What happened to cod in Canada?
-increasing cod catch, and the population crashed in 1960s and 1970s -early 1990s the population completely collapsed -still hasn't recovered
Has the number of fishing boats changed much since 1937?
-the number of boats has not changed very much, change in where the fish come from, fewer fish and chip shops...
-fishing= overtime moves offshore as local stock become depleted
What is the global state of fish stocks?
-52% fully exploited
-17% over exploited
-20% moderately exploited
What is the conflict of interest with fishing?
there is a big conflict of interest: -have recreational and commercial fishers -first not as regulated, second is -politics vs science
What are the goals of protected areas? (3)
1.Protect particular species 2.Preserve biodiversity: focus on areas of high species richness/ endemism 3.Preserve large and functioning ecosystems and their services
What is a marine protected area?
-a named, discrete geographic marine or estuarine area, together with its overlying water and associated flora and fauna, that has been designated to protect or conserve marine life and habitat
What is a marine reserve?
-a marine protected area in which all of the physical, biological, and cultural resources are protected from removal or disturbance
What is a marine park?
-a marine protected area in which all of the physical, biological, and cultural resources are protected from removal or disturbance for commercial purposes; and some of the physical, biological, and cultural resources are protected from removal or disturbance for recreational purposes. -not as tightly controlled as marine reserves
What is a marine conservation area?
-a marine protected area in which some of the physical, biological, and cultural resources are protected from removal or disturbance for commercial and recreational purposes. -only some bits protected, so less tight
Has there been an increase in marine protection in recent years?
-yes, huge increase since 1975 -but still only less than 1% of the ocean as marine park areas -and even less where all fishing is forbidden
How much of Australian waters is protected?
-11% -each state has their own protecetd area programme
What are the ecological responses to marine protected areas?
get a range of ecological responses when compare within protected areas and outside the protected areas -response in total biomass, density and abundance, size and diversity
-increase in biomass= 466% -density= 166% -size=28% -diversity= 21%
Is there a difference in ecological responses to protected areas in the tropics and temperate waters?
what the MPA responses are in tropical and temperate areas:
-there is a difference as in tropics the organisms are more r selected, reproduce more etc.
-in temperate: slower
-in biomass and density get much bigger change in the temperate regions: as capacity of countries ti enforce the rules of protecting= better in temperate areas
-takes only a few fishermen can offset the effect
-enforcement is harder in tropics as less developed countries
How is reproductive potential affected by size of the fish?
-vermilion rockfish= lives in USA, increases in size in animals = lead to big differences in fecundity -not a linear relationship -big ones have exponentially more offspring -bigger females produce more eggs, non linear response, orders of magnitude more
How are trophic cascades affected by fishing?
-at community level can get more complex responses: change potential for interactions between species: e.g. lobsters eat sea urchins, they eat kelp -in fished= urchin barrens as not eaten by lobster -in reserves= more lobster= control the urchins so the kelp can be more successful -kelp is better as more diversity in organisms as kelp is a good habitat for many
What is spillover?
eggs can be carried further, dispersed via currents -to see of marine protected areas benefit fished areas as eggs and juveniles spread -spillover= adult spillover is big in some areas, so increase in biomass
What is the evidence that spillover from marine protected areas occurs (Cod)?
set up marine protected areas in the cod overfished area near canada -the blue dots are how much fishing activity happened in places -but the activity is concentrated around the protected areas as the dispersal from the protected marine areas there were no scallops outside the protected and then on the edges outside= as spillover
Why is it hard to study larval movements?
dispersal= by gamates, larvae = small subject to large mortality -hard to study, cannot track them - very few species that we can effectively tag= chemical tags -cannot really follow the larvae -typically have to come up with an alternative ways= genetic markers= gene flow, but just longer term integrating picture
What was the case study for dispersal?
there were patterns in where the larvae of the fish settle to -spatial gradient was persistent over years= increased recruitment in the north side -in the south decrease in abundance -the gradient maybe due to the ocean currents -patch depletion hypothesis as the water goes down the coast fewer and fewer -in the north: wake region where currents converge, if currents are weak then retention of larvae and thus they settle near the convergence how to test this?: suing environmental markers: otoliths= calcium carbonate crystals in their brains -auditory and pressure sensors - they have ring structures, they get laid down over time -can tell how old, can get growth history -how much food they are exposed to will refelct in ooliths= bigger ring etc. -do islands influence how much food etc is the water? -yes, differences depending on the coastal structure and currents= upwelling -much more food around islands often as upwelling. nearshore waters are more nutrient rich -larvae near island will be different -industry on the island -in the south lot of industry -higer = retention -if collect the fish at different locations= get different signatures in the recruits -increase recruitment with increase retention -on the other side= negative relationship -recruitment is highest when individuals from somewhere else -so have different types of recruitment - wind convergence= good for local recruitment -when low recruitment= that is when the currents move away from the island, very strong eddies change the flow -change in cicrulation are
How can ooliths be used?
-different water masses have different properties= different density, temp etc. -this influences how much they take in into the oolith -so can tell where they were
What is the retention and dispersal syndrome?
dispersal: • Depleted trace metals! • Slow growth rate! • Small size at settlement! -retention:• Elevated trace metals! • Fast growth rate! • Large size at settlement!
What is the summary of the case study?
-Reconstructing larval dispersal histories using environmental markers! Summary" ! • Larvae recruiting to St. Croix come from multiple larval sources! ! • Clustering of traits suggests two distinct larval syndromes: retained larvae and dispersing larvae! ! • Larval retention has a strong positive influence on recruitment success to leeward reefs! • Recruitment success to leeward reefs is correlated with variation in island wake circulation!
How does export of larvae differ in species?
--big differences in how the taxa disperse -seaweeds not much as tiny -only meters -invertebrates are variable, some are short lived -fish= big dispersal differences 10s-100s of kilometers
What is synthesis of the lecture?
-what happens in early life of an organism is important -really high mortality in larval stages -small changes in match or mismatch may have a large effect