Saturday, August 30, 2014

Striped bass and striper hybrids in our James River exhibit

September is the month we do our major exhibit work, including fish moves. Our first priority is to release any animals that will be too large to keep until next spring and replace them with smaller animals that can be kept comfortably at least until next collecting season. The first exhibits to down-size were the James River and James River Shallow exhibits. Earlier this year we added yellow perch that had grown too large for the Yellow Perch exhibit, and walleye that were transferred from the National Aquarium in DC when it (sadly) closed.

Two year old yellow perch
A walleye in James River exhibit

But we also acquired some captive bred striped bass (~30) and hybrids (~ 12 white bass x striped bass) from a hatchery to replace the adult striped bass which are the signature species in this exhibit. These hybrid and striper juveniles were initially about 4 inches when we got them but have been growing rapidly in our James River Shallow exhibit. They are now large enough to replace the striped bass adults in the main exhibit which have grown too large for the exhibit and were released last week. Below is a video of the very active school of stripers and hybrids just put in the main portion of the exhibit.
video
Stripers and hybrids school in their new exhibit

It is difficult to discern the hybrids from the pure bred striped bass, especially in the video. Generally, the hybrids demonstrate physical traits of the white bass that differ from pure bred striped bass: a higher shoulder profile, more irregular stripes, and a darker back in adults. All three species, white, striped, and hybrid are very aggressive predators and grow rapidly. Next spring we will have to remove a portion of this school to make room as they grow and by next fall we may have to start the process all over again.

The iconic striped bass


A hybrid striper 
Striper above, hybrid below

The shallow portion of the exhibit has been thoroughly scrubbed, cleaned, re-decorated and re-populated with a variety of smaller fishes and plants from our collection including a new female wood turtle taking the place of the irreplaceable "Woody" who recently passed away of old age.

"Woody" was the mischeivious, charasmatic long-time resident male wood turtle in James River

Thursday, June 19, 2014

Video of a massive mountain redbelly dace congregation

video
Occasionally when we are out in the field, we are fortunate enough to run across unusual or unexpected animals, or even better if you're far enough out there and get really lucky, you can witness unusually large groups of animals displaying natural behaviors and paying you no heed. In this case, a large shoal or "school" of nuptial mountain redbelly dace - with some rosyside dace, crescent shiners, and even a crayfish in there - have gathered on a chub nest to mate and are on full display. The beauty of these fish is hard to rival and create a living mosaic of red, gold, yellow, olive, black, white and silver.

Thursday, June 12, 2014

Mating season! Male redline darters fight it out, gilt darters mate, greensides mate

A large dominant male gilt darter in breeding colors

Late spring is breeding season for the majority of Virginia freshwater fishes; depending upon water temperatures, most darter species breed somewhere between early April to late May. Prior to (potential) spawning, male darters develop more intense coloration and exaggerated patterning than their normal appearance to outdo their male rivals in the hopes of attracting a female.
Male redline darter on display

Mature males will often spar with one another over territory or a single female, nipping at each others's fins and tails (see video below) often violently. Theoretically the dominant male wins out, but often the female pays either off them little notice and casually swims away as the males are still fighting. 
video
Two male redline darters fight over a female

Once a couple has paired off, they typically engage is some sort of courtship behavior that signals the beginning of actual mating. Many darter species show similar courtship and mating behaviors; for example the males of Genus Percina and many Etheostoma species as well swim alongside the female often weaving along her body from side to side, then when she settles into a good spot (presumably for laying eggs) he hovers over her and quivers his entire body so fast its a blur. Both videos below show this behavior from two species of each respective Genus. 
  video
Two gilt darters mate while a stoneroller watches and then rudely interupts

video
Two greenside darters mate and then also get rudely interrupted by a stoneroller

As seen in both video, these behaviors - at least in our stream exhibit - also trigger a feeding response in the other fishes looking for an easy meal of freshly lain eggs...or they are just excited by the activity. In either our exhibit or in the wild, successfully fertilized eggs face very long odds to reach maturity, but that's the reason these spawning events are so critical. They must find the right mate with good genes, create enough fertilized eggs to account for all the natural mortality, and spawn at a time when their young will have maximum food available as they grow. Because after their little spawning dance, mom and dad have done all they are ever going to do for their offspring. 






                                          




Friday, May 30, 2014

Barrel fish or drift fish - rare and unusual fish captured in shallow Virginia waters


Members of our husbandry staff were collecting on the Eastern Shore of Virginia last week and captured an unusual species rarely found in Virginia, especially near shore. This small saltwater fish at first appeared to be gold to orange-ish colored (see below), but overall color is a dubious trait to use for identification. Often fish under stress appear paler than their normal coloration, or may simply be an unusual color morph. It could not be identified in the field by its body shape either: disproportionately large eyes, an unusual fin configuration - stumpy dorsal spines with a larger soft dorsal element - down-turned mouth, and a blunt rounded snout. Thankfully, it was captured undamaged and brought back to the museum alive where we currently have it in one of our quarantine systems.
 The fish immediately upon capture

Just in the tank...

And most recently in its "natural" coloration.

