The Recent Fish Kill Near Pensacola Was Due to Stratification… Say What?

The Recent Fish Kill Near Pensacola Was Due to Stratification… Say What?

This began with a call from one of my volunteers who was checking salinity at Shoreline Park.  She reported the salinity, but also reported to smell of dead fish – though she could not see them.  I visited Shoreline Park the following day on another project and could smell it as well.  There was a large amount of dead seagrass washed ashore from a recent storm and I thought this may be the cause of the smell because I did not see the dead fish either.

 

When I got home, I checked the FWC fish kill database.  It reported a redfish kill in Pensacola Bay.  It is unusual to see a kill of only one species.  Many times, these are releases from fishing activity, particularly bait, and thought this must be the case – FWC did not mention the cause.  I let the volunteer know and asked to keep an eye out.

 

I reported this to the Escambia County Division of Marine Resources to (a) let them know, and (b) to find out if they had any idea of cause.  They replied that the location was incorrect.  The kill was actually near Galvez Landing on Innerarity Point.  He (Robert Turpin) had visited the site and did find any dead fish.  I have a lot of volunteers over that way so asked each to take a look.  They did not see any dead fish.  I asked them to keep an eye out and collect a dead fish if they saw one for testing.  Often when a large fish kill occurs, and it is only one species, the suspect cause is disease.  Tissue samples could confirm this.

 

And then came another call.

This time it was from one of our Master Naturalist who lives on the eastern shore of Mobile Bay.  He wanted to know what was up with all of the dead redfish along the shore of the bay.  He sent photos and his beach was littered with them.  I reached out to Mississippi/Alabama Sea Grant to see if they knew what was going on.  They had heard about the situation and knew the Alabama Department of Natural Resources was collecting samples.  The Gulf Islands National Seashore then reported large numbers of dead redfish along the National Shores property in Mississippi, something was up.

Dead redfish on the eastern shore of Mobile Bay.
Photo: Jimbo Meador

I eventually got word from Dr. Marcus Drymon at the Dauphin Island Sea Lab.  They had a team working on this.  Their team reported that stratification of the Gulf had created a hypoxic (low dissolved oxygen) layer on the bottom and the male “bull redfish” had gathered for breeding and died.

 

So, we are back to our title – what is stratification and how did this cause the fish kill?

 

Stratification is the layering of the water.  Less dense water will sit atop the more dense.  Water temperature or salinity can cause this density difference and layering.  Colder and/or saltier water is denser and will form the bottom layer.  If you have high winds, it will mix the water and the stratification disappears.  Tides and currents can affect this as well.

 

What they believe happened recently was excessive amounts of rainfall created a large layer of freshwater to move from Mobile Bay into the open Gulf.  The combination of tides and wind allowed a stratified layer to form.  The oxygen that marine life uses is dissolved into the water at the surface and referred to as dissolved oxygen (DO).  If the system is stratified, then the oxygen dissolved at the surface will not reach the bottom and hypoxia (low DO) can happen.  They this is what happen.  It just so happens that the large male redfish (bull reds) had congregated just offshore for breeding.  They are more sensitive to low DO than the smaller females and any juveniles.  So, the males died.  To answer the question as to why other fish did not die (what you typically see in a DO related fish kill) – the numbers were not mentioned by there was one reference to 4.0 ppm.  This is the high threshold of hypoxia.  Many fish can tolerate at this concentration, but the male redfish could not.

 

So, that is what we think happened.  The perfect storm of the demise of a group of male redfish just off of Mobile, and the carcasses drifted to other locations.

Tilefish of the Florida Panhandle

Tilefish of the Florida Panhandle

I am going to be honest and say that I know very little about this fish.  I did not know they even existed until I attended college.  Shortly afterwards, my father-in-law asked “hey, have you ever heard of a tilefish?” – to which I responded yes… He was having lunch at a restaurant in Apalachicola, and it was on the menu.  My father-in-law was an avid fisherman and knew most of the edible species, but he had not heard of this one.  The rumor was that it was pretty good, though my father-in-law chose not to eat it that day.

