Lecture 15 pt.2 Flashcards
(21 cards)
What is seen in large predatory marine fishes from the study by Myers and Worm in 2003?
Biomass of large predatory marine fishes has plummeted across world oceans
What happens to the food webs when overfishing occurs?
It contains fewer steps, or trophic levels
In the example of “fishing down” shown in class, what occurs when larger saithe fish are wiped out?
It shortens the food web to 4 levels instead of 6, disrupting ecosystems. Because small saithe are not large enough to catch cod, thus is must eat even smaller fish, such as herring
What are the Global trends of mean trophic level for marine and inland areas?
Over time, 1950-1990, the mean trophic level has gone down for both marine and inland areas
What is the purpose of harvesting marine bivalves?
For poultry-feed and edible lime- in E. India
What is Size-Selective harvesting?
preferential removal of larger individuals from a population
Which predators do size-selective harvesting?
Only humans, no other predator
Common practice for size-selective harvesting is in?
most fisheries
Which species are affected by size-selective harvesting?
both marine and terrestrial species
What aspects are affected by size-selective harvesting?
- fecundity and biomass
- survival of offspring
- reproductive investment
- growth and age(size) at maturity
- sex ratio
What is seen in the Cabrillo National Monument study on Tegula aureotincta? (2003)
The size of Tegula aureotincta has declined and gotten smaller since pre-1960. A control group was used at CNM to compare and confirmed that size-selective harvesting is causing the size of species to become smaller
What can illegal harvesting of one species lead to?
the decline of another species
What is the story of the Vaquita an example of?
That illegal harvesting of one species can lead to the decline of another species. Illegal harvesting of Totoaba swim bladders has lead to the decline of the Vaquita
Why is Totoaba so sought after?
Their swim bladders- “aquatic cocaine”
- in chinese markets a single dried swim bladder can fetch $5000-10000; a kg for >$100,000
What is “natural” or “pristine”?
knowing how an ecosystem looks in absence of any human impacts is essential for proper management and conservation
What is the “shifting baseline syndrome”?
By Daniel Polly, 1955- the baseline of what is “pristine” changes with every generation
What is the result of the “shifting baseline syndrome”?
the result is a gradual accommodation of the creeping disappearance of resource species
What is the Black abalones on intertidal rocks an example of?
The shifting baseline syndrome
What is Sustainability?
Does not exclude exploitation, instead it is based on the premise that it is possible to exploit natural resources and also make them last indefinitely
What is Conservation efforts?
Largely focused on stopping exploitation and preserving biodiversity
What are some proposed solutions to the over-harvesting problem?
- Enforcement of existing regulations
- Better approaches to harvesting- realistic limits, preservations of size distributions
- Economic incentives to fishers and hunters
- Alternative sources of protein (ex- aguaculture)
- Better awareness of the problem
