This past week hundreds of dead fish washed ashore between Escambia and Okaloosa counties. Most were of one species but there were others who died and it appeared they had been in the water for quite a while. Determining the cause of fish kill can be tricky. You can observe how many different species were involved, and how many of each species. You can also review changes in the biological and chemical environment of the water system impacted. Fish kills occur for a variety of reasons but many are connected to either a decline in dissolved oxygen, the presence of red tide, or some pathogen that may be affecting the fish.
Dead fish near Ft. Pickens in Pensacola. Photo: Rick O’Connor
Excessive nutrients, many times associated with heavy rain, can trigger algal blooms that can eventually lower the concentration of dissolved oxygen; however high water temperatures can do the same. When dissolved oxygen levels drop below 4.0 mg/L most fish are stressed, and most fish leave. Some fish however are very sensitive to these changes and die, menhaden are one of them. The Florida Fish and Wildlife Conservation Commission listed menhaden as one of the species found on the beach but there were others as well, actually the majority were scaled sardines. The Florida Department of Environmental Protection monitors dissolved oxygen at the beach each week and their data indicated no problems prior to the kill. The Escambia County Division of Marine Resources measured the dissolved oxygen after the kill and found levels to be normal. Some would point to the abundant amount of green algae, “June grass”, as a sign of an algal bloom but mass amounts of June grass appear each summer and fish kills typically do not follow them.
Red tides are blooms of a particular microscopic single celled creature called Karenia brevis. When these photosynthetic protist are disturbed they can release a toxin which dissipates through the water and can become part of the aersols produced by waves. Many species of fish and marine mammals struggle with red tides and mortality due these outbreaks are common. Records of red tide blooms go back as far as the early colonial period and have been part of Florida for centuries. They typically form offshore and move inland with the wind and currents. Once they reach shallow waters human released nutrients can increase populations of K. brevis and enhance the problems they cause. They are more common in southwest Florida but do occur in the panhandle. Agencies along the Gulf coast monitor for red tide outbreaks each week. The Escambia County Division of Marine Resources does so here and found no traces of K. brevis before or after the kill.
As far as pathogens, or another possible cause, we are not sure. The Florida Fish and Wildlife Conservation Commission has officially listed the cause as “unknown”. Fish kill data in Escambia County shows changes over the years. In the 1970’s there were a fewer fish kills reported each year but each kill involved hundreds of thousands of fish, many times menhaden. Today there are more fish kills reported but many of these reports are a single fish or fewer than 10. This is the first large number kill we have had in a while. Escambia County Sea Grant reports water quality information, including fish kills and red tides, for the Pensacola Bay area each week on their website (http://escambia.ifas.ufl.edu). Fish kill information for the state of Florida can be found at http://myfwc.com/research/saltwater/health/fish-kills-hotline/. If you have any questions about local fish kills contact Sea Grant at your local county extension office.
Pregnant Bull Shark (Carcharhinus leucas) cruses the sandy seafloor. Credit Florida Sea Grant Stock Photo
Shark Safety Tips
UF/IFAS Extension – Florida Sea Grant
By L. Scott Jackson (Bay County) and Rick O’Connor (Escambia County)
Recently, two teens were victims of unusual shark attacks in North Carolina. The two attacks occurred within minutes and miles of each other. A similar incident happened in the Florida Panhandle in 2005. One teen lost her life and one lost his leg. The attacks were within days of each other and the distance between the two attacks was less than 100 miles. Experts identified Bull Sharks as being responsible for both Panhandle shark encounters.
Bull Sharks migrate north as ocean waters of the Gulf and Atlantic warm. As the nearshore environment cools in the late fall and winter, Bull Sharks follow the receding warm water and eventually move out of the local area. Bull Sharks are an aggressive shark responsible for a reported 100 attacks on humans resulting in 21 fatalities. (Reported from 1580 to 2014 Source: International Shark Attack Files).
Experts suggest Bull Sharks may be responsible for many shark attacks where the species is unknown or not identified.
Overall, the number of shark encounters is slowly trending higher as more people swim and participate in other water related activities. However, negative encounters with sharks remain a rare occurrence. In 2014, Florida reported 28 shark bites with no fatalities. On average, only one shark attack fatality is reported every other year in the United States. The risk of shark attack is very low compared to other potential recreational hazards. For example, in 2014, 26 people died as a result of lightning strikes in the United States, with six of those being in Florida.
