By Joe Reynolds
The summer solstice arrived today around the Lower New York Bay watershed region at 7:09pm. Heralding its arrival was the warmest day of the year so far. Officially, the temperature was something like 92 degree in the shade, but directly under the sun, the temperature was closer to 100 degrees. No doubt about it, the sultry days of summer are here.
As the tide was coming in, I went for a walk along Sandy Hook Bay after work to cool off. The scent of suntan lotion was still fresh in the air from what must have been hundreds of people at the beach earlier in the day. Yet, I doubted anyone noticed what I was seeing.
All along the high tide line on the bayside beach were countless tiny molted shells from juvenile Horseshoe Crabs. Hundreds were scattered all about the seaweed and other debris that got washed in from last evening's spring tide. I tried to pick up as many as I could before the mosquitoes and flies got the best of me.
The molts were small, some just about a half-an-inch wide while others were about an inch and a half wide. If your didn't know what a Horseshoe Crab was or realized that they molt as they grow, a person might have thought these were dead little crabs or sea creatures strewn on the beach. On the contrary, this was evidence of new life in the bay!
Here on the beach was proof that baby Horseshoe Crabs call Sandy Hook Bay and the much larger Lower New York Bay home. The next generation of crabs just casted off their old hard shell a few days ago. They crawled out the front, and left the old shell behind. Now they are bigger and growing towards adulthood. A new generation of Horseshoe Crabs are surviving downstream from New York City.
Horseshoe crabs grow by molting or shedding their shell during the summer. These "molts" or old shells are then often found on tidal bayside beaches. Likely the result of a recent molt from a juvenile Horseshoe Crab. These little crabs often live in the shallow edge of the bay for the first several years of their life, then moving on into the deeper, darker waters of the bay as it get older.
All Horseshoe Crabs begin life as an egg. Spawning by adults takes place in May and June, with peak spawning occurring on evenings of high tides during the full and new moons. Eggs hatch about two weeks later, usually during the next moon cycle. A tiny Horseshoe Crab, about the size of a pea, crawls or swims into the surf where it will survive by hiding out in the knee deep waters of the bay, feeding time and again when the tide goes out and burrowing in the sand to escape predation during other times of the day.
Throughout its first year in the bay, a young-of-the-year crab will molt several times. The little crab will grow about 45% in its first molt and increase by about 75% during its second molt. While these numbers sound impressive, this activity just brings the crab in size to about 1/2" wide. Still miniature in size and vulnerable to predators. It also takes about 24 hours for the new soft shell to harden, leaving the little critter unprotected and helpless.
By the time a young Horseshoe Crab reaches its second or third year in the bay, it will shed its shell only once a year. After each molt, the crab will increase in size between 25 to 30 percent until they become fully grown. Once the crab is an adult, it will stop molting.
Horseshoe crabs molt 16 times over an 8 to 12 year period. In general, it takes about eight to nine years for a male Horseshoe Crab to reach adulthood, and it takes a female Horseshoe crab about 12 years to mature, as females are normally larger than males because they have to carry the eggs.
It takes a long time for a young Horseshoe Crab to become an adult. Each day is a fight for survival. As the summer season begins, though, a good many of the crabs that were born last year or even two years ago seem to have what it takes to endure near one of the most urban coastlines in the world. Without the survival of these young Horseshoe Crabs, the annual spectacle of scores of crabs coming up onto beaches around Lower New York Bay to spawn in May and June will be no more.