Tilefish
Photo: NOAA

I have never seen it on a menu, and only a few times in the local seafood markets, but according to Hoese and Moore1 by the late 1970s there was a small commercial fishery for this fish emerging in Louisiana, as was a small recreational fishery.  In Florida, since 2000, there have been 15,435 commercial trips for this fish with an average of 321 each year.  The value of this fishery over that time is $33,118,554 with an average of $689,969.90 each year.  The average price for the fishermen was $2.62 per pound with the highest being $5.14/lb. on the east coast and that in 2022; the Gulf fishermen are getting $4.16/lb. right now.

 

The highest number of landings per county since 2000 was 340 in Palm Beach County in 2000.  Only eight times has there been more than 200 landings in a single year over the last 22 years.  Five of those were in Monroe County (Florida Keys) and three were again in Palm Beach County.  The vast majority were less than 100 landings in a single year, this is not a large fishery in Florida either.

 

Are they harvested here in the Florida panhandle?

Yes… Bay, Escambia, Franklin, Okaloosa, Wakulla, and Gulf Counties all reported landings.  Bay County seems to be the hot spot for panhandle with landings between 50-100 each year since 2000.  Most of the other counties report less than 10 a year and several only reported one.  Again, this is not a large fishery, but it was sold at a restaurant in Apalachicola and is said to be good.  Hence, I decided to include in this series.

 

Hoese and Moore report four species of tilefish in the Gulf of Mexico.  The sand tilefish (Malacanthus plumeri) is a more tropical species.  The tilefish (Lopholatilus cheamaeleonticeps) and the gray tilefish (Caulalatilus microps) seem to be the target ones for fishermen.  Both are reported from deep cold water near the edge of the continental shelf.  FWC reports them from 250 – 1500 feet of water where the temperatures are between 50 – 60°F.  Because of their tolerance to cold water, their geographic range is quite large; extending across the Gulf, up the east coast to Labrador.  They live in burrows on hard sandy bottoms and feed on crustaceans.  The National Oceanic and Atmospheric Administration2 reports this as a slow growing – long lived fish, up to 50 years of age.  In their cold environment, this makes sense.

 

This is not a well-known fish along the Florida Panhandle but maybe one day you will see it on the menu, remember this article, and take a chance to see if you like it.

 

References

 

1 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana and Adjacent Waters.  Texas A&M Press.  College Station TX. Pp. 327.

 

2 Golden Tilefish. 2020. Species Directory. NOAA Fisheries. https://www.fisheries.noaa.gov/species/golden-tilefish.

Sea Bass and Grouper of the Florida Panhandle

Sea Bass and Grouper of the Florida Panhandle

When you look over the species of sea basses and groupers from the Gulf of Mexico it is a very confusing group.  Hoese and Moore1 mention the connections to other families and how several species have gone through multiple taxonomic name changes over the years – its just a confusing group.

Gag grouper.
Photo: National Oceanic and Atmospheric Administration

But when you say “grouper” everyone knows what you are talking about, and everyone wants a grouper sandwich.  This became a problem because what people were serving as “grouper” may not have been “grouper”.  And as we just mentioned what is a grouper anyway?  The families and genera have changed frequently.  Well, this will probably get more technical than we want, but to sort it out – at least using the method Hoese and Moore did in 1977 – we will have to get a bit technical.

 

“Groupers” are in the family Serranidae.  This family includes 34 species of “sea bass” type fish.  Serranids differ from snappers in that they lack teeth on the vomer (roof of their mouths) and they differ from “temperate basses” (Family Percichthyidae) in that their dorsal fin is continuous, not separated into two fins.  These are two fish that groupers have been confused with.

Banked Sea Bass.
Photo: National Oceanic and Atmospheric Administration.

We can subdivide the serranids into two additional groups.  The “sea basses” have fewer than 10 spines in their dorsal fin.  There are 10 genera and 18 species of them.  They have common names like “bass”, “flags”, “barbiers”, “hamlets”, “perch”, and “tattlers”.  They are small and range in size from 2 – 18 inches in length.  Most are bottom reef fish with little commercial value for fishermen.  Most are restricted to the tropical parts of the Atlantic basin but two are only found in the northwestern Gulf, one is only found in the eastern Gulf, and one has been found in both the Atlantic and Pacific.  The biogeography of this group is very interesting.  The same species found in both the Atlantic and Pacific suggest an ancient origin.  The variety of serranid sea bass suggest a lot of isolation between groups and a lot of speciation.

