JMBA2 - Biodiversity Records
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: firstname.lastname@example.org
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.
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% condence 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).
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 Pacic 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
of Scotland in 2002 (www.marlin.ac.uk/Velellavelella.htm). According to Lynam et al. (2005) jellysh
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.
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. Jellysh 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.