- Coastal Ecology
Dr. Overstreet Honored
July 22, 2014 - Dr. Robin Overstreet, professor emeritus in the Department of Coastal Sciences, received the Eminent Parasitologist Lectureship Award at the American Society of Parasitologists (ASP) Conference, July 24-27 in New Orleans.
GCRL scientists, in partnership with the Mississippi Department of Marine Resources (MDMR), raise spotted seatrout in the state-of-the-art CMAC facility. Currently, the fish are used primarily for wild-stock enhancement, although their use in the restaurant industry is being explored as well.
The spotted seatrout, sometimes referred to as speckled trout or speck, is the most popular recreational fish species in the northern Gulf of Mexico. Naturally predatory and occasionally cannibalistic, their natural tendencies make cultivating them in tanks challenging.
Captive wild adult spotted seatrout spawn in the CMAC. Scientists regularly skim for eggs, and the hatched larvae transferred to specialized larval rearing tanks. The larvae eat microscopic invertebrates called rotifers and artemia, both of which are also bred in the facility. Later, they are fed artificial pellets and grown to fingerling size before being tagged and released in Mississippi waters.
Hurricane Katrina destroyed the initial stock in 2005. Since then the program has been reestablished and more than 300,000 spotted seatrout have been successfully released.
Scientists tag the fish before releasing them in order to monitor them in the wild. The ultimate goal is to calculate the cost effectiveness of stock enhancement, including determining the optimal size, locations, and time of year for releasing reared spotted trout.
Like with other species, spotted seatrout benefit from GCRL’s recirculating, closed-water systems because very little discharge occurs as a result of the environmentally-friendly technology. In fact, GCRL is the only facility in the world growing spotted seatrout at this size using closed systems.
GCRL has enjoyed a long history as a leading facility for studying shrimp, the most valuable aquaculture product in the world. At the CMAC, shrimp aquaculture is being studied to accelerate the development of a domestic marine shrimp farming industry. Shrimp is now the number one preferred seafood in the US—however, over 90 percent of the shrimp consumed in the U.S. come from foreign producers.
GCRL research could help reduce the $3 billion to $4 billion annual deficit the U.S. suffers by importing shrimp from foreign markets. A competitive domestic shrimp farming industry could greatly boost the US economy.
Shrimp produced at the CMAC are better and safer than foreign imports. They can be sold fresh, never frozen, and are produced in low water use production systems designed to decrease risk of disease and eliminate environmental impact caused by commonly used shrimp aquaculture methods.
Aquaculture of blue crabs is under study at GCRL. Despite the blue crab’s complex life history and cannibalistic nature, GCRL scientists are able to raise larvae in high salinity systems at the East Beach site. After development to postlarvae (megalopae) they are harvested.
Researchers move the megalopae to the CMAC where they molt into the first crab stage. There, the small crabs live in large raceways and are gradually acclimated to lower levels of salinity before transfer to ponds. Because blue crabs require “hiding spaces” during development, small chambered enclosures called “bio barrels” are placed in the raceways to provide shelter for the crabs while they are molting. After four weeks, crabs around one inch in carapace width are harvested and transferred to ponds for grow-out.
The ultimate goal of the GCRL research is to use pond-raised crabs to develop new aquaculture products: a bait crab and an “appetizer” soft crab. GCRL-produced bait crabs introduced to local recreational anglers at annual fishing tournaments have beenwell received. Local diners “taste-tested” softshell crabs produced from ponds at a local restaurant and gave them high marks. (Keep this only if we have pictures of diners, etc. Otherwise, strike it.)
Demand for softcrabs exceeds supply and the need for live bait for recreational fisheries continues to grow. Hatchery-reared crabs provide a way to increase fishery production without increasing fishing pressure on wild-caught crabs.
Once common to coastal rivers and estuaries of the northern Gulf of Mexico, striped bass declined and nearly vanished in the 1960s. GCRL’s Striped Bass Restoration Project has been actively working to replenish the coastal striped bass population since 1967. As a result, more than 14 million striped bass have been raised in GCRL research facilities and released into Mississippi rivers, including the Pascagoula, Pearl, Biloxi, Tchoutacabouffa and Jordan.
In 2005, Hurricane Katrina destroyed GCRL striped bass tanks, raceways and overall facilities. In 2007, GCRL began harvesting stripers in 10 half-acre ponds in Lyman, Miss., in a facility owned by the MDMR. More than 50,000 6-inch stripers are growing in the Lyman ponds, each of which contain 1 million gallons of water. There, researchers have had to face a new set of challenges, including problems with unchecked algae growth.
Researchers tag the stripers upon release to monitor the survival rate and see if the stocking and release sites are optimal. Sport fishers in the area assist GCRL scientists by reporting stripers caught in the wild.
The ultimate goal of the program is for released striped bass to reproduce in large enough numbers to reduce or eliminate the need for yearly restocking.
The red snapper supports major commercial and recreational fisheries in the Gulf of Mexico. The species observed a significant decline between the 1970s and 1990s and is subjected to close management and severe harvest restrictions in US waters. The red snapper is considered a primary candidate for US marine finfish aquaculture for both stock enhancement and commercial production.
The red snapper aquaculture program is a collaborative effort between GCRL and the Mississippi Department of Marine Resources (MDMR). GCRL began developing red snapper aquaculture in the early 2000s and is currently the only facility that has the capacity to grow red snapper larvae. Red snapper larvae are especially challenging to culture because they require very small copepod crustaceans as an initial live feed. The production of these copepod preys is itself difficult and still performed at an experimental scale.
Red snapper eggs are currently obtained by inducing ovulation and spermiation of pre-mature females and males caught in the wild. Eggs and sperm are collected by hand stripping and the eggs are fertilized in-vitro with the sperm to produce embryos. Larvae are fed invertebrates live preys (copepods, rotifers and artemia) before being weaned on dry feed and grown to tagging size.
Juveniles produced for stock enhancement are tagged using coded-wire tags or identified using genetic tags, and released on offshore reefs monitored by MDMR in order to evaluate their survival and recruitment to the fishery. Grow-out of red snapper to market size is also being evaluated in intensive closed recirculating systems.
Current program objectives include increasing the production capacity of juveniles for stocking on Mississippi offshore reefs, developing captive spawning technologies, and improving husbandry methods for the production of juvenile fish for stock enhancement as well as market size red snapper.