Monday, February 21, 2011

Marine Extinction - three

Remember this post?
In it, I postulated that we haven't managed to cause the global extinction of a single marine Fish - yet!

Well, I might have been wrong.
Enter the 2003 paper Extinction vulnerability in marine populations in general and Azurina eupalama, pictured above, the Galapagos Damsel or Blackspot Chromis in particular. A small, drab planktivorous Fish, it apparently went extinct when the 82/83 El Niño eliminated the local plankton production for a year.

But then again, as usual, things may be way more complicated.
I am truly blessed in being able to access a network of unbelievably knowledgeable and smart people, and having asked the question, one of my Fish gurus commented as follows.

This little known species was the subject of much discussion between Dr. Ross Robertson of STRI, myself and others on our ichthyological expeditions in the Tropical Eastern Pacific, or TEP.

Our consensus was that it would be premature to pronounce Azurina eupalama extinct for several reasons:
It may be a “boom or bust” species existing in very low numbers until conditions are propitious for a population explosion. Being drab, small and unexceptional-looking it would pass unnoticed by all but a few knowledgeable scientist divers, who might never encounter remnant, small, scattered populations.
The ocean is a big place!

Luzonichthys earlei is a species in Hawaii with extreme population fluctuations and there are others like that here.
Like its sibling species north of the equator in the TEP, A. hirundo, it is a cold water species.
In places like the Galapagos it may usually live at great depths, or retreat to cool depths in warm or even normal temperature regimes. Richard and I recently published a paper describing 5 new damselfish species we found with rebreathers, all from below 80 meters. The family does go deep.

Finally, and to me most importantly, the center or core of the population of this species could very well be elsewhere, likely in the relatively faunally unknown areas of the TEP along the coast of Equator and northern Peru, spreading to marginal habitat areas like the Galapagos or Cocos Island under certain transient conditions, only to disappear when conditions revert to the norm.

There are also analogs for this pattern in Hawaiian fauna.
Species of fish and mollusks present in the cooler waters of the Northwestern Hawaiian Islands have historically appeared in the main Hawaiian Islands for awhile and then vanished utterly. If we only had collecting experience from Kauai to the Island of Hawaii it would certainly look like several species of endemic Hawaiian cowries such as Cypraea rashleighana or C. burgessi have become extinct within the last 30 years.

This idea of a core population existing outside its historically recorded range is a testable hypothesis, of course.
Ross and I tried to get permission to take the STRI RV Urraca to Isla de la Plata off Equator, a likely core area well-situated to seed areas down current like the Galapagos.
Alas we were unsuccessful.

Life is resilient and adapted by evolution to the conditions and even the extremes of conditions in its habitat.
The thought that a marine species existing through long eons of geological time would crash utterly during one single recent weather event is hard for me to swallow.
I shave with Occam’s Razor.

Methinks the question of marine fish extinctions in recent times remains open…….though I will admit that I am losing hope regarding the Placoderms!

Me too!
But there's still hope for Megalodon! :)

Back to the marine extinctions, please read this.
Amid a sad list of local, regional and alas, global extinctions of various marine organisms, I find Anampses viridis, the Mauritius Green Wrasse, possibly a victim of sedimentation and nutrient pollution . It is once again an endemic which makes it particularly vulnerable and according to this equally sad list of most recent extinctions, it has not been reported since 1839. But then again, as witnessed by several spectacular range extensions that we have documented on Shark Reef, the published geographical distribution of Fishes remains always in flux, and there's a slim chance that it may suddenly turn up elsewhere.
If the Bull Sharks of Tonga have managed to remain hidden until 2006 despite probably being a breeding population, so can a small green Wrasse!

Not hopeful - but fingers crossed!

PS when I sent him this post, my guru commented

Anampses viridis, the Mauritius Green Wrasse, is a mystery fish, known only from a few dried specimens and last collected before 1840 when described by Valenciennes.

One wonders if it is a valid species, where and from what depth it was actually collected (collecting data can be unreliable from that era…note the range of Amblyglyphidodon curacao), and, if a valid species presently extinct, what factors contributed to its extinction.
Not much human marine impact in that area in the early 19th century.

Extinction is a natural process and the fate of all species.
Man may not necessarily be implicated in all recent extinctions………one hopes.

So there!

1 comment:

Liz said...

I am an environmentalist myself and promoting solid waste management. Most of the rivers near urban and rural areas are much affected by the waste of daily life. Most of it are plastic bags, diapers and some sewage waste that leaked. I really feel sorry for the marine life they are the most that is affected. To count, that is not the only species extinct due to pollution. Though we cannot blame anything on humans some are extinct due to increased population of its natural predator.