Questions and Answers
What is overharvesting?
What is the current estimated population of Northern Elephant seals?
over 100,000
The annual catch falls below 10% of historic high is known as a _____.
collapsed fishery
Bycatch occurs when trawling damages the benthic zone, causing loss of habitat for both target and non-target species.
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What does 'fishing down the food chain' mean?
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Which of the following is a long-lived fish species susceptible to overfishing?
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_____ is the number 1 threat to oyster ecosystems.
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What are some negative effects of overharvesting?
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Which method of harvesting oysters is considered bad?
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How do oysters reproduce?
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What caused the 'Golden Years' of Chesapeake Bay's Oyster Harvesting?
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What are the main reasons for declines in oyster harvesting?
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What defines a sustainable fishery?
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Where are mahogany trees primarily harvested?
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Study Notes
Overharvesting
- Involves harvesting wild species faster than their reproduction rates, impacting both flora and fauna.
- Rare tree species decline due to wood product harvesting.
- Marine life, including fish and shellfish, faces severe population decreases from overharvesting, driven by commercial and recreational activities.
Northern Elephant Seal
- Historically hunted for fur and blubber during the 1700s and 1800s.
- Believed extinct until a small population of 30 was found in 1892.
- Hunting was banned in 1922, leading to population recovery over 100,000 today.
- Reduced genetic diversity, with 20 genes showing zero variability.
Collapsed Fishery
- Classified when annual fish catch falls below 10% of its historic high.
Bycatch
- Occurs during trawling, damaging benthic habitats and affecting both target and non-target species.
Fishing Down the Food Chain
- The decline of top marine predators shifts fishing efforts to lower trophic levels.
Orange Roughy (Slimehead)
- Transitioned from bycatch to target species; notable for long lifespan (~149 years) and slow growth.
- Late to mature, making it highly susceptible to overfishing.
- Stocks near New Zealand and Australia have faced significant crashes since the late 1970s.
- Contains higher mercury levels compared to other fish, averaging 0.3-0.86 ppm versus 0.09 ppm for most other edible species.
Threats to Oyster Ecosystems
- Overharvesting is identified as the primary threat to oyster populations.
Negative Effects of Overharvesting
- Results in economic losses, habitat destruction, and diminished ecosystem services.
Ways of Harvesting Oysters
- Dredging is considered harmful, while oyster tonging and hand removal are sustainable methods.
Oyster Reproduction
- Mature oysters release gametes into the water, progressing from a swimming larval phase to a sessile adult stage and using chemical cues from shells for settlement.
Chesapeake Bay's Oyster Harvesting "Golden Years"
- Peak harvesting exceeded 10 million bushels in Maryland and Virginia.
Factors Leading to Declines in Oyster Harvesting
- Major contributions to declines include overharvesting, disease, water pollution, sedimentation, and increasing natural predation.
Sustainable Fishery
- Defined by healthy fish stocks, functioning ecosystems, and biodiversity protection, with effective management practices.
- 104 fisheries certified as sustainable and 143 undergoing assessments.
Mahogany Trees
- Important timber species in tropical forests found in Mexico, Bolivia, Brazil, and Peru.
- Harvesting and deforestation over two centuries have significantly reduced populations.
- Harvesting mainly from natural forests; timber plantation efforts frequently fail due to insect damage.
- Contributes 32% of Mexico's tropical timber production.
- Land management includes communal ownership, subsistence farming, and the establishment of forest reserves.
- Profits from timber sales reinvested into community projects, shared among residents.
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Description
Test your knowledge on overharvesting and its impact on ecosystems with these flashcards. Learn about specific species affected, such as the Northern Elephant seal, and the consequences of harvesting at unsustainable rates. Perfect for students studying environmental science or ecology.
