[Coral-List] Coral-List Digest, Vol 110, Issue 12Lionfish after the hurricanes?

[Durwood M. Dugger]

Hi Vanessa and all,

You aren’t the only ones to notice significant changes/declines in observed Caribbean lion fish populations occupying Caribbean reef systems. My wife (Dr. Sabine Alshuth-Dugger) and I have been a making UW photographic surveys of the southern reef corals of Bonaire, NA for the past decade. We spend our summer months (2-3) in Bonaire diving if not everyday at least several times each week. The fist lion fish in the Caribbean was captured 1985 in Dania, FL and well before Hurricane Andrew (but there were probably previous unconfirmable previous sightings), a second was captured in 1992 and their populations expansion is documented here:

(https://flowergarden.noaa.gov/education/invasivelionfish.html <https://flowergarden.noaa.gov/education/invasivelionfish.html>)

and better here:

http://lionfish.gcfi.org/ <http://lionfish.gcfi.org/>

However, it is also informative if not frustrating to note that lion fish began to show up in the Mediterranean in 1992 as well - theorized to be migrating through or via the Suez Canal. Yet the modern day (their were older ones) Suez Canal opened to trans ocean ship navigation in 1869 - so why no lion fish for more than a hundred years - until 1992?

(https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=963 <https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=963>)

(https://en.wikipedia.org/wiki/Suez_Canal <https://en.wikipedia.org/wiki/Suez_Canal>)

Regardless of the source(s) of the Caribbean lion fish introductions - Bonaire was inundated with large numbers of juvenile and mature lion fish first observed in 2009 where lion fish seemed to be all over the Caribbean. Consequently, in the years of survey dives in Bonaire we have observed them frequently, their population growth, and now - in what appears to be their ongoing decline over the past couple of years. While lion fish population studies are not part of our interest or survey their conspicuous decline in the past couple of years is hard to miss.

In our dives during the past two years the numbers of lion fish observed in both popular (marked) and remote (unmarked and not visited as much by dive tourists) dive sites - have declined dramatically. Our dives take us from our shore entries to nearby depths of 110 ft. (where we have seen lion fish on many occasions  on most of our cross-sectional reef survey dives. We tend to dive unmarked dive sites mostly, but not always, and not always on the southern end of the island where the reefs are less disturbed by sport divers. This gives us a limited overview as to what is happening generally on the islands reef ecosystems. This year in about 25 dives on the southern end of the island we counted a total of 5 lion fish (not even one per dive) in mostly mid to smaller sizes. Since we do a lot of coral macro-photography we are up close to the nooks and crannies of the reef - where lion fish tend to be found and seen - if they are there. At the peak of lion fish populations - we might have seen as many as thirty lion fish per dive. 

In Bonaire, lion fish have been subject to legal/licensed (by STINAPA) and well promoted spear fish hunting for at least five years by sport divers. However, the efficiency of this spear fishing seems to be too low (especially while observed lion fish populations continued to increase until recently and during the heavily promoted hunting) to achieve the dramatic drop in lion fish populations we have seen beginning two years ago and especially considering we dive areas that are not normally visited (or lion fish hunted) by most other divers. 

Our current and unsupported by any of our own specific observations, but a shared and growing observation based theory - is that a number of reef fish predator species (sharks, groupers, barracuda, green and other large morays) are learning slowly how to prey on lion fish effectively (as has been documented in numerous video episodes on YouTube, a few here: 

https://www.youtube.com/watch?v=Ig6ZjmHAKHU <https://www.youtube.com/watch?v=Ig6ZjmHAKHU>

https://www.youtube.com/watch?v=BSn22wqJ5mA <https://www.youtube.com/watch?v=BSn22wqJ5mA>

https://www.youtube.com/watch?v=RovpqhoiqZY <https://www.youtube.com/watch?v=RovpqhoiqZY>

and in formal papers below) - or that a native pathogen is effecting lion fish populations (though I am not aware of any sick/dying/dead lion fish documented sightings indicative of a lethal pathogen epidemic among lion fish). 

Bonaire also has large and conspicuous numbers of very large (2+meters) day time active - free swimming and some times aggressive Green Moray Eels. We see them on almost every reef we dive. We think the Green Moray would be the most effective and likely top predator for lion fish in the Bonaire Reef systems. Additionally Bonaire has a comparatively limited number of other large predator fish - at least on the southern leeward reefs. Of course it is possible that the lion fish population decline in Bonaire is a combination of all of these factors. 

Bonaire is typically south of most passing hurricanes, but does get some effects and occasionally on its leeward shore. Once a every decade or two, Bonaire may be hit with a significant and damaging hurricane that definitely effects and damages the in shore reef systems - depending on angles of approaches. This year several tropical storms - starting June 19th  (60 mph winds) passed over or near while we were there (from end of May to  Aug. 20th), but they had minimal observable effect on the leeward southern reefs that we observe regularly. 

While lion fish distribution may be augmented by hurricanes (see - http://lionfish.gcfi.org/ <http://lionfish.gcfi.org/> time line and while thinking about the 2004-2005 hurricane season.)  the impacts of hurricanes in reducing lion fish I think is improbable - except in shallow extensive ecosystems like the Keys or the Bahamas where shallow water turbulence may be impossible to escape from by lion fish. Even so I would guess population redistribution is the result rather than significant mortalities. I think it especially improbable in ocean island ecosystems that hurricanes effect lion fish population significantly, and especially in Bonaire since the lion fish are very capable of migrating the short distances to much deeper unaffected depths (like many other fish do) as a hurricane approaches and protected from the inshore turbulence in deeper and less affected waters during a hurricane passage. Finally, we should not forget that the lion fish evolved in the Pacific where tropical typhoons are common and regular and would have the necessary behavioral and biological adaptations necessary to survive tropical cyclones by any name.

Certainly not scientifically documented by us, but we think that lion fish populations are more probably being reduced by increased predation - probably more fish predators (albeit lion fish predators seem to have extended lion fish predation learning curves). Watch the grouper eating lion fish video above and note the clearly “learned" approach to eating the lion fish head first as well as the time invested in the approach that has to be from previous reward. This kind of learning takes time, appropriate reward feedback and may have to be enhanced over generations. This kind of generational learning may account for what may be lion fish population declines in some/many? Caribbean locations. And less the affects by human predation - and not by hurricanes. Extended lion fish predation learning curves by their new predators might be seen here:

(http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021510 <http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0021510>)

Predator extended learning curve duration may also account for earlier (too early on the predator learning curves) works that seemed to show little predator effects on lion fish populations as here: 

(http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0068259 <http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0068259>)

In reading the comments herein on lion fish population changes and declines we think it is particularly interesting to note that these changes and declines seem to be observed and occurring perhaps broadly and near simultaneously in the Caribbean. We hope lion fish populations continue (as in not being a temporary phenomenon) to decline along with their reef ecosystem balance impacts. and that even broader observation of this phenomenon and its cause(s) can be detailed, studied and documented across the Caribbean. Just our two cents.

Best regards,

Durwood M. Dugger, Pres.
ddugger at biocepts.com
BCI, Inc. <http://www.biocepts.com/BCI/Home.html>