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.

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. 

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!