Harborwalk Eco Tour

Charlotte Harbor is considered one of the most productive estuaries in Florida. In its early history, it is thought to have supported the largest known hunter/gatherer society the Calusa Indians. Most (60%-90%) of the food came from fishing, including sharks, rays, catfish, pinfish, and pigfish, in addition to shellfish like oysters, whelks, and clams [1].

Plants that were gathered made up the rest of the diet, including sea grape, prickly pear, and palmetto. There is only mild evidence that any horticultural activities were conducted in the area during their reign from about 4000 years ago to the time of European contact. Some evidence for cultivated crops (perhaps only as garden crops) included gourds, papaya, and chili pepper, but surprisingly no maize [1].

Sea level changes due to changing climates would have made fishing more challenging during their 5000-year time periods. They would have harvested the fishes with hook and line, spears, tidal traps, and nets. As a testament to the vast productivity of the area, shell mounds are scattered throughout Charlotte Harbor.  Some of the mounds may have been sacred burial grounds, some were lookout hills to watch for their rival Tocobaga Indians whom they may have traded with or warred with[2] to the north, and others just plain garbage piles.

1.            Hutchinson, D.L., et al., The Calusa and prehistoric subsistence in central and south Gulf Coast Florida. Journal of anthropological archaeology, 2016. 41: p. 55-73.

2.            Marquardt, W.H., TRACKING THE CALUSA: A RETROSPECTIVE. Southeastern archaeology, 2014. 33(1): p. 1-24.

Charlotte Harbor is an estuary, which means, it has a mix of salt and fresh water, known as brackish water.  The salt content (salinity) of Charlotte Harbor can range from 0 parts per thousand (0ppt) to 40ppt, which is considered hypersaline because it is more than the average ocean salinity of 35 ppt as measured during the Challenger Expeditions [1].

If you are a creature that lives in the Charlotte Harbor estuary, you must be pretty tough. The changing conditions of the estuary make it a physiologically challenging place to live. Organisms need special adaptations to withstand the osmotic pressure put on their cells (water pressure pushing against a salty area). Some fish like the juveniles of snook can change the characteristics of the cells within hours in their gills to maintain homeostasis (salt and water balance) [2]. This important sportfish is found in all parts of the estuary due to this special adaptation.

Not many other species can tolerate these low and changing salt conditions. Those that can tend to have thriving populations due to being exposed to fewer predators and access to abundant food resources. It is the juveniles of most species that can live in the estuary. It is a reason why several shark species pup (give birth) in the esturary. Adult sharks cannot tolerate low salt condition, and the worst enemy of a baby shark is a bigger shark, so being able to “hide” in the low salinity areas gives them added protection.

In addition to salinity changes, some organisms must withstand being submerged then exposed to air for hours at a time and must endure temperature extremes.  Oysters and barnacles are experts at overcoming these challenges. When underwater, these species open themselves to allow water to filter through for feeding and waste removal and then “clam up” when the tide drops, and they are above the water.  Temperatures vary on daily and seasonal bases. The summer sun and winter cold fronts add further to the harsh environment estuarine species endure.

1.            Thompson, C.W. and J. Murray, Report on the scientific results of the voyage of H.M.S. Challenger. Vol. 1. 1895, London: Her Majesty's Stationary Office.

2.            Quintero, I., Effects of salinity adaptation on blood osmolality and gill morphology of juvenile common snook centropomus undecimalis (Bloch). 1988, Thesis (M.S.)--University of South Florida, 1988.

Charlotte Harbor is the second largest open-water estuary in Florida and is the Gateway to the Gulf of Mexico.  Its approximately 270 mi2 open water area is protected by numerous barrier islands (CHNEP 1998). The most famous opening to the Gulf is Boca Grande Pass where the World’s Richest Tarpon Tournament occurs annually.

