Challenge 4 - sustainable management of our marine reserves Flashcards
what is the solution to trying to recover overfished populations?
> be better at selecting appropriate species
better management of quotas
when fish declines occur, recovery is slow to non-existent
what are Marine Protected Areas?
> an area that is reserved by law for the protection of the organisms within the boundary - usually associated with lower or no fishing pressure.
16% of Moreton bay now fully protected - green zones
Rare - less tan 1% of marine areas are protected.
what are the benefits of MPAs?
> huge benefits in terms of ecosystem health
prevents exploitation
increases biomass, density, size and diversity
what were some changes in the Anacapa reserve one it was declared a MPA?
> change in ecosystem dynamics
i.e., if you remove the fishing pressure, then the organism that used to be fished now has a decreased pressure, so increases in number, for example the lobster. This has the flow on affect of reducing the number of sea urchins, as more lobsters are around to eat them. Then, because there are less urchins, the urchins food source of kelp increase in number, thus potentially negatively impacting the ecosystem.
this effect is called mesopredator release.
what is an example of mesopredator release?
the atlantic cod are predators. Their prey actually preys on the juvenile cod. Therefore, when the cod is fished in large numbers, the number of their prey increases, which then lowers the number of juveniles as the prey are eating the juveniles. This means that there are no longer any cod left, because the adults are over fished, and the remaining juveniles are eaten by the uncontrolled prey.
what is the benefit of a network of marine parks?
> maintain genetic variation
allow the flow of genetic material
allow there to be one functional population
they protect animals when they are adults.
what is an ecological network?
> functional connections between different entities.
> they occur via movement
what are some key parameters MPAs must have to be beneficial to a population?
> they must be larger than the average movement of adults.
this is because the adults are vulnerable to fisheries when they are outside the MPA
spill-over effects can occur when the adults migrate out of the MPA
understand the diagram and know for which fish it is going to be helpful for.
understand the table and how if your MPA is for example 10-100km big, it can help all the organisms within that bracket and lower brackets.
what does an MPA network mean for larvae?
> leaving is NOT risky for larvae, as they are not susceptible to fisheries.
the key point here is that larvae must be able to reach the next MPA for them to have any beneficial effect.
i.e., the spacing of MPAs good news because marine propagule dispersal is much larger than terrestrial.
also good news because marine animals with small dispersal distances are usually seaweeds and invertebrates that are not actively harvested.
describe the graphs showing estimated larval dispersal distances with the spacing between MPAs
understand this:
> 500km spacing means only organisms that can disperse distances greater than or equal to 500km will benefit from this kind of spacing.
what is the best combination of distance between MPAs and the size of the MPA?
MPA size = 20 km
spacing = 50km apart
can networks benefit both conservation and fisheries?
yes!! MPAs act as production sites for fisheries, as they produce lots of large fish, who then spill over the side and are available for harvest.
what are the effects of MPAs on yields in all scenarios?
> if adults move too much - yields will be unaffected
if larval dispersal is less than reserve size - reserves will decrease yields
if there are sources and sinks (i.e., unprotected areas) of larval production and there is poor management outside - reserves may increase yields.