This is obviously a small fish and one that presumably will not be of too much interest in a world of such recognizable and iconic fishes such as sailfish, white sharks and clownfish but that is precisely what is interesting about this little fish. To even verify what I suspected this to be - even the all knowing internet was of no help! - I consulted Dr. Kent Carpenter, a fish systematics expert and author of A Field Guide to Coastal Fishes: from Maine to Texas (my favorite Mid-Atlantic saltwater ID book) and he confirmed it belongs to the Genus Hyperoglyphe and is either a barrelfish or black driftfish, which are very similar species at this life-stage. There is very little information on either species and even less ecological information available (e.g. diet, temperature tolerances, etc); the basis for good husbandry practices. What is known is that they are largely deep water offshore schooling fish as adults, frequent flotsam as juveniles - this one probably came near shore riding along with vegetation - and there is a small market for them as a food fish overseas. Not a whole lot to go on. But so far it has adapted well, eats a large variety of foods, does like to hang out near structure, and is very active, as seen in the video.

video

So this small, dark, somewhat skittish but ever-wiggly fish is a mini-mystery. Just one of nearly 30,000 fish species from around the world; it has its place in the world but goes almost wholly unnoticed. I am professionally and personally interested in witnessing its growth and behavior and then releasing it back into the ocean where it belongs, to drift off once again into obscurity. 











Thursday, May 8, 2014

Baby crayfish - video

Red crayfish in one of our holding tanks

We currently have a large number of surplus crayfish segregated by size in several holding tanks. Like other crustaceans, crayfish molt - shed their rigid exoskeleton or shell for a soft larger shell that awaits underneath - as they grow, and become vulnerable during this period until the new shell hardens. Significantly larger crayfish can and will injure or even kill much smaller crayfish even when they are not molting.

 A crayfish exhibiting a typical crayfish greeting
Two neighboring adults in their respective PVC pipes 

Crayfish at all life stages will cannibalize each other so they need to have places in which they can hide and protect themselves from predation. To minimize conflict and for protection between molts, each crayfish is given a PVC tube which they can use as a burrow and fend off tank-mates. However, adult crayfish not only fight with their neighbors, but occasionally find mates as well. When they do "find love", they mate face to face with their claws and legs locked together, making it difficult upon first glance to tell if they are fighting or...not fighting. Recently a few pairs have been doing a lot of "not fighting" in the adult tank and the results are evident in the video that follows. 
video

As shown next to a metric ruler, the juveniles are currently 7 - 9 mm long

 After mating, the mother broods the eggs below her tail and the hatched young often remain with her for a while after. When they can feed (on detritus, or in their case crushed fish flakes) and protect themselves they simply head off on their own. These cute little crayfish are already pretty scrappy and quite active; in fact they are probably several molts old at this point and more than capable of fending for themselves. So in anticipation of the inevitable crayfish battles to come, I constructed a habitat specifically designed for the needs of our young crayfish community. 
A newly constructed, state of the art, all inclusive, crayfish condo





Wednesday, May 7, 2014

American oyster castle project - by Aquarist Carol Paulson

The aquarium staff at the Virginia Living Museum makes a concerted effort to lend our time and resources to conservation projects on site and in the field. On April 25, fellow aquarist Patrycja Lawryniuk and I got the opportunity to work on the Idaho Reef Castle Project in collaboration with the Nature Conservancy. This is phase two of an ongoing project the Nature Conservancy has developed to reestablish American oyster populations in coastal waters. The primary goal of this phase is to construct a reef using oyster "castles"; concrete-based structures that resemble castles. These oyster castle blocks are positioned in long rows and then stacked to raise the surface of dead oyster reefs, allowing them to become functional three dimensional habitats with sea level rise.
The surface area allows more oyster spat to settle on castles
Oyster castles provide three-dimensional habitat for a variety of animals

This project site is located on the Eastern Shore near Machipongo, approximately an hour and a half drive from the VLM. To reach the reef from our launching point, we boarded a Carolina skiff to the project site less than a mile offshore. Because the site is located in shallow water, each construction day is planned around the tides so we went out at around 11AM (low tide) so lower castle pieces were visible.
The castle reefs replace natural reefs that are disappearing from the Bay
 
At low tide, the top level of the oyster "castles" is exposed above the water along with oysters that settle upon them. However, oysters thrive in these nutrient rich tidal flats and are able to survive periodic exposure by tightly clamping their shells shut and filling their mantle with seawater. As filter-feeders, oysters help to maintain healthy water quality by removing excess nutrients from the water. When oysters are filter-feeding, they relax their valve muscle, thus opening the shell allowing nutrient-rich seawater to enter.
 

American oysters are an essential component of the Chesapeake bay aquatic ecosystem. Oyster bars provide secure structure for various plants to thrive on and three dimensional habitat that are home to a multitude of small fishes, crustaceans and invertebrates.
 
Additionally oyster reefs help to minimize coastal erosion by dampening wave action and stabilizing soft sand and mud substrate. Oyster reefs are critical to the success of coastal marine ecosystems, yet their populations have been depleted due to overfishing, dredging, habitat loss, and pollution; their current population in the Bay are less than one percent of historic levels. This project is aimed to alleviate oyster population loss by providing a habitat for oyster spat to survive and flourish to their once-sustainable population.

Patrycja Lawryniuk is proud of her castle
 Carol Paulson supervises

 
 
Carol and Patrycja are always happy to help out!

Saturday, April 5, 2014

Tripletails get up close and personal on video

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

Tripletail

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.