What are those little things on the hull?

We once stationed élan for nearly four months in the open ocean, just to leeward of Christmas Island (Republic of Kiribati), a large coral atoll 2° above the equator in the central-eastern tropical Pacific. We buried the anchor in deep white sand at the base of a coral ledge 45 feet deep, the easterly trade winds holding the hull back over a large, featureless basin in 70 feet of water. The pass was treacherous, and the inner anchorage featured a 25-mile fetch, so we sat out the South Pacific cyclone season on the outside of the lagoon. This dictated a before-dark return to the boat each evening, not the norm for most ports, but we found ourselves more entertained by the nightly show of marine life than anything possible on land. Further, the thrill of catching giant trevally, yellowfin tuna and wahoo a short dinghy ride away along the ocean dropoff, and at times actually from the sailboat, became addictive to say the least — not to mention dropping over the side for daily first-class scuba dives.

The unique opportunity to live stationary in oceanic conditions resulted in a multitude of interesting brushes with marine life, none more fascinating than the discovery that the hull had become a settling station for one of the world’s most sought-after crustaceans, the spiny lobster.

The first time I began scraping the gooseneck barnacles off the bottom, I noticed the crystalline flickering of tiny forms, about an inch or so long, kicking away from my brush. Quickly stowing the brush, I focused closely among the barnacle stalks of an uncleaned area of hull, and found a sea of tiny, transparent antennae and shrimp-like bodies. Some had slight pigmentation, and one or two had undergone metamorphosis from the clearer, more flattened puerulus stage to the first postpuerulus molt, tiny replicas of the adults, complete with splashy white dots and iridescent purple, indicating they were the colorful painted lobster, Panulirus versicolor.

The perfectly clear individuals, on the other hand, had likely settled out of the ocean plankton the previous night, after at least six to nine months adrift in the open sea, transforming from a disk-shaped phyllosoma larva to a perfect little mini-lobster, called the puerulus. This stage becomes progressively more pigmented for each of about seven nights, and then molts again.

While working as an associate scientist for Harbor Branch Oceanographic Institution, I had conducted a yearlong study of the postlarval settlement of the spiny lobster Panulirus argus in Antigua, West Indies. We tie-wrapped “pages” of air-conditioner filter material, called “hog’s hair,” to PVC pipe frames and anchored them around the island with cinder blocks.

What triggers the mysterious arrival, metamorphosis out of the plankton, and settlement of these animals after all that time at sea remains largely unknown, but we did learn a great deal about certain aspects of the phenomenon. They certainly show up in fairly specific habitats, usually featuring complex macroalgae growth on hard substrate. Scientists previously discovered their affinity for hog’s hair and their sensitivity to the phases of the moon. We eventually collected 22,817 postlarvae and transported them back to the lab for growth and rearing experiments aimed at development of a lobster farm.

The family Palinuridae provides sailors with delicious spiny lobster species in the subtropical and tropical oceans throughout the world. The Caribbean version spawns in the springtime. Males deposit a spermatophore on the underside of the female’s carapace, which she carries around until needed to fertilize her eggs. The sticky, usually orange egg mass resides on the ventral surface of the tail. The eggs hatch in about three weeks and then begin the long, complex, open-ocean larval phase that occasionally ends with metamorphosis and settlement on a boat hull. From this diminutive beginning it takes on the order of three years to reach legal harvest size.

You may accumulate some postlarval spiny lobsters in a variety of different anchorages, particularly those in close proximity to open ocean water or in harbors nestled on the windward side of a landmass. Of course your chances increase with the amount of bottom growth on the hull, so a meaningful science lesson for the kids constitutes one more excuse to delay that bottom scrubbing, and better yet, get them to do it so they’ll see those little lobsters firsthand.

By Ocean Navigator