Potential Impacts of Harvest and Use of Baitfishes

THE BAITFISH PRIMER

Harvesting may impact the ecosystems from which baitfishes are taken (termed donor ecosystems) and the ecosystems into which baitfishes are released (termed recipient ecosystems).

Impacts on donor ecosystems

Since the early 1900s, there were concerns regarding the depletion of the baitfish supply, followed by concerns about the declining numbers of sportfishes as a result of forage fish depletion. If carried out carelessly, baitfish harvesting may directly alter the abundance of targeted (legal baitfishes) and non-targeted (illegal baitfishes) species in the donor ecosystem. Removal of a substantial number of legal baitfishes could potentially have shortand long-term effects on the abundance of forage fishes. To minimize such impacts, bait harvest areas are assigned to specific licensees who manage the resource for sustainability. Commercial bait harvesters accomplish this by cycling harvesting locations within their bait harvest area, so that no one location is overharvested. Resident anglers should follow this practice as well.

Care should be taken to safely return non-targeted species (other than invasive fishes) to the water immediately. If nontargeted species are not immediately returned, these populations could suffer an increased mortality, which may alter species interactions within that ecosystem. Such alterations may result in changes in species composition, increases in invertebrate (e.g., crayfishes) size and abundance, and decreases in productivity, abundance and growth rates of other fish species (including sportfishes).

The techniques used to harvest baitfishes may impact the habitat that all aquatic organisms (including baitfishes) depend on for the necessities of life. Baitfishes are typically harvested using seine nets or traps. Seining has greater impacts on habitat, as it is an active method that may cause uprooting of aquatic vegetation, removal of woody debris and disturbance of bottom substrates - all important habitat components required by aquatic organisms for survival.

Traps leave a smaller ecological footprint. This technique is more passive, resulting in little disturbance to the surrounding habitat. Many commercial bait harvesters use traps, especially in vegetated areas. Traps and dipnets (which also have minimal impacts) are the only harvesting methods allowed to be used by resident anglers.

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Impacts on recipient ecosystems

The impacts of fishes (baitfishes and other species) illegally released into recipient ecosystems have been well documented and can be summarized in four categories.

1.Food web changes

Introduced species have been shown to negatively impact food webs - the links between predators (e.g. sportfishes) and prey (e.g. baitfishes). Introduced fishes, such as the Round Goby, can out-compete native species for food and other resources, or even prey on native species and their eggs.

These impacts may reduce the abundance of native prey that would, in turn, reduce the abundance of the sportfishes dependent upon these prey species for food.

2. Habitat changes

The behaviour of introduced species can cause changes to habitat. For example, the destruction of aquatic vegetation and increased turbidity caused by the feeding and the spawning of the Common Carp is well documented. Native species relying on that habitat would be greatly impacted by such changes.

3. Introduction of disease

Diseases and parasites, may be transferred to native species through introduced species. Exposure to these diseases or parasites may lead to decreased abundance of native species. The spread of “whirling disease” from stocked trout to wild trout is an example of this problem. The spread of disease may occur through baitfish transfer; however, the extent and impact of such transfers is not well understood.

4. Genetic impacts

Native species are well adapted to their environment. Introduced individuals, not adapted to their new environment, may spawn with native individuals of the same species. Their offspring may look the same, but be less adapted to their environment. Introduced individuals may also spawn with native individuals of closely related species. Their offspring, termed hybrids, may be less adapted to their environment, or may become infertile. In most cases, spawning between introduced and native species will lead to the decreased abundance of native species.

These impacts are not limited to introduced baitfishes. Bait bucket water may also carry microscopic invasive species, such as spiny waterflea, fish hook waterflea, and zebra mussel larvae. These invasive species also have harmful impacts on our aquatic ecosystems.

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