cephalopod populations in antarctic waterseprints.uni-kiel.de/8327/1/2009 piatkowski_cephalopod...

171

There are ca. 800 cephalopodspecies worldwide but relatively few ofthese species occur in polar seas incomparison to the rich squid popu-lations in subpolar and adjacent seas.

In the Southern Ocean, there arefewer than 50 species of squids andoctopodes. However, several squidspecies occur in large numbers and areconsumed by seabirds, seals and whales

Uwe Piatkowski

Cephalopod populations in Antarctic waters

amounting to a total estimate of ca. 34million t annually (Clarke 1983). Bio-mass and total annual production areunknown and probably much higherbut no Antarctic cephalopods have beenexploited commercially. However, majorcephalopod jigging and trawl fisheriesexist nearby e.g. around the FalklandIslands and off New Zealand (see Pützand Poncet, this book).

Of the ca. 20 squid species whichregularly appear south of the AntarcticPolar Front, only a few are consideredas being truly Antarctic. Of those, onlytwo species are endemic: the Antarcticneo-squid Alluroteuthis antarcticus andthe glacial squid Psychroteuthis glacialis(Fig. 1). They are of pivotal importancein the high-Antarctic food web. Bothspecies prey on krill and myctophids

Figure 1. Left: Psychroteuthis glacialis. Early life stage, mantle length 15 mm. Right: Pareledone felix. Female, mantle length 45 mm.

172

(lanternfish) and are known to be themajor prey of emperor penguins andelephant seals (see Zimmer and Wilson,this book).

As Antarctic top predators accumu-late the indigestible cephalopod beaksin their guts, studies of the top predators’stomach contents yield valuable infor-

mation about species composition, sizeand distribution of Antarctic cepha-lopods which are otherwise inaccessibleto scientific sampling. In contrast tosquid, information on Antarctic octo-podes has grown considerably recentlyas they can easily be sampled byscientific bottom trawling. In fact,

during the past decade we describedtwelve new octopod species from bottomtrawl samples taken during severalexpeditions with the RV Polarstern in thevicinity of the Antarctic Peninsula (e.g.Allcock et al. 2007) (Fig. 1). The samplesillustrate a higher than expected octopodspecies diversity and supply new in-formation on their distribution patternsand ecological aspects. The samples alsoconfirm that the isolation of the South-ern Ocean and the Antarctic continentalslope and shelf over the past 35-40million years has contributed to the evo-lution of a rich endemic fauna and theradiation of Southern Ocean octopodesinto the deep sea (Strugnell et al. 2008).

Furthermore, the trawl samplesshow that during recent years, octopuspopulations have gained significantlyhigher abundances around the Ant-arctic Peninsula than in similar areasnearby. This elevated abundance oc-curred after the rapid depletion of de-mersal fish stocks and may indicate apossible shift in the structure of the eco-system (Vecchione et al. 2009).

Bilöd

Todarodes philippovae and T. sagittatus inAntarctic and Arctic waters. The speciesname in the Antarctic stamp is incorrect.Collection: U. Piatkowski.