 

The ”groupers” have 10 or more spines in their dorsal fin.  There are two genera in this group.  Those in the genus Epinephelus have 8-10 spines in their anal fin and have some canine teeth.  Those in the genus Mycteroperca have 10-12 spines in their anal fin and lack canine teeth.  Within these two genera there are 15 species of grouper, though the common names of “hind”, “gag”, “scamp” are also used.  Most of these are found along the eastern United States and Gulf of Mexico.  Five species are only found in the tropical parts of the south Atlantic region, five are also found across the Atlantic along the coast of Africa and Europe, and – like the “sea bass” two have been found in both the Atlantic and the Pacific.  They range in size from six inches to seven feet in length.  The Goliath Grouper can obtain weights of 700 pounds!  Like the sea bass, groupers prefer structure and can live a great depths.  Unlike sea bass they are heavily sought by commercial and recreational anglers and are one of the more economically important groups of fish in the Gulf of Mexico.

The massive size of a goliath grouper. Photo: Bryan Fluech Florida Sea Grant

One interesting note on this family of fish is that most are hermaphroditic.  The means they have both ovaries (to produce eggs) and testes (to produce sperm).  Sequential hermaphrodism is when a species is born one sex but becomes the other later in life.  This is the case with most groupers, who are born female and become male later in life.  However, the belted sand bass (Serranus subligarius) is a true hermaphrodite being able to produce sperm and egg at the same time – even being able to self-fertilize.

 

For many along the Florida panhandle, their biogeographic distribution and sex do not matter.  It is a great tasting fish and very popular with anglers.  For those with a little more interest in natural history of fish in our area, the biology and diversity of this group is one of the more interesting ones.

 

Reference

 

1 Hoese, H.D., Moore, R.H. 1977.  Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters.  Texas A&M Press.  College Station TX.  Pp. 327.

Celebrating the Okaloosa Darter

Celebrating the Okaloosa Darter

World Wildlife Day was celebrated on March 3, 2022.  This year’s theme is “Recovering key species for ecosystem restoration.” We celebrate this day to bring attention and awareness to many of the plants and animals that are considered threatened and endangered species and highlight efforts to conserve them. It is estimated that over a million species are currently threatened with extinction.

Turkey Creek Niceville, FL (credit E. Zambello)

Florida is considered a very biodiverse state having a great variety ecosystems and unique plants and animals that inhabit these areas.  This makes Florida an attractive place to live but can result in increased pollution and land use changes that can be threats to this biodiversity. One local species that experienced this type of pressure is the Okaloosa darter. This tiny 1 to 2 inch fish dwindled to as few as 1,500 individuals surviving when it was declared endangered in 1973.  Factors such as its small range, competition from other species, and historical land use practices including artificial impoundments, erosion, and siltation, contributed to its demise.

The Okaloosa darter prefers to live in small, clear, lightly vegetated streams fed by ground water seepage from sand hill areas.  This highly specialized habitat is found in only six streams in Okaloosa and Walton Counties and almost exclusively within Eglin Air Force Base’s boundaries.  Environmental managers from Eglin Air Force Base partnered with U.S. Fish and Wildlife Service and other agencies and worked diligently to reduce land use impacts and rehab the impaired streams over the past several decades. They reclaimed clay pits near stream headwaters, improved road crossings to reduce sedimentation and enhanced the habitat for the darter.

Okaloosa darter photo credit: FWS.gov

Due to these efforts, the population of Okaloosa Darters has increased to more than 600,000 and the species has now been down listed from endangered to threatened.  In fact, the projects have been so successful that the darter is now being considered for delisting as a threatened and endangered species under the Endangered Species Act. This is something to celebrate on this World Wildlife Day as an example of how we can recover key species for ecosystem restoration.  The best news is that Eglin Air Force Base’s Jackson Guard Unit is continuing to make on-base conservation a priority, not only for the Okaloosa Darter, but for other plants and animals under their purview.

