156
J. Atkinson
balance between gravitational settling and background diffusion, or in response to
local resuspension (J.F. Atkinson and H. Rubin, in prep.). These layers most likely
playa significant role in the cycling of hydrophobic contaminants.
3.3 Fisheries and Aquaculture
The sport fishery industry has suffered greatly in the Great Lakes, due to loss of
stock, changes in the structure of the food chain, slowed growth in existing stock,
interference by nonindigenous species, and chemical contamination of game fish.
The commercial fishing industry has essentially disappeared. This is partly a result
of poor management and overfishing in early years. If fishing is to be brought
back as a viable resource in the Great Lakes, there needs to be a better
understanding of population dynamics, predator/prey interactions, and
reproduction and growth patterns, in order to evaluate different management
options such as stocking. There are obvious economic repercussions involved in
these kinds of decisions, and understanding the system in terms of food chain
dynamics or possible bioaccumulation of chemicals can only be attained through
development of comprehensive multidisciplinary models.
3.4 Invasive Species
The impacts of invasive species on native species and on the ecosystem as a whole
have been devastating. As noted previously, for instance, the sea lamprey played a
major role in decimating fish stocks in the middle of the previous century. Over
the years, there have been several hundred "invasions" by exotic species, some
with minimal effects and some with major consequences. The main species
receiving most attention currently is the zebra mussel. These freshwater mussels
colonize intake pipes and cause significant problems for water supplies, industries
and power plants that need to withdraw water from the lakes. Being extremely
efficient filter feeders, they have also significantly affected water clarity in the
lakes, and there is evidence that they are contributing to increased bioavailability
of PCBs for fish, particularly through the round goby, another invader. Zebra
mussels are very effectively altering the overall ecosystem food chain dynamics
and there is concern, for example, over the ability of the system to support a Great
Lakes fishery, due to lack of food at the base of the food chain (this is,
interestingly, the opposite problem of eutrophication, which is where lake
management issues began).
Concerns for other invasive species are summarized by Botts and Krushelnicki
(1995), among others. Recently, the question of importing potential bacterial
pathogens in the ballast water of ships also has been raised, and this may be the
next major management issue.
J. Atkinson
balance between gravitational settling and background diffusion, or in response to
local resuspension (J.F. Atkinson and H. Rubin, in prep.). These layers most likely
playa significant role in the cycling of hydrophobic contaminants.
3.3 Fisheries and Aquaculture
The sport fishery industry has suffered greatly in the Great Lakes, due to loss of
stock, changes in the structure of the food chain, slowed growth in existing stock,
interference by nonindigenous species, and chemical contamination of game fish.
The commercial fishing industry has essentially disappeared. This is partly a result
of poor management and overfishing in early years. If fishing is to be brought
back as a viable resource in the Great Lakes, there needs to be a better
understanding of population dynamics, predator/prey interactions, and
reproduction and growth patterns, in order to evaluate different management
options such as stocking. There are obvious economic repercussions involved in
these kinds of decisions, and understanding the system in terms of food chain
dynamics or possible bioaccumulation of chemicals can only be attained through
development of comprehensive multidisciplinary models.
3.4 Invasive Species
The impacts of invasive species on native species and on the ecosystem as a whole
have been devastating. As noted previously, for instance, the sea lamprey played a
major role in decimating fish stocks in the middle of the previous century. Over
the years, there have been several hundred "invasions" by exotic species, some
with minimal effects and some with major consequences. The main species
receiving most attention currently is the zebra mussel. These freshwater mussels
colonize intake pipes and cause significant problems for water supplies, industries
and power plants that need to withdraw water from the lakes. Being extremely
efficient filter feeders, they have also significantly affected water clarity in the
lakes, and there is evidence that they are contributing to increased bioavailability
of PCBs for fish, particularly through the round goby, another invader. Zebra
mussels are very effectively altering the overall ecosystem food chain dynamics
and there is concern, for example, over the ability of the system to support a Great
Lakes fishery, due to lack of food at the base of the food chain (this is,
interestingly, the opposite problem of eutrophication, which is where lake
management issues began).
Concerns for other invasive species are summarized by Botts and Krushelnicki
(1995), among others. Recently, the question of importing potential bacterial
pathogens in the ballast water of ships also has been raised, and this may be the
next major management issue.