Species Accounts
Acipenseridae - Sturgeons - Esturgeons
Sturgeons are found in fresh and coastal waters around the Northern Hemisphere. There are 24 species with 5 occurring in Canada and 1 in the NCR. This family contains the largest freshwater fishes and life span is reported to exceed 150 years although fish of great size are difficult to age accurately. Some species live entirely in fresh water while others are anadromous, spending some time in the sea but returning to fresh water to spawn. The NCR species spends all its life in fresh water. Sturgeon roe or eggs are known as caviar and form an expensive delicacy. The flesh is also eaten, and is tasty when smoked. The swimbladders of sturgeons have been converted to isinglass, a transparent gelatin used in a variety of products including as a wine and beer clarifier and in jams and jellies. The total Canadian catch of sturgeons in 1988 was 53 tonnes. Their migratory habits have made them victims of pollution and hydroelectric schemes and sturgeons are no longer as large nor as numerous as in the past. Slow growth makes them susceptible to overfishing. Fossils extend back 100 million years and related but extinct families to 310 million years ago.
Lake Sturgeon / Esturgeon jaune
Acipenser fulvescens Rafinesque, 1817
Taxonomy
Other common name include Freshwater, Common, Great Lakes, Red, Ruddy, Black, Rock, Stone, Dogface, Shellback or Bony Sturgeon, Smoothback, Rubber Nose, Esturgeon de lac and Camus; or for young - Escargot, Maillé and Charbonnier. Acipenser is from the Latin for "sturgeon" and fulvescens means "brownish".
Key CharactersThis species is unique in having 5 rows of bony scutes or plates along the body, (1 dorsal, 2 lateral and 2 ventrolateral), 4 barbels in front of the transverse mouth under an elongate snout, no teeth in adults, and an upturned caudal fin skeleton (heterocercal) such that the upper tail lobe is larger than the lower.
Description
Dorsal fin rays 35-40, anal fin rays 25-30, dorsal plates 8-17, lateral plates 29-43, ventral plates 6-12, 1 large plate between the caudal fin and the anal fin in addition to the fulcrum (a flat bony plate), and 25-40 gill rakers. The scutes may almost disappear in old sturgeons but are sharp and obvious in young. The skeleton is cartilaginous, there is a spiracle and a spiral intestinal valve.
Colour
Back and upper flank dark brown, olive-green or grey and belly white to yellow-white. Flanks may be reddish. Fins are dark brown or grey. Body cavity organs are black but the peritoneum is silvery and only slightly pigmented. Specimens smaller than 30 cm have 2 black blotches on the upper snout, a black blotch between the dorsal and lateral plates above the pectoral fin base and another similarly positioned below the dorsal fin, and smaller spots on much of the rest of the head and body. Lower parts of the body are greenish.
Size
Reaches an estimated 312.0 cm and 184.57 kg, the largest freshwater fish in North America. The world, all-tackle angling record wa recognised as a 41.84 kg fish caught in the Kettle River, Minnesota in 1986 although much larger fish have been caught on rod and line. The Ontario record as of the year 2000 from Georgian Bay weighed 76.2 kg and is the International Game Fish Association Record (1999). The fish was caught in 1982. Newspaper records of large sturgeons caught in the Ottawa River are reprinted in Szabo (2004) and listed here. One fish snagged in Lac Deschênes had a sleigh harness entangled around its gills, apparently lost ten years before when a horse fell through the ice (Pembroke Observer, 7 June 1901, p. 1). Catches in the Ottawa River include a 5' 3", 85 lb one caught between Aylmer and Ottawa (Toronto Star, 22 May 1908, p. 1), a 5'4", 100 lb one caught illegally - the fisherman was fined (Globe and Mail, 2 November 1921), a 5'6" (1.65 m), 175 lb (79.5 kg) one from Lac Deschênes that had to be towed 2 miles to shore to be landed (Globe and Mail, 17 May 1927, p. 1; Harkness and Dymond (1961); McAllister and Coad (1975)), a 217 lb (98.5 kg) one from near Montebello that either bit or swiped the angler on landing (Globe and Mail, 26 March 1931, p 1; Toronto Star, 26 March 1931, p. 6; Butler, 2006; Harkness and Dymond (1961); Egan (2000)), a 5', 75 lb one caught with a minnow net (Toronto Star, 3 July 1939, p. 26), a 4' one caught by its tail from a ferry between Rockliffe and Gatineau Point (Toronto Star, 8 June 1949, p. 48), a 60 lb one that leaped out of the water at Rockliffe boathouse (Toronto Star, 19 August 1949, p. 1), a 3', 15 lb one that jumped into a boat - it apparently was trying to rub leeches of its body on the side of the boat (Toronto Star, 2 July 1953, p. 10), a 51.5", 45 lb one near Orleans (Globe and Mail, 23 June 1962, p. 4), and a 5'10" (1.8 m), 107 lb (48.6 kg) one from the Deschênes Rapids (Ottawa Citizen, 7 July 1972, p. 3; Cote (1972); Leggett (1975)).
