by Rick O'Connor | Sep 21, 2018
When I was in high school we were required to take a semester of communism during our senior year – the idea was to “know the enemy”. That is what we plan to do here… But, the enemy is a microscopic plant.
Its name is Karenia brevis. It is one of about 10 species of Karenia found in the ocean but it is the dominant form in the Gulf of Mexico. Karenia is referred to as “phytoplankton”, which suggests it is a microscopic plant. But in fact, it is in the Kingdom Protisita, not Plantae.
The dinoflagellate Karenia brevis.
Photo: Smithsonian Marine Station-Ft. Pierce FL
It is “plant-like” in that it has chlorophyll and can produce its own food. It differs in that it is a single cell. They are a type of phytoplankton called “dinoflagellates” because they have two flagella. The next question of course is what is flagella? It is a hair-like structure used by the cells for location. Though they can swim, they cannot out swim a current and so drift in the ocean – using their flagella to move up and down within the current and orient themselves.
The cell is covered with a protective shell called a theca, which as grooves, known as girdles, in which the flagella lie – one running east-west, the other north-south. They are between 18-45 microns long with the north-south flagella extending to look like a tail. They are members of the Gulf of Mexico community. Always out there, always have been. Typically, a plankton sample might find 1000 cells / liter. At these concentrations there does not seem to be a problem.
A problem?
What’s the problem?
The problem is that in its defense, K. brevis will release toxins. The toxin is a cocktail of lipophilic polyether compounds called brevotoxins. At low, or background concentrations, the levels of brevotoxins does not seem to effect marine organisms much at all. However, when the population of cells increases, to say 2 million / liter, fish kills can occur. The state of Florida will close shellfish harvesting if the concentrations reach 5000 / liter.
This brevotoxin is pretty strong stuff. It effects the nervous and immune systems, and effects the respiratory system. For marine vertebrates, it is deadly. At concentrations over 1,000,000 cells / liter, it can cause death for fish, dolphins, sea turtles, and manatees. Shellfish are filter feeders. During large blooms of K. brevis shellfish can consume enough to make humans very sick if they consume the shellfish.
So what causes their numbers to increase from 1000 to 1,000,000 cells / liter?
Summer…
Though K. brevis is not a plant, it is plant-like. Plants like sunlight and fertilizers. Warm shallow seas of southwest Florida are perfect. Nutrients are available in the environment and growth begins. Most blooms (large growth spurts) occur offshore. They love high salinities and not as common in our estuaries. However, they are plankton – wind and currents can move them closer to shore. During the raining season (summer) run-off from land brings with it nitrogen and phosphorus (nutrients) which can enhance a bloom. The fish kills begin, the respiratory problems for humans are annoying, and the tourist become concerned. Red tide can certainly have an impact on the local economy.
Globally, algal blooms seem to be increasing. Red tide can last a few days or a few months, each year varies. These are not exotic species; they are local Gulf residents who are finding warmer, saltier seas that they love. Algal blooms typically occur from September to February and though are common in southwest Florida, can extend across the Gulf to Texas – which the Florida panhandle is experiencing currently.
As Dr. Karl Havens mentions in his article attached, we cannot control the weather, but we can control the amount of nutrients we allow into our waterways. We should consider management practices that do just this to reduce the effects of these naturally occurring blooms.
Below are other articles from Sea Grant on this topic.
Frequently Asked Questions About the 2018 Red Tide Bloom – Betty Staugler, Florida Sea Grant
http://blogs.ifas.ufl.edu/charlotteco/2018/08/14/frequently-asked-questions-about-the-2018-red-tide-bloom/.
Understanding Florida’s Red Tide – Betty Staugler, Florida Sea Grant
https://www.flseagrant.org/news/2018/08/understanding-the-florida-red-tide/.
Watching and Waiting: Uncertainty About When the Algal Blooms Will End – Dr. Karl Haven, Florida Sea Grant
https://www.flseagrant.org/news/2018/07/watching-and-waiting-uncertainty-about-when-algae-blooms-will-end/.
REFERENCES
About Florida Red Tides. Florida Fish and Wildlife Conservation Commission. http://myfwc.com/research/redtide/general/about/.
