Saturday, April 5, 2014

Tripletails get up close and personal on video

Tripletails Lobotes surinamensis are unusual fish but are even more unusual to find in our area; they are occasional late summer visitors to Virginia waters. They are more common further south particularly in the Gulf states where they hang around structure either inshore (pilings, bridges) or offshore (buoys, wrecks) often very close to the surface. Due to this habit, anglers can "sight cast" to them - actually see the fish in the water before throwing a lure or bait - with live shrimp. These are muscular fish with a broad body, capable of putting up a strong challenge, but are excellent food fish as well. Unfortunately for fishermen and tripletails alike, they are not abundant anywhere throughout their range, but what they lack in numbers they make up for in size; adults may get up to 40 pounds and 3 feet long!

Amazonian leaf fish Monocirrhus polyacanthus


At first glance a juvenile tripletail resembles an Amazonian leaf fish, with very similar body structures and coloration which both utilize as camouflage despite their vastly different habitats. The irregular patterning of blacks, browns, tans, and pale yellows of both species masterfully mimics dead, floating leaves; mangrove leaves for the tripletail and any type of leaf from the flooded Amazonian canopy for the leaf fish. To further enhance the illusion, they float sideways, seemingly motionless, passively adrift with the currents. This is a popular strategy in the fish world as the juvenile (and adult) stages of many species also mimic vegetation with coloration, patterning, and elaborate appendages. Two additional local species who do so are lookdowns and Atlantic spadefish.

The green-gold vertical bars and long fin appendages help camouflage juvenile lookdowns in sea grass.

Not only does this strategy help young fishes avoid predation, but in fact it makes adult tripletails very effective ambush predators. By mimicking a lifeless bit of flotsam around structure, tripletails drift slowly at an odd angle amongst unsuspecting fishes and shrimp feeding on or using the structure for cover, then use their large protrusible mouths to create enormous suction that inhales their prey. In captivity, the tripletails display this instinctive behavior and "hide" in plain sight, drifting listlessly near a support beam until feeding when they become aggressive and active.

The two tripletails shown in the video ( ~ 16" long)  are in a grow-out tank and hopefully will grow large enough to one day be floating strangely near the surface of our Chesapeake Bay Aquarium, slightly sideways and barely moving, prompting visitors to ask in concern "what's wrong with that fish?" Nothing, it's a tripletail, that's what they do.

Friday, April 4, 2014

Lined seahorses (H. erectus) station video of them feeding like "real horses"

We recently put four lined seahorses onto exhibit that were bred on-site at the VLM. Aside from simply raising them to adulthood - which is a task in itself - we also "train" them to feed in a particular location. This is a process that requires a lot of patience but ultimately helps in multiple ways:  it allows us to control the amount of food given each day, it allows us to observe them at feeding (and see if one is not), it ensures the food is being eaten and not falling through uneaten into the substrate, and therefore it also prevents excess food buildup which can lead to disease and water quality issues.

The process begins early while we raise them in our nursery tanks, only after the seahorses are finally on a non-live diet (months before exhibit size). Once they are eating mysis regularly we then feed only at a "station" or particular spot designated specifically for feeding. Food is delivered via a clear plastic rigid tube (old gravel washer) directly to the station, which in this case is a clam shell. Eventually, they become accustomed to the routine and not only come to the station just prior to feeding time, but will line up side by side and feed, similar to regular horses at a trough as seen in the video!