Distribution
Found from western Québec including James Bay, all of Ontario and most of Manitoba and westward in the North Saskatchewan River to Alberta. South to Alabama, northern Mississippi and Arkansas west of the Appalachian Mountains. In the NCR it is restricted to the Ottawa River and mouths of tributaries.
Origin
This species colonised the NCR from a Mississippian refugium (Guénette et al., 1993; Ferguson and Duckworth, 1997).
Habitat
Lake Sturgeon are found in shallow areas of lakes and large rivers at about 4-9 m although they may descend to 43 m. These shallow areas are the highly productive shoals where food items are most available. Mostly the bottom is mud. Older fish tend to be in deeper waters and all age groups move away from shallower waters in summer to return in fall, presumably in response to temperature and oxygen changes. They are not usually found in water over 23.8°C and prefer waters at 15-17°C. Occasionally sturgeon are reported to jump and can end up in boats (Harkness and Dymond, 1961; Egan, 2000; 2003). A 50 lb (22.7 kg) sturgeon 58 inches (1.47 m) long leaped out of the water and landed in a rowboat crewed by two girls on the Ottawa River. Sturgeon are quiet tough and can survive several hours out of water and are relatively easy to tag, spine clip and weigh and measure in mark-recapture studies when water and air temperatures are cool.
Age and Growth
Accurate age determination is difficult in long-lived species like sturgeons. Maximum female age is estimated to be 96 years and for males 55 years. There is a report of one fish aged at 154 years from Lake of the Woods. Growth is slower in the north than the south and fish are older. Maturity has been estimated at 8-20 years for males and 14-33 for females, varying with locality. St. Lawrence River female sturgeon reach sexual maturity at an estimated 27 years and 1.33 m and the mean interval between spawnings is 9.4-9.7 years, higher than reports for other populations.
Ottawa River fish mature at 19-20 years and 30 inches (76.2 cm) for males and 26 years and 33 inches (83.8 cm) for females with few males exceeding 45-50 years and females living longer (Harkness and Dymond, 1961). In the Hull-Carillon section of the Ottawa River, 94% of the sturgeon caught in a 1988 study were less than 27 years old (the mean age of first maturity of females) and the species here is not very abundant nor as old, long or heavy as compared to those in the St. Lawrence River (Fournier, 1988; Fortin et al., 1992). Haxton (2002) sampled sturgeons in the Ottawa River over a 5-year period (1997-2001). Three of his areas fall within the NCR - Lac des Chats (above the Chats Falls Dam, mostly upriver of the NCR, sampled 1998), Lac Deschênes (Chats Falls Dam to Chaudière Falls, wholly within the NCR, sampled in 2000) and Lac Dollard des Ormeaux (below the Chaudière Falls to the Carillon Dam, much of it within the NCR, sampled in 2001). Eleven sturgeon were taken in Lac des Chats, none in Lac Deschênes, and 42 in Lac Dollard des Ormeaux. Sturgeon were more abundant in some sections higher up the Ottawa River outside the NCR. The mean total length for Lac des Chats sturgeon was 109.9 cm and mean weight was 8450 g. The mean total length for Lac Dollard des Ormeaux sturgeon was 78.7 cm and mean weight was 2039 g. The latter population showed some signs of recruitment despite being downriver of the NCR. The sex ratio is about 1:1 at birth but by age 40 years it is 6:1 in favour of females. Garvey (2001) found only 8 sturgeon in the disturbed Lac Deschenes over 298.21 hours of fishing compared to 117 fish over 152 hours in the undisturbed Lower Allumette, upriver. Mean total length for Lac Deschenes fish was 121 cm and mean weight was 10.39 kg.