Indian River Lagoon Species Inventory. Karenia brevis. Smithsonian Marine Station at Ft. Pierce. http://www.sms.si.edu/irlspec/Kareni_brevis.htm.
Pierce, R.H., M.S. Henry. 2008. Harmful Algal Toxins of the Florida Red Tide (Karenia brevis): natural chemical stressors in South Florida coastal ecosystems. Ecotoxicology. 17(7). Pp. 623-631. http://www.sms.si.edu/irlspec/Kareni_brevis.htm.
by Rick O'Connor | Sep 2, 2018
Most kids who grew up on the Gulf Coast grew up catching blue crabs. These animals are common along our shorelines, relatively easy to catch, and adventurous because they may bite you. I caught my first one in 1965 and we proudly displayed the boiled shell over the kitchen bar for many years. This is also a popular seafood target with an estimated commercial landing value of $56,950 in the Pensacola Bay area in 2017.
Blue crabs are one of the few crabs with swimming appendages.
Photo: Molly O’Connor
But who is this crab that we enjoy so much? What do we know about it?
As you probably already know, it is one of an estimated 30,000 species of arthropods we call crustaceans. Crustaceans differ from insects and arachnids in that they have five pairs of legs and two sets of antenna. Insects typically have a head, thorax, and abdomen – however, in the crustaceans the head and thorax are fused into what is called a cephlathorax and covered with a section of the shell called the carapace. Like all arthropods, their body are completely covered in a chitinous shell that serves as their exoskeleton. This exoskeleton must be periodically shed (molting) so they can continue to grow. Crustaceans tend to molt about 10-11 times each year and typically in the summer months. To molt, crustaceans will remove some of the salts and minerals from the shell into their tissue, this weakens the shell enough to separate it. The crack is usually between the cephlathorax and abdomen. When they emerge, they are completely soft and about 30% larger than before – it is amazing to see this large crab emerge from the small shell it once lived in. Because of the softness of the body after molting, this is usually done under the cover of darkness for protection. The salts and minerals it removed during pre-molting are now used to harden the new shell – which can take a couple of days. It is at this stage we call them “soft shells”.
The crustaceans include many different kinds of arthropods – most notably are the crabs, shrimps, and lobsters. There are over 4500 species of crabs and they differ from shrimps and lobsters in the fact their abdomen flexes beneath their body – you do not see the “tail” you see in a lobster or shrimp – but its there. Crabs can also move very well laterally, which their cousins are not so good. Blue crabs differ from other crabs in that their last pair of legs are modified as paddles and the animal can swim. They can swim forwards, backwards, and laterally – and they are often seen swimming at the surface. There are other crabs who have these swimming paddles and they are all called protunid crabs.
Blue crabs perceive their world through their eyes, antenna, and sensory cells on their body. They are very good at burying in the sand – eyes and antenna exposed – and sensory cells all working – seeking prey and avoiding predators. Their eyes differ from ours in that they have numerous lenses, compared to our single one, and are called compound eyes. Each lens does not provide them with an image of you or me however. Rather each lenses provides them with a single pixel of light. It is much like the image you see on television when they are trying to block out a brand name, or someone’s face. The more pixels (lenses) you have, the clearer the image. Those this type of eye does not give as clear an image as ours; it is very good at detecting motion and has served the arthropods very well over the years.
For blue crabs, food can be just about anything. They are active hunters – usually using the ambush method of capture (buried in the sand), but are also known scavengers – eating any bits of food they can find. Those enjoy crabbing know this – you can put just about anything as bait in a crab trap and it works. They have numerous predators including fish, birds, mammals, and sea turtles.
Male and female blue crabs.
Photo:
Blue crabs can be found in a variety of salinities (euryhaline). Males are typically found in the lower salinities of the upper bay. Females join them during mating season – which is in late spring and summer. Males cradle the females beneath his legs for several days waiting for the right location and moment to breed. Fishermen refer to them as “doublers” during this time. The females will molt and the male will then deposit his sperm into a sac called a spermatophore – which he then deposits to the female. She will then migrate to the more saline lower portions of the lower bay, while he remains and seeks another female. This may be the only spermatophore she receives her entire life – which can be up to five years, though most do not live beyond three years. She will use sperm from this spermatophore over that time to fertilize eggs.
