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Species Introduction

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Species Introduction Species Introduction Teacher’s Instructions: 1) Have students read the background information about species introduction in the General Background’. - they may take turns to read it out loud if you choose - after each “section” of reading, ask if they can think of other examples (for instance, ask them to think of other effects of introduced species) and add to their notes - some examples have been provided for you - to add to reasons why species are introduced: - to try save a species from extinction - to give a species a better chance of survival - to provide prey for predators - to add to the effects of introduced species: - harmful to humans - added competition to other species - added predation to other species - spreads disease - other species that have been introduced to Manitoba: - domestic dogs - wild turkeys - domestic pigs - carp 2) Have them read the Rainbow Smelt Background and answer the questions in the following assignment. 3) Correct the assignment as a group. 4) Work as a class to develop a set of notes on the general consequences of introducing species to an ecosystem. - have students tell you their generalizations - post them on the board to prevent repetition - have the class add to the General Background notes if need be 1 of 7 Species Introduction Objective: - to discuss the potential consequences of introducing new species to an ecosystem Tasks: - read the General Background information on species introduction - research rainbow smelt (a species that has been introduced in Manitoba) - complete the following assignment - develop a set of notes with the rest of the class about the consequences of species introduction Key Terms: - biodiversity: the number and variety of organisms living in a certain area - sustainability: to keep in existence, to maintain - domestic: tame; not wild - opportunistic: taking advantage of anything that has possible benefit - contaminants: impurities, poisons, pollution, etc. - biomagnification: increase in concentration of a pollutant from one link in a food chain to another (as you move up the food chain the concentration of pollutants increases) - trophic: feeding level - enzyme: proteins that act as catalysts in reactions - catalysts: increase the rate of a reaction but is not consumed during the process - trawl: a large net that is dragged at the bottom of an ocean or lake - gill net: a net that is set in the water, it is stationary and fish that swim into it are caught - implemented: put into effect General Background: In any given habitat there are many organisms. Some of these organisms may be classified as native species and some may be classified as exotic species. Native species are organisms which occur naturally in a specific location. Exotic species are organisms that have been introduced to a certain location. There are many reasons for introducing species to a habitat. Some of these reasons include: - to help control over-grown populations or nuisance species (introduce a predator) - reduce crowding (re-locate some species) - for human use (to consume or gain a profit) - to increase the biodiversity of an ecosystem (to increase it’s sustainability) - to “beautify” an environment (whether appropriate or not) - accidental release or introduction (not on purpose) 2 of 7 Species Introduction Species introduction can have both positive and negative effects. For instance: - prey populations can be controlled with the introduction of predators and this may prevent disease and stress in that population - humans can use the species for profit - the sustainability of an ecosystem can be increased - ecosystems can suffer if the population of introduced species is not controlled - food chains can become disrupted - resources can be depleted Many species have been introduced into Manitoba. The following are a few examples. - domestic cats (introduced several hundred years ago) - wild boars (native to Europe and Asia) - domestic horses (from Spain, introduced in the 16th century) - cattle (from India, introduced in the 16th century) - purple loosestrife (native to Eurasia, introduced in the 1880’s) - carp (introduced around 1938) - rainbow smelt (introduced in 1991) 3 of 7 Species Introduction Rainbow Smelt Background: Rainbow smelt are small fish, 15 to 20 centimeters long, that look similar to a tullibee. They are very narrow, silver in colour, and have long teeth, some of which are on the tongue. Smelt are invaders in Manitoba and are not welcome because of the damage they may do to native fish populations. They have been found in Lake Winnipeg. They may have migrated naturally through river systems from Ontario, or may have been introduced by accident as live bait. Rainbow smelt is native to the eastern coast