Charlotte Harbor, like other Gulf coast estuaries can be categorized as a drown river valley due to the sea level rise flooding the Peace, Myakka, and Caloosahatchee Rivers. It is also characterized as a bar-built estuary due to the barrier islands that rim the coastline [1].  Approximately 40 million years ago the limestone bedrock of the area was formed as the warm shallow sea that covered most of Florida evaporated, leaving behind calcium carbonate. This bedrock cratered and formed sinkholes that were later partially filled with sand and clay from the erosion of the Appalachian Mountains.

During the last ice age, the coastline of the area was about 80 miles west of its present location due to the sea level being about 400ft lower at that time.  The mouths of the rivers got flooded and the low spots became Charlotte Harbor.

Charlotte Harbor is only about 6 ft in average depth. This shallow-water estuary is therefore dominated by tides and winds [1]. During the winter when strong northeast winds blow, the water gets pushed out to the Gulf of Mexico, and many shallow, flat area become exposed, giving wading birds like herons and egrets an opportunity for expanded foraging areas.

1.            USGS. Tales of the Coast - America's Coasts.  [cited 2023; Available from: https://www.iwr.usace.army.mil/Missions/Tales-of-the-Coast/Americas-Coasts/Drowned-Valley/.

2.            Hine, A.C., et al., Karst Sub‐Basins and Their Relationship to the Transport of Tertiary Siliciclastic Sediments on the Florida Platform. 2009, John Wiley & Sons, Ltd: Chichester, West Sussex, UK. p. 179-197.

Charlotte Harbor had been fortunate enough to have had its seagrass coverage remain relatively stable through 2011 in spite of the many years of development in the area [1]. However, very recently, there has been a decrease of 23% in seagrass coverage from 2018- 2021 [2]. Seagrasses create a vital habitat for commercially harvested shrimp, recreationally important sportfish, and myriads of ecologically important crustaceans, shellfish, and fishes. Because so many species depend on seagrasses, they are considered keystone species. Seagrasses are important habitats for fishes even at very early stages of their life. For example as soon as the sportfish spotted seatrout, and the important forage species gobies, and blennies will swim down into the seagrasses where the water currents are diminished, and even though they cannot swim strongly against tidal currents, they can maintain themselves in a habitat that protects them from predators and offers abundant food resources [3]. 

There are three main species of seagrasses in Charlotte Harbor and three other less abundant species. Turtle grass, shoal grass, and manatee grass are the species commonly found in the harbor.  Shoal grass is a thin, flat-bladed grass found in the shallow areas throughout the harbor. You may see sparse patches of this species from this boardwalk if you look carefully.  It is considered a colonizing species as it can withstand severe changes in salinity and being exposed to the air for hours.

Turtle grass is a thick, flat-bladed grass found in slightly deeper areas than shoal grass, although they are often intermingled. It mostly must stay submerged with the exception when it is nearly dormant in the winter and exposed to the air during cold fronts that blow the water out of the harbor. Surprisingly, turtle grass is mostly eaten by manatees.

Manatee grass has a long and cylindrical shape and tends to be found in the areas deeper than both turtle and shoal grasses. It is mainly found in the saltier areas of the harbor.

1.            Stafford, H., et al., Florida Seagrass Mapping and Monitoring Progam. 2011.

2.            Rose, K. Eyes on seagrass. 2023  [cited 2023; Available from: https://sfyl.ifas.ufl.edu/charlotte/sea-grant/eyes-on-seagrass/.

3.            Mitchell, M.E., The ecological importance of notocord flexion in fishes. 1989, University of South Florida.

The fish that you see regularly jumping out of the water are actually mullet. Although a Florida judge in a 1916 fisheries violation case for catching mullet out of season was dismissed. The reason: mullet were birds and therefore not subject to the fisheries rules! It’s true! It’s not a fish story! The lawyer, Pat Whitaker, convinced the judge that because the mullet spent time in the air and had a gizzard like other birds but no other fish, that they must be birds and therefore his six clients should be acquitted [1]. 

Striped mullet, Mugil cephalus, is a is a species that is commercially and recreationally harvested, although commercial harvest has been greatly curtailed when the net ban went into effect in 1995. Smoked mullet is a favorite way to eat mullet. They are caught for their roe (male and female reproductive sacs) and sold in overseas Asian markets for high prices.

