DIVE DRY WITH DR. BILL #743: ALIEN INVADERS
In my youth, about a billion years ago, we worried about alien invaders. Back in the days before Star Wars or Star Trek, we had Flash Gordon. The launch of Sputnik by the Soviets heightened our interest in space and, for some, our fear of what was out there. But I'm not writing a column about astronomy and outer space (despite teaching the subject back in the 70s). Today, I'm still concerned about alien invaders of another type. Read on.
Those of you familiar with my column over the years know about my battle to educate the public about a very nasty alien invader and try to get California's Dept. of Fish & Wildlife to do something about controlling it. I coined a common name for it, "devil weed," but its scientific name is Sargassum horneri. This invasive seaweed came not from outer space but from across the Pacific Ocean in the Seto Inland Sea of Japan.
I've worked with Japanese scientists who are concerned because elevated sea temperatures in Asia due to global warming are actually reducing this important seaweed in their waters. They harvest it for food, fertilizer and biofuel and it has significant commercial value in its native range. I had hoped such uses would stimulate companies in our region to harvest it here and reduce the threat it poses to our native seaweeds including the giant kelp forests that are a signature feature of SoCal diving.
When a species has such commercial value, it quickly becomes a target for exploitation. Many of us have seen the decline in local species such as abalone, lobster, white sea bass and giant sea bass currently or in the past as a result of over-exploitation and other factors. If you want to decimate a species, highlight its commercial value and its numbers will soon plummet.
Another example of an alien invader that has devastated regions it has invaded is the red or common lionfish (Pterois volitans). Fortunately it is not present in our waters of the eastern Pacific due to cool temperatures here. It would probably need a 7mm wetsuit to survive. It is native to the western Pacific, Indian Ocean and Red Sea where temperatures are more to its liking (and, honestly, mine).
However, this species has also invaded the western Atlantic both in the SE states and in the Caribbean beginning with the earliest sightings off Florida in the mid-1980s. Although some have suggested the initial source was due to hurricane damage to an aquarium, genetic studies suggest multiple sources. This species is a popular aquarium species, but often grows too large for a home aquarium causing some owners to release them.
Like our "devil weed," the red lionfish has a tremendous reproductive potential. A single female may release two million eggs a year and reproduce all year long. The fertilized eggs and larvae disperse with ocean currents allowing the lionfish young to quickly colonize other habitats. This high reproductive potential is one characteristic that makes it (and other exotics) highly invasive species.
I have dived waters where this fish is native (Philippines, Palau, Thailand, Australia and the Red Sea) and where it is an exotic (Bahamas, Bonaire and South Florida). In its native region it co-evolved with potential prey species and predators over many years allowing ecological balance to be achieved. In its new range it has no native predators (although some species are beginning to acquire a taste). Its diet includes a wide range of native fish and invertebrates none of which evolved in the presence of this voracious predator and therefore have not developed defenses against it. It is said that native fish stocks in ivaded regions have plummeted as much as 90 percent.
In Bonaire I filmed lionfish hunts where these slow moving fish were speared and contained in a container called a "zookeeper." The next day the lionfish were delivered to Bruce Bowker's Carib Inn dive center in a form I could truly appreciate... fried! They were delicious. Folks in areas this species has invaded have turned to lionfish tournaments and cookouts to control them. With any luck commercial fishers will follow and this species will be targeted and brought close to extinction!
© 2017 Dr. Bill Bushing. For the entire archived set of 750+ "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Our garibaldi against a forest of... devil weed, images of the red lionfish in both its native and invaded waters and speared lionfish being secured into "zookeeper."
In my youth, about a billion years ago, we worried about alien invaders. Back in the days before Star Wars or Star Trek, we had Flash Gordon. The launch of Sputnik by the Soviets heightened our interest in space and, for some, our fear of what was out there. But I'm not writing a column about astronomy and outer space (despite teaching the subject back in the 70s). Today, I'm still concerned about alien invaders of another type. Read on.
Those of you familiar with my column over the years know about my battle to educate the public about a very nasty alien invader and try to get California's Dept. of Fish & Wildlife to do something about controlling it. I coined a common name for it, "devil weed," but its scientific name is Sargassum horneri. This invasive seaweed came not from outer space but from across the Pacific Ocean in the Seto Inland Sea of Japan.
I've worked with Japanese scientists who are concerned because elevated sea temperatures in Asia due to global warming are actually reducing this important seaweed in their waters. They harvest it for food, fertilizer and biofuel and it has significant commercial value in its native range. I had hoped such uses would stimulate companies in our region to harvest it here and reduce the threat it poses to our native seaweeds including the giant kelp forests that are a signature feature of SoCal diving.
When a species has such commercial value, it quickly becomes a target for exploitation. Many of us have seen the decline in local species such as abalone, lobster, white sea bass and giant sea bass currently or in the past as a result of over-exploitation and other factors. If you want to decimate a species, highlight its commercial value and its numbers will soon plummet.
Another example of an alien invader that has devastated regions it has invaded is the red or common lionfish (Pterois volitans). Fortunately it is not present in our waters of the eastern Pacific due to cool temperatures here. It would probably need a 7mm wetsuit to survive. It is native to the western Pacific, Indian Ocean and Red Sea where temperatures are more to its liking (and, honestly, mine).
However, this species has also invaded the western Atlantic both in the SE states and in the Caribbean beginning with the earliest sightings off Florida in the mid-1980s. Although some have suggested the initial source was due to hurricane damage to an aquarium, genetic studies suggest multiple sources. This species is a popular aquarium species, but often grows too large for a home aquarium causing some owners to release them.
Like our "devil weed," the red lionfish has a tremendous reproductive potential. A single female may release two million eggs a year and reproduce all year long. The fertilized eggs and larvae disperse with ocean currents allowing the lionfish young to quickly colonize other habitats. This high reproductive potential is one characteristic that makes it (and other exotics) highly invasive species.
I have dived waters where this fish is native (Philippines, Palau, Thailand, Australia and the Red Sea) and where it is an exotic (Bahamas, Bonaire and South Florida). In its native region it co-evolved with potential prey species and predators over many years allowing ecological balance to be achieved. In its new range it has no native predators (although some species are beginning to acquire a taste). Its diet includes a wide range of native fish and invertebrates none of which evolved in the presence of this voracious predator and therefore have not developed defenses against it. It is said that native fish stocks in ivaded regions have plummeted as much as 90 percent.
In Bonaire I filmed lionfish hunts where these slow moving fish were speared and contained in a container called a "zookeeper." The next day the lionfish were delivered to Bruce Bowker's Carib Inn dive center in a form I could truly appreciate... fried! They were delicious. Folks in areas this species has invaded have turned to lionfish tournaments and cookouts to control them. With any luck commercial fishers will follow and this species will be targeted and brought close to extinction!
© 2017 Dr. Bill Bushing. For the entire archived set of 750+ "Dive Dry" columns, visit my website Star Thrower Educational Multimedia (S.T.E.M.) Home Page
Image caption: Our garibaldi against a forest of... devil weed, images of the red lionfish in both its native and invaded waters and speared lionfish being secured into "zookeeper."
