SE Atlantic Ocean 2019 - seafo

SE Atlantic Ocean 2019

Sailing order – SE Atlantic Ocean 2019 – Leg 1

RV Dr. Fridtjof Nansen
Cruise Number: 2019401

Leg 1
START: 24 January, Cape Town, Republic of South Africa
END: 25 February, Cape Town, Republic of South Africa

SURVEY AREA

Background

In the report from the 2015 Scientific Committee (SC), the following priority was expressed:
Chapter 21.11 The SC considered alternative study areas for future scientific cruises, if
opportunities arise. It was agreed to prioritize two such areas within the CA, both including
existing fishing areas and fishing closures. The two areas are:

a) Discovery and Meteor Seamount complexes in Sub-Area D, including Closures #12 and
14.[#14 and 15 changed numbers to 6 and 7].
b) Existing fishing areas and Closure #1 in SEAFO Division A1, if possible, all closures and
existing fishing areas in Sub-Area A.

OVERALL OBJECTIVES

benefit regional science and enhance the global understanding of the Southeast Atlantic ecosystems

• to analyse occurrence and abundance of benthopelagic fish and sessile epibenthos, including
  indicators of VMEs
• sample target fish resources to obtain more biological data, including tissue samples for genetic studies

en route recording of mesopelagics, seabirds, and mammals, as well as the standard EAF-Nansen
sampling regional biological and chemical oceanographic data, microplastics and litter etc.

Key Questions to be addressed

   1.   Geomorphology, benthic habitats and benthos
   2.   Fish resources
   3.   Large epipelagic fish (tuna and tuna-like species, sharks), mammals, turtles and seabirds
   4.   Physical, chemical and biological oceanography
   5.   Debris (litter on the surface and seabed)
   6.   Microplastics
   7.   Mesopelagic acoustic scattering layers en route

   Key activities related to EAF-Nansen programme themes

   Related to Theme 7:
   Enhanced baseline information on bathymetry, geomorphology and distribution and quality of benthic
   habitats and their biota, including VME taxa.

OUTCOMES & DELIVERABLES

•   Survey reports to SEAFO, describing methods, samples collected (number and
    type) and initial findings in relation to the questions to be addressed.
•   Datasets for additional analysis (contributing to Science Themes as indicated
    above)
•   Samples and voucher specimen collections for post-survey analyses (see table
    below)
•   Original papers for primary scientific outlets.
• Oceanographic raw data for international databases

Survey Design

SAMPLING METHODS AND PROTOCOLS
1) Using multi-beam echosounders to obtain detailed maps of sea bottom

Echograms from 18-hour repeat
study of an aggregation of fish
above the Valdivia North seamount
summit (EK60, 38KHz). Upper
figure: full time-series starting at
13:00 UTC (15:00 local time) on 6
February and ending at approx.
07:00 UTC on the next day; Lower
left: detailed echogram from
nighttime (02-03UTC), Lower
right: same from daytime (13:00
UTC)

SAMPLING METHODS AND PROTOCOLS
         VAMS (Video Assisted Multi Sampler)

      VAMS IN OPERATION

      Observed from the free swimming
      ROV
            Sonar
            Altimeter
            CTD
            Oxsygen
            Fluorescens
            Current meter
            HD camera
            Van Veen Grabbs
            *Corer, sampler for surface layer, Manipulator arm etc.

Preliminary detailed planning
The Discovery seamount complex lies approximately 900NM from Cape Town. Depending on ships speed it will take
between 3,7 (10kn) and 5,3 days (7kn) to reach the complex. To cross the complex and continue to the Meteor
complex will take 1,7-2,4 days. Crossing the Meteor seamount will take 0,5-1 day. The total steaming time is
calculated between 11,3 (10kn) and 16,2 (7kn) days. Between 15-20 days available for surveying:

Discovery seamount complex with suggested VAMS transects and sampling stations (the orange points are shown
only to illustrate a possible distribution of stations on a VAMS line – the location of these will very likely change).
The detailed coverage is meant to indicate that parts of a seamount will be covered with a tighter (0,5 or 1NM) grid.
VAMS sampling sites will cover areas open for fishing, areas restricted to longline fishing only and the closed areas.

                                                                      A

Meteor seamount complex with suggested VAMS transects. The detailed coverage is meant to indicate that parts of
a seamount will be covered with a tighter (0,5 or 1NM) grid.

Survey effort
The Discovery seamount complex consists of 13 seamounts. VAMS stations on all 13 will not be possible, thus
certain tops will not to be prioritised. The map below shows the Discovery seamount complex based on
GEBCO depth data. The time spent to survey selected seamounts will vary depending on the size of the
seamount. The general approach will be to cross the seamounts at the centre from approximately 2000 m depth.
Exploratory transects will be followed by a tight/narrow coverage of areas deemed interesting based on results
from the exploratory transect. VAMS locations will then be selected based on results from the detailed
coverage. A detailed bathymetric coverage of an area corresponding to a smaller seamount (A in Figure 2)
would take approximately 17 hours (1 NM spacing) or 34 hours (0,5NM spacing). Collection of VAMS data
will be limited to daytime (12hours) given that only one shift will be operating the VAMS. During this period a
maximum of three VAMS dives could be done, though based on earlier studies on average only 2 stations are
sampled, including CTD. In general, the location of the dives and collection of benthic samples will be done on
the lower/middle slope, the upper slope and the top / plateau. This leaves 12 hours at night for detailed
multibeam coverage. If approximately 1,5 days are set aside for each VAMS location, then app. 7 such
locations could be covered during a 11 day period on Discovery. Correspondingly 3-4 locations could be
covered on the Meteor in 5-6 days.