There are three species of mullet found in Charlotte Harbor and striped mullet are the largest, growing  to about 3 pounds (1.4 kg) and about 2 feet in length (60 cm) [2]. Large spawning aggregations form from November through February in preparation for migrating offshore for spawning. The juveniles return to the estuary to live and grow, feeding on benthic (bottom) algae and small organisms.

No one knows why striped mullet jump. It is suspected that jumping could be a response for stirring up anoxic (low or no oxygen) sediments while feeding. Others have suggested that it could be a way to remove irritating parasites. 

Striped mullet are ecologically important as they tie up nutrients in their biomass through algae consumption. They are a local favorite for the table, especially when smoked, and they provide soothing entertainment when you see them jumping out of the water on a glassy calm evening.

1.            Peeples, V., Mullet for Thanksgiving, in Florida Weekly - Charlotte County Edition. 2013, Florida Weekly.

2.            Whitfield, A.K., J. Panfili, and J.D. Durand, A global review of the cosmopolitan flathead mullet Mugil cephalus Linnaeus 1758 (Teleostei: Mugilidae), with emphasis on the biology, genetics, ecology and fisheries aspects of this apparent species complex. Reviews in fish biology and fisheries, 2012. 22(3): p. 641-681.

What you are seeing is the tea-stained water that is coming from the Peace River to your left (East). The water is carrying tannins that is the product of the natural decomposition of plant and to a lesser extent, animal material along the shores of the river and its watershed.  The tannic acid lowers the pH of the water compared to the mouth of the estuary at the Gulf of Mexico. The watershed of the Peace River (the drainage area) is tremendously large, draining over 2300 square miles of orange groves, farmland, and ranch land. 

The River carries freshwater that floats on top of the saltwater coming in from the lower part of the harbor. The water flows upstream and downstream depending on the tides and winds. Eventually, the salt and freshwater mix to form brackish water. There is a seasonal component to the salt characteristics here in the upper estuary. The water in front of you becomes saltier during the winter dry season and can become completely fresh during the rainy summer season. The tannin-stained water can make it all the way to near Boca Grande Pass during the height of the rainy season.

These changing conditions create an environment that relatively few species can withstand. For example, there are just over 300 fish species in the harbor compared to over 800 species in the adjoining Gulf of Mexico where salinities, temperature and other parameters are more stable. However, the species that are hardy enough can thrive and grow in large populations. Estuaries are extremely productive and play host to 72% of the commercially and recreationally harvested species either as eggs, larvae, juveniles, or adults.

If you see a large nest with big sticks high on a pole or dead tree near the water, then it is likely an Osprey nest. The Osprey, Pandion haliaetus, is a large bird of prey that has strong talons with a reversable toe that allows it to grasp fish with two toes in the front and two in back. Additionally, they have a barbed pads on the soles of their feet to hold their slippery prey[1]. They are distinguished from Bald Eagles by their size (smaller), color, brownish black instead of dark black, and the black band of feathers extending from their eye and going down the side of their necks.

Ospreys’ diet are 99% fish, and they have a high success rate of prey capture – hence their nickname “fish hawk”. They have been observed capturing a fish every 1 in 4 tries and can be as high as 70% [2]. Success rate can depend on age. Young Osprey have been observed trying to catch an adult striped mullet. They get a hold of the struggling fish but are not strong enough to carry it out of the water, so the mullet goes free. When they are successful, these raptors have a good aerodynamic sense as demonstrated by the way they hold their fish headfirst into the wind for greater flight efficiency.

Nesting osprey pairs will continue to build their nests annually and defend the area immediately surrounding it, although they are not territorial beyond that. The nests can get as big as 13 feet deep (4m) and 6 feet (2m) across, but the nests around Charlotte Harbor are much smaller. The female will lay 1-4 eggs that take 36-42 days to hatch.

Although we see Ospreys year-round, there is a part of the population that migrate to our area in the winter from northern areas, partly claiming snowbird status [3].

