Smallmouth Bass Invasion!

Source: Netawek Ikjikum Vol. 4 – Issue 4 March 2009
By N.B. CARDA Barry LaBillois

The Miramichi River is one of a few river systems that have very few predators, but, this longtime freedom took a different twist on September 26, 2008 when an angler caught a smallmouth bass on Miramichi Lake.

Miramichi lake is a 221 hectare headwater lake of the southwest Miramichi River system. To confirm the presence of smallmouth bass in the lake, the New Brunswick Department of Natural Resources conducted a survey of the lake on September 29 to October 3, 2009 using boat electro fishing equipment and gill nets. A total of five young-of-year bass were captured via electro-fishing and two bass of indeterminate age were captured in the gill nets. Using backpack electrofishing equipment, they examined selected sites on the Southwest Miramichi and the 5.3 km stream that connects Miramichi Lake to the Southwest Miramichi, named Lake Brook. Again, young-of-year, reported to be in “good condition” were discovered, though their distribution appeared to be limited to the first 300m downstream from Miramichi Lake.

Smallmouth bass are not native to the Miramichi River or even to the Province of New Brunswick. The smallmouth bass arrived in New Brunswick waters from Maine waters, through the St. Croix watershed in 1868. Smallmouth bass is not an endemic species in the Maritimes provinces but they are presently known to be in 188 lakes or rivers in Nova Scotia and 69 lakes and 34 rivers in New Brunswick.

When smallmouth bass are introduced into a water system, they prey heavily on smaller fish, and out-compete other fish species, and can become a dominate component of the food chain. Based on the surveys conducted in September and October, and the initial confinement procedures, it appears that smallmouth bass in Miramichi Lake are currently at low population densities, and that their distribution outside of the lake may be limited.

On January 27 & 28, 2009 a meeting took place at the Coastal Inn Champlain, Moncton, to discuss the potential impact of smallmouth bass introduction on Atlantic Salmon; The objectives of the meeting were: to review the historical distribution, biology, habitat requirements of and availability to smallmouth bass in the Maritime provinces, to examine evidence for negative interaction between Atlantic salmon and smallmouth bass, to conduct a risk analysis of smallmouth bass impacts on the ecosystem of the rivers of the Gulf Region, with a specific risk analysis of impacts to Atlantic salmon in the Miramichi River, and to evaluate options for and the effectiveness of mitigation measures for minimizing the risks associated with range extension of smallmouth bass. The risk analysis conducted followed the guidelines established by the Centre of Expertise for Aquatic Risk Assessment (CEARA) for assessing the biological risk of aquatic invasive species in Canada.

The overall risk to the aquatic biota for Miramichi lake is considered high with low uncertainty. The overall risk for Southwest Miramichi is considered to be moderate but with high uncertainty. A range of containment, control, eradication options, including their effectiveness and impacts on the ecosystem components were reviewed in the general context of non-native fish introductions and specifically for the Miramichi Lake.

The highest probability of controlling or eradication of non-native species is through the use of multiple approaches. The likelihood of controlling and/or eradicating smallmouth bass is reduced when actions are delayed which would give them the opportunity to become more widely dispersed.

The following is a chart of control measures:

smbchart

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