The eggs develop in a sponge mass that develops beneath her abdomen. This egg mass is orange when in early development and becomes a darker brown with age as the larvae consume the yolk. There can be between 750,000 and 2,000,000 developing eggs within this mass. The females are called gravid at this stage and it is illegal to harvest gravid crabs in Florida.
The eggs hatch in about two weeks and a small microscopic mosquito looking larvae emerges – at this stage, they are called zoea. The zoea drift into the Gulf of Mexico where they feed and molt. Eventually they return to the estuary and become a microscopic crab with a tail – this stage is called a megalops. The megalops will feed and molt. The tail will eventually flex beneath and the crab becomes sexually mature. The entire process from hatching to sexual maturity is about 12-18 months.
These are fascinating animals. They are very common and a large part of the coastal culture of the Florida panhandle. Kids will have great fun catching them with a hand net, letting them swim in their beach buckets, but be sure to let them go before you head home and watch those claws – they do know how to use them. It is a great animal.
The famous blue crab.
Photo: FWC
Recreational Blue Crab Harvest Regulations in Florida
No size limit
10 gallons whole / harvester / day
Harvesting gravid females is prohibited
Five crab traps / person – cannot be placed in navigation channels
Trap closed season in Florida panhandle – Jan 5-14 in odd years.
References
Barnes, R.D. 1980. Invertebrate Zoology. Saunders College Press. Philadelphia PA. pp. 1089.
Blue Crab. Callinectes sapidus. Chesapeake Bay Program. 2018. https://www.chesapeakebay.net/discover/field-guide/entry/blue_crab.
Florida Fish and Wildlife Conservation Commission. Commercial Landings in Florida. 2017-2018. http://myfwc.com/research/saltwater/fishstats/commercial-fisheries/landings-in-florida/.
Florida Fish and Wildlife Conservation Commission. Recreational Blue Crabbing. http://myfwc.com/fishing/saltwater/recreational/blue-crab/.
by Rick O'Connor | Aug 17, 2018
As a kid growing up here along the Gulf Coast, I had never heard of an osprey. Now, there is at least one mating pair on almost every body of water in the Pensacola Bay area. Where did this once unknown bird come from? How has it successfully colonized our coastal waterways?
Osprey nesting sites are commonly near water, and their food source.
The osprey, like many other fish eating birds, was a victim of the DDT story. This miracle pesticide was developed to battle insects attacking food crops but was found to be useful against mosquitos and many other unwanted pests. It was sprayed everywhere using planes, trucks, and tractors. With an extremely long half-life, wherever it landed it was going to be around for a while – it can still be found in the sediments of the Pensacola Bay System. It was one of those compounds that was difficult to excrete through an organisms excretory system – thus it accumulated within their tissues, and as organisms fed on other organisms, it was passed up the food chain – bioaccumulation. Birds of prey who fed on fish would accumulate DDT as well. It caused the shells of their eggs to become thinner – so nesting was not successful – and many of the aquatic birds of prey (pelicans and eagles alike) declined in number. DDT was banned in 1970s and many of these fish eating birds have made a remarkable recovery – a true success story.
So who is this fish eating bird of prey that can be found on dead trees and light posts all over the bay area?
Ospreys (Pandion haliaetus) are members of the family Accipitridae – the hawks and eagles.
They are predators with hooked bills and sharp talons to grab and dispose of prey. Ospreys can be identified by the hawk like silhouette hovering over a local waterway searching for fish – their primary food. They are usually in pairs and, at times, the young are hovering nearby. Their call is a high pitch chirping sound and if seen on a tree, or on their nest, they are brown on top and white beneath. These birds are common along both fresh and saltwater bodies of water.
Ospreys prefer waterways where fish are plentiful. For more successful hunting, they like waters that are relatively shallow and nesting locations that protect the young from mammalian predators. Many local osprey prefer large dead trees for their nests, and will often use manmade structures – such as power poles, navigation markers, and special platforms on poles placed there for the purpose of osprey nesting.