1.            Osprey.  August 5, 2023]; Available from: https://www.allaboutbirds.org/guide/Osprey/.

2.            Gresham, J. Osprey & Prey Season.  August 5, 2023]; Available from: https://www.dcr.virginia.gov/state-parks/blog/osprey-prey-season.

3.            Osprey Pandion haliaetus.  August 5, 2023]; Available from: https://myfwc.com/wildlifehabitats/profiles/birds/raptors-and-vultures/osprey/.

Brown Pelicans, Pelecanus occidentalis, are a bird you may see perched on the boardwalk railing nearby or flying overhead in the classic “V” formation. If you see them fluttering their pouch, they are cooling themselves down. During the mid twentieth century through the 1970s, the pesticides endrin and DDT nearly wiped out the species in areas like Louisiana. The birds had to be reintroduced there from Florida populations. Now through the disuse of these pesticides, the populations have recovered and they have been delisted from being endangered [1].

Brown Pelicans are expert fishers who dive from on high and crash into the water collecting numerous small fishes, along with about 2.6 gallons (9.8 L) of water [1]. They will also go after fish released by anglers, and they aren’t too proud to scoop up the carcass of a filleted fish. Pelicans will look for small schooling fish to dive on, to efficiently maximize their caloric intake compared to the energy expended to catch the fishes.

After a dive, they will filter out the water and swallow the fishes. Occasionally, you will see seagulls near pelicans feeding and will pick off any fishes that happen to get away. You can even sometimes see a seagull standing on the head of a Brown Pelican!

Brown Pelicans are large birds whose wingspan of 84 inches (213 cm) give them powerful lift, and their webbed feet make them strong swimmers.

They nest in local mangroves building nests of about 30 inches (76 cm) across and 9 inches (23 cm) high.  The female will lay 2-4 eggs in a clutch, and the male shares incubation duties. The eggs hatch in 29-35 days and fledglings leave the nest after 77 – 84 days [2].

Brown Pelicans live in Charlotte Harbor year-round, and they have close relatives, White Pelicans, that migrate from the northern Midwest and enjoy Charlotte Harbor during the winter. White Pelicans mainly stay in the saltier areas lower in the estuary. Their feeding behavior is different than Brown Pelicans as they sometimes team up while swimming to corral fishes close together then they plunge their heads into the water at the same time to scoop up the fishes.

1.            Brown Pelican Life History.  August 16, 2023; Available from: https://www.allaboutbirds.org/guide/Brown_Pelican/lifehistory.

2.            Brown Pelican.  August 16, 2023; Available from: https://myfwc.com/wildlifehabitats/profiles/birds/shorebirdsseabirds/brown-pelican/.

Anglers dream about catching the common snook Centropomus undecimalis. It is a species that gets “hook smart” early in its life.  They are great fighting fish that will go on long runs and even break water in shallow areas. Thousands of people come to Florida to catch a monster snook that can reach over 40 inches (1m) and 50 pounds (22Kg) [1]. Although it is considered a wonderfully mild-tasting fish, that was not always the case. It used to be considered a trash fish or “soap fish” because of its soapy flavor. When the technique of fileting was used on snook, the soap flavor was eliminated, and it is now considered excellent table fare.

There are three species of snook reliably known to inhabit the waters of Charlotte Harbor [2], but the most abundant species is the common snook, which is larger than the other species found here. The common snook is considered a euryhaline species, that is, it can live in a wide variety of salinities. They can withstand changes in salinity that few species can match. 

Most adult snook will migrate from the upper reaches of the harbor (around here) and go to the inlets to the Gulf of Mexico to spawn. The eggs hatch within a day or two and the larvae are guided by tidal currents to the low salinity areas of the harbor where yearling juvenile snook live, including the nearby Peace River [3].

Snook are sensitive to cold and have succumbed to cold and red tide in recent years, so there are strict harvest regulations for them. A fisheries-independent monitoring program helps monitor the snook populations here. If you find a tag in a snook, you can report it and get information about the individual, but remember harvest regulations still apply, and if it is a closed season, you must return the fish unharmed to the water.