A comparison of the spawning population below the Chats Generating Station was made for sample years 2001-2004 and the study of Dubreuil and Cuerrier (1950) for 1949 fish by Haxton (2006). The spawning stock in 2003 was estimated to be 202 fish, mean size was greater (118.0 cm total length for 2001-2004 compared to 101.7 cm in 1949), weight-length relationships did not vary between studies, and fish less than 110 cm total length comprised only 31.1% of the sample compared to a majority of 69.9% in 1949. This latter observation suggest the population is suffering a recruitment problem. Recruitment did occur because fish were aged at 13 to 46 years, and therefore were not relicts of the pre-1949 population. Ages in the 1949 survey were 15-62 years. Interestingly only males were found in spawning condition, suggesting spawning females could be rare in this section (Lac Deschênes) of the Ottawa River enclosed by dams at Chats and Ottawa.
Haxton (2008) summarises knowledge of sturgeon in the Ottawa River and found the greatest abundance in unimpounded river reaches, a condition found outside the NCR. The von Bertalanffy growth equation for Ottawa River fish was Lt = 133.7(1-exp-0.058(t-(-3))) and condition was described by w = 5.6 x 10-4l3.50. Length and age at 50% maturity was 106.7 cm and 20.4 years fro males and 112.2 cm and 25.4 years for females Fecundity was estimated at 12,170 eggs/kg. Annual mortality was estimated at 15%.
Food
Food is slurped from bottom sediments and includes a wide variety of animal and plant material found in and on the bottom. Sediment is also taken in and ejected from the gill slits or the mouth. The food is detected by the barbels which lightly touch the bottom as the sturgeon swims slowly along. The tubular mouth is protruded as soon as food is detected. Recorded food items are crayfish, other crustaceans, clams, snails, aquatic insects, fish eggs (such as those of Yellow Perch), algae and rarely fish. It is not considered to be a serious predator on the eggs of other fishes. Sturgeon may leap out of the water, a habit attributed to efforts to rid themselves of parasitic lampreys. 61 Silver Lampreys have been recorded on a single Lake Sturgeon, 1.3 m long and 16 kg in weight, caught in the St. Lawrence River, although these were not considered to be enough to kill the sturgeon.
Reproduction
Spawning occurs in April to June at 9-18°C in flowing water or rocky lake margins with wave action. In the Ottawa River at the Fitzroy-Quyon Rapids in 1949 the period was 29 May to 6 June at 56-60°F (10.0-15.6°C) (Harkness and Dymond, 1961). Sturgeon also spawn downstream from Chaudière Falls below Victoria Island in the heart of Ottawa (Haxton and Chubbock, 2002). Peak spawning in Lac des Chats was 12 June in 2006 and 5-15 June in 2007, and in Lac Deschênes was 4-8 June 2001, 4-12 June in 2003 and 8-14 June in 2004. Depths are usually 0.6-4.7 m for spawning generally. Lake populations may migrate up rivers for 400 km to reach spawning grounds although the distance traveled is usually less and fish are generally sedentary outside spawning. Males arrive first on the spawning grounds. The large female is in spawning condition for a short time and is flanked by up to 6 males. The spawning process may involve splashing, vibrations and leaps clear of the water. Eggs and sperm are shed at intervals over a few days and the eggs adhere to rocks. The spawning act lasts only 5 seconds. The eggs are black, up to 3.5 mm in diameter and in very large fish could exceed 3 million. Ottawa River fish produced up to 7179 eggs per pound of fish (Harkness and Dymond, 1961) or 54,000 eggs per kilogramme of ovary (Dubreuil and Cuerrier, 1950). Incubation lasts 5-8 days at 15.6-17.8°C. Spawning occurs at estimated intervals of 1-7 years in males and 4-9 years in females, with longer intervals in the north.
Importance
This species has been used historically for food fresh or smoked, the eggs as caviar, the swimbladder as isinglass (a form of gelatin) and skin as leather. Oil from sturgeon in the Ottawa River has been used by native peoples, mixed with ochre, to delimit pictographs at Oiseau Rock in western Pontiac County, Québec (www.cycloparcppj.org/oiseau/rocheroiseau_a.htm, downloaded 18 April 2005). Haxton (2002) reviews literature that show this species was abundant in the Ottawa River before 1900 and was harvested for food by aboriginal people (see also Gaffield (1997)). Dymond (1939) records catches from 1881 onward in the general vicinity of the NCR but trends cannot be determined as fisheries data is recorded from different areas at different dates. For example, in 1898 the catch was 63,450 lbs (28,806 kg) in the Ottawa River from Carillon to Pontiac in Québec, the highest recorded. Harkness and Dymond (1961) report past commercial fisheries in the Ottawa River and its lake-like expansions, and the Madawaska River and the Mississippi River and Lake (now absent from the latter two river basins). Commercial fisheries for sturgeons above and below Hull from the Québec side of the Ottawa River is documented by Pluritec (1982b). Fournier (1988) estimated that the fishery in the Hull-Carillon section of the Ottawa River yielded 0.7 kg/ha; Fortin et al. (1992) reporting a catch of about 10 tonnes by three fishermen in this sector. 94% of the catch was less than 27 years old, the age at which more than half the fish are mature. The section of river above Hull contained older fish and exploitation was less strong. The population was overexploited. Ontario Ministry of Natural Resources (OMNR) and Gouvernement du Québec Faune et Parcs (1999) report that a strictly controlled tag and quota system was to be implemented on the Ottawa River to ensure a sustainable harvest rate of 0.1 kg/ha/yr. Ontario fishermen are prohibited from harvesting sturgeon. Séguin (1970) mentions a request to open a commercial fishery on the Gatineau River but this apparently never developed.
