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Dive Time with Tim Grollimund
Wrasses — the smartest fish?
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Posted - Thursday, December 20, 2012 06:38 PM EST
Creole wrasses cruise through the south end of Molasses reef near the pillar coral. (Photo by Tim Grollimund)
While I was researching goatfish for the last column, I realized there is another group I have not paid enough attention to in my reef travels. Wrasses.
This is a large and diverse family. Wrasses seem to be everywhere. They are quick and colorful. Perhaps some of the most vibrant colors on our reefs belong to the family of wrasses.
Worldwide there are over 500 species of wrasse. Here we have about 20. Most species are carnivorous, feeding on small crustaceans.
Creole wrasse, however, cruise the reef in large schools trolling for plankton. The largest school I’ve seen of Creole wrasse has been on the south end of Molasses Reef between Fire Coral Cave and Permit Ledge, running out past the pillar coral spot. This is the same place we consistently see schools of horse eye jack, chub and barracuda.
Puddingwife and bar jacks hunt together from time to time. Bar jacks and puddingwife wrasses form teams, and both benefit from the association. In the bar jack’s case, a threefold in increase in biting behavior was observed during the joint foraging. They were more efficient eating small benthic invertebrates than going after fish on their own, their normal prey. Puddingwife search and bite activity also increased during the time spent with a bar jack.
The most widely studied of the Labridae family are the blueheads. The juveniles and initial phase colorations are distinctly different than the terminal adult males. They are the little yellow herds you see all over the reef. Yes, herds, not schools. Herds consist of initial phase males and females, usually dominated by a terminal male, depending on the size of the reef area.
They breed in late afternoon. When terminal males mate, they pair with one female at a time, rocket upwards a few feet off the reef and release gametes at the apex of the run. The males average 30 to 50 females a day. What a life! No wonder they call them terminal phase males.
Studies show the size of the reef and the resident population is an important factor in the composition and behavior of the reproductive process. Smaller reef areas (under 600 square meters), with small populations (up to 200 individuals) have very few initial phase males. Terminal males have a territory with a small number of females. They defend these areas. Meanwhile, the younger initial phase males try to get a little action on the side. They are called “sneakers.”
If a terminal male disappears, there is an initial phase male ready to take its place. Or, a female can change into a male and develop into a terminal male in a few days.
On larger reefs (over 100 square meters and more than 400 individuals), there are many more initial phase males — up to 50 percent of the population. Group spawning is much more popular in this scenario.
Herds are pack hunters, often raiding the egg clusters of redlip blennies, damselfish and sergeant majors. And of course, the initial phase wrasses are excellent cleaners, accounting for about 10 percent of the cleaning activity on the reef. For a good overview of bluehead wrasse, seehttp://animaldiversity.ummz.umich.edu/accounts/Thalassoma_bifasciatum/
I saw a couple references about the intelligence of wrasses. Giacomo Bernardi of the University of California, Santa Cruz, documented orange-dotted tuskfish in Palau using a rock as an anvil to crack open a clam. This is pure entertainment. Scroll down to the bottom of the page for the video:http://news.discovery.com/animals/fish-uses-tool-110929.html.
Beyond the clam and anvil activity, the blackspot tuskfish uses starfish to help procure sea urchin feet. The wrasse harasses the urchin so it will grab on to the reef for defense. Since a hustling starfish cannot catch a sprinting urchin (a true watching-paint-dry-race), the action of the wrasse slows the urchin down so the starfish can catch up. They call this tortoise-and-hare-hunting (just kidding). When the starfish attacks and upends the urchin, the wrasse swoops in for some tasty tootsies. Check it out here: http://www.advancedaquarist.com/blog/are-wrasses-the-smartest-fish.
Wrasses are also being used in commercial applications. In Scotland and Norway, they are being used on salmon farms to keep the cultivated salmon clean, and more importantly, reduce the dependence on chemical lice treatments.
Since this is my last column for 2012, I wanted to wish you Merry Christmas and Happy New Year. I enjoy writing Dive Time quite a bit — today’s column is number 50. I am truly fortunate to have this gig, and I wanted to say thank you to everyone who reads my words and views my images — and especially to David Goodhue and The Reporter for taking a chance on me.
We had significant highs and lows this year — Ken Nedimyer and the Coral Restoration Foundation are CNN Heroes. But Aquarius Reef Base is slipping away into government shortsighted oblivion. If I had the funds, I’d launch them both to worldwide recognition. Please consider the needs of these two worthy causes in your annual charitable giving decisions.
Dive Time has made me a better photographer, increased my knowledge of the marine world, and provided opportunities to meet and interview some truly fascinating people. Thank you. See you next year!
Tim Grollimund is a freelance photographer and PADI divemaster based in Key Largo. He can be reached at tim@timgimages.com or through his web site at www.timgimages.com. Tim is actively involved with the Coral Restoration Foundation and the Aquarius Foundation.