Download Contaminants in Eels

Introduction to Toxicology
EV 460/660 & BI 460/660
Fall 2014
Contaminants in Freshwater Eel Flesh
Presented by Andrew Bueltmann
I. Introduction
A. American Eel Biology
1. Panmictic species: Randomly mate within breeding population
2. Semelparous: die after reproduction event
3. Facultative Catadromous: hatch in saltwater, grow in freshwater, return to saltwater
to spawn
B. American Eel Life Cycle
1. Hatch in Sargasso Sea as leptocephali larvae (leaf-like in shape and transparent)
-drift along oceanic current until reach coast
2. Metamorphose into glass eel (eel like in shape and retain transparency)
3. Acquire pigment and become elvers when in estuarine environment
4. Become yellow eels (growing stage)
-either grow in estuaries or move further into freshwater
5. Become silver eels (maturation is reached)
-migrate back to Sargasso Sea to spawn and die
C. American Eel Range
1. Vast range from the northern tip of South America up North America towards the
southern portion of Greenland.
D. American Eel Population Status
1. Most States seem to support stable populations; however, data indicates population
declines
E. Factors thought to negatively influence population
1. Habitat degradation (i.e. damming, leveeing, and other river training structures)
2. Overharvest
3. Climate Change
4. Water Pollution
II. Water Pollution
A. One of the most hazardous effects on the ecosystem
B. Main causing factor are industries
1. Sewage
2. Agriculture runoff
3. Litter
C. How chemicals are absorbed
1. Mostly via passive molecular diffusion
2. Once absorbed tend to bioaccumulate and then biomagnifies within the food chain
D. Mostly accumulates in the flesh
1. Flesh is mostly what is consumed by humans
2. Important source of omega 3 fatty acids which:
- Decrease triglycerides
- Lower blood pressure
- Reduce blood clotting
E. However, flesh is where most contaminants are concentrated
III. Two types of contaminants found in eel flesh
A. Polychlorinated biphenyls (PCBs)
1. Synthetic chemical compound
-manufactured from 1929-1979 (banned)
-many different forms
- ~30% of 1 million tons may still be present in the ecosystem
B. Effects on Eel
1. Impair larval survival
-PCBs are passed on through the embryo from the mother
2. Impaired reproduction
-reduces retinoid and thyroid hormone amounts (needed for early d
evelopment)
C. Effects on humans (according to EPA)
1. Probable human carcinogens
- Rare liver cancers and malignant melanoma in PCB workers
2. Immune Effects
- Decrease in thymus gland size
3. Reproductive Effects
- Decreased birth weight
D. Fish Advisory
1. Suggests eels containing PCBs to only be consumed once a month depending on
water body
E. Methylmercury
1. Organic form of mercury formed when mercury binds to organic compounds
- Thermometers
- Minerals (coal)
2. Methylmercury-containing bacteria may be consumed by the next higher level in the
food chain
3. Released methylmercury in water can be quickly absorbed by plankton Krabbenhoft
and Rickert, 2009
D. Mercury
1. Still Used today
2. Natural Element found in minerals and manmade items
- Minerals including coal
- Manmade
- Thermostat
- Light bulbs
3. Many different effects on Eel
- Reduced Fecundity
- Death
E. Methylmercury Human Effects
1. Neurological
- Adverse effect on a baby’s growing brain and nervous system
2. Impacts on:
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Cognitive thinking
Memory
Attention
Language
Motor and visual spatial skills
IV. Next Step
A. Sample Eels using 2 gear types
1. Electrofishing
2. Slat Traps
B. Collect Water Quality Data
1. Conductivity
2. Temperature
3. Velocity
4. pH
C. Data Collection
1. Weight
2. Length
3. Otoliths
4. Organs
- Kidneys
- Livers
5. Blood Samples
D. Expected Results
1. Low to moderate levels of PCBs and Methylmercury
- Fluctuate drastically based on size
2. At least trace amounts of both in all fish
V. Conclusion
- Freshwater eel populations are declining
- Water Pollution may be playing a role in the decline
- Eel flesh does contain PCBs and Methylmercury
- Both contaminants may have adverse effects on fish and humans
- Knowledge gap between species may be filled with future study
QUESTIONS
1. Why is it important to understand basic eel biology and life cycle when wanting to understand adverse toxic
effects?
2. Name two types of contaminants found in eel flesh
3. How is Methylmercury formed?
4. How does inorganic mercury enter into waterways?
5. Name an adverse effect of PCBs on eels