Naturalist Fact: Alligator Gar

 

http://www.thealexandriazoo.com/mAllAnimals.html

http://www.thealexandriazoo.com/mAllAnimals.html

 

Alligator gar (Atractosteus spatula) are a true prehistoric creature that have remained a hearty predator for millions of years. They have been compared with the earliest terrestrial tetrapods which evolved from the ocean during the late Devonian period. Alligator gar are the largest species in the Gar family (Lepisosteidae), reaching up to 400 pounds and 12 feet in length! The rostrum, or mouth of an alligator gar is short and broad with two rows of extremely sharp alligator-like teeth on the upper jaw, unlike other species of gar which contain one row of teeth. These fish have an elongated body with a single dorsal and anal fin posterior near the heterocercal (rounded) caudal fin. A thick row of nonoverlapping and diamond shaped ganoid scales cover the body, acting as an armor layer to protect from predation. Alligator gar are generally dark olive-brown in color, with dark brown fins and a yellow belly. It is easy to spot gar in a body of water because they contain a lung-like gas bladder which they inflate by taking in gulps of atmospheric oxygen from the water surface! This allows them to reach various levels of the water column by inflating and burping out gas from their gas bladder.

It is common to find alligator gar in slow-moving pools and creeks extended from larger rivers, bayous, lakes, and swamps—mainly in the Mississippi Delta. Alligator gar are mainly piscivores, or consumers of fish, but also eat snakes, small mammals, turtles, and birds. Females generally lay 138,000 eggs which cling to vegetation or rocky substrate in which two or three males will fertilize simultaneously. Females can also live up to 50 years, while males only live up to 25 years old!

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Naturalist Fact: Lemon Shark

Lemon sharks are one of the most common shark species in the waters surrounding LSSI. (photo: Albert Kok)

Lemon sharks are one of the most common shark species in the waters surrounding LSSI. (photo: Albert Kok)

Negaprion brevirostris are known as lemon sharks because of their light brown to yellowish skin, which helps them blend in with the sandy ocean bottoms. Although identifying sharks is often difficult, lemon sharks are fairly easy due to their coloration and the fact that their two dorsal fins (top fins) are about the same size, unlike most sharks. They also have a blunt snout, flattened head and stocky body. These sharks grow to a maximum length of about 11 feet and weight of over 400 pounds.

Lemon sharks live in shallow waters preying upon bony fish, rays, and sometimes crustaceans. Females give birth at about 6-7 years of age from April through September. There are 4-17 pups in each litter, and the pups are 24-26 inches long at birth. The lifespan of lemon sharks is estimated at about 25 years. Lemon sharks do well in captivity and experiments on lemon sharks have shown they learn as quickly as some mammals and remember things for at least 6 months without reinforcement. This is a very social shark species. They are often seen in groups and have a structured hierarchy system based on size and sex. They generally don’t show any aggressive behavior with each other and coordinate in groups for hunting purposes in places that the hierarchy is strictly followed.

Although lemon sharks are among the world’s largest shark species, they are rarely dangerous to humans. The International Shark Attack File has only reported 10 unprovoked bites by lemon sharks, none of which were fatal.

The lemon shark is targeted by commercial and recreational fishermen along the US Atlantic Ocean, Caribbean, and in the eastern Pacific Ocean. Their fins are highly prized and exported to Asia for shark fin soup. Their skin may be used for leather and their meat can also be consumed, all of which make this shark very marketable. There is some concern that populations in the western north Atlantic and eastern Pacific Ocean are declining due to over-fishing.

This is one of the most common shark species in the waters surrounding LSSI. You can catch them in the surf from March to November with heavy tackle and large cut bait. They should be released as quickly as possible once landing them to reduce stress on the fish.

