The bay scallop (Argopecten irradians) was once common in the lower portions of the Pensacola Bay system. However, by 1970 they were all but gone. Closely associated with seagrass, especially turtle grass (Thalassia testudinum), some suggested the decline was connected to the decline of seagrass beds in this part of the bay. Decline in water quality and overharvesting by humans may have also been a contributor. It was most likely a combination of these factors.
Scalloping is a popular activity in our state. It can be done with a simple mask and snorkel, in relatively shallow water, and is very family friendly. The decline witnessed in the lower Pensacola Bay system was witnessed in other estuaries along Florida’s Gulf coast as well. Today commercial harvest is banned, and recreational harvest is restricted to specific months and to the Big Bend region of the state. With the improvements in water quality and natural seagrass restoration, it is hoped that the bay scallop may return to lower Pensacola Bay.
Since 2015 Florida Sea Grant has held the annual Pensacola Bay Scallop Search. Trained volunteers survey pre-determined grids within Big Lagoon and Santa Rosa Sound. Below is the report for both the 2024 survey and the overall results since 2015.
Methods
Scallop searchers are volunteers trained by Florida Sea Grant. Teams are made up of at least three members. Two snorkel while one is the data recorder. More than three can be on a team. Some pre-determined grids require a boat to access, others can be reached by paddle craft or on foot.
Once on site the volunteers extend a 50-meter transect line that is weighted on each end. Also attached is a white buoy to mark the end of the line. The two snorkelers survey the length of the transect, one on each side, using a 1-meter PVC pipe to determine where the area of the transect ends. This transect thus covers 100m2. The surveyors record the number of live scallops they find within this area, measure the height of the first five found in millimeters using a small caliper, which species of seagrass are within the transect, the percent coverage of the seagrass, whether macroalgae are present or not, and any other notes of interest – such as the presence of scallop shells or scallop predators (such as conchs and blue crabs). Three more transects are conducted within the grid before returning.
The Pensacola Scallop Search occurs during the month of July.
2024 Results
A record 168 volunteers surveyed 15 of the 66 1-nautical mile grids (23%) between Big Lagoon State Park and Navarre Beach. 152 transects (15,200m2) were surveyed logging 133 scallops. An additional 50 scallops were found outside the official transect for a total of 183 scallops for 2024.
2024 Big Lagoon Results
75 volunteers surveyed 7 of the 11 grids (64%) within the Big Lagoon. 67 transects were conducted covering 6,700m2.
101 scallops were logged with an additional 42 found outside the official transects. This equates to 3.02 scallops/200m2. Scallop searchers reported blue crabs and conchs, both scallop predators, as well as some sea urchins. All three species of seagrass were found (Thalassia, Halodule, and Syringodium). Seagrass densities ranged from 5-100%. Macroalgae was present in six of the seven grids (86%) but was never abundant.
2024 Santa Rosa Sound Results
93 volunteers surveyed 8 of the 55 grids (14%) in Santa Rosa Sound. 85 transects were conducted covering 8,500m2.
32 scallops were logged with an additional 8 found outside the official transects. This equates to 0.76 scallops/200m2. Scallop searchers reported blue crabs, conchs, and sand dollars. All three species of seagrass were found. Seagrass densities ranged from 50-100%. Macroalgae was present in five of the eight grids (62%) and was abundant in grids surveyed on the eastern end of the survey area.
2015 – 2024 Big Lagoon Results
Year
No. of Transects
No. of Scallops
Scallops/200m2
2015
33
0
0.00
2016
47
0
0.00
2017
16
0
0.00
2018
28
0
0.00
2019
17
0
0.00
2020
16
1
0.12
2021
18
0
0.00
2022
38
0
0.00
2023
43
2
0.09
2024
67
101
3.02
Big Lagoon Overall
323
104
0.64
2015 – 2024 Santa Rosa Sound Results
Year
No. of Transects
No. of Scallops
Scallops/200m2
2015
01
0
0.00
2016
01
0
0.00
2017
01
0
0.00
2018
01
0
0.00
2019
01
0
0.00
2020
01
0
0.00
2021
20
0
0.00
2022
40
2
0.11
2023
28
2
0.14
2024
85
32
0.76
Santa Rosa Sound Overall
1731
36
0.42
1Transects were conducted during these years but data for Santa Rosa Sound was logged by an intern with the Santa Rosa County Extension Office and is currently unavailable.
Discussion
Based on a Florida Fish and Wildlife Research Institute publication in 2018, the final criteria are used to classify scallop populations in Florida.
