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First mass stranding of Velella velella in New Zealand

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Several million Velella velella per km were stranded on two west coast beaches from the end of October to the beginning of November 2006, and high numbers along the entire west coast of New Zealand. A few Velella strand most years, but this appears to be the first mass stranding ever recorded. The greatest length of 124 floats averaged 26 mm, and 72% were left sailors.
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JMBA2 - Biodiversity Records
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First mass stranding of Velella velella in New Zealand
John E.C. Flux
Ecological Research Associates of New Zealand, 230 Hill Road, Belmont, Lower Hutt, New Zealand. E-mail: ux@paradise.net.nz
Several million Velella velella per km were stranded on two west coast beaches from the end of
October to the beginning of November 2006, and high numbers along the entire west coast of
New Zealand. A few Velella strand most years, but this appears to be the rst mass stranding ever
recorded. The greatest length of 124 oats averaged 26 mm, and 72% were left sailors.
INTRODUCTION
On 5 November 2006 along six km of rocky
beaches between Makara and Boom Rock (41°11'S
174°44'E ) enormous numbers of by-the-wind-
sailors (Velella velella) were dead and dying on the
tideline. There were a few pelagic barnacles with
them, but only ve Portugese-man-of-war (Physalia
utriculus), and no violet snails (Ianthina spp.). A
100x100 mm sample of the dried bodies layered 25
mm deep on the beach yielded 250 individuals, or
25,000 m–2. The tideline averaged about 1 m wide
(Figure 1), giving a total for the 6 km stretch of at
least 100 million Velella.
Two days later at Paraparaumu beach (40°54'S
174°59'E) live Velella were being washed ashore at
a density of about 1 m–1, but the dried bodies on
the tideline averaged about 100 m–1, assessed over
50 m. As this is a long, uniform beach extending for
100 km, it may give a better estimate of the scale
of the stranding than Makara Bay, which could have
accumulated specimens drifting south-east. The
prevailing strong to gale winds over the previous two
weeks had been from the north-west. As at Makara,
dead Velella were piled about 100 mm thick and metres wide over the entire length of Pukerua Bay
(41°02'S 174°54'E), in contrast to the few individuals found each year for the past 17 years, and
comprised two main strandings about a week apart (M.J. Meads, personal communication).To check
how widespread the stranding was, members of the New Zealand Ornithological Society Beach
Patrol, who walk tidelines regularly throughout New Zealand counting dead birds, were contacted.
They reported far larger numbers of Velella than usual from Northland, Waikato and Southland, so
apparently the whole of New Zealand was affected.
The maximum length of a random sample of 124 oats (the skeletal part remaining when the
animal dries) was 26.06 mm, 95% condence interval 24.4–27.7, range 11–46 mm. Of this sample 90
(72.6%) were left sailors (i.e. would drift to the left of the wind direction—the discription right and
left handed is preferable to saying the sail runs north-west–south-east or north-east–south-west,
because this reverses depending on whether the observer considers the animal is sailing like a yacht
or drifting sideways, as it does).
DISCUSSION
There are no records of previous mass strandings in New Zealand, although a few Velella drift
ashore every year, especially on Northland beaches (Powell, 1959; Morton & Miller, 1968). Schuchert
(1996) listed all the New Zealand material, and only one of 69 was a left sailor, plus ‘several’ seen in
1994 off Kapiti Island which were all right sailors. In contrast, 72.6% in the present mass stranding
were left sailors.
In North America mass strandings occur on Pacic beaches occasionally, and may deposit up to
2.5 kg ash-free dry weight per metre of shoreline (Kemp, 1986). The distribution of Velella appears
to be extending north in the northern hemisphere, reaching Millport Marine Station in the west
Figure 1. A typical section of the tide-line at Makara Bay. Width of photograph 1.2 m.
J.E.C. Flux First mass stranding of Velella velella in New Zealand
JMBA2 - Biodiversity Records
Published on-line
2
of Scotland in 2002 (www.marlin.ac.uk/Velellavelella.htm). According to Lynam et al. (2005) jellysh
abundance is increasing in numerous marine ecosystems worldwide, and if this is associated with a
temperature rise, or stormy weather, caused by global warming, or over-shing, it may be useful to
document mass strandings as an index of future changes.
I thank Mike Meads and members of the Ornithological Society for information on strandings, and Lisa
Gershwin and Dennis Gordon for helpful comments and access to literature.
REFERENCES
Kemp, P.F., 1986. Deposition of organic matter on a high-energy sand beach by a mass stranding of the cnidarian
Velella velella (L.). Estuarine, Coastal and Shelf Science, 23, 575–579.