Osprey feed almost exclusively on fish. They are unique in the hawk world in that their talons can adjust so that the captured fish can be turned parallel to the osprey’s body – making it more aerodynamic when returning to the nest. Hunting osprey hover over the water searching and then dive, talons first into the water. They can only reach depths of about three feet so they typically hunt for surface schooling fish, or in shallow waters. Most of their captures are between 8-10 inches and include such fish as speckled trout, mullet, and catfish.
These birds are monogamous (mating pairs breed for life). During the breeding season, the male will collect sticks for the construction of their large nests. Bringing them back to the female, she will begin to arrange and construct the nest. The male provides seagrass and flotsam for the inner lining. There is a pre-courtship dance where the returning male flies over the nest with a fish. The pair produce between 3-4 eggs. Both parents will incubate the eggs but the female does the lions share. She will incubate while the male hunts. Returning with a fish for her, she will fly to a nearby branch to feed while he incubates the eggs – though they have seen the males incubate even without feeding the female. Evening incubation is always the female.
After hatching, the male will bring food to both the female and young. She does not leave the young at all for about 14 days. Afterwards, they will be left alone for periods of time, and are usually fledged by 50 days. Data shows that young fledglings rarely disperse more than 30 miles from the nest they hatched from – suggesting slow dispersal of this species. The mating pair will return to the same location for nesting every year for up to 30 years.
There are few predators of osprey due to their nesting habits. In some locations, where they nest on the ground, coyotes have been a problem. Locally, bald eagles are known to try to grab hatchlings and, occasionally, adults. There have been reports of crocodiles taking adults from the water in South Africa; this may be the case in South America as well, but no reports of American Alligators doing the same.
This is now a common bird along our shores and is a true conservation success story.
References
National Audubon Society Field Guide to North American Birds; Eastern Region. Ed. J. Bull, J. Farrand Jr. pp. 795.
Osprey. Neotropical Birds. Cornell Lab of Ornithology. https://neotropical.birds.cornell.edu/Species-Account/nb/species/osprey/overview.
by Rick O'Connor | Aug 17, 2018
Being in the panhandle of Florida you may, or may not, have heard about the water quality issues hindering the southern part of the state. Water discharged from Lake Okeechobee is full of nutrients. These nutrients are coming from agriculture, unmaintained septic tanks, and developed landscaping – among other things. The discharges that head east lead to the Indian River Lagoon and other Intracoastal Waterways. Those heading west, head towards the estuaries of Sarasota Bay and Charlotte Harbor.
A large bloom of blue-green algae (cyanobacteria) in south Florida waters.
Photo: NOAA
Those heading east have created large algal blooms of blue-green algae (cyanobacteria). The blooms are so thick the water has become a slime green color and, in some locations, difficult to wade. Some of developed skin rashes from contacting this water. These algal blooms block needed sunlight for seagrasses, slow water movement, and in the evenings – decrease needed dissolved oxygen. When the algae die, they begin to decompose – thus lower the dissolved oxygen and triggering fish kills. It is a mess – both environmentally and economically.
On the west coast, there are red tides. These naturally occurring events happen most years in southwest Florida. They form offshore and vary in intensity from year to year. Some years beachcombers and fishermen barely notice them, other years it is difficult for people to walk the beaches. This year is one of the worst in recent memories. The increase in intensity is believed to be triggered by the increase in nutrient-filled waters being discharged towards their area.
Dead fish line the beaches of Panama City during a red tide event in the past.
Photo: Randy Robinson
On both coasts, the economic impact has been huge and the quality of life for local residents has diminished. Many are pointing the finger at the federal government who, through the Army Corp of Engineers, controls flow in the lake. Others are pointing the finger at shortsighted state government, who have not done enough to provide a reserve to discharge this water, not enforced nutrient loads being discharged by those entities mentioned above. Either way, it is a big problem that has been coming for some time.
As bad as all of this is, how does this impact us here in the Florida panhandle?
