The evidence accumulated by the Large Pelagic and Hake Longlining Association of Namibia points out that it is mostly the albacore and bigeye tuna that are
negatively impacted by the seismic testing currently being conducted in both
the Namibian and South African EEZ.
In Namibia
and South Africa, the seismic explorations are threatening livelihoods, jobs,
investments and the already ailing respective economies. The past tuna
season has been dismal at best and it is speculated that this seismic testing
being conducted is the direct result. For your reference the tuna export
company that I am employed as the trade manager has only exported this past
season 10% of what’s considered “normal” volumes.
The albacore pole and line industry is
seasonal (October to May), which impacts on its economic viability, and given
the very poor catches these past three years, particularly this season, it
needs support more than ever before, to secure its future.
One of the major consequences is that of the International Commission for the Conservation
of Atlantic Tunas (ICCAT is a RFMO – Regional Fishery Management Organisation) quota utilization. Since tuna is
migratory, ICCAT sets the respective tuna and swordfish quotas for the entire Atlantic
Ocean. ICCAT moderates the albacore tuna quota sharing arrangement between Namibia
(5000mt), South Africa (5000mt), Brazil (3500mt), Chinese Taipei (13500mt) and
Uruguay (1200mt) Namibia is fortunate to be able to work with South African
Tuna Pole and Line (P&L) vessels to catch its quota, because Namibia currently
only has a limited number of its own vessels. Annually ICCAT adjusts each
country’s quota according to catches; size of the country’s fishing fleet, the
importance of the tuna on the local economy, amongst other criteria. Should a country
under perform, then they stand a real chance of losing a portion of their quota
to another nation. Each country has to govern and regulate their fishery in accordance
to the ICCAT rules and regulations. ICCAT’s annual conference will be held in
Cape Town this year and we are all looking forward to hosting this important event.
There is a large concern in the Namibian large pelagic sector as three years ago (2011), more than
4000 tonnes of albacore tuna was caught by around 40 vessels landing into
Luderitz alone. During 2012 only around 1800 tonnes was caught, and
devastatingly, only around 600 tonnes for 2013 so far where over 70% of the
annual catch is during February to March – everything points to increases in seismic exploration in Namibia and
northern South African waters being the main reason, due to fish avoidance. The
tuna are migratory and are mostly caught off the “Tripp” underwater
seamount, close to the border of South Africa, where much of the seismic
exploration activity has and is currently still taking place. Low catch performance also threatens the
likelihood of the International Commission for the Conservation of Atlantic
Tunas (ICCAT) further decreasing Namibia’s quotas.
There are also other possible other impacts on
tuna catch rates such as the effects of the sonar that are fitted to most of
the vessels which direct impacts are unknown at this stage. El Nino
(climate change),
stronger than usual winds, swell as well as currents and water temperatures
during the fishing season have directly impacted the ability to successfully
catch tuna. This past season we have found that there has been an abundance of
feed around the fishing grounds and it is speculated that the tuna could not be
hungry enough to catch. There are no records of landings of albacore during its
migratory cycle through international waters before it reaches our waters
again. Large volumes of the school could be caught by vessels operating in
international waters and therefore less and less fish reappears each year.
This map below show an interpretation of the migration route of albacore tuna based upon catches:
Area 1. October – April.
Area 2. September – January
Area 3. August – December
This map
indicates the albacore migratory route south to north showing catch
concentration zones. Which route it takes from the northern point is unknown as
this graph is based on landings only. The majority of Namibia’s catch is on Tripp
Sea Mount. I'm not a 100% sure of migratory periods
for area 2 & 3 but this looks somewhat accurate based upon landings in South Africa.
The effect of noise pollution on marine animals is documented as they
are highly sensitive to acoustic sound. Marine fish and mammals depend on sound
for various functions such as; avoiding predators / hazards, navigation,
reproduction, communication with group members and young, food-finding and sensing
their environment. (Source:
Dr. Simon Harding & Dr. Lindy Weigart, October 2012. Scientific Synthesis
of the Impacts of Underwater Noise on Marine and Coastal Biodiversity: Key
Findings and Future Research Needs. International Biodiversity Conference,
India UNEP/CBD/SBSTTA16/INF/12)
The seismic noise being generated by the exploration for oil and gas penetrates
the sea floor 100kms+ below. The airgun sends a very loud blast between 230-250
decibels at predetermined intervals towards the seabed. The decibels may
increase according to whether it is 2D or 3D testing being conducted. The
effects of the seismic airguns are far reaching as such recorded by the moored hydrophones
along the Mid-Atlantic Ridge some 4,000km!!! (Nieukirk et al. 2012)
Seismic surveys are carried out during
marine oil and gas exploration in order to investigate subsea geological formations. During seismic
surveys high-level, low frequency sounds are directed towards the seabed from near-surface sound sources
towed by a seismic vessel. Signals reflected from geological interfaces below the seafloor are
recorded by multiple receivers (or hydrophones) towed in streamers. Analyses of the returned signals allow
for interpretation of subsea geological formations. Seismic surveys are
undertaken to collect either 2D or 3D data
Airguns are used on an individual
basis or in arrays. Usually and in the past a single source airgun array consisting of
three strings of 10 airguns (30 in total) is used. While a single airgun could
typically produce sound levels of the order of 220-230 dB re 1 mPa @ 1m, arrays
produce sounds typically in the region of 250 dB re 1 mPa @ 1m. The majority of
energy produced is in the 0 to 120 Hz bandwidth, although energy at much higher
frequencies is also recorded. High-resolution surveys and shallow penetration surveys
require relatively high frequencies of 100 to 1000 Hz, while the optimum
wavelength for deep seismic work is in the 10 to 80 Hz range. One of the required
characteristics of a seismic shot is that it is of short duration (the main
pulse is usually between 5 and 30 milliseconds). The main pulse is followed by
a negative pressure reflection from the sea surface of several lower magnitude
bubble pulses. Although the peak levels during the shot may be high, the overall
energy is limited by the duration of the shot.