Lemon-shark-(30)

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Naturalist Fact: Cownose Ray

Cownose Ray (Rhinoptera bonasus)

Photo from CheseapeakeBay.net

Photo from CheseapeakeBay.net

First things first: despite their common names of “cownose stingray” and “skate”, cownose rays are technically neither! Cownose rays are unique, so they belong to their very own family of rays. However, these interesting-looking ocean-dwellers can still pack a stinging punch, so avoid the venomous barb at the base of the tail. According to legend, Captain John Smith had an encounter with a cownose ray in Virginia, and the location still bears the name “Stingray Point”.

Despite these cautionary tales, cownose rays are known for their passiveness and will only sting when provoked. They are a common site along their shallow Atlantic coast migration path; found as far north as New England and as far south as Brazil. They often travel in large groups, called “schools”, that are formed based on the sex and age of the rays. Since they use their fins for locomotion, these underwater schools resemble flocks of large birds in underwater flight.

Cownose rays typically reach a wingspan of three feet, which comes in handy when they forage. The rays use their large fins to disturb mollusks in the seafloor sediments, and then they crush their prey using powerful dental plates.

On Little St. Simons, look for cownose rays along the edges of Mosquito Creek during a kayaking adventure—sometimes they even raise a fin to “wave”!

Fun Fact: The stinging barb on a cownose ray grows the same way as your finger nails, so the rays you see in “Touch Tanks” at aquariums are regularly clipped for safety.

 

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Living Shoreline promotes fish habitat and erosion control

Barrier islands are very dynamic landscapes. As the tides, currents, and winds sweep around the island, it continuously changes the landscape. Where you first arrive to the dock at Little St. Simons Island, there has been a wooden bulkhead adjacent to the dock creating a vertical barrier between the creek system and the upland.

Imagine a section of healthy marsh joining the higher ground and the creek. That’s what we invision as we replace this bulkhead with a Living Shoreline.

Bulkheads will weaken and eventually fail over time, and we have been planning on replacing the current bulkhead (constructed in 1995) for several years. However, rather than building another bulkhead that inevitably will have to be replaced again sometime in the future, we are putting in a “Living Shoreline.”

This Living Shoreline will be a more natural slope from the upland into the marsh habitat, and as the name suggests, create excellent habitat for the many organisms that utilize the different zones between the low tide mark and the high tide mark. We will be planting native plants that thrive in the marsh zones whose root systems will help stabilize the sediments, and using recycled oyster shells as structure to recruit new living oysters to the site, which will create habitat for myriad of marine organisms including several species of fish. To learn more about the benefits and implementation of a Living Shoreline, visit NOAA’s resource pages or learn about a similar project on Sapelo Island.

Tom Bliss with UGA’s MAREX and Jan Mackinnon with DNR’s Coastal Resources Division remove their nets after a fish sampling session.

Along with stabilizing the shoreline in a more natural and efficient way, one of the goals of this project is to enhance fish habitat. In order to get some baseline data on what is already hanging out around our dock, with the help of the University of Georgia’s Marine Extension (MAREX) team, we have been sampling the fish populations around the dock for the past year.

Next comes the construction! Scheduled to start in the middle of February, we will begin removing the old bulkhead, and creating the living shoreline. With the guidance of cicil engineer Tom Havens and landscape architect Thomas Angell who specializes in ecologically-sensitive environmental design, we will transform our current bulkhead garden into a seamless junction with the marsh.

In the meantime, as you park your car at the Hampton Marina, you might notice a mountain of oyster shells. As these are put into mesh bags (8,000 mesh bags to be exact!), they will be the foundation for which oyster spat (free-swimming larval oysters) will attach. Overtime, they will grow into a living oyster reef, one of those living oyster reefs that are vital to the functioning of the marsh ecosystem.

Of course, Little St. Simons Island cannot take on such a big project on our own. Our primary partners include: UGA Marine Extension, The Nature ConservancySapelo Island National Estuarine Research Reserve, Georgia Department of Natural Resources, Coastal Resources Divsion, NOAAWe are also working with volunteers from these organizations to help implement the project: Coastal WildScapes, Americorps.