George Burgess with the International Shark Attack File has compiled a list of action strategies you can use to reduce the chances of a negative encounter with a shark:
Keep these tips in mind the next time you hit the beach!
- Avoid being in the water from sunset to sunrise. This is when sharks are most active and have a competitive sensory advantage.
- Stay in a group, and do not wander too far from shore. Isolated individuals are more likely to be attacked than large groups; in addition, the farther you are from shore, the farther you are from help.
- Consider your clothing: avoid wearing shiny jewelry, because the reflected light resembles the sheen of fish scales.
- Avoid brightly colored or patterned clothing, because sharks see contrast particularly well.
- Do not enter waters being used by sport or commercial fisherman – sharks can sense the smells emitted from bait at incredible distances.
- Avoid entering waters with sewage output and/or entering the water if you are bleeding. Such additions to the water can act as strong olfactory attractants to sharks.
- Know your facts! Porpoise sightings do not indicate the absence of sharks. In fact, the opposite is often true. Also be on the lookout for signs of baitfish or feeding activity – diving seabirds are good indicators of such action. Animals that eat the same food items are often found in close proximity. Remember, a predator is never too far from its prey.
- Refrain from excess splashing while in the water, and do not allow pets in the water because of their erratic movements.
- Exercise caution when occupying the area between sandbars or near steep drop-offs, as these are favorite hangouts for sharks.
- Do not enter the water if sharks are known to be present, and evacuate the water if sharks are seen while there. And, of course, do not harass a shark if you see one!
- Stay calm if you do see a shark, and maintain your position in as quiet a manner as possible. Most sharks merely are curious and will leave on their own.
- Relax! You are more likely to be injured by lightning than attacked by a shark. To learn more about your relative risks, see: The Relative Risk of Shark Attacks to Humans
Our beautiful Emerald Coast is an alluring wild habitat. Simply put – Swimming at the beach is not the same as swimming in a backyard pool. Have fun at the beach but be mindful and respectful of potential hazards. Knowing what to do to be safe will actually help you enjoy time at the beach while keeping worry and concern at a minimum.
Follow these beach safety tips for helping your family enjoy the beach while protecting coastal wildlife.
For many who are seafood lovers there is nothing like a good grouper sandwich; makes me hungry just to write that. Groupers are members of the one of the largest families of fish in the Gulf of Mexico. There are 33 species in the family Serranidae, which include sea bass and perch, and many are sold as “grouper” in the seafood markets. There are 10 species of searranids that are in the genus Epinephelus and are considered the true groupers. One of these, Epinephelus itajara , is a monster; this is the Goliath Grouper.
Three goliath groupers over wreck in southwest Florida. Photo: Bryan Fluech Florida Sea Grant
As the name states, these fish can reach 6 feet in length and over 700 lbs. Goliath groupers are generally found on structure such as artificial reefs, near drill platforms, and on natural bottom. They tend to stay near the reefs they inhabit but will travel long distances for breeding. Data suggest that the highest concentrations of these fish are in southwest Florida but they disperse across the Gulf and along the Atlantic coast of south Florida. The large spawning aggregations occur offshore, generally from July through September, and the planktonic larva drift into the mangrove estuaries of southwest Florida. Here the young fish live for 5-6 years feeding on the abundance of food found there and then head back offshore searching for reefs to call their own. Many head to the northern Gulf and our area. Though they are large they feed relatively low on the food chain, consuming primarily crustaceans and slow moving reef fish.
They were a huge trophy fish back in the middle 20th century. Fishermen could not resist the chance to have a photograph with one of these behemoths. Because of this popular activity, and the loss of their mangrove nursery grounds due to development, their numbers diminished across the state and today there is a “no harvest” rule for the fish. However some divers are indicating their numbers are increasing and that the Florida Fish and Wildlife Conservation Commission should to revisit the rule.
In response FWC’s research group, Fish and Wildlife Research Institute, in St. Petersburg conducts an annual “Goliath Grouper Count”. Modeled after the Christmas Bird Count conducted each year by the Audubon Society, the Goliath Grouper Count occurs during the first week of June. The counts have been occurring in south Florida for a couple of years but for the first time the panhandle will be participating this year. If you are a diver and interested there is a particular protocol that needs to be followed when counting. You can find out more by contacting Rick O’Connor in Pensacola at (850) 475-5230 or Scott Jackson in Panama City at (850) 764-6105 to obtain the protocol and the data sheets. The official count will run between June 1 and June 15.