Though we are not seeing the impacts central and south Florida are currently experiencing, we are not without our nutrient discharge issues. Most of Florida’s world-class springs are in our part of the state. In recent years, the water within these springs have seen an increase in nutrients. This clouds the water, changing the ecology of these systems and has already affected glass bottom boat tours at some of the classic springs. There has also been a decline in water entering the springs due to excessive withdrawals from neighboring communities. The increase in nutrients are generally from the same sources as those affecting south Florida.
Florida’s springs are world famous. They attracted native Americans and settlers; as well as tourists and locals today.
Photo: Erik Lovestrand
Though we are not seeing large algal blooms in our local estuaries, there are some problems. St. Joe Bay has experienced some algal blooms, and a red tide event, in recent years that has forced the state to shorten the scallop season there – this obviously hurts the local economy. Due to stormwater runoff issues and septic tanks maintenance problems, health advisories are being issued due to high fecal bacteria loads in the water. Some locations in the Pensacola area have levels high enough that advisories must be issued 30% of the time they are sampled – some as often as 40%. Health advisories obviously keep tourists out of those waterways and hurt neighboring businesses as well as lower the quality of life for those living there.
Then of course, there is the Apalachicola River issue. Here, water that normally flows from Georgia into the river, and eventually to the bay, has been held back for water needs in Georgia. This has changed flow and salinity within the bay, which has altered the ecology of the system, and has negatively impacted one of the more successful seafood industries in the state. The entire community of Apalachicola has felt the impact from the decision to hold the water back. Though the impacts may not be as dramatic as those of our cousins in south Florida, we do have our problems.
Bay Scallop Argopecten iradians
http://myfwc.com/fishing/saltwater/recreational/bay-scallops/
What can we do about it?
The quick answer is reduce our nutrient input.
The state has adopted Best Management Practices (BMPs) for farmers and ranchers to help them reduce their impact on ground water and surface water contamination from their lands. Many panhandle farmers and ranchers are already implementing these BMPs and others can. We encourage them to participate. Read more at Florida’s Rangeland Agriculture and the Environment: A Natural Partnership – https://nwdistrict.ifas.ufl.edu/nat/2015/07/18/floridas-rangeland-agriculture-and-the-environment-a-natural-partnership/.
As development continues to increase across the state, and in the panhandle, sewage infrastructure is having trouble keeping up. This forces developments to use septic tanks. Many of these septic systems are placed in low-lying areas or in soils where they should not be. Others still are not being maintained property. All of this leads to septic leaks and nutrients entering local waterways. We would encourage local communities to work with new developments to be on municipal sewer lines, and the conversion of septic to sewer in as many existing septic systems as possible. Read more at Maintaining Your Septic Tank – https://nwdistrict.ifas.ufl.edu/nat/2017/04/29/maintain-your-septic-system-to-save-money-and-reduce-water-pollution/.
And then there are the lawns. We all enjoy nice looking lawns. However, many of the landscaping plans include designs that encourage plants that need to be watered and fertilized frequently as well as elevations that encourage runoff from our properties. Following the BMPs of the Florida Friendly Landscaping ProgramTM can help reduce the impact your lawn has on the nutrient loads of neighboring waterways. Read more at Florida Friendly Yards – https://nwdistrict.ifas.ufl.edu/nat/2018/06/08/restoring-the-health-of-pensacola-bay-what-can-you-do-to-help-a-florida-friendly-yard/.
For those who have boats, there is the Clean Boater Program. This program gives advice on how boaters can reduce their impacts on local waterways. Read more at Clean Boater – https://floridadep.gov/fco/cva/content/clean-boater-program.
One last snippet, those who live along the waterways themselves. There is a living shoreline program. The idea is return your shoreline to a more natural state (similar to the concept of Florida Friendly LandscapingTM). Doing so will reduce erosion of your property, enhance local fisheries, as well as reduce the amount of nutrients reaching the waterways from surrounding land. Installing a living shoreline will take some help from your local extension office. The state actually owns the land below the mean high tide line and, thus, you will need permission (a permit) to do so. Like the principals of a Florida Friendly Yard, there are specific plants you should use and they should be planted in a specific zone. Again, your county extension office can help with this. Read more at The Benefits of a Living Shoreline – https://nwdistrict.ifas.ufl.edu/nat/2017/10/06/the-benefits-of-a-living-shoreline/.