Scallop Population / 200m2
Classification
0-2
Collapsed
2-20
Vulnerable
20-200
Stable
Based on this, over the last nine years we have surveyed, the populations in lower Pensacola Bay are still collapsed. However, you will notice that in 2024 the population in Big Lagoon moved from collapsed to vulnerable for this year alone.
There are some possible explanations for this.
The survey effort in Big Lagoon was stronger than Santa Rosa Sound. 75 volunteers surveyed 7 of the 11 grids. This equates to 11 volunteers / grid surveyed and 64% of the survey area was covered. With Santa Rosa Sound there were 93 volunteers who surveyed 8 of the 55 grids. This equates to 12 volunteers / grid surveyed but only 14% of the survey area was covered. Most of the SRS grids surveyed were in the Gulf Breeze/Pensacola Beach area. More effort east of Big Sabine may yield more scallops found.
There is the possibility of different teams counting the same scallops. Each grid is 1-nautical mile, so the probability of one team laying their transect over an area another team did is low, but not zero.
It is known that scallops have periodic population booms. Our search this year may have witnessed this. We will know if encounters significantly decrease in 2025.
Whether there was double counting this year or not, the frequency of encounter was much higher than in previous years. There were multiple reports from the public on social media about scallop encounters as well, and in some places we did not survey. It is also understood that scallops mass spawn. So, high density populations are required for reproductive success. The “boom” we witnessed this year suggests that there is a population of scallops – albeit a collapsed one – in our bay. It is important for locals NOT to harvest scallops from either body of water. First, it is illegal. Second, any chance of recovering this lost population will be lost if the adult population densities are not high enough for reproductive success.
Acknowledgements
We would like to thank ALL 168 volunteers who surveyed this year. We obviously could not have done this without you.
Below are the “team captains”.
Harbor Amiss Glen Grant Eric Stone
David Anderson Phil Harter Neil Tucker
Laura Baker Gina Hertz Christian Wagley
Melinda Bennett Sean Hickey Jaden Wielhouwer
Samantha Bergeron (USM class) John Imhof Keith Wilkins
Cheri Bone Jason Mellos Christy Woodring
Cindi Cagle Greg Patterson
Cher Clary Kelly Rysula
A team of scallop searchers celebrates after finding a few scallops in Pensacola Bay.
Volunteer measures a scallop he found. Photo: Abby Nonnenmacher
Rick O’Connor Florida Sea Grant; Escambia County
Thomas Derbes II Florida Sea Grant; Santa Rosa County
The University of Florida/IFAS Extension & Florida Sea Grant faculty are reintroducing their acclaimed “Panhandle Outdoors LIVE!” series on St. Joseph Bay. This ecosystem is home to some of the richest concentrations of flora and fauna on the Northern Gulf Coast. This area supports an amazing diversity of fish, aquatic invertebrates, turtles and other species of the marsh and pine flatwoods. Come learn about the important roles of ecosystem!
Registration fee is $40. You must pre-register to attend.
The Panhandle of Florida is home to many estuaries along the coast, from the Escambia Bay System in the west to the Apalachicola Bay System in the east. These estuaries are very important and are the intersection where rivers (fed from their respective watersheds) meet the Gulf of Mexico and contain many different organisms that help filter the waters before they reach the Gulf. These organisms include oysters, marsh plants, seagrasses, scallops, tunicates, and other invertebrates. In this two-part article, we will explore marsh plants, seagrasses, oysters, and scallops.
Marsh Plants
Marsh Plants is a broad term for a family of grasses that lines the shore and contain grasses like Smooth Cordgrass (Spartina alterniflora), Saltgrass (Distichlis spicata), and Gulf Cordgrass (Spartina spartinae). These plants help trap sediments before they enter the estuary and are excellent at erosion prevention. When the water encounters the plants, it slows the flow, and this allows for sediments to collect. Marsh Plants are a great tool for shoreline restoration and are a major part of the Living Shorelines Program. The roots of the plants are also very efficient at removing nutrient pollutants like excess nitrogen and phosphorus which are major influencers in eutrophication. Marsh Plants also absorb carbon dioxide from the atmosphere and have been tabbed as “superstars of CO2 capture and storage.” (CO2 and Marsh Plants)
Marsh Grass and Oyster Reef in Apalachicola, Florida – Thomas Derbes II
Seagrasses
Seagrasses are different than Marsh Grasses (seagrasses are ALWAYS submerged underwater), but they offer some of the same ecological services as Marsh Grasses. The term seagrasses include Turtle Grass (Thalassia testudinum), Shoal Grass (Halodule wrightii), Widgeon Grass (Ruppia maritima), and Manatee Grass (Syringodium filiforme) to name a few. Seagrasses help maintain water clarity by trapping suspended sediments and particles with their leaves and uptake excess nutrients in their roots. Seagrasses are very efficient at capturing carbon, capturing it at rates up to 35 times faster than tropical rainforests. (Carbon Capture and Seagrasses) They also provide habitat for crustaceans, fish, and shellfish (which can filter the water too) and food for other organisms like turtles and manatees.
