Answer: Should I be worried about this fish?

In our previous episode... 

WHILE diving in the Somosomo Strait on September 8th of this year, I found this fish down at 10m, busily picking up chunks of coral and moving them from place to place.  

The question for this week was "Should I be worried about this fish?" 

You SearchResearchers did an excellent job of answering the questions.  

1.  What IS this fish, and should I worry about it being aggressive? 

2.  If so, WHEN should I worry?  Everyday?  Or just sometimes?

3.  Should I have been worried on the day I took the photo? 

1.  How can we identify a random fish like this?  

As we've discussed before, you could spend a lot of time looking at photos of fish. But there a literally a lot of fish in the sea, and it could take a while.  A much better approach is to use some kind of key to identify the category of fish, and then zoom in to photos once you know a bit more.  (This is really the best, most general method of identifying any kind of plant or animal. Use a key.)  

My first query was to figure out where the "Somosomo Strait" is--that's not hard--it's an island in the Fiji archipelago that's known for great scuba diving.  (Makes sense. Of course that's where I'd go!)  

So now I want to find a good fish ID key, my query was: 

     [ fish identification key ] 

which led me to Fishbase.org which has a really extensive index AND a great key system.  They're pretty serious about their fish.  

Here's a piece of their home page.  I immediately noticed the "Quick Identification" link and clicked on that.  

Once there, you'll see a set of options.  Each is a category of fish--click on it, and you'll go the subcategory, etc etc, until you reach the fish family you're interested in examining.  Here's the top of their visual key: 

In this case, I'm going to click on the fish that looks most like the one in the image.  So here I click on "Ray-finned fishes."   That takes me to the next choice point in the key: 

Now at this point, I MIGHT click on "Puffers and Filefishes" (the same of the mystery fish looks pretty much like the fish on the far left of that category), or I might scroll down and click on "Dories" farther down the page.  But "Dories" are, as the note down there says, "most are deep sea."  So I'll click on "Puffers and Filefishes" and see what's there. 

At that page, I see something that looks a LOT like the mystery fish.  See the "Baslistidae (Triggerfishes)"?  I suspect that's our kind of fish.  An Image search for: 

     [ Fiji triggerfish ] 

quickly brings up a bunch of triggerfish, including one that's a perfect match.  Clicking on that then tells me it's a Titan triggerfish (Balistoides viridescens).  A quick Image search on the Latin name [ Balistoides viridescens ] gives me yet another confirmation: 

So we've identified our fish.  

Now, is it aggressive?  Let's do this search to see if we can find anything out about the behavior of the Titan triggerfish.  

     [ behavior Balistoides viridescens ] 

Note that I didn't search for "aggressive" here--that's just ASKING for confirmation.  Instead, I searched for "behavior" because maybe it's perfectly passive 99% of the time, and rarely aggressive.  If I searched for "aggressive," I'd be sure to find every single page talking about it's aggressive tendencies.  It would be a fair research question.  

When I did this I was slightly surprised to learn that (despite me trying to be fair), the Titan triggerfish HAS been observed being fairly aggressive to other fish (and humans) who enter their territory.   

The Wikipedia Titan triggerfish article says that "...The titan triggerfish is usually wary of divers and snorkelers, but during the reproduction season the female guards its nest, which is placed in a flat sandy area, vigorously against any intruders. The territory around the nest is roughly cone-shaped and divers who accidentally enter it may be attacked. Divers should swim horizontally away from the nest rather than upwards which would only take them further into the territory. Although bites are not venomous, the strong teeth can inflict serious injury that may require medical attention..."  

Zounds!  As you can see from the photos, any fish with teeth like (who bites coral!) would have an impressive bite.  

Just to double check this, I used Google Scholar on that same query and found several articles documenting aggressive behavior of the Titans.  Interestingly, several of the articles (e.g. "Lek-like spawning, parental care and mating periodicity of the triggerfish Pseudobalistes falvimarginatus" [1]) point out that the males set up a mating ground (a "lek") where they establish, and defend, territories to which the females come and deposit their eggs. Both parents care for the eggs, although the female is "confined to the nest by the male."  Mating was semi-lunar, several days before the new and full moons on days when high tide occurred near sunset.  (Note that this paper is about a related fish, Pseudobalistes, but at the end of the paper, the authors say that this is also true for the Titans as well.)  

Okay. So the question NOW is "was Sept 8 near a new or full moon when a high tide was near sunset?"  

Phases of the moon are easy to figure out:  

     [ phase of the moon calendar ] 

And yes, Sept 8 WAS a full moon according to www.moonconnection.com   

What about the tides?  My query was: 

     [ high tide Fiji September 8 2014 ] 

(I gave the date because I wanted the historical record, not this week's tides.)  

I found a very nice chart that gave the tides AND sunset times for Fijian waters:

The second and fourth columns are the high tide times.  Holy cow!  5:46PM was the high tide AND sunset was just 15 minutes later at 6:00PM FJT!  

So YES... I should be careful!  

Search Lessons:  

1.  Know the geography.  In this case, fish look very much alike, but can be different worldwide.  Knowing that Somosomo Strait is in Fiji really helps. 

2. Use an identification key.  There are keys for fish, plants, animals, insects, fungi, flowers, etc etc.  Know that a good key is almost always the best approach for identifying something.  

3.  Do not bias the results by including "leading terms" in your query.  In this case, the Titan triggerfish really IS aggressive, but don't search for trouble to begin with.  Let the data guide you to that interpretation--don't overlimit you search results to only those with evidence that confirms your already existing biases.  

Note:  Rosemary made a great observation about using Search-By-Image for this Challenge.  It's such an interesting finding that I'll write a separate post about that.  

[1] Gladstone, William. "Lek-like spawning, parental care and mating periodicity of the triggerfishPseudobalistes flavimarginatus (Balistidae)." Environmental Biology of Fishes 39.3 (1994): 249-257.