Though we may not be experiencing the dramatic problems that our friends in south Florida are currently experiencing, we do have our own problems here in the panhandle – and there is plenty we can do to keep the problems from getting worse. Please consider some of them. You can always contact your local county extension office for more information.
by Rick O'Connor | Aug 3, 2018
In recent weeks, the country has heard about shark attacks off the Carolina coast and great whites off the northern coast of the Gulf of Mexico – then of course, we just completed “Shark Week”. This sometimes makes visitors to our beaches a bit unnerved about swimming. Each year we hear about how other activities we engage in are much more dangerous than swimming in the Gulf where there are sharks – and this is true – but we may still have a concern in the back of our minds. So – we will give you some information that will hopefully enlighten you on the issue of sharks.
First, what kind of sharks are in the Gulf and how common are they?
According to Dr. Hoese and Dr. Moore from Texas A&M, there are 30 species of sharks who have been found in the Gulf of Mexico – and this includes the great white. They range in size from the Cuban Dogfish (3 ft.) to the whale shark (60 ft. in length). Each has their own niche. Some, like the large whale sharks, are plankton feeders. Others, like the blue and mako, are open ocean travelers covering large stretches of water hunting prey. Others, like the blacktip and spinner, are more common near shore – close to estuary outfalls where food is plentiful. And others still, like nurses sharks, are bottom dwellers feeding on slow fish and crustaceans.
The Bull Shark is considered one of the more dangerous sharks in the Gulf. This fish can enter freshwater but rarely swims far upstream. Photo: Florida Sea Grant
As far as how common they are – I was involved in shark tagging in the early 1980’s and we tagged several species. Blacktips and spinner sharks were very common. We also tagged a lot of bull and dusky sharks – though dusky sharks are declining. Tiger sharks were not as common at the time. It was believed this was due to an increase in shark rodeos in the 1970’s – which were popular during the “Jaws” films. However, those events stopped for several years and recent shark events have once again captured tigers. There are five species of hammerheads that were tagged – the scalloped and bonnethead were the most common. White sharks and makos are in the Gulf but were never tagged. It was believed they spent more time offshore (where we were not sampling). Both species have been seen closer to shore in recent years, but there are no reports of any problems from this. It is possible they have been doing this all along and were just undetected. Blacknose, finetooth, and silky sharks were also frequently tagged.
People are probably not surprised to hear that sharks frequent the bays. Many of the species mentioned above do so. The small (3 ft.) Atlantic sharpnose shark is one of the most common. Sawfish were once common in the estuaries but have declined significantly across the region to do over harvesting in the early 20th century. They are currently protected.
You have probably also read that bull sharks have been found in freshwater rivers – and this is the case. Some have been found several miles up river systems.
What type of prey do sharks prefer and how to do they select and hunt for them?
This, of course, varies from species to species. Plankton feeding whale sharks generally cruise slowly through the water column filtering small fish and crustaceans – the same as the great whales. They do tend to feeding in deeper water during the day and closer to the surface at night. They are following what is known as the Deep Scattering Layer. This is a large layer of zooplankton (animal plankton) that migrates each day – deeper (600 feet or so) during the daylight hours and closer to the surface in the evenings.
Bottom dwelling sharks feed on benthic creatures like flounder and crabs. Many have the ability to detect their prey buried beneath the sand using electric perception they have.
Many species of sharks are what we call “ram-jetters”. This means they do not have a pump system to pump water over their gills. So, in order to breath, they must swim forward. Swimming continuously requires a lot of energy. Most of them are what we call opportunistic feeders – meaning they will grab what they can. Stomach analysis of such sharks find primarily fish and squid, but other creatures have been found – such as birds and even other sharks. The general rule here is seek prey that is “easy”. If your objective in feeding were to obtain energy – it would not make since to chase prey that would require a lot of energy to catch. Simple first, and take opportunities when you can. It is the ram-jetter species that people are most concerned. Swimming and taking opportunities. However, evidence suggest that we are not a prey of choice, not good opportunities. More on this in a minute.