Grassbeds are also full of life, albeit small creatures. Photo: Virginia Sea Grant
Oysters
Crassostrea virginica (or as we know them, the Eastern oyster) is a native species of oyster that is commonly found along the eastern coast of the USA, from the upper New England states all the way to the southernmost tip of Texas. Eastern oysters are prolific filter feeders and can filter between 30-50 gallons of water per day. As filter feeders, they trap nutrients like plankton and algae from the environment. In areas of high eutrophication, oysters can be very beneficial in clearing the waters by trapping and consuming the excess nutrients and sediments and depositing them on the bottom as pseudo-feces. With oyster farms popping up all over the Gulf Coast, the filtering potential of estuaries is on the rise. (Between the Hinge)
Oysters, The Powerful Filterers of the Estuary – Thomas Derbes II
Scallops
Bay Scallops (Agropecten irradians) were common along the whole Florida Gulf Coast, but their numbers have taken a recent decline and can only be found in abundance in the estuaries to the east of St. Andrews Bay in Panama City, Florida. Scallops make their home in seagrass beds and are filter feeders. While scallops do not contain the filtering potential of an oyster (scallops filter 3 gallons of water per day as an adult), they are still a key part of filtering the estuary. Just like oysters, scallops feed off of the suspended particles and plankton in the water column and deposit them as pseudo-feces on the bottom. The pseudo-feces also help provide nutrients to the seagrasses below.
Bay Scallop. Photo: FWC
I hope you enjoyed this first article on filterers in the estuary system. While oysters are known as the filterers of the estuary, I hope this has opened your eyes to the many different filterers that call our estuary home. Stay tuned for Part 2!
Bay scallops (Argopecten irradians) have been an important part of the economy of many gulf coast communities within the Florida Big Bend for decades. It was once abundant in all gulf coast counties of the state but beginning in the 1960s populations in many bays began to decline to levels where they are all but nonexistent. The cause of this decline has been associated with many factors including a decline in water quality, a decline in suitable habitat (sea turtle grass beds – Thalassia), and overharvesting. Most likely the cause included all of these. Since the collapse of both the commercial and recreational fishery, Gulf coast communities have been trying to address all three of the stressors above. Multiple monitoring projects are ongoing in the Pensacola Bay area and one of those is the Great Scallop Search.
The Great Scallop Search was developed by Sea Grant Agents in Southwest Florida and expanded, through Florida Sea Grant, to Northwest Florida. In each location volunteers snorkel a 50-meter transect line searching for live bay scallops, as well as monitoring the status of the seagrass habitat. Since 2015 317 volunteers have logged 634 hours surveying 407 50-meter transects in 106 grids in Big Lagoon or Santa Rosa Sound. In that time 4 live scallops have been logged, though we hear anecdotal reports of additional scallops being found in these bodies of water.
Survey Method
Volunteers select and survey one of 11 grids in Big Lagoon, or one of 55 grids in Santa Rosa Sound. Once on site, the volunteers anchor and record preliminary information on the data sheet provided. Two snorkelers enter the water and swim on opposite sides of a 50-meter transect line searching for live scallops. Any live scallop found is measured and returned. The species and density of the seagrass is recorded as well as the presence/absence of macroalgae on that seagrass. Four such transects are surveyed in each grid.
2023 Results
2023
SRS
BL
Total
Other
# of volunteers
72
No significant difference between 2022 and 2023
# of grids surveyed
8
8
16
Slight decrease from 2022. 16 of the 66 grids (24%) were surveyed.
# of transects surveyed
26
51
77
A decrease from 2022. More surveys were conducted in Big Lagoon than Santa Rosa Sound.
Area surveyed (m2)
2600
5100
7700
1.9 acres
# of scallop found
2
2
4
Four live scallops are a record for this project. It equals the sum of all other live scallops since the project began.
