Ontario Ministry of Natural Resources
Lake Superior Management Unit

Lake Sturgeon in Lake Superior

Background
Historically, lake sturgeon occurred in most of the larger Canadian tributaries of Lake Superior (Goodier 1982). Lake Superior stocks were decimated during the development of the commercial fishery in the early part of the 19th century (Goodier 1982). Initially, low commercial value of lake sturgeon, coupled with the tendency of fish to destroy fishing nets, prompted most fishermen to regard lake sturgeon as a nuisance that should be removed and eliminated (Scott and Crossman 1973; Brousseau 1987). However, by 1860, lake sturgeon began to command high prices and fishermen targeted the species, hastening their decline. The construction of dams blocking access to traditional spawning grounds, log drives in large rivers and streams causing scouring of the bottom or littering of substrates with bark, shoreline development, dredging of river channels for shipping purposes, and the effects of pollution also impacted lake sturgeon populations.

Current Regulations
Currently, commercial harvest of lake sturgeon in the Canadian waters of Lake Superior is prohibited. First Nations are allowed to take lake sturgeon for subsistence and ceremonial reasons, although the extent of this fishery has not been documented. The Lake Superior recreational fishery is limited only by a one day closure (December 24th) and a one fish a day catch limit with no length restrictions. In Lake Superior tributaries, minimum length limits (114 cm) exist for the area between the Pigeon River international border east to and including the Nipigon River. Within this same area, the season is closed from May 15th to June 30th. Lake sturgeon angling is closed in all other Lake Superior tributaries from May 14th to June 15th (east of the Nipigon River to Sault Ste. Marie) although no length restrictions apply.

Lake Superior Management Unit: Lake Sturgeon Activities

Introduction
In 1994 the Lake Sturgeon Subcommittee was formed and was charged with describing the current status of lake sturgeon (Ancipenser fulvescens) in Lake Superior and developing a rehabilitation plan for lake sturgeon in the lake.

In Ontario, seven tributaries to Lake Superior are known to support self-sustaining populations of lake sturgeon. These tributaries include the Big Pic, Black Sturgeon, Goulais, Gravel, Kaministiquia, Michipicoten and Nipigon Rivers.

Goal For Restoration
The overall goal for lake sturgeon rehabilitation in Lake Superior is to maintain, enhance and rehabilitate self-sustaining populations where the species occurred basin wide. To facilitate this goal, baseline information was required into the population status of lake sturgeon in historic spawning streams.

In 1998, the Lake Superior Management Unit initiated field surveys of three Canadian Lake Superior tributaries: the Kaministiquia, Nipigon and Black Sturgeon rivers. The purpose of the study was to collect baseline information and define areas of habitat utilization for lake sturgeon.

Methods
The presence of lake sturgeon was determined through gill netting from April 27-June 23, 1998. Netting gear consisted of single, monofilament gillnet panels in a variety of lengths. Nets consisted primarily of 216 (8.5") and 241 (9.5") mm stretched mesh monofilament nets. Additional nets utilized included 254 (10") and 305 (12") mm multifilament nets 100 yards long and one 305 (12") and one 381 (15") mm net, each 50 yards long. All captured lake sturgeon were sampled for fork and total length, girth, weight (when possible) and sex (when possible) and were tagged with both a disc tag and an anchor tag applied anterior to the dorsal fin. Aging structures were collected from only four fish due to rapidly rising water temperatures, which increased the risk of infection.

Study Areas
The Kaministiquia River is one of the largest tributaries of western Lake Superior. Fish are able to migrate approximately 47 km upstream before encountering Kakabeka falls, a natural 39.0m waterfall. This majority of the river is deep and meandering, with a slow base gradient and an average depth of 2.5m. Upstream power dams control the flow of the river.

The Nipigon River provides the largest discharge into Lake Superior. Alexander Dam, approximately 9.0 km upstream from the river’s entrance into Lake Helen, is a barrier to upstream migration.


