Tuesday, July 12, 2016

Watch That Fish Move! By Don Orth

Fishes have an amazing variety of body forms, each of which is uniquely adaptive. In many cases, the best way to understand the significance of the adaptation is to watch the fish in action. Here are a few video clips that demonstrate that form follows function.

The Tangerine Darter Percina aurantiaca  is a large darter that is common in the Tennessee River drainage.   It darts among the spaces between boulders and cobbles that form the streambed.  Watch as the Tangerine Darter makes short darting movements in this underwater video (video courtesy of  Ed Scott).  

Tangerine darter Percina aurantiaca Photo by Brett Albanese.  Source
The tail-slap

Thresher sharks (Alopias spp) use their long tail to daze, smash, or kill schooling prey fish, such as sardines.  Watch this Thresher shark hunt with its tail!   Click here for the video.  Simon Oliver and his co-investigators at the School of Ocean Sciences, Bangor University, videotaped thresher sharks and discovered that the tail-slap can be administered either sideways or overhead, depending on the alignment of the sardine bait ball.  After the tail-slap, the thresher shark turned 180 degrees and consumed the dead and/or stunned sardines.  The sequence occurs quickly, lasting only 1.13 to 3.40 seconds.  During the strike, the average speed of the tip of the thresher shark tail was 14 meters per second!
Sequence of still images of thresher shark body movements throughout the tail-slap. Photos from Oliver et al. (2013).
The Ambush

In contrast to the active tail-slap hunting strategy, gars (Lepisosteidae) are sit-and-wait predators that passively wait and then ambush prey.  This video from the clear springs of Florida show the coloration of the Florida Gar Lepisosteus platyrhincus and its dominant behavior, the sit and wait posture.   Most of the time the gar lies motionless near the water surface.  When a prey fish is nearby it will slowly stalk until its head is positioned laterally to the prey fish.  They then use a rapid sideways lunge of the head during the strike and impale the prey on the numerous sharp teeth. . This lateral lunge lasts only 25-40 milliseconds (Porter and Moto 2004). 

Florida Gar Lepisosteus platyrhincus  Source
The Jump

Fish have both a sustained and burst swimming mode. One unusual behavior is the jump, where a fish uses the burst swimming mode to leap clear from the water.  Many times I have seen the jumping behavior of Common Carp Cyprinus carpio.  However, I have no satisfactory answer to “why do carp jump?”  My favorite hypothesis is that the jumping behavior forces more oxygen over the gills. But no one really knows.  But look at that carp jump! 

Tambaqui Colossoma macropomum jump for a different reason.  In the flooded forest of the Amazon the Tambaqui jumps to eat tree fruits and nuts.  The Tamaqui deposits the tree seed after passage through the gut, thereby dispersing the seed.  Watch the Tamaqui jump to capture a fruit from a tree. 

The Camouflage Carpet

Wobegong, or carpet sharks (family Orectolobidae), are named for the ornate pattern that resembles a carpet.  Like a swimming carpet, the well-camouflaged Wobegong Carpet Shark moves along the bottom.  Watch the slow swimming camouflaged carpet shark! When it holds a single position the wobegong becomes an ambush predator and swallows prey whole.  Watch the swallower.

The Mimick
Ornate Ghost pipefish Solenostomus paradoxusmimicks soft corals, hydroids, whip corals and gorgonian corals.  The small protrusions that cover the animal's body help break outline so it blends with its complex microhabitat. Watch that pipefish!  It’s not so much the movement as the mimicry.
Ornate Ghost pipefish Solenostomus paradoxus  Source
The Beach Burrower

California grunion, Leuresthes tenuis, and the Gulf grunion Leurestheses sardinas provide a easy-to-observe beach burrowing behavior at high tide during their breeding.  You have to watch that fish.  Watch as the female grunions burrow into the sand to deposit their eggs. 
Grunion life cycle is synchronized by the lunar cycle where breeding occurs at high tides.  Illustration by Greg Martin
So watch the fish and learn more about their unique adaptations.   Share your observations and videos with others.


Oliver SP, Turner JR, Gann K, Silvosa M and D'Urban Jackson T  2013.  Thresher sharks use tail-slaps as a hunting strategy. PLoS ONE, 8 (7): e67380.http://dx.doi.org/10.1371/journal.pone.0067380

Porter, H.T. and P.J. Moto 2004. A comparison of strike and prey capture kinematics of three species of piscivorous fishes: Florida gar (Lepisosteus platyrhincus), redfin needlefish (Strongylura notata), and great barracuda (Sphyraena barracuda). Marine Biology 145:989-1000.  http://link.springer.com/article/10.1007/s00227-004-1380-0

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