By Patrick Cooney
The disconnect of East and West was no longer so vast with the driving of the Golden Spike on the United States Transcontinental Railroad on May 10, 1869. Seth Green, an entrepreneur who is often credited with
Sunday, June 16, 2013
Monday, June 10, 2013
Doctor Fish: What seems to be the problem?
Monday, June 3, 2013
What can fish tell us about ecosystem health?
by Brandon Peoples
Chances are if you’re reading this post, I don’t have to convince you that clean water is important. We’re responsible to ourselves to maintain enough clean water to support our society. Most obviously, we must maintain water quality for human consumption. In addition, agencies are required to manage water quality to protect imperiled species and fishery resources.
So exactly how do we do that?
Chances are if you’re reading this post, I don’t have to convince you that clean water is important. We’re responsible to ourselves to maintain enough clean water to support our society. Most obviously, we must maintain water quality for human consumption. In addition, agencies are required to manage water quality to protect imperiled species and fishery resources.
So exactly how do we do that?
Tuesday, May 28, 2013
The Adipose Fin: Old Mysteries with New Answers
If you are a fish, your fins are obviously critical for making a living. Fins provide a long list of essential functions, from generation of movement to stabilization, turning, stopping, and dynamic lift (to name a few). Yet only select families of fish—namely trouts and salmons and catfishes—possess
Monday, May 20, 2013
Can you say Anadromous, Catadromous, Amphidromous, Oceanodromous, or Potamodromous?
By Patrick Cooney
Can you say 'potamodromous' and can you guess what it means?
A) A mood disorder caused by eating too many potatoes.
B) A dinosaur that lived in water but could crawl across land.
C) A migration of fish entirely in freshwater.
Can you say 'potamodromous' and can you guess what it means?
A) A mood disorder caused by eating too many potatoes.
B) A dinosaur that lived in water but could crawl across land.
C) A migration of fish entirely in freshwater.
A)
B)
C) 
B)
C) 
Monday, May 13, 2013
Hypoxia
"Currently, hypoxia and anoxia are among the most widespread deleterious anthropogenic influences on estuarine and marine environments, and now rank with overfishing, habitat loss, and harmful algal blooms as major global environmental problems." Diaz et al. 2008
We increasingly hear these terms on the news every summer—so what is going on in our estuaries? The main cause of various problems in our waters is hypoxia, or reduction in dissolved oxygen in the water, which is generally defined as dissolved oxygen levels below 2 mg/L. However, complications to fish and aquatic life often begin at levels below 4 mg/L. An escalation of hypoxic events and durations has been seen around the U.S. in the past decade.
Although fish don’t breathe as humans do with lungs and air, they still take in oxygen from the water as it goes over their gills. Reduction in oxygen in the water is similar to what hikers experience at high altitudes where the reduced oxygen air is considered "thin." Just as we humans would get short of breath, tired, and less active, fish experience the same type of problems when oxygen is depleted from their waters.
So what causes hypoxia in rivers, bays, estuaries, and oceans? The short answer is that as excess nutrients enter these systems, large amounts of aquatic plants and algal blooms (some toxic) quickly develop. Although this may seem like a good thing—extra plants, production, food!—this extra organic matter dies and sinks to the bottom of the systems. The subsequent decaying processes drain oxygen from the waters creating hypoxic conditions that are not quickly alleviated. Excess nutrients come from many sources, although fertilizer and waste runoff from agricultural lands has traditionally been the main point source. However, as populations grow and urbanization increases, non-point sources of nutrients are growing. Increased impervious surfaces send water (and all nutrients collected in that water) directly into rivers instead of waters filtering through the ground. In pursuit of a picture perfect green lawn excess fertilizer is washed into the watershed. This might not seem like that much of an increase, but when you multiply that by the hundreds of thousands of yards in a watershed, a lot of fertilizer is making its way to our estuaries.
Fish kills are a highly visible consequence of hypoxia, but these events are relatively rare compared the widespread non-lethal hypoxic conditions that occur. Fishes can generally detect and avoid hypoxic waters, but doing so causes other problems for the fishes. To avoid hypoxic waters a fish must expend extra energy swimming and finding appropriate habitat. If an oxygenated refuge is found fish must then compete in these smaller areas for space and limited food resources. My work with fish distribution during hypoxic episodes showed a two-fold increase in fish densities in refuges and a reduction in stomach fullness of juvenile spot (Leiostomus xanthurus). Many times larger predators are also pushed into compacted refuges increasing encounter rates and mortality for juvenile fishes.
Beyond immediate impacts of hypoxia in fishes, some of my recent work shows that fish in areas with numerous recent hypoxic events had a reduction in short-term growth rates by almost 50% than fish in the same areas after periods of no hypoxic events.
Although fish may have successful avoidance strategies to reduce immediate death from hypoxia, they still pay a price. And reduction in growth can result in higher mortalities, less over-winter survivability, and decreased biomass production of the fishery. Wu (2009) found that fish exposed to hypoxia had reduced reproductive abilities, thus hypoxia of today effects fish generations of tomorrow. These are just a few of the far reaching consequences of hypoxia, as further and prolonged hypoxia fundamentally changes an ecosystem and alters physical, chemical, and biological structures.
Hypoxia is a serious problem, but making changes in our water systems can lead to improvements in the oxygen levels, if we act now.