The data collected allows for
interpretation where the most likelihood of deposits of natural resources such
as gas and oil may be found.
An airgun
array being fired
during a marine
geophysics research project:
And aft view of the seismic airgun and hydrophones being trailed behind the vessel
A view of the seismic airgun explosion
Documented research on noise impacts on fish or invertebrates have
shown the following:
• Disruption
in schooling and migration (Sarà et al. 2007)
• Disruption
of homing or orientation (Simpson et al. 2010).
• Masking
of mating calls (Vasconcelos et al. 2007)
• Decreased
feeding efficiency (Purser and Radford 2011)
• Reduced
catch rates of 40-80% > 30 km from seismic survey (Engås et al. 1996)
• Seismic
noise deafened fish ears- no recovery after 58 days (McCauley et al. 2003)
• Massive
hearing trauma in 4 squid species (Andre et al. 2011)
• Increased
stress signs (Buscaino et al. 2010; Graham and Cooke 2008; Wysocki et al. 2006;
Santulli et al. 1999)
Noise Impacts on Whales and Dolphins
• Increased
stress hormones (Rolland et al. 2012)
• Change
in feeding or mating calling behavior (Parks et al. 2007; Castellote et al. 2012; Melcón et al. 2012; Risch et al. 2012), even 200 km away
• Disruptions of feeding and
displacement over days (McCarthy et al. 2011; Tyack et al. 2011; Miller et al.
2009)
• Displacement over weeks (Castellote
et al. 2012) or years (Morton & Symonds 2002; Bryant et al. 1984)
• Sudden
unexpected permanent hearing damage (Reichmuth et al. 2009)
• Catatonic behaviour, loss of control
of muscle movement (Gray & Van Waerebeek 2011)
• Hearing
damage in whales causing more net entanglement (Mann et al. 2010; Todd et al. 1996)
• Decreased
species diversity (Parente et al. 2007)
We know that marine animals are highly dependent on sound. Noise
can cause deafness, avoidance of important habitat, stress, and declines in
fisheries’ catch rates. The seismic testing affects ecosystem-wide, cumulative,
and synergistic impacts on marine biodiversity and genetic resources.
These pictures below clearly illustrates the effect of the seismic testing on other species:
In this picture one can notice the "triangular fish ears" before the seismic blast.
After the seismic blast one can notice the absence of these "triangles" considered to be the fish's ears.
From: McCauley et al. 2003
Seismic
testing activities around
Namibia’s Tripp Sea
Mount fishing grounds
These maps below show the extent of the seismic testing being conducted off our coast.
Overview of recent seismic surveys off Namibia and South Africa (18 months)
At the
beginning of 2012, the seismic surveys (in red) in Namibia started in January
through March during the peak of the tuna season. The seismic surveys (in yellow and orange) on
the South African side of the border were very close to Namibia’s Tripp
Seamount fishing grounds, starting in October 2012 and running through to May
2013. On the Namibian side of the border
(in blue) the surveys started in February 2013.The majority of the seismic activity is between the October – April months of the Namibian tuna
season, and some overlaps with the South African season of August to January respectively.
There are a few “Immediate” Solutions” available to the tuna industry.
Such could possibly be the undertaking
seismic exploration outside the tuna season, due to the risk of the
seismic operations impact on the fish’s migration patterns. (I will discuss this topic with regards to the the migration patterns of the Australian bluefin tuna case in a later blog posting) A quieter airgun alternative such as
vibroseis could be utilized as long as this is scientifically proven to be
effective. Undertake research to assess how far away from
fishing grounds seismic testing should occur for there to be no impact on
migrating tuna.
I would like to conclude that the pole and line fishery, due to low financial
margins and recent poor catches is struggling financially. The sector fears
seismic exploration could financially destroy the fishery if immediate actions
are not taken. Seismic testing is consequently a trans-boundary issue with South Africa and Namibia and possible consultation with the Benguela Commission may be necessary. The effects on fish, especially fish distribution and
seismic avoidance, as well as food chain organisms are scientifically proven.
It remains to be seen if the tuna will follow their usual migration pattern and
return this year.
References:
- · CapFish SA (Pty) Ltd Notices to Mariners of Offshore Seismic Surveys
- · Dr. Simon Harding & Dr. Lindy Weigart, October 2012. Scientific Synthesis of the Impacts of Underwater Noise on Marine and Coastal Biodiversity: Key Findings and Future Research Needs. International Biodiversity Conference, India UNEP/CBD/SBSTTA16/INF/12
- · Ministry of Fisheries & Marine Resources catch statistics
- · Ministry of Mines and Energy seismic exploration license data.
- · Presentation made by K. Lauffer of the Large Pelagic and Hake Longlining Association of Namibia and David Russel
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