Term
| Loss of these organisms can lead to: |
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Definition
trophic cascades
alteration of community structures
decrease in ecosystem diversity and integrity
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Term
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Definition
| those that cause mortality of top predators |
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Term
Antarctic Krill Abundance
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Definition
nAntarctic marine system, South Georgia: data on krill abundance and predator abundance was collected between 1980-2000.
nTop predators included: Seals penguins and various marine birds.
nPredator abundance decreased during the study period for reasons including accidental mortality from long line fishing.
nWhen the predator population suffered declines, Krill community structure was altered, less krill entering the older age classes.
n1990’s: Predator demand for krill and krill availability were very close. Mortality from predators removed population buffer and thus increased the number of years where krill were not sufficiently available
nMarine Areas in New Zealand experiencing a decrease in algal forests and an increase urchin abundance, due to the decrease in the urchins natural predators.
nUsing Marine reserves predator density was increases.
nSnapper increased 6-9 %
nSpiny Lobster increased 1.6-3.7 % (account for 45% of predation on urchins)
nPredation rates on urchins was significantly increased in the reserve areas.
nDemonstrates that conservation of top predators can reestablish lost trophic interactions..
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Term
| The Importance of Life Histories |
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Definition
nMortality and predation rates of Yellow fin Tuna and Blue Shark were compared.
nBoth species are subject to accidental long line mortality.
nBlue Sharks typically exploited by “fining” practices of the Asian market.
nBlue Sharks are also victim to by-catch at a rate of 8*10^6/year.
nYellow fin tuna are one of the most economically important fish species.
nUsing bioenergetics models researchers estimated consumption rates of the two species, size dependent, natural and fishing mortality were taken into account.
nUsing population models fishing induced mortality was increased.
nWith calculated predation rates, renewal models were used to evaluate what level of fishing mortality would still allow for sustainable populations of the species.
nSignificant effects were seen when F= 0.4/year(Yellow fin Tuna) F=0.2/year(Blue Shark)
nDifferent reactions to fisheries pressures can be attributed to differences in life histories.
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Term
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Definition
nSince the industrialization of fishing the mean trophic level size has also been decreasing. In most fisheries around the world several trophic level species are exploited at a time.
nMost awareness and conservation efforts stem from public affection and tend to focus on marine mammals. Although a move in the right direction conservation efforts need to be more ecologically based.
nThe Sustainable Fisheries Act was passed in 1996, this act moved toward incorporating more information about habitats and ecosystem characteristics into management plans.
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Term
| actions taken for by catch |
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Definition
nReduction in by-catch was an initial stage in reducing fisheries impacts on top trophic species.
nAlong with by-catch the elimination of invasive predators was also proposed.
nFor sea turtles marine and birds this is beneficial and feasible since invasive predators can degrade habitats and prey upon marine bird eggs.
nHowever for sharks and other marine predators this may have no benefits at all because by-catch is mainly the concern.
nMitigation by paying for by-catch that is difficult to avoid has been proposed, however this may not be feasible or realistic.
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Term
| action taken for california sea otters |
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Definition
nLoss of Sea Otters led to the increase in population size of lower trophic levels including slow grazing species.
nDue to marine conservation efforts directed towards these species restoration efforts became popular amongst the general public.
nWhen numbers of Sea Otters increased biodiversity increased as well. Kelp Forest integrity was resumed due to the reestablishment of balance between predators and slow grazers.
However when compared to fishing pressure it was observed that Sea Otter pressure was greater than that of the fishery upon the lower trophic levels |
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Term
| discussion and future directions |
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Definition
nEcosystem based fisheries: a strategy that aims to regulate human activity toward maintaining long term system sustainability.
nPolicies and actions should aim to protect habitats required by fish throughout all life stages.
nReduce impacts of fishing on other components of the ecosystem.
nCommercial fisheries with less participants and less capital invested.
nGreater thought into the allocation of resources among commercial and recreational users.
nFinancial returns to the general public.
nDecrease in the short term overall harvest of certain species.
nThis method uses knowledge of ecosystem processes, whole ecosystem models and human impacts on marine fisheries to manage and restore ocean ecosystems to what they once were.
nOcean ecosystems can parallel terrestrial ecosystems that are generally better understood.
nTerrestrial habitats have agricultural use. Conservation and restoration of these habitats can have costs to food production for people.
Marine habitats provide homes for the food that is hunted. Therefore restoration of habitats can essentially preserve sustainable harvests
nMarine reserves have the potential to conserve top predators and their key role to their habitats.
nHowever with marine reserves we must also remember to continue to sustain fisheries economic stability and integrity.
nTwo main issues arise with protecting marine predators
nWill the marine reserves effectively protect marine predators.
nCan these top predator species serve as ecological indicators and aid in design plans for marine reserves.
nTo be effective for both fisheries and conservation benefits marine reserves must simultaneously conserve multiple species or whole habitats and maintain sustainable levels of stock specific species.
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Term
| Discussion and Future Directions: Terrestrial Reserves as models for Marine Reserves. |
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Definition
nProposes that Marine reserves be developed with terrestrial ecosystems and species in mind.
nTerrestrial reserves aim to maintain biological diversity and efficiently include a full spectrum of the life involved, and ensure long term diversity in our changing world.
nTo achieve these goals within a marine reserves managers need to understand the types and degrees of differences between marine and terrestrial ecosystems.
nEcological, genetic and evolutionary patterns and processes need to be fully understood as well as the processes that threaten these attributes.
nReserves can be an effective way to maintain sustainability and biodiversity locally and globally.
nThree basic questions must be answered before designing marine reserves.
1.How large must the reserve be?
2.How many reserves should there be?
3.Where should the reserves be located?
nThere is no single answer for any of the questions, each marine system must be uniquely studied for understanding of its processes, and managed to these unique attributes as well.
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Term
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Definition
nThe importance of top predators has been seen in many ecosystems a familiar one being Yellow stone wolves. The loss of top predators can have long ranging effects through the ecosystem.
nHowever in marine ecosystems which are generally less understood there are many threats to predators and many different kinds of predators each with unique characteristics and ecosystems.
nBy maintaining top marine predators within ocean ecosystems there is hope to restore ailing fisheries as well as marine biodiversity.
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