1.            Sea Stats: Snook - tackle busters. Available from: https://f50006a.eos-intl.net/ELIBSQL12_F50006A_Documents/Snook18.pdf.

2.            Poulakis, G.R., Matheson, R.E., Mitchell, M.E., Blewett, D.A., & C.F. Idelberger. (2004). Fishes of the Charlotte Harbor estuarine system, Florida. Gulf of Mexico Science.  117-150.

3.            MacDonald, T.C., Snook abundance trends, habitat use, and recovery from environmental perturbations, in Snook Symposium 2021. 2021, Florida Fish and Wildlife Commission.

If you shine a bright light onto the waters around here, you may see little red spotlights.  That is the reflection of the eyes of alligators.  Alligator mississippiensis, the American alligator, can grow to 14 feet (4 m) and weigh over 1000 lbs (450 kg) [1]. Young smaller than 4 feet (1.2 m) are relatively harmless and can even get eaten by larger alligators.

Populations of gators were drastically reduced when DDT was used as a pesticide during the 1940s until it was banned in the United States in 1972 with the help of Rachel Carson’s “Silent Spring” book. Alligator populations have now exceeded 1.3 million. DDT disrupted the reproductive development of both male and female gators. Females went through their reproductive age too quickly before they could mate.  Male reproductive systems became underdeveloped [2].

As an apex predator, alligators keep other populations in check. They are opportunistic feeders and eat just about anything including fishes, turtles, birds, and small mammals. While it is rare to be bitten by an alligator, the chances of an attack are higher where males are vying for territory and females are protecting a nest that is made above the waterline near the shore. Available statistics from 1948 – 2022 reveal 453 occurrences of alligator bites on humans. Of these, 141 minor bites required no treatment beyond simple first-aid, and 26 attacks were fatal during this time [3].

Alligators favor lower salinity water, but they are found throughout Charlotte Harbor. They can be mistaken for crocodiles, which are rare and found in the saltier areas of the estuary. Gators are abundant enough to be harvested under controlled conditions. Nearly 8,000 were taken in 2022 through the licensing system required for harvesting alligators.

When you see an alligator, do not feed them! They become fearless of people, and that can increase the chance of getting bitten, so it is best to enjoy them from a distance, knowing the vital role they play in the Charlotte Harbor ecosystem. You could even savor some succulent gator bites prepared from gator tail.

1.            Alligator Facts.  August 10, 2023]; Available from: https://myfwc.com/wildlifehabitats/wildlife/alligator/facts/.

2.            Guillette, L.J., et al., Alligators and Endocrine Disrupting Contaminants: A Current Perspective. American zoologist, 2000. 40(3): p. 438-452.

3.            Florida Fish and Wildlife Conservation Commission Alligator Bites on People in Florida.  August 10, 2023]; Available from: https://myfwc.com/media/1716/alligator-gatorbites.pdf.

Manatees are gentile giants that can grow up to 13 ft and weigh more than 3500 lbs [1]. There are approximately 7,500 manatees in Florida waters [2], and while they are no longer considered endangered they were downlisted as a threatened species by the US Fish and Wildlife Service [3], and imperiled species in Florida [2].

Manatees’ nearest relatives are dugongs from the Pacific Ocean and the extinct sea cows from the Arctic Ocean. Pachyderms like elephants are relatives as well. Being mammals, manatees have hair, give live birth, and mothers take great care of their calves for about 2 years, teaching them the areas they need to know for survival. This includes showing them feeding grounds and the warm water refugia like Warm Mineral Springs in the upper harbor they need during cold fronts.

In addition to being cold sensitive, manatees succumb to red tide’s neurotoxin. In 1996, there was a major mortality event that was attributed to red tide. It was unusual in that most of the manatees that died were big and otherwise healthy animals. There was a red tide bloom that was present during a strong cold front. Manatees had been seeking refuge in warm waters, and as it slowly warmed, the large animals began to go to their feeding grounds and on the way encountered the intense red tide and died from drowning because they could not raise their snouts above water. There was high red tide associated mortalities of manatees in 2003, 2013, and 2018.