Tiger sharks are interesting. It is in their stomachs we find such things as hubcaps, metal, and other sorts of garbage. Because of their tooth design, they are also capable of eating sea turtles.
How often do shark attacks on humans actually occur and what were the people doing that may have enticed it to happen?
Records on human shark attacks are kept at the International Shark Attack File at the Florida Museum of Natural History in Gainesville, FL. This data set only logs unprovoked attacks – those where the people were doing their thing and all of a sudden… Not those where humans were pulling them into their boats after fishing or grabbing their tails while diving.
Blacktip sharks are one of the smaller sharks in our area reaching a length of 59 inches. They are known to leap from the water. Photo: Florida Sea Grant
Based on this data – there have been 3031 unprovoked shark attacks reported worldwide since 1580 A.D. This equates to seven attacks / year. Granted… not all attacks are reported, particularly from the undeveloped regions of the world – and from early history, but it does give us something to look at.
Currently, we are averaging between 70 and 100 shark attacks worldwide and between 5-15 of these are fatal. Honestly, this is very low when compared to other activities in which humans participate.
| Year |
Deaths from Other |
Deaths from Shark Attacks |
| 1959 – 2010 |
Lightning strikes – 1970 |
26 |
| 2004 – 2013 |
Rip Currents – 361 |
8 |
| 2001 – 2013 |
Dog bites – 364 |
11 |
| 2000 – 2007 |
Hunting accidents – 441 |
7 |
| 2002 – 2013 (Florida only) |
Boating accidents – 782 |
2 |
As you can see… the risk is much lower.
It is true that most of the shark attacks worldwide are in the United States (46%) and that most in the U.S. are in Florida (56%). However, it is believed that this is due to the number of Americans (and Floridians) who enjoy water activities. In Florida, most of the encounters have been on the east coast – 89% of them! There have only been 65 attacks reported from the west coast – only 37 from the Florida panhandle – since 1580 A.D. There have only been six reported from Escambia County and one from Santa Rosa in that time.
As far as what people were doing when a shark attack occurred – most were surfing, but swimming has increased in recent years. This is believed to be connected to the increase in the number of humans swimming. The human population visiting beaches, particularly in the U.S., has increased significantly. Most shark attacks occur in near shore waters – which would make sense… that is where we are. Most are the “hit & run” version – meaning the shark hits the person and runs… not returning. Based on Florida reports, it is believed most of these are blacktips, spinners, and blacknose sharks. These rarely end in a fatality. “Bump & Bite” – meaning the shark circles, bumps the person, and then bites, are not as common. It is believed most of these are from great whites, tigers, and bull sharks. The few fatalities that happen are usually from this form of encounter.
Summary
When assessing “risk” in an activity you have to consider “control”. This means that the more you are in control of the situation, the less risky the activity seems to be. Most feel that in the water, the shark is in control – this increases our fear and risk concern. However, as mentioned in this article, many of the other activities we are involved – where we think we are in control – are far more risker than swimming on the open Gulf of Mexico.
However, shark attacks do occur and there are a few things swimmers can do to reduce their risk.
- Do not swim alone – all predators will try and isolate an individual from a group before they attack – much easier to attack an individual than a group
- Do not swim near dusk or after dark – to increase their chance of hunting success, sharks are more actively hunting in low light conditions
- Remove shiny objectives like jewelry – sunlight hitting metal objectives can appear to be baitfish to a shark
- Avoid blood in the water – it is true they have an excellent sense of smell – small amounts of blood in the water can be detected as far away as 100 feet suggesting easy prey nearby. Avoid swimming near fishing activity where bait and fish blood may be discharged into the water
I have been swimming in the Gulf all of my life. It is too much fun to worry about a low risk encounter with a shark. Follow the simple rules suggested by the ISAF and you should not have any problems.
Resources
The International Shark Attack File – https://www.floridamuseum.ufl.edu/shark-attacks/.
Hoese, H.D., R.H. Moore. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana & Adjacent Waters. Texas A&M Press, College Station TX. pp. 327.