Scallop Size (cm)
4.5, 5.0
4.0, 4.5
Surveys with Seagrass
Halodule
5
12
17
17/21 surveys – 81%
Thalassia
8
11
19
19/21 surveys – 90%
Syringodium
0
2
2
2/21 surveys – 10%
Grass Density
100% grass
3
9
12
12/21 surveys (57%) were 100% grass
90%
1
0
1
Note: Volunteers typically select area for transects
75%
3
1
4
with a lot of grass.
70%
1
0
1
50%
3
9
12
5%
1
0
1
Macroalgae
Present
4
4
8
Absent
2
10
12
12/21 surveys (57%) had no macroalgae.
Abundant
2
2
4
Sediment Type
Mud
0
1
1
Sand
7
8
15
15/21 surveys (71%) were sandy.
Mixed
1
4
5
21 surveys were conducted covering 16 grids. 8 grids were surveyed in each body of water.
A total of 77 transects were conducted covering 7,700 m2 and four live scallops were found.
Two of the scallops were found in Big Lagoon and two in Santa Rosa Sound.
All scallops measured between 4-5cm (1.6-2”).
The number of live scallops found this year equaled the total number found over the last eight years.
Most of the transects included a mix of Halodule and Thalassia seagrass ranging from 100% coverage to 5%. The majority of the transects were between 50-100% grass. Four transects had 100% Thalassia. Three of those were in Santa Rosa Sound, one was in Big Lagoon. The diving depth of the volunteers ranged from 0 meters (0 feet) to 2.4 meters (8 feet). Macroalgae was present in 8 of the 21 surveys (38%) but was not abundant in most.
Volunteer measuring one of the four collected bay scallops in 2023 from Pensacola Bay.
Photo: Gina Hertz.
Summary of Project
Year
Volunteer
Grids Surveyed
Transects Surveyed
Live Scallops Found
2015
87
28
101
0
2016
96
31
111
1
2017
5
4
16
0
2018
20
7
32
0
2019
13
6
20
0
2020
5
2
16
1
2021
17
6
24
0
2022
74
22
87
2
2023
72
16
77
4
TOTAL
317
407
8
MEAN
35
14
45
0.4
To date we are averaging 35 volunteers each event, surveying 14 of the 55 possible grids (25%). We are averaging 45 transects each year (4500 m2), have logged 407 transects (40,700 m2) and have recorded 8 live scallops (< than one a year).
Discussion
Based on the results since 2016 this year was a record year for live scallops. Whether they are coming back on their own is still to be seen. Being mass spawners, bay scallop need high densities in order to reproduce successfully, and these numbers do not support that. The data, and comments from volunteers, suggest that the grasses look good and dense. Thalassia, a favorite of the bay scallop, appear to be becoming more abundant. This is a good sign.
Though small and few, bay scallops are trying to hold on in Pensacola Bay.
Photo: Gina Hertz
As I write this, we are in the middle of our 2023 Scallop Search, an event we do each year to assess whether the scallops in Pensacola Bay are trying to make a comeback on their own. Each year I am amazed at how popular this little mollusk is. On the day I am writing, I will be working with a marine science class from the University of Southern Mississippi driving over from Ocean Springs. This past weekend I worked with two families who trailered their boat from Enterprise Alabama to participate. Those on the eastern end of the panhandle are well aware of the popularity of this creature. Folks from all over the southeast travel there to go scalloping. Many of the locals in my area, when I am training them how to do a scallop search, tell me that they head east and go scalloping every year. Some even have condos for that week and it is a large part of their annual vacation plans. And many of the locals here would love to see them return to Pensacola Bay.
This is a creature that draws a lot of attention. But most know very little about it. They know it has small eyes and can swim – actually… I have recently found that not everyone knows they can swim. We know they like grassbeds and they can be harvested in the summer. They may have done this long enough to know the prime spots within the grassbeds to search for them – their “sweet spots”. But not much more.
So… let’s meet the bay scallop.
Volunteers conducting the great scallop search.
Photo: Molly O’Connor
Its scientific name is Argopecten irradians. It is a mollusk in the class Bivalvia and the family Pectinidae. There are numerous species, and the group is found all over the world. The greatest variety of them are from the Indo-Pacific region, and in each case, they are a popular seafood. Most can swim, though erratically – they are not Michael Phelps – and they use this ability to avoid predators such as starfish, which they can see with the set of simple eyes.
There are five subspecies of A. irradians. A. irradians irradians, known as the bay scallop, or Atlantic Bay scallop (and from here is just “the scallop”) is our local variety. It is found from Cape Cod to the Gulf of Mexico. They begin life as a microscopic egg produced during the mass spawning of the hermaphroditic parents (hermaphroditic meaning each parent can produce sperm and egg). The timing of the release of gametes is triggered by warming water and usually occurs in the late summer/early fall. This early egg stage sinks to the bottom where it remains for a few weeks before hatching.