Manatees have been in the area for a long time. Manatee fossil bones have been found in the Peace River and the nearshore Gulf of Mexico. You can scuba dive in less than 30 feet of water to collect fossil manatee ribs, sea turtle ribs, stingray spines, and shark teeth. Hopefully, with the continued efforts to protect the manatee through research and regulation, we will have manatees to enjoy for the future.
 

1.            Florida Manatee Facts and Information.  August 5, 2023]; Available from: https://myfwc.com/education/wildlife/manatee/facts-and-information/.

2.            Florida Manatee Program.  August 5, 2023]; Available from: https://myfwc.com/wildlifehabitats/wildlife/manatee/.

3.            Manatee.  August 5, 2023]; Available from: https://www.fws.gov/species/manatee-trichechus-manatus.

Like seagrasses and oysters, mangroves may be considered a keystone species. A species that supports many other nearby species. There are three types of mangroves we have in Charlotte Harbor, red, black, and white. The species you see on the shorelines are red mangroves Rhizophora mangle also known as the “walking trees” because of their long prop roots. The way red mangroves tolerate salt is different from the other two species of mangroves in that they exclude the salt from entering the tree rather than excrete it like black and white mangroves do [1].

All three species obtain oxygen from above-ground structures. In red mangroves, oxygen is obtained from prop roots, black mangroves have finger-like extensions called pneumatophores that rise above the sediment and supply oxygen to the plant during low tide. White mangroves will grow peg roots when they are inundated for long periods of time [2].

Mangroves are vital to the survival of many different species. Birds like the roseate spoonbill, brown pelican, egrets and herons will nest in the branches [3]. Oysters and barnacles will attach themselves to prop roots, and highly sought after fish species like snook and redfish utilize these habitats too. The suite of prey species of gamefish are distinct when the seagrasses are near mangroves, showing a complex relationship with these important habitats [4].

Mangroves protect shorelines from storm erosion. They are a tropical species and are killed during the rare hard freezes experienced in Charlotte Harbor. If you look west to what is called the west wall, you will see mangroves recovering from the most recent freeze and from hurricane damage – a process that can take decades without human intervention.

We have helped restore mangrove habitat through planting of the propagules (hatched seeds that have dropped from the trees). Early attempts at restoration failed until scientists learned that the mangroves need to be exposed to salt early in their life to develop salt tolerance. Our efforts are successful now.

1.            Adaptations: Mangroves.  August 5, 2023]; Available from: https://www.floridamuseum.ufl.edu/southflorida/habitats/mangroves/adaptations/.

2.            Mangroves species profiles.  August 5, 2023]; Available from: https://www.floridamuseum.ufl.edu/southflorida/habitats/mangroves/species/.

3.            Florida's Mangroves.  August 5, 2023]; Available from: https://floridadep.gov/rcp/rcp/content/floridas-mangroves.

4.            Poulakis, G.R., D.A. Blewett, and M.E. Mitchell, The effects of season and proximity to fringing mangroves on seagrass-associated fish communities in Charlotte Harbor, Florida. Gulf of Mexico Science, 2003. 2: p. 171-184.

If you see a dorsal fin breaking the surface of the water, most likely it will be a Bottlenose Dolphin. Sharks’ dorsal fins will be seen above water too, but you can distinguish the mammal versus the cartilaginous fish by the way they swim. The tail fins of dolphins are oriented horizontally and so their swimming motion is up and down while sharks’ tails are vertically oriented and move side to side. Although dolphins will turn on their side to chase prey in extremely shallow water, throwing a big wake behind them.

Tursiops truncatus is the genus and species that composes the scientific name of the Bottlenose Dolphin. Scientists use scientific names to ensure no confusion about the species they are referencing. There is also a popular sportfish species called a dolphin. Servers in restaurants must sometimes clarify that they are not serving the mammals or “Flipper”, but the tasty dolphin fish Coryphaena hippurus. 

