Thursday 19 July 2018

Starfish Report 2018

Evasterias troscheli
We had a minus-4 tide the other day and I got in an epic mile-long wade along the tidelands. The biological diversity was outstanding; next best thing to diving.

Among the prolific sea life present were three starfish, all of which presented reasons for hope, if not celebration, that the starfish plague may be slowing down, now that it's wiped out most of our sea stars.

I was first delighted to find several blood stars (Henricia leviuscula). These striking neon echinoderms have been a favourite since childhood. Seldom found intertidally – testimony to the rare opportunity of this very low tide – they were before the die-off omnipresent on mud-bottomed diving grounds.

One adult specimen I found had small scrapes on its disc. These might have been signs of incipient viral infection, or abrasions caused by being dashing about in the "surf" created by passing boats. I also found a few tiny individuals; normal for this time of year. With the exception of that first adult, none showed visible signs of disease (yet?).

Sadly, not a single sunflower star (Pycnopodia helianthoides), of any size, in any condition, was present. It does seem this beautiful if rapacious species, a fixture in quiet northern water until very recently, has been driven to extinction.

Further proof are the leather stars (Dermasterias imbricata) that now stud the beach and shallows. Formerly thinly represented on lower Sound
Adult Henricia leviuscula
beaches, because a favourite Pycnopodia food, Dermasterias is now virtually the only star left.

That population, at any rate, enjoys a natural immunity to the horrific seastar wasting disease, and appears healthy.

Finally, good news and bad on the mottled starfish (Evasterias troscheli) front. Good, because I encountered several specimens of this similarly once characteristic species. Bad, because every one was tiny; a year old, at most.

The wasting virus tends to take a few years to locate and destroy its victims, thus the average size of this species indicates it hasn't yet been able to out-manœuver the plague.

But its presence at all on this ravaged beach suggests that a healthy breeding population exists in the deeper, colder water offshore. With luck and a bit of Darwinian cunning, it may yet return.

Thus the state of the starfish.

It's hard to express how painful all of this is. They may be "just starfish", but this attractive class has been such an integral part of my life, albeit unrecognised till they were gone. Along with most other people, it never occurred to me I might one day wake up to a North Pacific functionally bereft of seastars.

And the creeping suspicion we'll lose many more beloved habitats and life forms before we've seen the end of the Anthropocene.

Immature Henricia

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