Most trout fishermen, except for perhaps real sow-trout hunters, enjoy eating speckled trout almost as much as they do catching them. It can be dismaying, however, when one flips the first fillet over and sees the flesh riddled with large white worms.
Spaghetti worms are common parasites of saltwater fish in the drum family, which includes speckled and white trout, black drum, redfish and croakers. While they look alike to most fishermen, several different worms use these fish as hosts. Most common in sea trout is Poecilancistrium caryophyllum. Worms found in black drum are most often Pseudogrillotia pleistacantha. For ease of discussion, we will dispose of these tongue-twisting Latin names, and refer to them all as spaghetti worms.
In trout, they are most common in the middle of the fillet, in the area just below the dorsal fin, with a few found near the tail. Research has shown that approximately 40 percent of Louisiana and Mississippi speckled trout are hosts to spaghetti worms, with an average of between one and two worms occurring per fish. It may appear that many more worms exist, but often one worm is cut into several pieces during filleting.
Spaghetti worms in black drum are most common near the tail of the fish, with a typical fish hosting five to 15 specimens. Occasionally, in large black drum, they are so common that this area of the fish looks like it has more worm tissue than fish flesh.
The spaghetti worms we see in these fish are really parasitic tapeworms of sharks, and are just using the trout or drum as an intermediate host. The cycle begins with eggs produced by an 8-inch-long adult worm, which lives in a shark's intestine. After being passed into seawater, the egg hatches into a tiny swimming larva called a coracidium. If this larva is eaten within two days by a small marine crustacean like a copepod, it develops into another stage called a procercoid.
At this stage, some uncertainty exists as to what happens. The copepod may be eaten by a trout, passing the larval worm on to the trout. However, since small animals like copepods are seldom eaten by larger trout and since very few trout under 10 inches long have spaghetti worms, another host is suspected. More than likely, a small baitfish like an anchovy eats the copepod, and then it in turn is eaten by the larger trout.
In any case, once the larval worm is in the trout's digestive tract, it tunnels its way out of the system and into its flesh, where it may live for several years. The worm's life cycle is completed when a shark eats the trout, and its digestive juices liberate the encysted worm to latch on the shark's intestine wall. There, it feeds parasitically on food in the shark's gut, matures into an adult and releases eggs to start the cycle all over.
The fact that a spaghetti worm may live several years surprises many fishermen, since they often claim that more fish are infected in one season than another. This may possibly be due to different populations of trout with different infection rates, moving up and down in a marsh system seasonally.
The number of trout carrying worms seems to be directly related to the characteristics and quality of the water in which the trout live. In general, the saltier the water and the less polluted, the higher the levels of infection. This may be due to either one of the intermediate host's or the larval worm's needs for saline, unpolluted waters.
Another interesting fact is that once a trout becomes host to one or several spaghetti worms, it seems to develop immunity to further infections. If this were not the case, large, old fish would have many more worms than a 12- or 14-inch fish, but they don't. In fact, they often have fewer worms than smaller trout.
It seems that either the trout outlives the worm or the trout's internal defenses kill the worm. Whatever the case, after it dies, the worm is dissolved by the trout's body fluids. Larger, older fish often show opaque white areas in their flesh where encysted worms once were.
While the spaghetti worm may be somewhat unappealing to the eye, it certainly doesn't prevent good eating. Since, they are large enough to easily see, they are simple to remove during the filleting process. Simply grab the worm between the knife blade and thumb, and gently pull it out. With a little practice, it becomes easy.
Many people don't even bother to remove them before cooking. After cooking, they are unnoticeable and cannot be tasted.
While cooking does, of course, kill the worm, even without cooking they are not a human health problem. No human infections have been recorded, and researchers have been unable to infect warm-blooded animals with the parasite.
So, good fishing and "bon appetit."
Jerald Horst is co-author of the Angler's Guide to Fishes of the Gulf of Mexico, a 444-page, color-illustrated book on fishes, written for saltwater fishermen. The book is available in better bookstores, or can be ordered by calling 800-843-1724.