

~ Findings
~ Introduction 
~ Facts

Selected highlights
~ Hydroacoustic recording
~ Mesoscale ring structures
~ New squid species
~ Fish fauna
~ Charlie-Gibbs fracture zone
~ Bottom fauna
~ Gelatinous zooplankton

 Download
~ Full press release (in pdf.)
~ Resumé of the findings (in pdf.)

See also
~G.O. Sars-cruise-journal

 

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