They are in the group of toothed whales that include Sperm Whales and Orcas and porpoises. Bottlenose Dolphins grow to 6-12 feet (1.8-3.6 m) and can life to around 50 years old [1]. They are different than porpoises in that they are beaked whales whereas porpoises don’t have that snout protruding from their head.

Bottlenose Dolphins, who are safeguarded through the federal Marine Mammal Protection Act, use clicks and squawks for communication and echolocation to find prey[2]. Some dolphins in the Everglades have been seen making mud rings around schools of mullet where fish are startled and jump out of the ring and into the mouth of a hungry dolphin.

Females and young calves will travel in pods to protect themselves from sharks and to feed more effectively. Calves are born after a 12-month gestation and will swim just behind the mother for easy access to milk and to benefit from the slipstream made by the mother. They nurse for about 20 months and leave the mother in 3-6 years.  Mature male pairs may form life-long bonds, helping each other find mates and food [1].

1.            Dolphin.  [cited August 17, 2023; Available from: https://myfwc.com/wildlifehabitats/profiles/mammals/aquatic/dolphin/.

2.            Common Bottlenose Dolphin.  8/17/2023]; Available from: https://www.fisheries.noaa.gov/species/common-bottlenose-dolphin.

Probably the most famous of fishes in Charlotte Harbor is the tarpon, Megalops atlanticus. Even people like Thomas Edison came to Charlotte Harbor and fished for tarpon, although the rumor was that he took his boat out to the Caloosahatchee River and dropped a bare hook from the boat, just so he could have some peace and quiet.

While Edison was not enthusiastically going after silver kings, people come from all over the world with an avid passion to Boca Grande Pass southwest of here, “The Tarpon Capital of the World”, and enter the “World’s Richest Tarpon Tournament” hosted by the Boca Grande Area Chamber of Commerce. They come to compete to catch (and now release) these powerful and acrobatic fighters.

Tarpons have an unusual life history that includes a specialized larval stage called a leptocephalus. It is a long ribbon-like, clear stage with fang-like teeth. As the leptocephalus gets older, it begins to shrink before it metamorphoses into a juvenile tarpon.

Charlotte Harbor has habitats that juvenile tarpon utilize that are unattractive to most other fishes. They inhabit backwater areas with muddy bottoms with low oxygen levels in the water.  Tarpons can gulp air into their gas bladder to extract oxygen, an adaptation that allows them to survive in these low-oxygen areas [1]. The gas bladder is efficient enough in exchanging gases that it is acknowledged as an ABO, air breathing organ.

Tarpons can grow to 8 feet and 280 pounds and over 60 years in age, although they don’t get that big around here [2]. They are commonly caught near the Peace River US-41 bridge to your left. If you see a large fish that rolls at the surface so you see its dorsal (back) fin with a long thread behind it, you may be seeing a tarpon just getting a quick breath of air.

1.            Seymour, R.S., N.C. Wegner, and J.B. Graham, Body size and the air-breathing organ of the Atlantic tarpon Megalops atlanticus. Comparative biochemistry and physiology. Part A, Molecular & integrative physiology, 2008. 150(3): p. 282-287.

2.            Tarpon Facts.  August 8, 2023]; Available from: https://myfwc.com/research/saltwater/tarpon/information/facts/.

What a gem, the oysters of Charlotte Harbor: One of nature’s clean-up crew . . . and tasty too!

Charlotte Harbor is a place where you can go out on your boat and take some oysters right out of the water, shuck them, and eat them, especially with lemon or lime and a bit of hot sauce. In addition to being a tasty natural treat, they perform a great service for the estuary. Adult Crassostrea virginica can filter up to 44 gallons (166 L) of water a day using their gills to filter out microscopic plankton and other small particles for their food [1].

Oyster filtration is very helpful in the estuarine ecosystem. By filtering the plankton out of the water, water clarity is maintained, allowing sunlight to penetrate to seagrasses – another vital estuarine habitat [2]. In the past, this filtration capability of the whole oyster population in an estuary could filter the same amount of water held in an estuary within the residence time of water in that estuary. However, with the loss of oysters, that is no longer the case except in Apalachicola Bay[3]. There are efforts restore populations of oysters here in Charlotte Harbor. Just to the left and past the US-41 bridges, there is an area where oyster shell was placed. This shell serves as an attractant to veliger larvae, where they settle, become attached spat, then juveniles, eventually becoming an adult oyster.

