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Figure 1.1 Alien Species Introductions
To adequately address a problem with invasive species, a plan should need to be strategized to assess the threat level of an invasive species, choose a method with the least amount of environmental degradation, and ultimately, what can be done to restore a healthy ecosystem. Wittenberg suggests (Figure 1.1) that there are four significant options when approaching these species: prevention, early detection, eradication, and control.
Prevention, of course, is the first method of choice as well as the most cost-effective. If an invasion occurs and is detected early, there can be measures taken, so it does not progress in the process of becoming an alien. There can be laws and regulations, the prohibition of a particular area, or community education efforts to seize the population of the species. Once the population becomes large enough, prevention is no longer plausible, and there will need to be an implementation of an eradication process. These processes are more of a challenge, more extended, and more expensive. Besides, there is not a guarantee that the eradication effort will have a likely outcome.
When the species becomes non-preventable, and eradication is difficult or too expensive, the last step is control and management. The goal is to reduce the abundance and density of an invasive to keep it far below the acceptable threshold. The descriptions of the most popular methods for marine invasive control and management are below.
Chemical Control
Chemical Control
This process includes chemicals that include herbicides and insecticides. These have been developed to meet the markets for control of pests and the elimination of disease vectors. Past case studies have shown that chemical control is a quick way to decrease invasive populations below a threshold of ecologically sustainable impact. In the past, this process has known to cause unexpected damage such as the killing of non targeted species and long-lasting impacts on the environment and possibly humans. Today, there are more specific products on the market with fewer adverse non-target effects. A drawback to this is the cost of development, testing, and registration of a new compound.
Example: Using fish poison rotenone to control fish populations in ponds and other small bodies of water
Biological Control
Biological Control
This type of control uses natural enemy populations or naturally synthesized substances against alien species to contain pest populations. The aim is not to eradicate, instead, reduce the invasive's competitiveness with natives. In a successful biological control program, the invasive population will shrink to an acceptable level. However, the populations of both the prey + host and predator + parasitoid will remain present in balance. Also, biopesticides can be used, such as bacteria, viruses, and protozoa. The main disadvantages of this are the level of control of the natural enemy as well as the effects they have on non-target species.
Example: Introducing natural enemies to reduce the populations of water weeds
Mechanical Control
Mechanical Control
This method is one of the most cost-effective and can be carried out by individually removing the target species by hand or by using specialized tools. This method is ideal for the control or possible eradication of small-scale infestations. A more advanced method would be the use of a machine to harvest or remove the target species. Mechanical control is highly labor-intensive, which is a considerable cost, which is why volunteer groups complete most efforts.
Example: Handpicking aquatic snails from a tidal zone.
Habitat Management
Habitat Management
As human disturbances cause most invasions, it is a possibility that achieved improvements are by the changes in the human behavior that caused them, such as changing abiotic factors or hunting. In terms of marine aliens, a change in the number of nutrients or water available for plants could alter the plant community. Also, the consumption of marine species can help reduce the population substantially. However, the possibility of exported invasives as a food source creates the chance for them to become introduced to another area.
Example: Improving the water quality and addressing eutrophication to control invasive aquatic organisms
Education
Education
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