Egan (2000) records a commercial harvest of this sturgeon on the Ottawa River as early as 1883 although this is from areas upriver of the NCR near Renfrew and Rolphton. The sturgeon were caught on longlines left overnight. the flesh was smoked, an oil and isinglass extracted, and caviar taken. Gutted sturgeon were sent in dry ice to New York City in the early 1950s and the roe was sent to a packer in North Bay. Today, although commercial fishing for this species is not allowed in the NCR the value of caviar elsewhere is $200/kg and flesh is $40/kg, and by 2006 $400/kg (Butler, 2006). The caviar is reputedly second only to that of Caspian Sea sturgeons.
Dams, pollution and overfishing have reduced populations in Canada. Populations in the Ottawa River were reduced by dam construction which blocks spawning, nursery and feeding migrations, fragments populations and alters habitats, by land clearance for agriculture and logging, by pollution from saw mills and untreated sewage, and by intensive commercial fishing at least in the past (Guénette et al., 1993; Ferguson and Duckworth, 1997; Haxton, 2002; Haxton and Findlay, 2008). Even blasting for a marina on the Ottawa River killed sturgeons around 1970. The Lac Dollards des Ormeaux stretch of the Ottawa River was closed to fishing for sturgeon in 1990 because of a decline in abundance and high contaminant levels (Haxton and Chubbock, 2002). On 1 July 2008 Ontario instituted a zero catch and possession limit on recreational fishing for sturgeon, except for traditional usage.
88,287 kg were caught in 1961 in Canadian waters but the Lake Erie catch alone in the late nineteenth century exceeded 2,268,000 kg. In the Québec portion of the St. Lawrence River commercial yields are very high, up to 3.4 kg/ha with 138.8 tonnes being taken in 1986. These stocks have been over-exploited. They are caught with gill nets, longlines with up to 600 hooks, and seines. One unexpected detrimental factor to sturgeon survival is discarded rubber bands used by Canada Post to bind mail. These are washed through storm sewers into the St. Lawrence River where they become threaded onto the pointed snouts of sturgeon grubbing in the mud for food. Out of 800 fish studied near Québec, 64 had elastic bands. The bands become embedded in the sturgeon's head, interfere with feeding and leave the fish open to infection. Sturgeon with bands weigh one-third less than normal.
It is not a major sport fish in Canada but large specimens are occasionally hooked or snagged to the great surprise of the angler. Some anglers do pursue this giant fish using minnows, meat or worms as bait or spinning gear and hand lines. Sturgeon fight strongly and may leap. There are catches of one sturgeon for every 4 hours fishing effort near Medicine Hat, Alberta. There are winter spear fisheries in the U.S.A. and they are caught through the ice at Petrie Island on the Ottawa River (local informant, 10 February 2007). The Ontario Ministry of Natural Resources publishes a print and on-line "Guide to Eating Ontario Sport Fish" (www.mnr.gov.on.ca/MNR/) and has advisory limits for eating this species in the Ottawa River. Environnement Québec also has recommended limits, in meals per month (1 to 8) for size of fish (small, medium or large), for such areas as Lac Deschênes at Aylmer and Quyon, Deschênes Rapids, the Ottawa River below Gatineau, above Hull, and at Masson, the Lièvre River above and below Buckingham and the Gatineau River at Chelsea, among others (www.menv.gouv.qc.ca, downloaded 13 October 2004). As these limits are apt to change, anglers consuming this fish should consult the most recent version.
This species was placed in the "Not at Risk" category in 1986 by the Committee on the Status of Endangered Wildlife in Canada (Houston, 1987) but is listed as threatened in Canada by Peterson et al. (2003).
© Brian W. Coad (www.briancoad.com)