Snook in the Florida Panhandle

Snook in the Florida Panhandle

Snook… Wait did you say Snook in the Florida panhandle?

Yep… they are not common, but they have seen here.

 

For those who do not know the fish and do not understand why seeing them is strange, this is a more tropical species associated with tarpon.  In the early years of tourism in Florida tarpon fishing was one of the main reasons people came.  Though bonefish and snook fishing were not has popular as tarpon, they were good alternatives and today snook fishing is popular in central and south Florida… but not in the north.

This snook was captured near Cedar Key. These tropical fish are becoming more common in the northern Gulf of Mexico.
Photo: UF IFAS

This fish is extremely sensitive to cold water, not liking anything under 60° F.  They frequent the same habitats as tarpon, mangroves and marshes.  They are euryhaline (having a wide tolerance for salinity) and can be found in freshwater rivers and springs.  Actually, near river mouths is a place they frequent.  The younger fish are more often found within the estuaries and adults have been found in the Gulf of Mexico.  Again, this is a more tropical fish with records in Florida north of Tampa being rare.  In the western Gulf the story is the same, almost all records are south of Galveston, Texas.  Until recently…

 

Hoese and Moore1 cite a paper by Baughman (1943) that indicated the range of the fish had actually moved further south.  One reason given was the loss of the much-needed salt marsh and mangrove habitats from human development.  But in recent years there have more reports north of Tampa.  Purtlebaugh (et al.)2 published a paper in 2020 indicating an increase in snook captured in the Cedar Key area of the Big Bend beginning in 2007.  At first records only included adults, and the thought was these were “wayward” drifters in the region.  But by 2018 they were capturing fish in all size classes and there was evidence of breeding going in the area.  The range of the fish seemed to be moving north.  The study suggests they still need warm water locations to over winter, and, like the manatees, springs seem to be working fine.  But another piece of the explanation has been the reduction of hard freezes during winter in this part of the Gulf.  Climate change may be playing a role here as well.

 

There seems to be other tropical species dispersing northward in a process some call “tropicalization” including the mangroves.  There have been anecdotal reports of snook near Apalachicola where mangroves are becoming more common, and I know of two that were caught in Mobile Bay.  There are mangroves growing on the Mississippi barrier islands as well.  While explaining this during a presentation I was doing for a local group, a gentleman showed me a photo of a snook on his phone.  I asked if he caught it in the Pensacola area.  He replied yes.  When I asked where, he just smiled… 😊 He was not going to share that.  Cool.

 

There is no evidence that snook have established breeding populations are in our waters.  Especially after this winter with multiple days with temperatures in the 30s, it is unlikely snook would be found here.  But it is still interesting, and we encourage anyone who does catch one, to report it to us.

 

References

 

1 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico; Texas, Louisiana, and Adjacent Waters. Texas A&M Press. College Station Tx. Pp 327.

 

2 Purtlebaugh CH, Martin CW, Allen MS (2020) Poleward expansion of common snook Centropomus undecimalis in the northeastern Gulf of Mexico and future research needs. PLoS ONE 15(6): e0234083. https://doi.org/10.1371/journal.pone.0234083.

Pipefish of the Florida Panhandle

Pipefish of the Florida Panhandle

I recently posted an article about the seahorses of the Florida panhandle.  It would be remiss of me if I did not include their close cousins the pipefish.  Where seahorses are well known but hard to find, pipefish are easy to find but not well known.

The seahorse-like pipefish.
Photo: University of Florida

Pipefish are in the same family as seahorses, Syngnathidae, and are basically elongated seahorses.  Pulling seine nets in local grassbeds we often catch them.  Students always ask what they are.  “Are these needlefish?”  is a frequent question.  I reply “no, they are pipefish”.  Which then comes “pikefish?”.  To which I reply “No, PIPEfish… like P-I-P-E… – they are basically elongated seahorses”.  And then there is always – “coool”.  To which I reply “yes… very cool”.

