The story below was taken from The New Brunswick Reader, July 18/98
Dinosaurs of the
Story and photos by Peter Oxley
Fisherman at their nets near browns Flat, N.B. These men are retrieving sturgeon for research at the Canadian Sturgeon Conservation Centre at the old fish hatchery in Loch Lomond.
The St. John and Kennebecasis rivers are home to two species of living dinosaurs. The animals in question are not horrific, flesh-eating, reptile-like behemoths but rather the gentle sturgeon cruising covertly under dark waters.
Sturgeon are large ancient fish that are said to have stopped evolving 250 million years ago. What is truly fascinating is that they survived the sudden disappearance of the dinosaurs. Fossils of these creatures have been found indicating they have changed little over time. Looking at a live sturgeon, it is easy to see they are ancient. The primordial lobes of our brains can easily identify the rows of bony armor-like plates, or scutes, as being ancient.
The sturgeon shape is much the same as its efficient and compact compatriot - the shark. Unlike the flesh-eating shark, sturgeon have a small tube (or as scientist say, an inferior mouth) located on the underside of their massive heads that they use to suck up food off the river beds. They feed on a variety of bottom-dwelling organisms such as worms, shrimp, mollusks and even some plants. Another interesting morphological feature is their lack of bones. Instead, Sturgeon have a cartilaginous skeleton, again like their ancient brothers in arms - the sharks.
Now a little science about the order acipenseriforms, or fish that look like sturgeon. There are 25 species, they all inhabit water in the northern hemisphere and they all can get pretty big. Adult sturgeon range from 80 centimetres to five metres depending on the species. The kaluga (cousin of the beluga, as in beluga caviar -not cute white whales) can reach an enormous five metres and 1,000 kilograms. They are considered to be the largest fresh-water fish in the world. But don't worry they, too, are gentle giants and besides, they inhabit the Amur river in China not the St. John River in New Brunswick. But that isn't to say that we don't have our share of big fish as well.
The St. John and Kennebecasis rivers are home to two interesting and distinct species of sturgeon. The largest is the Atlantic sturgeon which can grow to 400 kilograms. A specimen of this magnitude hasn't been seen since the turn of the century but today Atlantics are still caught that top the scales at a respectable 80-100 kilograms. It has essentially the same life cycle as another anadromous (going from the sea to fresh-water rivers to spawn) fish - the familiar Atlantic salmon.
Atlantic sturgeon make their way into the rivers in the late spring and up to early fall. They travel up the river above the tide line and spawn in fast-moving water over gravel and rocks. Spawning usually occurs at night. The females spray their eggs into the water column and a few males will fertilize the eggs as they travel downstream. The release into the water column triggers an adhesive to form on the eggs that will cause them to stick on the first surface they come into contact with - usually a softball-sized rock on the bottom. As small particles of sand and silt travel downstream, they also adhere to the sticky egg until it is coated in a protective layer of armor. Mother Nature is a keen inventor.
A large female can produce as many as one million bird-shot sized eggs so a lot of spawning can go on over a few days. One million eggs seems like a lot of eggs, right? It is, but, as nature always does, checks and balances are built into the grand scheme to protect against over-population. Because these fish produce so many eggs, it is not uncommon for a mature female to spawn only every four years and it may take 15 years to reach sexual maturity. As you guessed it, the males reach sexual maturity earlier and can spawn every year. Once the spawn is complete, the fish spend a leisurely summer vacationing in the river feeding on a rich assortment of food and when fall rears it's frigid head, the mature sturgeon head down river to the greener, warmer pastures of the Bay of Fundy and farther south.
The other sturgeon that inhabits the St. John and Kennebecasis rivers is the smaller and less understood shortnose sturgeon (also known as the snub-nosed or fresh-water sturgeon, among other names). This little fish grows to a maximum of about 20 kilograms, which is not too shabby compared to a 20 centimetre trout. The shortnose sturgeon can be anadromous but they seem to halt their downstream migration at Grand Bay. Anyone who has donned scuba gear in that area can tell you, it is essentially sea water down deep.