A Nipigon River Lake Sturgeon

The Black Sturgeon River is narrower than the Nipigon and Kaministiquia rivers and is comprised of two distinct sections. The majority of the lower river (9.0 km) below the Trans-Canada Highway is comprised of a slow, deep (4.0m) channel of silt and sand. Above this, the river consists of a stretch approximately 5.2 km in length, comprised of a pool-riffle complex containing large amounts of cobble and gravel. Approximately 1.0 km above the highway the river again changes from a pool-riffle complex to a slow moving section. The camp 42 Dam is approximately 2.1 km upstream of the highway and prevents all upstream migration of fish.

Results
Excluding recaptures, a total of 58 lake sturgeon were caught in the Kaministiquia (n=54), Nipigon (n=2) and Black Sturgeon (n=2) rivers, tagged and released (Table 1).

Table 1: Study dates, number of netting days and number of fish captured in three Lake Superior tributaries in 1998. Recaptured fish are not included in the total number of fish captured.

River

Study Dates

Number of netting days

Number of fish captured

Kaministiquia

Early - April 27-May 15
Late - June 22-23

13
1

53
1

Nipigon

May 25-30

4

2

Black Sturgeon

Lower - June 8-12
Upper - June 15-17

4
2

1
1

Total Length Distribution
Mean total length of lake sturgeon captured in large mesh nets from the Kaministiquia River was 120.1 cm (n=54) (Fig. 1). Total length distribution suggests a normal distribution of sizes. Mean total lengths of lake sturgeon from the Black Sturgeon and Nipigon River were not meaningful since only 2 fish were netted in each river.


Total length frequency distribution for lake sturgeon captured in the Kaministiquia River, Ontario, 1998.

Movements
Based on the recapture of tagged fish, lake sturgeon in the Kaministiquia River did not exhibit any discernible movement patterns. Ten of the fish tagged in the Kaministiquia River were recaptured once and one fish was recaptured twice. Two fish exhibited upstream movements of over 6.0 km. Three fish exhibited smaller upstream movements of approximately 1.0 km. Five lake sturgeon moved an average of 5.9 km downstream and a single fish moved 6.1 km downstream, was recaptured, and then moved back upstream and was recaptured at the original tagging site. A single lake sturgeon, tagged in the Kaministiquia River in 1987 (Cullis et al. 1988), was also captured during this study. The fish was originally tagged at km 9 of the river and was recaptured at km 12. This fish was sampled, re-tagged and released.

Nipigon River lake sturgeon did not exhibit any interpretable movement as both fish were recaptured the day after tagging in the same location. Neither of the two lake sturgeon caught on the Black Sturgeon River were recaptured.

Population Estimates
Population estimates were not made for the Black Sturgeon or Nipigon rivers due to small sample sizes. Based on recaptures in the Kaministiquia River, a Schumacher-Eshmeyer estimate of population size suggested there were 140 lake sturgeon in the examined area. The 95% confidence intervals for this estimate ranged from 77-234 fish. This estimate is applicable only to fish susceptible to capture in the large mesh gill nets used during the study. Because the study concentrated on a nine km stretch of the river, this estimate suggests an approximate population of over 15 adult lake sturgeon per km in 1998 during the spring period. The population estimate suggests densities of approximately 1.2 fish per ha in the lower reaches to 5.0 fish per ha in the upper reaches.

Future Projects
The Lake Superior Management Unit is undertaking a lake sturgeon radio telemetry study on the Kaministiquia River with the following objectives:

This project involves capturing adult lake sturgeon using large mesh gill nets and surgically implanting radio tags, with trailing whip antennae, into the body cavity. The whip antenna is externalized through a separate incision posterior to the main incision. Radio tags will be monitored by boat using a programmable scanning receiver and a hand held antenna. A land based, automatic data logging station will also be situated along the river to provide continuous logging of movements. The duration of the study is approximately three years.

 

 


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