 

Pipefish have the same body armor, body rings, and long tube snout of the seahorse.  However, they lack the curled prehensile tail for a more elongated body, looking more a grass blade than their cousins.  They actually have a caudal fin (the fin most call “fish tail”).  Most range between 3-6 inches long but the chain pipefish can reach a length of 10 inches, this is the “big boy” of the group.  Like seahorses, they hide in the grass using their tube-shaped mouths to suck in small planktonic food.  Like the seahorses, the males’ possess a brood pouch to carry the fertilized eggs and give live birth (ovoviviparous).

 

The pipefish can quickly be divided into two groups – those with long snouts, and those with short – and this can be easily seen when captured in a net.  After that identification gets a bit tricky, you have to count rays in the fins or rings on the body.  It is sufficed to say, “it’s a pipefish” and leave it at that.

 

Those with long snouts include the Opossum, Chain, Dusky, and Sargassum pipefish.

 

The Opossum Pipefish (Microphis brachyurus) is about 3 inches long and was not reported from the northwestern Gulf of Mexico according to Hoese and Moore1.  In the eastern Gulf, our way, it is considered rare but has been found in salt marshes, seagrasses, and in Sargassum mats drifting in from the Gulf.  The Florida Museum of Natural History list this fish as a “marine invader”2.  In 1991 NOAA listed it as a species of concern due to its decline across the region3.  There are reports of this pipefish entering freshwater creeks within our estuaries.

 

The Chain Pipefish (Syngnathus louisianae) has a very long snout and is the “big boy” of the group reaching 10 inches in length.  It is quite common along the panhandle and has one of the larger ranges of this group, found all along the Atlantic coast, throughout the Gulf of Mexico and in the Caribbean.

 

The Dusky Pipefish (Syngnathus floridae) is a long-snout, large pipefish reaching a length of eight inches.  It prefers higher salinity than many pipefish and is found throughout the Gulf of Mexico and along the Atlantic seaboard often offshore.

 

The Sargassum Pipefish (Syngnathus pelagicus).  This is a good scientific name for this fish (pelagicus) for it lives on the large mats of Sargassum weed that drifts across the oceans.  Because of this it has a worldwide distribution.  This longnose pipefish reaches the typical length of six inches.  It lives as many other pipefish do hiding in the grass snapping up food when it comes close enough but it’s habitat is often drifting offshore and inshore sightings of this species are rare.

 

There are three species of “short-snout” pipefish.

 

The Fringed Pipefish (Anarchopterus crinigerus) is a smaller pipefish reaching only three inches.  It seems to be absent in the western Gulf but is found along the Florida panhandle, the Gulf coast of peninsula Florida, and through the Caribbean to Brazil.

 

The Northern Pipefish (Syngnathus fuscus) reaches a length of six inches.  It is very common along the Atlantic seaboard but Hoese and Moore1 report only four specimens from the Gulf of Mexico.  This one would be considered very rare, and an expert should identify it if one thinks they have it.

 

The Gulf Pipefish (Syngnathus scovelli) is one of the more common pipefish collected in our waters.  It is a short-snout species reaching the typical six inches but has these distinct bluish-gray bars that run vertically along the sides.  It is found throughout the Gulf of Mexico and even into some freshwater habitats.  The Florida Museum of Natural History also list this species as a marine invader4.

 

I am not sure how much seining you do along our waterways, but if you do any within the grassbeds you are sure to find one of these unique and interesting fish.

 

References

 

1 Hoese, H.D., Moore, R.H. 1977. Fishes of the Gulf of Mexico. Texas A&M Press, College Station TX. Pp. 327.

 

2 Opossum pipefish.  Discover Fishes.  Florida Museum of Natural History.  https://www.floridamuseum.ufl.edu/discover-fish/florida-fishes-gallery/opossum-pipefish/.

 

3 Opossum Pipefish.  Species of Concern.  National Oceanic and Atmospheric Administration, National Marine Fisheries Service.  https://www.nrc.gov/docs/ML1224/ML12240A312.pdf.

 

4 Gulf Pipefish.  Discover Fishes. Florida Museum of Natural History.  https://www.floridamuseum.ufl.edu/discover-fish/florida-fishes-gallery/gulf-pipefish/.