Two of the worlds 15 eel species swim to the Saragasso Sea to spawn. The Saragasso Sea is a large area of the Atlantic Ocean east of Georgia and the Bahamas. Higher salinity from low rainfall and warmer water are believed to be the attractions for these creatures, whose behavior, in part, remains a mystery to scientists.
Both American eels and European eels leave their respective coastlines and head for the Saragasso Sea in the fall. An 18-inch long eel is a common size for a mature eel, though they can grow to 36 inches. Size, more than age, appears to be the maturity trigger that sends them off to spawn thousands of miles from where they grew up.
The females produce one to two million eggs, which hatch in two days. These soon become larvae, shaped like willow leaves, and which grow slowly while they drift on the oceans currents. They are somehow drawn into the currents that become the Gulf Stream on the North American side, until they reach the Continental Shelf off New England. On the shelf they metamorphose into the glassy eel, and at that stage, head for shore. They make their way up the rivers or streams to ponds that will be home for up to 40 years.
The glassy eels begin eating the smallest stuff in the water. By the time they are a few inches long they are eating insect larvae and eventually small fish. An 18-inch eel is about 15 years old. When it is time to go they leave in large numbers, often during heavy rains that fill the stream they are riding out.
They manage to get back to the Saragasso Sea, with its slightly saltier and warmer water, which is just the way they like it. There are other places in the worlds oceans where eels from other continents travel for spawning.
Glass eels were, for a while, sold at high prices for small quantities. Japanese buyers paid a few hundred dollars a pound, but got thousands of these glass eels per pound. These were flown back to Japan to be grown into tons of mature eel. Eel in Japan and Europe is a highly prized seafood.
This all shines a light on another mystery about eels. Why is the seed stock sold off for pennies apiece when a voracious market exists for mature eels just across the pond?
The American eel, not long ago thought be robust may not be replacing itself. Eels have not been on the radar screen of management, and not until very recently has management begun to develop management programs. Some see a drastic decline in American eel populations. There is evidence that natural cycles beyond the scope of management may be at work. There are scientists who see a strong correlation between European eel recruitment and sea surface temperatures and the shifting position of the Gulf Stream. If these hemispheric scale factors effect American eel recruitment, then another look at what local protection can really do, may be necessary.
There are a few things known to be impacting eel populations in some way. Dams have blocked off access to rivers, streams and lakes. It is estimated that these alone are responsible for a 91% decline of the American eel. Elvers cluster at the foot of dams unable to pass. On the way downstream adult eels are found just downstream of dams with electric turbines. These wounded, stunned and dead eels inadvertently passed though the whirring turbines.
Long stays in polluted fresh water has left some with cancers, mutations and high levels of chemicals in their flesh.
With large markets in Japan and Europe for eel, and an expanding market for seafood in general, addressing the largest factor impacting eel decline doesnt seem impossible. Fish ladders that work for other fish ought to work for eels. The cost of being in the eel fishery business it seems would be low compared to offshore groundfish or lobster.