Lynam, C.P., Hay, S.J. & Brierley, A.S., 2005. Jellysh abundance and climatic variation: contrasting responses in
oceanographically distinct regions of the North Sea, and possible implications for sheries. Journal of the
Marine Biological Association of the United Kingdom, 85, 435–450.
Morton, J. & Miller, M., 1968. The New Zealand sea shore. London, Auckland: Collins.
Powell, A.W.B., 1959. Native animals of New Zealand. Auckland: Unity Press.
Schuchert, P., 1996. The marine fauna of New Zealand: athecate hydroids and their medusae (Cnidaria:
Hydrozoa). New Zealand Oceanographic Memoir, 106, 1–159.
Submitted 11 June 2007. Accepted 24 July 2007.
... Velella velella Linnaeus, 1758, commonly known as the by-the-wind sailor , is a pleustonic, open ocean species found globally in tropical and temperate oceans (Daniel 1976, Bieri 1977, McGrath 1985, Evans 1986, Mianzan & Girola 1990, Flux 2008, Gul 2015. It is a holopelagic colonial anthoathecate hydrozoan belonging to the family Porpitidae. ...
... Velella velella is renowned for forming huge rafts at sea and for massive beach strandings that have been reported in many of the world s oceans (Evans 1986, Flux 2008, Purcell et al. 2015, Pires et al. 2018) and may deposit up to 2.5 kg ash-free dry weight per metre of shoreline (Kemp 1986). This highlights its importance in open-ocean carbon cycling and in transport of pelagic production to landmasses (Purcell et al. 2012). ...
... drift to the right in the downwind direction, Calder 1988, Fig. 2B). This form is less commonly observed than the left-sailing form, with most of the sightings occurring on the western shores of the southern hemisphere (Flux 2008, Araya & Aliaga 2018. The presence of V. velella in the Bay of Ranobe may be the result of Southeast Trade Winds that blow every day during the austral winter. ...
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... During a documented mass stranding in New Zealand in October-November 2006, a subsidy of approximately 100 million individual Velella were delivered to a six-kilometer stretch of beach ecosystem (Flux 2008). For the almost two decades prior to the 2006 New Zealand stranding, only a few individuals per year washed up on the same beaches (Flux 2008). Kemp (1986) documented similar mass strandings on beaches around Newport, Oregon, in 1981Oregon, in and 1984Oregon, in , with only scattered stranded individuals in 1982Oregon, in , 1983Oregon, in , and 1985. ...
... During strandings in 1984, an estimated 2573 g of ash free dry weight/m of shoreline (1223 g/m carbon, 347 g/m nitrogen) stranded on the beach. During a recent beach stranding in New Zealand, as many as 25,000 individuals/m 2 were deposited (Flux 2008). As an individual prey item, Velella provide approximately 2.9 kJ energy/g dry mass (with an individual Velella weighing an average of approximately 0.09 g dry mass) and are likely among the gelatinous organisms that are energetically cheap for predators to capture and digest (Arai et al. 2003). ...
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... Velella velella (Linnaeus, 1758), commonly known as by-the-wind sailor, is a cosmopolitan holoplanktonic, free-floating marine hydrozoan living in open waters at tropical and temperate latitudes (Daniel 1976;Bieri 1977;McGrath 1985McGrath , 1994Evans 1986;Mianzan & Girola 1990;Flux 2008;Gershwin et al. 2010;Purcell et al. 2015;Gershwin 2016;Pires et al. 2018). The polymorphic colony, up to 120 mm long (Bieri 1977), is enclosed in an oval chitinous pneumatophore, positively buoyant and characterized by an upright and triangular dorsal sail. ...
... This trend can be also seen comparing the two consecutive strandings in Santa Margherita Ligure. The average size of the last stranded colonies is in agreement with that recorded from the Atlantic Ocean in 2013 and 2014, (33 mm and 32 mm, respectively), and slightly larger in respect to that measured by Flux (2008) from New Zealand (average 26 mm). ...
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... V. velella distribution is quite unpredictable; it has a seasonal distribution, being the warmer periods when they occur, grow and reproduce more (Bieri, 1977;Purcell et al., 2012), possibly due to food and light availability and wind conditions (Bigelow, 1911;Bieri, 1977;Purcell et al., 2015); the ocean circulation and the wind regimes also contribute to their erratic dispersal (Bieri, 1977). The species is responsible for huge blooms and mass stranding throughout the world's oceans (Evans, 1986;Flux, 2008;Purcell et al., 2015). Those large blooms can reach the shore and impact the coastal systems as they are responsible for the deposit of big amounts of nitrogen and carbon (Bieri, 1977;Purcell et al., 2015;Savilov, 1968). ...
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