 A gem of an estuarine resident – oysters will make pearls when sand or some other irritant enters the shell. Nacre, a substance that is on the inside of the shell, also known as mother-of-pearl, will form layers around the sand. The result after a few years is a beautiful iridescent pearl!

1.            Ehrich, M.K. and L.A. Harris, A review of existing eastern oyster filtration rate models. Ecological modelling, 2015. 297: p. 201-212.

2.            Roger, I.E.N. and E.W. Koch, Modeling Seagrass Density and Distribution in Response to Changes in Turbidity Stemming from Bivalve Filtration and Seagrass Sediment Stabilization. Estuaries, 2004. 27(5): p. 793-806.

3.            zu Ermgassen, P.S.E., et al., Quantifying the Loss of a Marine Ecosystem Service: Filtration by the Eastern Oyster in US Estuaries. Estuaries and coasts, 2013. 36(1): p. 36-43.

If you look to the east of the 41 bridges, most of the time you will see the power lines filled with Cormorants, Phalacrocorax auratus. These birds are efficient fishers that amaze people for how long they can stay underwater. They have been seen diving as deep as 100 feet [1]. They are bold and will come up to boats to intercept a released fish.

A way to distinguish cormorants from another underwater swimming bird, the Anhinga, is its hooked beak. Anhingas have a straight bill to stab their fish prey. Both species will stretch their wings to dry out after a hunting session, but Cormorants are more often seen on perches high above the water because they do have some oil on their feathers which helps them fly, whereas Anhingas stay on low perches and have little flight capability when wet because they have no preen oil gland [1, 2].

Cormorants are social and form rookeries for nesting in the mangroves of Charlotte Harbor. The females lay 3-4 pale blue or green eggs per clutch and are incubated by both parents for 28 days when they hatch. The chicks can fly in 6-8 weeks and become independent at 10 weeks [1].

Cormorants play an important role in the ecology of Charlotte Harbor as nutrient recyclers. They can consume about 30% of their body weight per day [3], returning nutrients for photosynthesis production. If populations get out of balance Cormorants can have a negative impact on fisheries and acidify a very localized area through their guano. They are, however, an important organism that helps keep the checks and balances in the food web.

1.            Florida's breeding bird atlas: A collaborative study of Florida's birdlife. 2003  August 13, 2003]; Available from: https://myfwc.com/media/19687/bba_dcco.pdf.

2.            Anhinga.  August 13, 2023]; Available from: https://www.nps.gov/bicy/learn/nature/anhinga.htm.

3.            Schultz, D.W., et al., Modeling Population Dynamics and Fish Consumption of a Managed Double-Crested Cormorant Colony in Minnesota. North American journal of fisheries management, 2013. 33(6): p. 1283-1300.

Florida’s Gulf Coast is known for its beautiful sunsets overlooking the Gulf of Mexico. Sunseeker Resort Charlotte Harbor is a prime destination to watch the sun set over Charlotte Harbor.

Here you are facing West, the general direction in which the sun sets over the horizon. However, based on different times of year, the exact location of the sunset changes. Only on the vernal and autumnal equinoxes (the first days of Spring and Fall) does the sun set “due West,” and days and nights are usually equal length across the Earth. The rest of the year, the sun sets in positions around this Westerly point. Here, in the northern hemisphere, during summer months the sun sets more northerly and in the Winter months the sun sets more southerly. Therefore, depending on the current time of year, the sun will set more to the right (North) or left (South).

To measure the amount of daylight remaining, face the sun and extend your arm with your palm facing you and your fingers parallel to the horizon. Position your index finger just below the sun and your pinky parallel to the horizon. Count the number of fingers it takes to reach the sun from the horizon, if space allows line up your other hand directly below to continue counting. Each finger represents roughly 15 minutes until the sun sets and each hand approximately one hour.