I am writing today about non-natives, early detection and
BIASs. Non-native fishes are causing
serious problems to many aquatic systems. Carp for instance, can become so
abundant in rivers and lakes, that they crop
much of aquatic vegetation, taking away
important juvenile habitat for freshwater fishes.
Hundreds of large
herbivorous carp in a temperate river
Likewise, in Florida, populations Orinoco sailfin catfish can
dig thousands burrows in the sides of rivers, which reduces bank integrity, changing
the structure of rivers.
Unfortunately, once non-native fishes reach the abundances
of Orinoco sailfin catfish and carp in aquatic systems, there is not much
managers can do to get rid of them. But,
if fisheries managers can find these critters when they just become introduced,
then eradication is possible and managing these non natives becomes a lot cheaper! Therefore, much research has gone into
developing effective methods that can find these alien fishes when they are rare or
just become introduced.
Over the last three years we have discovered a new early
detection method for recently established non-natives. The method is simple,
just let predatory fishes find the non-natives for you. These BIASs (Biological
Invasive Auto Samplers) or predatory fishes go about their daily business swimming
around and eating other fishes. With some luck, the predatory fishes find and consume recently
introduced non-natives. All you have to do is catch BIASs remove their stomach
contents and identify the new non-native species….. Seems easy enough.
A recent anomalous weather event provided a unique opportunity
for us to test whether or not BIASs can find recently established non-native
fishes before other conventional methods.
In 2010, an extreme cold front virtually eliminated all of the tropical
non-native fishes from the Everglades estuary, restarting species invasions. The clean non-native slate in the Everglades
estuary created an ideal natural experiment to test whether or not 5 common
non-native species that were severely impacted by the cold front would first be
detected with sampling BIASs or from another common early detection method, electrofishing, as the re-colonize the estuary.
The five non-native species we chose to track are all
tropical new and old world fishes (pictured below). Two are catfishes, brown hoplo and walking
catfish, one eel species, peacock eel, and two spiny rayed fishes, the mayan
cichlid and the African jewelfish. And our
focal BIASs were largemouth bass, common snook, and bowfin.
The non natives we tracked
Sure enough, the BIASs did a great job finding and consuming
most of the non-natives. In fact, by sampling BIASs we found 2 non native
species that were not even known to have colonized the estuary! These were the
brown hoplo and the walking catfish. A large 20 pound snook ate the walking
catfish (below),
and a bass was the first to eat the hoplo.
Unlike the catfishes, jewelfish were found in bass diet samples and electrofsihing samples at nearly the same time.
Last, Mayan cichlids have yet to be captured by either method following the cold front.
Sampling with BIASs
was quite successful in detecting non-native fishes. In fact, sampling predator
diets detected two non-natives that were missed with conventional electrofishing techniques. Unfortunately,
one non native (peacock eel) was detected in the diets well after they were first detected
by electrofishing equipment.
In many active monitoring efforts such as electrofishing,
seine netting etc. predators are often subsequently captured. Since they are already captured, sampling their
diets does not take much extra training, time or money. Thus, I believe that incorporating this
sampling technique into early detection efforts can be very cost effective and may help identify and stop
the spread of some nasty invading fish!
Ross
Ross
Neat research man! Very cool idea
ReplyDeletethose are very small fish. try Reef fishing in Vanuatu. For sure you will ove to do it again and again.
ReplyDeleteThese are pretty small fish relative to whats on those reeefs. Trying to non-lethally remove the stomach contents of something like a massive dog tooth tuna would likely be more hassle than other methods. I am writing up this management brief now and will be adding a size limitation statement to the discussion... Thanks for the comment!
ReplyDelete