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Naturalist Fact: Spotted seatrout

The spotted seatrout (Cynoscion nebulosus), also known as speckled trout, is a common estuarine fish that is found in the Southern U.S. and Gulf of Mexico. Despite its name, spotted seatrout aren't members of the trout family (Salmonidae), but the drum family (Sciaenidae). During spawning season, all mature males of the drum family attract females by making a “drumming” sound. They produce the sound by the contraction of abdominal muscles against the swim bladder, a gas-filled organ that contributes to the ability of a fish to control its buoyancy.

Spotted seatrout reach sexual maturity at one to two years. They grow rapidly, reaching 8 inches in the first year and over 12 inches

by age 2. Small trout eat large amounts of shrimp and other crustaceans, but as they grow larger, their diets shift toward fish. Studies in Texas and Mississippi show that really large trout strongly prefer to feed on mullet. Often the mullet is half or two-thirds as large as the trout! Large females may reach 12 years of age and release over a million eggs during spawning.

Spotted seatrout are a good eating fish and, according to the NOAA, are in the top ten species for recreational fishing in the United States. Seatrout are found in and around seagrass meadows, deep holes, in the surf, and above oyster bars. Fishing with live shrimp near the bottom or attaching a float is the most popular way to search for trout. Casting with soft-bodied jigs, top-water poppers and spoons can be effective also. Spotted seatrout is listed as a “best choice” for sustainable seafood by the Monterey Bay Aquarium's Seafood Watch.

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Naturalist Fact: Canvasback Duck

Canvasbacks can be found in open waters around LSSI during the winter months as they migrate south and then again on their northern migration back to the breeding grounds. Canvasbacks breed in the prairie-pothole region of southern Canada and the females usually construct their nest over water.

Canvasbacks can dive up to 30 feet below the surface when feeding and prefer aquatic plants, but their diet also includes invertebrates such as snails and insect larvae and small clams.

 The canvasback was known as the “King of the Ducks” during the market hunting days of the late 1800's and early 1900's and because of their culinary reputation, canvasbacks were the most valuable of commercially hunted ducks, bringing three or four

times as much as mallards and other species. Canvasback numbers have rebounded since commercial market hunting was outlawed with the passage of the Migratory Bird Treaty Act in 1918. Today, the canvasback makes up just under 5% of Georgia’s annual duck harvest.

Canvasbacks are considered one of the fastest of all ducks on the wing with recorded speeds of over 70mph and, when migrating, canvasbacks often fly in an impressive V-shaped formation that resembles a squadron of airplanes at high altitude.

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Naturalist Fact: Flounder


There are two species of flounder that are commonly found in the tidal creeks and off the shore of Little St. Simons Island, the summer flounder and southern flounder. Both are members of the left-eyed flounder family Paralichthyidae. Summer flounder can be distinguished from the southern flounder by the presence of 5 to 14 eye-like spots called ocelli. Like most members of the left-eye flounders, they can change the color and pattern of their dark side to match the surrounding bottom, and are also capable of rapidly burrowing into muddy or sandy bottoms. Flounder lay buried with only their head exposed to ambush prey which includes many species of fish, squid, shrimp, and crabs. A small body cavity and the absence of an air bladder aid the fish in maintaining its position on the bottom. While primarily considered a bottom fish, they are rapid swimmers over short distances and can become very aggressive, feeding actively at middepths, even chasing prey to the surface. Flounder have a fascinating life history as well. After hatching, the larval fish swim in an upright position and the eyes are located on opposite sides of the head. As the young fish grows, the right eye begins to “migrate” to the left side of the head. When body length of about one-half inch has been attained, the eye migration is complete and the fish assumes its left-side-up position for life. Flounder migrate inshore and offshore seasonally in response to changes in water temperature. During winter and early spring, they are found offshore along the outer edge of the continental shelf where spawning occurs, but in late spring and early summer, they move inshore and concentrate in shallow coastal waters and estuaries. Flounder are considered to be a very important species along the Atlantic coast as it is important to both the commercial fishing industry and very popular for recreational fishing.