Both the shortnose sturgeon and the Atlantic sturgeon range from the coastal southern U.S. to the St. John and Kennebecasis (Atlantic's are also found in the St. Lawrence River and in parts of Newfoundland). We should take pride in the fact that the St. John and Kennebecasis rivers are considered to have the most robust populations (in terms of size and numbers) of shortnose and Atlantics of any river in North America. The shortnose sturgeon spawns in exactly the same way and in the same place as their big brothers, the Atlantics. The only difference is that they spawn earlier in the spring just as the river starts to drop. Because the shortnose sturgeon peaks out at 20 kilograms, it is believed to mature earlier than the massive Atlantic. The two fish look remarkably the same except that the shortuose is stockier with, you guessed it, a shorter nose. Some people mistakenly think that the shortnose is simply a juvenile Atlantic. This mistaken identity arises because juvenile Atlantics are rarely seen.
If you have spent time on the river, you have probably seen sturgeon but you mistook them for the leaper - salmo salar - the Atlantic salmon. I must confess, with all the years I spent rowing on the Kennebecasis River, I was sure that when a fish jumped it was a salmon. As I started working with sturgeon, I discovered my error.
In fact, a few years ago while rowing with my teammates, three agile shortnose sturgeon jumped within three metres of the rowing shell. My teammate muttered 'salmon' under his breath. I immediately recognized the large head and thin body as that of the shortnosed sturgeon.
The next two consecutive jumps clinched my identification. Salmon jump out of the water head first and re-enter the water head first. They probably jump to dislodge parasites in their, gills.
Sturgeon seem to jump mostly prior to an electrical storm. Their airborne style consists of a head-first exit with a tail-first entrance. Not great for style points but the big splash may serve to "burp" the air out of their swim bladders and allow them access to the deeper parts of the river. This observation was passed on to me by David Gorham, a fisherman and conservationist who has worked with sturgeon for many years. He claims that sturgeon go deep before a storm and are generally scarce until the electrical event is over.
Maybe sturgeon share the same sensitivity to electrical fields with their bad-boy cousins the sharks. It is said that a shark can sense the electrical discharge from a nine-volt battery from one kilometre away in open water. Lesson to be garnered from this: don't dive with your Walkman on.
In terms of predators, sturgeon have few. As tiny fingerlings they would be vulnerable to any fish with an appetite; however, as they grow, their bony plates, or scutes, become more developed and very sharp, making them less than palatable. Sturgeon have always been vulnerable to over-fishing by humans. This is due to their late sexual maturity (between six and 25 years depending on species) and because of the visibility of a 50 kilogram-plus animal thrashing about in spawning bliss. Dams have also cut sturgeon off from their preferred spawning habitat. They don't seem to be adept at negotiating fish ladders (these are usually constructed for smaller fish) and they usually become pureed when they try to swim down through the power-generating impeller.
In the Caspian Sea, the most productive sturgeon-fishing area in the world, numbers have been declining rapidly. This is due to a number of factors: firstly, dams built on the Volga River in the 1950s have seriously affected spawning habitat. Over-fishing since the breakup of the former Soviet Union has also taken its toll. The prime product from sturgeon, caviar, is to blame. According to TRAFFIC, an international conservation watchdog, illegal caviar smuggling ranks second only after illicit drugs as the contraband of choice. Caviar, like drugs, is small, easily transported and fetches a high price.
A sturgeon being milked of its roe
at the sturgeon conservation centre.
The good news is that in the United States and Canada, scientists have been working to develop culturing techniques to spawn and rear these amazing fish. In New Brunswick, the Canadian Sturgeon Conservation Centre has been working with both the Atlantic and snubnose species for the past two years and have successfully raised sturgeon from egg to adult. Fingerlings are being shipped to researchers all over the world for study and to those who are committed to enhancing world sturgeon populations.
Peter Oxley is a fish farmer in Saint John and a member of the Canadian Sturgeon Conservation Centre.