Gobies Revisited (now with Watersnakes!)

After last week, you are probably thinking one thing: “what about these gobies?”

Last week Ferrebeekeeper featured a post on the invasive round gobies from the Black Sea which have showed up in the Great Lakes.  The blobtastic little fish sneaked into the lakes by means of ballast water carried across the great oceans in international freighters and now they are wrecking up the place.   The gobies are outcompeting larger fish for resources.  They are devouring native mussels.  To quote the USGS website, “This species has been found to prey on darters, other small fish, and Lake Trout eggs and fry in laboratory experiments. They also may feed on eggs and fry of sculpins, darters, and Logperch (Marsden and Jude, 1995) and have also been found to have a significant overlap in diet preference with many native fish species.” Particularly hard hit are mottled sculpins, little round pebble-looking native fish which occupy(ied?) the ecological niche which the gobies are now taking over.  the fish horror stories contain some rather sad anecdotes of gobies biting sculpins and chasing them away and taking their lunch money and otherwise bullying them on the lake bed.  It is a rough world out there.

This mottled sculpin looks disgruntled

So are we just fated to dwell in a gobified dystopia from now on?  Well, actually, there are some positive things which the gobies are accomplishing and not everybody is sad they are here.  I was joking about gobies eating zebra mussels, the horrible invasive freshwater mussels which are filling up the Great Lakes and causing havoc to power plant and shipping infrastructure, however, it turns out the gobies do happily eat zebra mussels.  Additionally the gobies are not just eating other animals: they are also being eaten by them.  Because of the proliferation of round gobies, the previously endangered Lake Erie water snakes (Nerodia sipedon insularum) have become more prolific in number and the snakes are much fatter and happier (insomuch as we have records for these reptilian parameters).  The water snakes have been so successful at hunting gobies that they have been removed from the endangered species list (back before the act was watered down). 

Why, here’s a great writing mass of ’em! The world is getting better!

Larger gamefish like walleye, yellow perch, and bass and are eating the gobies, as are piscivorous birds like gulls, cormorants, plovers, and bald eagles(!).  Unfortunately there is downside to this as well.  Zebra mussels filter decaying cladophora algae out of the water.  This algae contains C. botulinum, a bacteria which contains the infamously dangerous botulism toxin.  If the predatory birds eat too many gobies they can be killed by the botulism and several mass die-offs have occurred.

What is the point of all of this (other, than, you know, the fact that it is happening in the world)?  I suppose this article is really about ecosystems–the complex webs of life we depend upon.  they are fragile in unexpected ways and resilient in unexpected ways.  We need to think about them more and learn more about them (witness what happened in all of my aquariums).  Thanks for the mindfulness lesson, ugly invasive goby!

 

 

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Gobies

“Northern riffleshell, snuffbox, clubshell and rayed bean” Remember those names for soon they may indeed be nothing more than memories.  An invader has come to America from the mysterious seas of Central Asia.  This interloper stowed away and came to America 30 years ago.  Authorities are powerless to stop the rampage of terror.  It has already conquered the sinister-sounding Lake Erie, a freshwater sea which is found deep in the hinterlands of…wait…Lake Erie borders New York ? [checks notes]

What on Earth is going on here?

You may think this absurd looking creature is a sentient hockey puck or the ghost of Jim Backus.  It is instead a goby…a tribe of fish which are sort of the prairie dogs of the sea.  This is the round goby (Neogobius melanostomus).  It is a hard-headed omnivorous fish which can live in both fresh and salt water.  Originally native to the Black Sea and the Caspian Sea, the tiny fish is thought to have come to the Great Lakes by stowing away in ballast water of a freighter.  Since its arrival in the Saint Lawrence Seaway, it has made the entire Great Lakes its home and it is now spreading along the rivers and creeks radiating from the lakes.

This is a pretty impressive feat and nobody is castigating the ugly little fish for being lazy or weak.  In fact it is even sort of endearing in a crude 1970s cartoon sort of way.

My god, what happened during that decade?

Unfortunately the gobies’ unstoppable appetite is leading to the extinction of indigenous freshwater mussels like the Northern riffleshell and clubshell mussels.  Freshwater mussels were already in trouble because of pollution, habitat loss, and stream degradation.  Now they have to contend with this formidable 9 inch long 2 ounce predator.  I have written this article with a joking touch, but, sadly, this sequence of events is no joke. Ecologists are worried that the gobies will continue to spread (particularly with the help of careless anglers, who use them as live bait).  Understanding and curtailing the proliferation of alien species causing havoc in unprepared ecosystems is one of the defining environmental challenges of our times (which are filled with environmental challenges), but so far nobody has figured out how to do so.  Perhaps in the future the Great Lakes will be filled with the descendants of round gobies eating zebra mussels.  Sometimes it seems like nobody and nothing can keep up with the pace of change.

 

Another Wicked Invader

The Zebra Mussel (Dreissena polymorpha)

Since 2011 is already shaping up rather grimly as the year of mass animal die-offs, it is time to revile the black-hearted invasive species which caused some of the the worst mass bird die-off in recent history.  I’m talking about the detested zebra mussel  an inch-long filter feeding bivalve mollusk with a pattern of brown zigzags on its shell.  The freshwater zebra mussel isn’t really that closely related to the marine mussels but shares many features with the Venus clams.

I am not too surprised if you feel ripped off that this dangerous invasive animal is a tiny shellfish.  But don’t dismiss the zebra mussel because of its diminutive size.  Zebra mussels are believed to be the source of deadly avian botulism poisoning that has killed immense numbers of birds in the Great Lakes since the late 1990s.  Additionally US powerplants and boat owners spend half a billion dollars a year scraping the creatures off water intakes for power plants and other underwater equipment.  The mollusks are also rather sharp and can injure wader’s feet–which necessitates wearing shoes in affected waterways.

Originally natives of the Black Sea and Caspian Sea, Zebra mussels spread via canal to the rest of continental Europe and then stowed away in fresh-water ballast and on anchor chains of ocean going boats to travel across the ocean to Great Britain, Ireland, Canada and the United States. The Great Lakes are being hit especially hard by them.  Whenever they spread to a new location the native freshwater mollusks are gravely impacted.

Zebra mussels on a Lake Erie beach (photo from Great Lakes Environmental Research Lab).

Of course the mussels’ impact is not entirely negative.  To quote the National Atlas of the United States (which, by-the-way is an interesting geography resource):

Zebra mussels do have a positive impact on some native species. Many native fish, birds, and other animals eat young and adult zebra mussels. Migratory ducks have changed their flight patterns in response to zebra mussel colonies. Lake sturgeon feed heavily on zebra mussels, as do yellow perch, freshwater drum, catfish, and sunfish. The increase in aquatic plants due to increased water clarity provides excellent nursery areas for young fish and other animals, leading to increases in smallmouth bass populations in Lake St. Clair and the Huron River. However, these native species do not feed heavily enough on zebra mussels to keep the populations under control.

We might as well enjoy the smallmouth bass and the clear water.  Nothing people have done has halted or even impacted the spread of the zebra mussels so it looks like we’ll have to learn to live with them.