of North America They usually feed on zooplankton, crustaceans, insects and fish. However, they are also known to be opportunistic feeders and will select the largest and most abundant food items available (Remnant, R., 1991). This means that they will eat almost anything they can get. In 1991, rainbow smelt were found in Lake Winnipeg, Manitoba. Rainbow smelt are very aggressive and have the potential to affect the ecosystem and fishing industry of Lake Winnipeg. For instance, smelt could cause changes in the structure of Lake Winnipeg. Rainbow smelt could disrupt the existing food chains as they can be considered prey, predators, and competitors. In Lake Winnipeg, many fish such as lake trout, northern pike, whitefish, yellow perch, and walleye could consume rainbow smelt. As such, these fish may contain higher concentrations of contaminants such as mercury. This would occur because smelt feed at a higher trophic position and biomagnification increases with higher trophic positions. (Johnston, T., 2001). Fish that eat smelt could experience “belly burn”. Smelt contain an enzyme that causes the stomachs of their predators to decompose quickly. Due to this, it is necessary for fishers to process these fish such as walleye more quickly. It has also been found that fish that prey on smelt have a higher fat content. This means that even though these fish may be large, they do not contain more meat or protein. Although smelt could increase biomagnification significantly, they may help the growth and survival rate of walleye (Lamont, D., 2003) Smelt are very high in protein and thus walleye would grow quicker and live longer on a diet of smelt. Nonetheless, smelt could also cause the reduction in growth and elimination of native species (Franzin., W., et. al., 1994). They would then be a theat to sport and commercial fisheries. Lake whitefish, a native species to Lake Winnipeg, would probably be affected the most by rainbow smelt. The population would decrease as smelt prey on larval whitefish. Also, smelt would compete with whitefish for food and space. (Franzin, W., et. al., 1994). This decline in whitefish stocks will result in a reduced commercial harvest of them. This will probably result in an economic loss to commercial fishermen. rainbow smelt 4 of 7 Species Introduction Rainbow smelt may also compete for food with the larvae of some fish. Adult rainbow smelt compete for the same food as larval cisco. Both of these species feed on plankton and smelt may reduce the number of larger plankton species found in Lake Winnipeg (Wain, D., 1993). And while some potential may exist for commercial fishing of rainbow smelt in Lake Winnipeg, they are not as valuable as native species commercially. So, more would have to be caught. Smelt are best caught using trawls and fishers on Lake Winnipeg are set up with gill nets. Further, Lake Winnipeg may not be suitable for trawling as it may be too shallow (Derksen, A., 1990). As smelt colonize in Lake Winnipeg, there would also exist the potential to develop an intensive smelt sport fishery. Sport fisheries for rainbow smelt have been developed on Lake Erie (Remnant, R., 1991). Some regulations have been implemented in order to help prevent the spread and colonization of rainbow smelt. For example, it is illegal to use live or fresh rainbow smelt as bait in Manitoba. Only smelt that has been previously frozen may be used. In conclusion, it seems that the introduction of rainbow smelt would have many negative effects on Lake Winnipeg and only a few beneficial ones. Smelt can cause the reduction and elimination of native species. They can also be responsible for a decline in the Lake Winnipeg fishing economy and increase biomagnification of contaminants in their predators. However, smelt may increase the growth and life span of walleye and there may exist the potential to develop sport or commercial fishing for them. Overall, they are not welcome in Manitoba and regulations have been put in place to help stop the spread of rainbow smelt. References: Derksen, A., (1990). Rainbow Smelt: Manitoba’s Newest Fish Species and its Implications to Fisheries Resources. Franzin, W., Barton, B., Remnant, R., Wain, D., Pagel, S., (1994). Range Extension, Present and Potential Distribution, and Possible Effects of Rainbow Smelt in Hudson Bay Drainage Waters of Northwestern Ontario, Manitoba, and Minnesota. South American Journal of Fisheries Management, 14, 65-76. Johnston, T., (2001). Rainbow Smelt Invasion and Mercury Dynamics in Boreal Lakes. http://biology.queensu.ca/~johnston/Smelt.html. Lamont, D., (2003) Trophy Walleye of Lake Winnipeg. http://www.completeangler.net/destination02.html. Remnant, R., (1991). An Assessment of the Potential Impact of the Rainbow Smelt on the Fishery Resources of Lake Winnipeg. Natural Resources Institute.
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