Situation

The horseshoe crab (Limulus polyphemus) has existed in its present form for about 450 million years.  It has survived several catastrophes that faced the planet including those that wiped out the dinosaurs.  Today there are four species remaining, three are found in Asia – the Tri-Spine horseshoe crab (Tachypleus tridentatus), the coastal horseshoe crab (Tachypleus gigas), and the mangrove horseshoe crab (Carcinoscorpius rotundicauda).  And then the one found along the east and Gulf coast of the United States – American horseshoe crab (Limulus polyphemus).  Despite all of the cosmic catastrophes this animal has overcome, all four species are in decline with the arrival of humans.

 

 

 

Humans have caused several problems for horseshoe crabs.  They have altered many nesting beaches and have commercially harvested them for their blood and to use as bait in the commercial eel fishing industry.  The Florida Fish and Wildlife Conservation Commission partnered with Florida Sea Grant to initiate a citizen science project where volunteers visit nesting beaches when the horseshoe crabs are there – collect them – measure them – and tag them.  This effort provides a lot of information including overall population status.

 

In the Pensacola Bay area horseshoe crabs are not as common as they are in other parts of the state.  In order to participate in the measurement/tagging project we first need to find where they are nesting – and that is the goal of the local project.

 

Method

Volunteers are trained on the basic biology and ecology of horseshoe crabs and assigned potential nesting beaches to survey during the spring high tides of both the spring and the fall seasons – this is when horseshoe crabs come to the beach to lay their eggs.  Volunteers record which beach they surveyed, how long the survey took, and any sign of horseshoe crabs they may have found – again, hopefully many on shore laying eggs.  Below are the results of the 2024 effort.

 

Results

In 2024 we trained 14 residents as citizen scientists for this project.  13 of those (93%) participated in at least one survey.

 

Spring Results

10 volunteers conducted 48 surveys between Mar 3 and May 29.  The surveys were conducted on 12 different beaches.  There were 9 encounters – all were either dead horseshoe crabs or molts.

 

Beach	# of Surveys	# of molts	# of HCs (single)	# HCs (male/female pair)	# dead HCs
Kees Bayou	1	0	0	0	0
Park West	13	1	0	0	0
Little Sabine	1	0	0	0	0
Morgan Park	12	0	0	0	0
Big Sabine	4	4	0	0	0
Redfish Pt.	2	0	0	0	0
Sanders Beach	6	0	0	0	0
Gulf Breeze N	1	0	0	0	1
Big Lagoon N	3	0	0	0	0
Johnson’s Beach	3	0	0	0	0
Ft. McRee	1	0	0	0	0
Ft. Pickens	1	1	0	0	2
TOTAL	48	6	0	0	3

 

Fall Results

3 volunteers conducted 57 surveys between Oct 2 – Dec 18.  The surveys were conducted on 5 different beaches. There were 37 encounters – all were either molts or dead horseshoe crabs.  32 of the 37 encounters were molts found on a single day.

 

Beach	# of Surveys	# of molts	# of HCs (single)	# HCs (male/female pair)	# dead HCs
Park West	4	0	0	0	0
Big Sabine	27	0	0	0	2
Naval Live Oaks South	16	1	0	0	0
Gulf Breeze N	1	32	0	0	0
Ft. Pickens	9	2	0	0	0
TOTAL	57	35	0	0	2

 

 

Discussion

13 volunteers conducted 105 surveys which included 13 different beaches.  Horseshoe crab encounters only included either molts or dead animals.  However, other citizens who were not part of the project did report live animals they saw while out and about.  These were reported from East Bay and Pensacola Beach (Santa Rosa Sound).  No nesting events were encountered.

 

Since this project began in 2021, we have encountered live horseshoe crabs – including male/female pairs – but have yet to discover a nesting event.  The breakdown of encounters is as follows…

82 molts

6 single live animals – seen at East Bay, Baby Beach, Little Sabine, and Gulf Breeze North.

6 dead animals

3 male/female pairs – seen at Redfish Pt. Ft. Pickens, and Baby Beach

 

These results suggest that for the 2025 season, we should concentrate our efforts at the following locations:

Gulf Breeze North on Pensacola Bay

Ft. Pickens on Santa Rosa Sound

Redfish Pt. on Big Lagoon

East Bay near Gulf Breeze

Baby Beach on Santa Rosa Sound

Little Sabine

 

If you are interested in volunteering, contact Rick O’Connor at 850-475-5230 ext.1111; roc1@ufl.edu.