The hatched larva remain microscopic, are transparent, resemble the parents, and are called spat. The spat become part of the plankton in local estuaries but eventually return to the grass in what is called “spatfall” where they attached to the seagrasses using byssal threads. They continue to grow, eventually release from the grass, and become the scallops we all know and love. Many species of scallops can live over 20 years, but our local one only lives for one.
As most know, adult scallops have two shells (bivalves) connected at the hinge on the dorsal side of the animal. Though they do add weight to the shell, a disadvantage for a swimmer, the “ribs” provide a sturdier shell. The two shells are connected by a single, large adductor muscle, which is used to open and close the valves during swimming. It is this adductor muscle we eat when consuming scallops.
Like all bivalves, scallops are filter feeders but unlike most bivalves they lack siphons to draw water in and out of the digestive tract. Rather they lie with their valves slightly gaped and allow water to pass over them. Plankton is collected by a mucous layer and then moved to the gut by cilia (small hair-like structures) where it is digested.
Bay Scallop.
Photo: FWC
Like all bivalves, scallops lack a brain as we know it but rather function using a series of ganglia (groups of nerve cells) connected to a nerve ring. These ganglia can control movement of the muscle, gills, eyes, and are connected to a statocyst, which tells the scallop how it is oriented in the water column.
There are numerous eyes aligned along the edge of each valve that can detect movement and shadows. It is believed that they use their eyes to detect potential predators and possibly initiate the swimming behavior they are famous for.
Living only one year, and reaching maximum size in late summer during spawning, scallop harvesting is regulated to that time of year in Florida. Once common from Pensacola to Miami, they are now only found in large numbers in the Big Bend region. Due to the loss of scallops in other areas, many visit the Big Bend each year to go scalloping, putting heavy harvest pressure on those stocks. There have been efforts to try and enhance the existing populations as well as restore historic ones. Here in Pensacola Bay, Florida Sea Grant works with volunteers to monitor the water quality and seagrasses, as well as assess how the few existing scallops are doing.
For more information on panhandle scallops, contact your local Sea Grant Agent at the county extension office.
The Florida Fish & Wildlife Conservation Commission and UF/IFAS Extension – Florida Sea Grant have partnered to implement an innovative community-driven effort to restore scallop populations, and we need your help! “Scallop Sitter” volunteers are trained to assist in Bay, Gulf and Franklin Counties. The goal of the program is to increase scallop populations in our local bays. Scallop sitters help reintroduce scallops into suitable areas from which they have disappeared.
Volunteers manage predator exclusion cages of scallops, which are either placed in the bay or by a dock. The cages provide a safe environment for the scallops to live and reproduce, and in turn repopulate the bays. Volunteers make monthly visits from June until December to their assigned cages where they clean scallops (algal and barnacles can attach), check mortality rate and collect salinity data that helps us determine restoration goals and success in targeted areas.
1. Click on the “reserve a spot” to select the county you are participating in.*You must provide your name, contact information and date of birth to secure an FWC permit for your cage!
2. You will be sent a registration survey via email (closer to the scallops, cage & supply pickup date or you may fill out a survey onsite) , view the virtual training link: https://myfwc.com/research/saltwater/mollusc/bay-scallops/sign-up/
and you’ll receive an invite to our Panhandle Scallop Sitter Facebook Group.
DEADLINE for steps 1 & 2 are May 25th!
3. Pick up your scallops, cage & supplies!
Pickup Information (all times local)
St. George Sound Volunteers
Date: Thursday, June 1st
Time: 10:00 AM – 1:00 PM
Location: FSU Coastal & Marine Lab (across the canal – see road signage)
3618 US-98, St. Teresa, FL 32358
St. Joseph Bay Volunteers
Date: Thursday, June 8th
Time: 10:00 – 1:00 PM
Location: St. Joseph Bay State Buffer Preserve Lodge
3915 State Road 30-A, Port St. Joe, FL 32456
St. Andrew Bay Volunteers
Date: Thursday, June 16th
Time: 10:00 AM – 1:00 PM
*We know issues happen from time to time with scallop populations. It’s a bummer. If you loose a significant amount of scallops early in this year’s program, we will do our best to accommodate our volunteers with a “second wave” scallop stocking event in August. Also, looking for other ways to help our program? We plan to offer cage building workshops in the fall, stay tuned!