What can be done to help:
Water Keepers with chapters across the US
Bays and Estuary foundations
Mississippi River Gulf of Mexico Watershed Nurtrient Task Force
Further reading:
An Assessment of Coastal Hypoxia and Eutrophication in U.S Waters
Spreading Dead Zones and Consequences for Marine Ecosystems. Diaz et al., 2008, Science 321, 926.
Effects of Hypoxia on Fish Reproduction and Development. RS Wu, 2009, In Hypoxia. Fish Physiology Volume 27, pages 79-141.
http://www.esa.org/education/edupdfs/hypoxia.pdf
http://www.whitehouse.gov/sites/default/files/microsites/ostp/hypoxia-report.pdf
 |
| Fish killed by hypoxic events. (Source: EPA) |
The Dead Zone. Fish kills. Hypoxia.
We increasingly hear these terms on the news every summer—so what is going on in our estuaries? The main cause of various problems in our waters is hypoxia, or reduction in dissolved oxygen in the water, which is generally defined as dissolved oxygen levels below 2 mg/L. However, complications to fish and aquatic life often begin at levels below 4 mg/L. An escalation of hypoxic events and durations has been seen around the U.S. in the past decade.
Although fish don’t breathe as humans do with lungs and air, they still take in oxygen from the water as it goes over their gills. Reduction in oxygen in the water is similar to what hikers experience at high altitudes where the reduced oxygen air is considered "thin." Just as we humans would get short of breath, tired, and less active, fish experience the same type of problems when oxygen is depleted from their waters.
So what causes hypoxia in rivers, bays, estuaries, and oceans? The short answer is that as excess nutrients enter these systems, large amounts of aquatic plants and algal blooms (some toxic) quickly develop. Although this may seem like a good thing—extra plants, production, food!—this extra organic matter dies and sinks to the bottom of the systems. The subsequent decaying processes drain oxygen from the waters creating hypoxic conditions that are not quickly alleviated. Excess nutrients come from many sources, although fertilizer and waste runoff from agricultural lands has traditionally been the main point source. However, as populations grow and urbanization increases, non-point sources of nutrients are growing. Increased impervious surfaces send water (and all nutrients collected in that water) directly into rivers instead of waters filtering through the ground. In pursuit of a picture perfect green lawn excess fertilizer is washed into the watershed. This might not seem like that much of an increase, but when you multiply that by the hundreds of thousands of yards in a watershed, a lot of fertilizer is making its way to our estuaries.
Fish kills are a highly visible consequence of hypoxia, but these events are relatively rare compared the widespread non-lethal hypoxic conditions that occur. Fishes can generally detect and avoid hypoxic waters, but doing so causes other problems for the fishes. To avoid hypoxic waters a fish must expend extra energy swimming and finding appropriate habitat. If an oxygenated refuge is found fish must then compete in these smaller areas for space and limited food resources. My work with fish distribution during hypoxic episodes showed a two-fold increase in fish densities in refuges and a reduction in stomach fullness of juvenile spot (Leiostomus xanthurus). Many times larger predators are also pushed into compacted refuges increasing encounter rates and mortality for juvenile fishes.
 |
| Fish compacted in nearshore surface waters during hypoxic event in the Neuse River Estuary 2007. (Photo: Geoff Bell) |
Beyond immediate impacts of hypoxia in fishes, some of my recent work shows that fish in areas with numerous recent hypoxic events had a reduction in short-term growth rates by almost 50% than fish in the same areas after periods of no hypoxic events.
Although fish may have successful avoidance strategies to reduce immediate death from hypoxia, they still pay a price. And reduction in growth can result in higher mortalities, less over-winter survivability, and decreased biomass production of the fishery. Wu (2009) found that fish exposed to hypoxia had reduced reproductive abilities, thus hypoxia of today effects fish generations of tomorrow. These are just a few of the far reaching consequences of hypoxia, as further and prolonged hypoxia fundamentally changes an ecosystem and alters physical, chemical, and biological structures.
Hypoxia is a serious problem, but making changes in our water systems can lead to improvements in the oxygen levels, if we act now.
What can be done to help:
- Minimize use of fertilizers on lawns and also encourage farmers to use practices that reduce over-fertilization
- Reduce and remove nutrients from waste water and urban runoff before they wash into the watershed
- Preserve land around streams, rivers, and marshes to help filter nutrients before they get into waters
- Find out what law makers in your state are doing about excess nutrient inputs into the water system
Water Keepers with chapters across the US
Bays and Estuary foundations
Mississippi River Gulf of Mexico Watershed Nurtrient Task Force
Further reading:
An Assessment of Coastal Hypoxia and Eutrophication in U.S Waters
Spreading Dead Zones and Consequences for Marine Ecosystems. Diaz et al., 2008, Science 321, 926.
Effects of Hypoxia on Fish Reproduction and Development. RS Wu, 2009, In Hypoxia. Fish Physiology Volume 27, pages 79-141.
http://www.esa.org/education/edupdfs/hypoxia.pdf
http://www.whitehouse.gov/sites/default/files/microsites/ostp/hypoxia-report.pdf
Monday, May 6, 2013
Why fishes need floods
In April of 2011, the river near my house was bigger than I had ever seen it. One afternoon I went to get a closer look at the flooding at a park near the dam. Although the park sat more than 20 feet higher than the normal river’s edge, water stood where children had played a few days before. As I watched luxury boats and floating docks bang against the dam, several loud splashes near the monkey bars caught my eye. A group of longnose gar was laying eggs on a patch of grass near the edge of the park!
Last week’s post focused on man’s success at reducing
Last week’s post focused on man’s success at reducing
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