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Naturalist Fact: Bonnethead Shark

Bonnetheads (Sphyrna tiburo) are the smallest species of the hammerhead family reaching an average size of 3-5 feet.  This shark can be distinguished from other hammerheads by its rounded, shovel-shaped head.  They are found in the Western Atlantic and Eastern Pacific oceans.  Unlike most sharks, they have molar-like teeth at the back of the jaw for crushing their prey such as hard-shelled invertebrates, crabs, shrimp, mantis shrimp, snails, cephalopods, as well as small bony fishes.  Their feeding behavior involves swimming across the seafloor, moving its head in arc patterns like a metal detector, looking for minute electro-magnetic disturbances produced by prey hiding in the sediment.  Studies of a colony of captive Bonnetheads revealed that this species has surprisingly complex behavior, body language and social organization.  18 Bonnethead body postures and movement patterns were identified including head shakes, back hunching, puffing out the gill pouches, jaw snapping, hitting other Bonnetheads, circling head-to-tail in lines of up to five, and (in males) clasper flexing.  Half of these appeared to regulate social activities.  A subtle, size-related dominance hierarchy was also noted among the sharks, with submissive individuals giving way to dominants as little as 5% longer than themselves.  This suggests they have a keen awareness of their own size relative to that of others sharing their environment.  Bonnetheads give birth to live young with a gestation period of 4 to 5 months, which is the shortest gestation period of all sharks.  Females reach sexual maturity when about 2 1/2 feet long.  They give birth in late summer or early fall to litter sizes of 8 to 16 pups.  During this time, the females lose their desire for food, which prevents them from feeding on their pups.  Males move to a different location, also an adaptation to avoid feeding upon their own young.  Bonnetheads are the only sharks known to exhibit sexual dimorphism, which is where male and female adults look different from one another.  Adult females have a broadly rounded head, whereas males possess a distinct protuberance at the top of the head.  In 2001 at a zoo in Nebraska, a female Bonnethead produced a pup in a tank containing three other females, but no males.  It was concluded after DNA testing that the reproduction was by parthenogenesis, a form of reproduction in which an unfertilized egg develops into a new individual. This type of asexual reproduction had been seen before in bony fish, but never in cartilaginous fish such as sharks, until this documentation.  The Bonnethead, with its early age at maturity and high litter size and population growth rates are very abundant and therefore considered a species of lesser concern.

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Naturalist Fact: Striped Burrfish

Two of the four burrfish in my home aquarium. (photo: B. Morrison)

The striped burrfish (Chilomycterus schoepfii) is striking in its appearance, with the body being light tan to yellow-brown above and white to yellowish and sometimes blackish below, and is covered with fixed and erect spines that give the animal the name burrfish.  The spines are sometimes bright orange.  Dark and wavy lines cover the sides of the body and most individuals also have large dark spots. Burrfish are in the diodontid family, along with other pufferfish.  The striped burrfish has a defense system in the form of an organ known as a buccal pump which allows it to inflate its body considerably when threatened to minimize the risk of predation.  These fish can be found as far north as Nova Scotia, although it is uncommon north of North Carolina.  To the south, it occurs throughout the Florida coast, Gulf of Mexico, Caribbean, and further south to Brazil.  Individuals can grow to reach a body length of 25 cm.  As a species, burrfish are hardy and may persist in water with a salt content of less than 7 ppt to as much as 47 ppt and tolerate a broad range of temperatures.  Juveniles and adults have been collected far upstream within rivers and bays.  They can be easily found off docks and floating at the surface of tidal creeks as juveniles in the warmer months.  They are not as common in the pet trade as other puffers, but burrfish are excellent aquarium fish.  Striped burrfish are predators on a variety of benthic invertebrates, including crabs, shrimp, mussels, miscellaneous crustaceans, and even sea whips and amphipods.

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